DIAS report
Søren Pedersen
Climatization of Animal Houses
A biographical review of three decades of research
DIAS report Livestock no. 66 • October 2005
Climatization of Animal Houses
A biographical review of three decades of research
DIAS report Livestock no. 66 • October 2005
Søren Pedersen
Department of Agricultural Engineering Danish Institute of Agricultural Sciences Schüttesvej 17
8700 Horsens
DIAS reports primarily contain research results and trial statements aimed at Danish conditions. Also, the reports describe larger completed research projects or acts as an appendix at meetings and conferences.
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Honorary Doctor at the Swe- dish Agricultural University, the author has prepared this review of his
Preface
Production conditions for domestic animals have changed very much over the last century re- garding housing conditions, herd sizes and production level and recently also due to national and international regulations on animal welfare and emission from animal facilities. Also the working conditions for stockmen have developed from part-time to fulltime occupation. Espe- cially in the last few decades, the development has been very fast. Each time new or changed production methods are taken into use, the indoor climate and the emission of gases and odour are affected in some way. Also the need for ventilation and supplemental heat is affected.
Especially changes in the evaporation of water from wet feed, spilt water and fouled surfaces, due to changed housing layout, manure management and feed composition have a drastic im- pact on both the indoor climate and the emission from animal facilities. The reason is that evaporation of water has a double effect. It increases the amount of moisture to be removed from the animal house and it reduces the ventilation rate, because part of the sensible heat for ventilation is converted and used for evaporation of water. Therefore, it is increasingly impor- tant to have optimal basic tools concerning design and management of animal houses. The goal of this report is to show the development over more than three decades in the climatization of animal houses for domestic animals, illustrated by the author’s involvement in research pro- jects, primarily carried out in commercial animal buildings for cattle, pigs and poultry.
The work has been carried out in working groups, seminars and workshops on climatization of animal houses in a national, a Nordic - NJF (Nordic Association of Agricultural Scientists) - as well as an international framework - CIGR (Commission Internationale du Génie Rural).
Especially participation in a CIGR working group on Climatization of Animal Houses since the Year 1977 has been an excellent inspiration source for ideas for new research themes over the years. Until around 1985 the work primarily focussed on improved production efficiency and then gradually shifted over to research related primarily to animal welfare and the outdoor environment locally as well as globally.
This report covers the author’s activities on different animal species, climate parameters and time periods, and it was decided to let the chronologic order over three decades make the main structure of the work.
Acknowledgments
I should like to thank my colleagues at DJF for supporting me with information and discus- sions on the elaboration of this report and especially to Head of Research Unit Svend Morsing FCB and associate professor Bjarne Bjerg, KVL for reviewing this report.
Also thanks to my colleagues at the Swedish Agricultural University for appointing me Honorary Doctor.
Abbreviations
Over the last decades many research institutes in Denmark have been reorganized or have merged together. It may be difficult to be familiar with these changes. The following informa- tion may be helpful in reading this report.
SR 1947-1978 The government Experimental and Testing Station for Farm Ma- chinery and Implements, (Statens Redskabsprøver). Site:
Bygholm, Horsens.
DLU 1959-1978 The Agricultural Experimental Center. (De Landbrugstekniske Undersøgelser). Site: Ørritslevgaard, Otterup.
SJF 1978-1994 National Institute of Agricultural Engineering (Statens Jordbrugs- tekniske Forsøg). Site: Bygholm, Horsens. Merger of SR and DLU in 1978.
SBI-lan -1991 Department for Farm Buildings, Danish Building Research Insti- tute (Afdeling for landbrugsbygninger, Statens Byggeforsknings- institut). Site: Hørsholm. SBI-lan merged together with SJF in 1991.
FCB-SH 1994 -1997 National Institute of Agricultural Engineering. Site: Bygholm, Horsens. In 1994 it became a department of Danish Animal Sci- ence (Statens Husdyrbrugsforsøg, SH).
FCB- DJF 1997- FCB became a department of Danish Institute of Agricultural Sci- ences, DIAS (Danmarks JordbrugsForskning, DJF) where DIAS is established as a merger of several institutes of agricultural sci- ences.
KVL The Royal Veterinary and Agricultural University, (Den Kongeli- ge Veterinær- og Landbohøjskole) Copenhagen.
DLBR Danish Agricultural Advisory Service (Dansk Landbrugsrådgiv- ning), Landscentret, Skejby.
LUS The National Committee for Pig Production (Landsudvalget for Svin), Axelborg, Copenhagen.
Content
1. Structure of animal production over a century 7
2. The early years of fundamental research 12
2.1 Ventilation equipment 12
2.2 Research on animal heat production 15
3. Improving production efficiency (1970-1985) 17
3.1 Ventilation equipment 17
3.2 Official tests of ventilation equipment 18
3.3 Under-floor suction from slatted floors in pig houses 21 3.4 Temperature stability in pig houses, 1971-1972 23 3.5 Effect of indoor climate and bedding on pig performance, 1974-80 27 3.5.1 Study 1. Influence of air velocity on pig performance at two
different indoor temperatures (1972-1974) 29
3.5.2 Study 2. Influence of variations in air velocity and temperature
on pig performance (1974-1976) 31
3.5.3 Study 3. Influence of variations in air velocity and temperature
on pig performance with and without bedding (1976-1978) 33
3.5.4 Conclusion of studies 1, 2 and 3 35
3.6 Effect of indoor temperature on daily gain of pregnant sows 35
3.7 Design of pig pens in the seventies 37
4. Improving indoor and outdoor environment (1985-2005) 39
4.1 Animal activity 39
4.2 Animal heat production at house level 44
4.3 Ventilation rate based on heat, moisture and carbon dioxide
concentrations 48
4.4 Animal heat and carbon dioxide production in respect to animal
activity 52
4.5 Ammonia emission 54
4.6 Dust reduction methods 56
4.7 Simulation of indoor climate, emission, ventilation rate and
supplemental heat 61
5. The future 63
5.1 Herd size and production level in 2025? 63
5.2 The hottest research themes in the near future 64 5.3 What will the housing design be like in 2025? 66
5.4 The indoor environment 69
5.5 Emission from animal facilities 74
6. Brief conclusion based on three decades of research 76
7. Literature 78
Sammendrag
Produktionsbetingelserne for husdyr har ændret sig meget over de sidste hundrede år med hensyn til staldforhold, besætningsstørrelse og produktionsniveau. I de seneste år også med hensyn til national og international lovgivning vedrørende husdyrvelfærd og emissionen fra stalde. Specielt i de sidste ti år er det gået stærkt. Hver gang produktionsmetoderne ændres, påvirker det staldklimaet og emissionen på den ene eller den anden måde. Også behovet for ventilation og tilskudsvarme påvirkes.
For at få indsigt i, hvilke faktorer der er bestemmende for, hvordan staldklimaet bliver, er det vigtigt at tage udgangspunkt i dyrenes varmeproduktion. Dyrenes samlede varmeproduktion, også kaldet ’dyrenes total varme’ er sammensat af ’fri varme’ (det der opvarmer den omgi- vende luft) og ’bunden varme’ (omfattende dyrenes vanddampproduktion). Fordampning af vand fra foder og våde flader bruger af den frie varme, hvorfor ændringer i fodersammensæt- ning og gødningshåndtering påvirker staldklimaet meget, idet fordampningen har en dobbelt effekt. Fordampningen forøger mængden af vand, der skal fjernes fra stalden, og det reducerer ventilationen. Også varmetabet gennem gulve, vægge og loft bruger af den frie varme, der er til rådighed for ventilation. Af andre forhold, der påvirker staldklimaet, kan nævnes sol- indstråling i dagtimerne og kuldeudstråling om natten.
Det er klimaanlæggets opgave at bortskaffe vanddampproduktionen ved udskiftning af luften.
Det er vigtigt at have ’værktøj’ til håndtering af disse staldklimasammenhænge. Et sådant
’værktøj’ er også nyttigt ved forståelsen af forskellige faktorers indflydelse på dyrevelfærd, arbejdsmiljø og emission af lugt, støv og gasser fra staldene.
Målet med nærværende rapport er at vise udviklingen indenfor staldklimateknik over mere end tre årtier, illustreret gennem forfatterens engagement i forskningsprojekter, specielt udført i stalde under normale produktionsbetingelser for kvæg, svin og fjerkræ. Arbejdet er udført i forskningsprojekter, seminarer og arbejdsgrupper om staldklimateknik i både nationale, nor- diske og internationale sammenhænge i NJF (Nordiske Jordbrugsforskeres Forening) og CIGR (Commission Internationale du Génie Rurale). Specielt deltagelse siden 1977 i CIGR arbejdsgruppen om ”Climatization of Animal Houses” har været en god inspirationskilde til at få idéer til nye forskningsområder igennem årene.
Indtil 1985 vedrørte arbejdet specielt, hvordan produktionen per dyr kunne øges, gradvist ændret til projekter, hvor dyrevelfærd, arbejdsmiljø og emissionen fra stalde fik en mere fremtrædende rolle, såvel lokalt som globalt.
Baggrunden for rapporten er forfatterens udnævnelse til æresdoktor ved Sveriges Lantbruks- universitet. Rapporten dækker forfatterens aktiviteter vedrørende forskellige dyrearter og kli- maparametre over forskellige tidsperioder. Det er valgt at lade kronologien over de tre årtier udgøre hovedstrukturen i rapporten.
I bogens første afsnit er der vist træk fra udviklingen i besætningsstørrelse og produktionsni- veau for kvæg, svin og fjerkræ over hundrede år. Herefter følger udviklingen fra 1970 til 1985, der er kendetegnet ved øget produktion, fulgt af perioden efter 1985, hvor arbejdet gradvist er drejet over mod dyrevelfærd og det omgivende miljø. Sluttelig er der givet et bud på, hvordan det kunne se ud i 2025.
1. Structure of animal production over a century
In former times herd sizes were small, often with several species in the same animal house as e.g. in Denmark, where it was common to have cattle and pigs together. In the 1950s and 1960s things changed with bigger herd sizes, higher stocking density and individual buildings for cat- tle and pigs. The development continued with more specialization and today cattle are normally housed separately in houses for calves, heifers and dairy cows. Also pigs are housed separately in sections for pregnant sows, lactating sows, weaners and growing-finishing pigs. Poultry pro- duction has been split up in houses for broilers and laying hens. In the following, the develop- ment in stocking density and production level for dairy cows, growing-finishing pigs and broil- ers is illustrated.
The increase in herd sizes is followed by a drastic reduction in the number of farms, of which there were around 200 000 in the 1950s, reduced to around 100 000 in 1980 and to 46 500 in 2003, of which 25 000 had livestock. There has also been a shift in the type of farms and to- day there are big industrial-like farms with high technology, part-time farms with different levels of technology and spare-time farmers with e.g. beef cattle.
Cattle
The structure of cattle production has changed drastically over the last century (Agricultural statistics, 1969, Statistical Yearbooks, 1969 – 2004 and personal communication). Figure 1 shows that until the sixties the average number of dairy cows per farm was below 10 cows, increasing to about 80 cows in the year 2005. Also the yearly milk yield per cow has doubled since the sixties, which corresponds to an increase in the animal heat production of 25%. Tak- ing into account the fact that the body weight of dairy cows has gradually increased in the same period, the increase in heat production is in fact 35%.
Dairy cattle
0 2500 5000 7500 10000
1900 1925 1950 1975 2000
Year Yearly milk yild per cow, kg
0 25 50 75 100
Cows per herd
Milk yield
Number
Figure 1. Number of dairy cows per farm and yearly milk yield per cow
Until the early fifties all dairy cows in Denmark were tied, but in 1952 the first loose housing system was built. The number of loose housing systems was increased to 17 in 1956 and to 175 in 1967 (P. Keller, personal communication).
The loose houses in 1967 comprised four different types, distributed as:
21 % enclosed buildings with deep litter 55 % open buildings with deep litter 15 % enclosed buildings with cubicles 9 % open buildings with cubicles
In the following ten years, the number of loose housing systems was relatively constant, but in the seventies many new facilities were built as loose housing. Because of problems with maintaining the deep litter, due to very moist manure as a result of feeding with sugar beets as the main feed ration, many farmers shifted to cubicle houses. In the eighties and nineties nearly all newly built houses were with cubicles and today most of the cattle are housed in cubicle houses. From the late nineties, further rationalization of the work has led to the im- plementation of milking robots on some farms. The first milking robot in Denmark was taken into use in 1998. In 2000 there were 85 farms using milking robots, increasing to 430 in 2005.
That means that 7% of all dairy farms in Denmark use milking robots and it is the highest percentage in the world. One milking unit can serve around 70 cows including dry cows and there are on average 2 units per herd. While the diurnal routine of feeding, cleaning and milk- ing is well-defined in traditional dairy housing, with fixed periods for feeding, cleaning, milk- ing, and resting, such a clear diurnal rhythm does not exist when free access to milking robots nearly 24 hours a day is used.
Together with the shift from tied cows to freely moving cows, natural ventilation has been taken into use in most of the cattle buildings, and a lower indoor temperature, created by means of a higher ventilation rate, has been accepted in wintertime, because the animals in this system are free to move away from areas with draft (too high air velocity). Another factor is the cattle’s big tolerance to low temperatures. In fact many dairy buildings have been venti- lated more out of concern for the stockman’s wellbeing than for that of the cattle. In loose housing systems much of the work is carried out in the milking parlour, as the indoor climate in the feeding and resting area is less important for the stockman.
As mentioned above, another change over time has been in the feed composition. At the be- ginning of the previous century, sugar beets and silage of sugar beet leaves were the main components of the roughage for cattle in the winter period, resulting in a very wet indoor en- vironment compared to e.g. animal houses in highland regions, where the roughage is mainly hay with low water content. Due to the mechanisation of the production of grass silage and the introduction of new corn types adapted to the Scandinavian climate, sugar beets are not used any longer as roughage, which has had a positive effect on the moisture evaporation from feed.
In former time calves, heifers and fattening calves were often housed together with the dairy cows in the farthest corner of the animal house. Due to lower heat production in the calves than in the cows, the temperature in that part of the house was lower than in the cow area and in accordance with air physics, the indoor relative humidity was very high with high risks of airway problems. In the sixties and seventies, when the herd sizes increased very fast, and due to work rationalization, it became common to have calves, heifers and fattening calves in separated houses. In the eighties calves were often kept in houses with a relatively high indoor temperature obtained by means of supplemental heating. Unfortunately, there were still prob- lems with the health of the calves. Investigations in the eighties, carried out at SH and FCB, showed that in the wintertime, the calf health was better in cold houses or hutches than in ac- climatized buildings.
Today most of the calves are housed in naturally ventilated, partly open, buildings with tem- peratures a few degrees above the outside temperature. EU directives only allow calves to be kept in single boxes until the age of 8 weeks, after which time group housing is required. In 2005 calves is housed in either boxes with deep litter or in hutches
In the seventies, due to rationalization, it became common to keep heifers and fattening calves in boxes with fully slatted floors without bedding. That system functioned well in respect to working conditions and manure handling, but it was not considered an animal- friendly sys- tem by the public, why the heifers in 2005 is housed in systems, distributed as follows:
15 % Boxes with fully slatted floor 30 % Cubicles
45 % Boxes with deep litter with a short feeding table 10 % Tied and other housing systems
Pigs
In addition, the structure of pig production has changed very much over time. Figure 2 shows that the number of growing-finishing pigs per farm (summer censuses) which was only around 10 on average until the fifties, increased to about 20 pigs in the sixties. In 2003 the av- erage number of growing-finishing pigs per herd was above 600 or 30 times higher than in the sixties.
Growing- finishing pigs
0 5 10 15 20
1900 1925 1950
Year
Pigs per herd
Growing- finishing pigs
0 200 400 600 800
1950 1975 2000
Year
Pigs per herd
Figure 2. The number of growing-finishing pigs (above 20 kg) per farm1900-1950 to the left and 1950-2005 to the right
Figure 3 shows that also the daily gain and the slaughter weight have increased over time. The daily gain for growing-finishing pigs in commercial production was around 500 g per day in the fifties, increasing to around 800 g per day in 2005, and the daily gain for pigs in breeding herds is now around 1000 g or twice as high as in the fifties. The pigs at commercial farms also have the potential of a daily gain of more than 800 g, but when it comes to obtaining a high meat percentage, as demanded by the market, the pigs are frequently fed so that they are restricted to a lower daily gain. Thus, a change in the ratio of meat/fat content, due to market demand, can very quickly affect the pigs’ daily gain at commercial farms.
The increase in daily gain also results in an increase in animal heat production. The level de- pends on the pigs’ ability to convert feed energy to growth instead of heat
Growing-finishing pigs
0 200 400 600 800 1000 1200
1900 1925 1950 1975 2000
Year
Daily gain, g
0 20 40 60 80 100 120
End weight, kg
Daily gain End weight
Figure 3. Daily gain and end weight for growing-finishing pigs
The space per animal (Figure 4) has changed drastically over time. In 1950, the total pen area of trough, lying and dunging area for growing pigs was about 1.5 m2 per pig. Due to increased production efficiency, rationalization and the use of fully slatted floors, the pen area including feeding troughs was in some farms reduced to 0.5 m2 per pig around 1980. In some cases the experiences with high density gave management problems and insufficient production results and there was also an increasingly more active public opinion on how to keep the animals.
In accordance with EU directives, the minimum pen area excluding feeding troughs must since 2003 be at least 0.65 m2 for growing pigs up to 110 kg and 1.00 m2 for growing pigs above 110 kg. Another EU directive prescribes that all pens for growing-finishing pigs must have at least 1/3 of the floor as solid or drained floor (max. 10% perforation) from 2013. In the same way another EU directive prescribes that destroyable rooting material must be avail- able for pigs and therefore it is foreseen that many pens will again be provided with a minor amount of bedding. Furthermore, a Danish rule prescribes that water sprinkling must be pro- vided in pig pens in warm periods, which will also affect the evaporation of water.
In former time, pregnant sows were kept in pens or boxes, but in the seventies it became popular to tether the sows individually with a necktie in a new housing type for pregnant sows. At a certain time nearly all pregnant sows were tethered. Due to new EU directives, pregnant sows will have to be kept in groups in the future. Two thirds of all pregnant sows are estimated to be un-tethered in 2005. From 1 January 2006 tethering of sows will be totally prohibited.
Also in the piglet production, the changes have been comprehensive. Fifty years ago it was normal to wean the piglets when they were about 12 weeks or older. Since then the weaning ages have gradually been reduced to about 7 weeks, and in a few cases down to 4 weeks, which is the lowest weaning age according to EU directives. Early weaned pigs need special care in respect to the indoor climate, with start temperatures of nearly 30oC. In the early sev- enties, a new type of weaner houses was developed with weaned pigs in one, two or three decks. The system with pigs in several decks functioned well from a production efficiency point of view, but due to an inconvenient working environment and public opinions on animal welfare, only houses with one deck have been used since the nineties.
Figure 4. Space per growing-finishing pig and use of slatted floors Until the sixties, when automatic feeding systems were developed for pigs, nearly all pigs were fed manually with dry feed. Since the sixties, both dry and wet feeding has been used.
The proportion of systems with dry and wet feeding has changed in the course of time, de- pending on which system was assumed to be the best regarding the economy at a certain time.
The trend in 2005 is toward more use of wet feeding and less use of dry feeding, which also has some positive effect on dust abatement in pig houses. Most of the pig houses today are mechanically ventilated with one or two climate zones, where it is possible to make a com- fortable microclimate near the animals. Pigs are more sensitive to low temperatures than cat- tle, and the present trend of early weaning of piglets requires careful climatization of pig houses for weaners concerning temperature, relative humidity and air velocity.
Increasingly important factors over the last twenty years have been new national and interna- tional rules on animal welfare, with restrictions on stocking density, floor types, rooting mate- rial and the rules and regulations regarding the outdoor environment concerning emission of ammonia and other gases.
Poultry
Until the fifties, broiler production related to the yearly replacement of old layers, which is why the broiler production was primarily based on the surplus of male chickens. In the sixties new broiler lines for meat production were taken into use and the herd sizes grew from around 50 on average per farm in the early fifties to above 30 000 birds per herd in 2005 (Figure 5).
The stocking density was increased over the years, but due to Danish regulations, it has been restricted to 43 kg bird per m2 floor area from 2003 and to 40 kg per m2 floor area from 2006.
In former times layers were kept in houses where they could freely choose to stay on the floor, to rest at the perch or in the nest, and often they had access to a poultry run. In the six- ties bigger layer houses were introduced due to rationalization and nearly all layers were housed in cages with limited space. The construction of new layer houses with cages without welfare facilities as e.g. perches, has been prohibited since 1 January 2003 and from 1 January 2012 all layer houses with cages must have minimum 750 cm2 per hen and be equipped with 15 cm perch per hen, nest boxes and a claw shortening device as e.g. sandpaper.
Growing-finishing pigs
0,0 0,5 1,0 1,5 2,0
1900 1925 1950 1975 2000
Year Pen area per pig, m2
0 25 50 75 100
Pens with fully slatted floor, % Pen area per pig
Fully slatted floor
Figure 5. Development in herd size and production level
Broilers are fed with dry feed and all the broiler houses are with mechanical ventilation. Also for poultry houses there are restrictions that affect the production methods and the indoor cli- mate, as e.g. the need for resting periods with darkness for broilers, which affects the diurnal broiler heat production. Another restriction is on layer houses regarding more space per hen.
Mink
Also the size of fur farms has been increased over time, from about 500 mother animals per farm in 1990 to 1400 mother animals per farm in 2005. In the same period, the number of fur farms has been reduced from 5000 to 1800.
In conclusion, the changes in cattle and pig production have been fast over the last century, but the changes in broiler production have been even faster.
2. The early years of fundamental research 2.1 Ventilation equipment
At the beginning of the 20th century, the ventilation was poor with no or very few openings (leakages) for natural ventilation, resulting in a high relative humidity in wintertime and risk of environmentally caused health problems for the animals.
In the twenties and thirties, some animal buildings were equipped with inlet openings in outer walls as described by Høgsbro (1937). Figure 6 to the left shows an example of such an inlet, which acted as a model for inlets until the sixties. The air jet from that type of inlet is directed slightly upwards when there is hardly any need for fresh air and directed upwards in a fully open position, with risk of draft, when the incoming air reaches the ceiling at a big angle or is rejected by e.g. horizontal beams. Today that type of inlets has been replaced by inlets where the air jet is directed downwards when there is an increased need for ventilation. (Figure 6 to the right, SR test report no: 1422, 1978) It gives a much better air movement in the animal house, especially in hot periods, when increased air velocity is beneficial.
Broilers
0 25000 50000 75000
1900 1925 1950 1975 2000
Year
Broiler per herd
0 50 100 150
Ages at 1400g, days
Days
Number
Figure 6. Inlet valve in the fifties to the left and an inlet in the seventies to the right Different types of outlets for natural ventilation were used, often made on site. Figure 7 shows a prefabricated chimney.
Figure 7. Examples of chimneys for natural ventilation before 1950 (BurupROAR B) With increased herd sizes, the need for efficient ventilation was also increased, and the first attempt to use fan ventilation was made already in the early 20th century (Høgsbro, 1937).
The prevailing ventilation principles were the negative pressure ventilation systems with inlets in the walls and exhaust fans in walls or ceiling. Still, in the early fifties, mechanical ventilation was rare in Denmark, and the only regulation of ventilation rate was manual con- trol of inlets and on/off control of fans via thermostats. Figure 8 shows a fan from that period.
Figure 8. Exhaust fans from the fifties with two fan blades, 2700 rpm. (SBI-Lan 17, 1960) Due to problems with draft from the inlets in negative pressure systems, the so-called equal pressure system was developed as shown in Figure 9.
Figure 9. Equal pressure ventilation system, developed in the late sixties (Fristamat) The basic idea of the equal pressure ventilation principles was to get rid of the wind influence on the air distribution in the animal house. Some types were based on a double fan as in Fig- ure 9, with exhaust in the central pipe and inlet in the outer ring. In respect to distribution of air, that is an appropriate, but complicated and energy consuming design. That is why that type has today been replaced by separated inlets and outlets.
In a certain period, positive ventilation systems were used, especially as a combination of a horizontal duct with nozzles and an open chimney. The advantages of that system is that the air distribution is not influenced by wind and that the energy consumption is much lower than for an equal pressure system, but unfortunately there is a risk of pressing moist air into those constructions where the water condenses, due to lower temperatures. By proper control of
fresh air in the inlet system and big outlet openings in the ridge, the risk is small, but farmers are inclined to close the outlet to reduce the air exchange and consequently the pressure rises.
That is why positive ventilation systems are not used or recommended any longer.
2.2 Research on animal heat production Pigs
Already in the1950s comprehensive experiments were carried out in Europe and the USA on animal heat and moisture production under laboratory conditions.
In Denmark, laboratory measurements on animal heat production have been carried out at KVL, SH and at DJF, often in respect to evaluation of the effect of feed compositions on ani- mal production.
The first Danish experiments with different temperatures for growing-finishing pigs with wood shavings as bedding were carried out in 1957-1961 by Sørensen and Moustgaard (1967) in SBI´s climatic laboratory in Roskilde. The results concerning daily gain and feed conver- sion for pigs in the interval of 40 to 90 kg showed that the optimum temperature was around 16oC, and that pigs are not as sensitive to temperature as shown in some old US experiments.
In the same laboratory, experiments with SPF (Specific Pathogen Free) pigs were carried out in 1973-1976 in pens with wood shavings (Pedersen and Petersen, 1976). In one experiment, 8 pigs were kept at a constant temperature of 18 oC in Chamber 1 and 8 pigs at a start tem- perature of 18 oC dropping to 12 oC over 6 weeks in Chamber 2. In another experiment, the pigs were kept at a constant temperature of 18 oC in Chamber 1 and at a start temperature of 12oC increasing to 18 oC over 6 weeks in Chamber 2. No clear difference in pig performance was measured.
Broilers
In the late sixties and early seventies comprehensive investigation on the optimal climate for broilers was carried out at Danish Building Research Institute’s climatic laboratory in Roskilde (Pedersen, 1975). This experiment concluded:
1. A starting temperature of 30 to 33 oC and a temperature reduction of 0.5 oC per day should be used from the beginning of the growth period of the chickens.
2. The production economy improves by increasing the final temperature within the range of 12 to 28 oC. Only pronounced changes in the prices of the grown chickens and in the cost of feed for day-old chickens can change this result.
3. An air velocity within the range of 0.5 to 1.25 m/s has a negative influence on the produc- tion economy at a final temperature ranging from 16 to 28 oC compared to an air velocity of 0.2 m/s.
A detailed description on how to ventilate animal houses in the thirties is given by Høgsbro (1937) followed by different publications from SBI, e.g. SBI Lan-15 (1958), SBI-Lan 17 (1960) and SBI Lan-26 (1968).
Figure 10 shows the relation between indoor temperature and total animal heat production, divided into sensible heat and latent heat (moisture), based on Figure 1a in SBI Lan-26 (1968), converted from kcal/h to W. The heat producing unit (hpu) was defined as a total heat production of 800 kcal/h, representative for a cow with a medium milk yield.
0 200 400 600 800 1000 1200
-10 0 10 20 30 40
Temperature, oC
Animal heat production, W
Sensible heat
Total heat Latent heat
Figure 10. Heat production guideline for cattle in the fifties
In the seventies a comprehensive review of international literature was carried out in order to get general guidelines for animal heat production for cattle, pigs and poultry at SBI. At the same time the hpu unit was adjusted to 1000 W in total heat production at 20oC as shown in Figure 11, (Strøm, 1978). The literature was analysed individually for cattle, pigs and poultry, and the division of “total heat” into “sensible heat” and “latent heat” was examined. Some dif- ferences between the three species were seen, but due to lack of sufficient data the collected information was used to make a common diagram for cattle, pigs and poultry. The new unit was about 11% bigger and corresponded better to the heat production for dairy cows in the seventies. Today dairy cows of big races produce around 1200 W, corresponding to 1.2 hpu, due to increased milk yield and body mass.
0,0 0,2 0,4 0,6 0,8 1,0 1,2
10 20 30 40
Temperature, oC
Animal heat production, W
Sensible heat
Total heat
Latent heat
Figure 11. General guideline for animal heat production (Strøm, 1978)
3. Improving production efficiency (1970-1985)
The period from 1970 to 1985 can be seen as the period when research was devoted to in- creased efficiency concerning improved animal productivity and reduced labour and where the concern about work environment, animal welfare and the environment was just awaken- ing. An overview of research projects on animal husbandry will clearly disclose that state- ment.
It was also the period when the investigation on the impact of indoor climate on production efficiency was continued in laboratories, whereas experiments under normal farm conditions were rare. One of the reasons is that it was complicated to make continuous measurements on climatic parameters as e.g. ventilation flow on housing level. Another reason was that the production conditions were less well-defined than in the climatic laboratory. Therefore ex- perts have often argued that it is not wise to make measurements at real farms. However, the animal production is carried out at real farms, so it is important to include the housing pa- rameters such as e.g. water content in feed and manure management in the measurements.
With today’s better equipment for measurements of ventilation flow and other climate pa- rameters it is possible to make reliable measurements also at commercial farms.
3.1 Ventilation equipment
Until the eighties all vertical exhaust units in Denmark consisted of a cylindrical pipe, with a fan and hood, often equipped with a damper. Figure 12 shows such an exhaust unit from the seventies to the left and a typical 1990-2005 design to the right, with a bell-shaped inlet and a conical diffuser as outlet. The development from a simple conical pipe, to the left, to the 1990-2005 design to the right, is the result of a fruitful cooperation between Danish compa- nies producing ventilation equipment and FCB.
Figure 12. 1970 design to the left and 2005 design to the right
Many different designs of inlet valves were developed in the seventies and eighties. Figure 13 shows an inlet where the opening area increases slowly at the first movement of the damper, which makes it easier to control it at low ventilation rates when it is cold outside.
Figure 13. Inlet developed in the eighties (SJF test report no. 850, 1991)
3.2 Official tests of ventilation equipment
The number of Danish companies producing ventilation equipment increased until the late eighties and also the need for documentation of volume flow, energy consumption and noise grew. Already in the sixties some preliminary tests on exhaust fans were carried out at SR (E.g. SR test report no. 728, 1965). These tests showed that a more reliable test plant was needed and in the early seventies SR, SBI and DLBR made a common paper on how to test Ventilation equipment. Figure 14 shows the test plant, designed by engineer F. Guul- Simonsen, SR, which was ready for use in 1975 and still fulfills the demand for a test plant.
The initial test procedure is described in the SR test report no.1341 (1978) from SR.
Figure 14. Cross-section of the ventilation test facilities at DJF
The work at SR was followed by Danish Standard (DS), which established an expert group to make a standard for test of ventilation equipment. The standard was issued as DS 6039, 1983.
All tests of fans at SR were carried out in accordance with DS 6039 until 1993 when a new common test procedure between Germany (DLG), The Netherlands (IMAG-DLO) and Den- mark (SJF) was issued (DLG D/81, 1993).
2.7 3.3
2.0 5.0
13.0
3.
0 Places for units Alternative mounting Straightener Booster fan Adjustable cone Straighteners
Nozzles
Section Section
Section Section
Around 600 official tests have been carried out since 1975. In addition, hundreds of requested tests have been carried out for companies, especially in the period 1995-2005.
Figure 15 shows examples of the test report layout at different times.
Figure 15. Layout of official test reports 1978-2005 at FCB
Figure 16 shows a newer exhaust unit during test (Pedersen and Strøm, 1995)
Figure 16. Test of exhaust unit at FCB
One of the first investigations in the test plant was an investigation of fan capacities measured in the laboratory and under normal production conditions (Pedersen and Guul-Simonsen, 1976). The main conclusions were:
The capacity for a dirty exhaust unit is 5-20% lower than for a clean one. A slot between the fan-blade tip and pipe of 15 mm reduces the fan capacity by 5-10%, compared to a slot of 4-5 mm. So-called multi-blade dampers reduce the fan capacity by up to 25%, depending on the cleanness and roughness of the damper. The use of a hood plus extension pipe reduces the capacity by 10-15%. An increase in pressure drop of 10 Pa reduces the fan capacity by 5%.
The capacity of a fan built into a complete exhaust system may be reduced by up to 50%
compared to the capacity of the fan section itself.
From the late seventies to the late eighties the efficiency of exhaust units was improved very much in respect to volume flow. Based on tested exhaust fans with diameters in the range 600-650 mm, the average volume flow, energy consumption and specific volume flow devel- oped over ten years as shown in Table 1.
Table 1. Development in fan performances over ten years
1978-81 1986-89
Negative pressure 0 Pa 20 Pa 0 Pa 20 Pa
Volume flow m3/h 7 590 6730 9 300 8 070
Energy consumption W 406 411 222 248
Specific volume flow m3/kWh 20 400 17 500 51 500 39 700 The table shows that the volume flow increases by approximately 20%. Simultaneously the energy consumption decreases by around 40% and the specific volume flow more than dou- bles. This development is due to the change from cylindrical exhaust units with hoods as shown in Figure 12 to the left and to the exhaust unit to the right in Figure 12 with a bell- shaped inlet and diffuser outlet.
After1990 the volume flow for tested units (600-650 mm) was still increasing in order to re- duce the cost price per m3 air capacity. As the potential for extra energy saving is small when the bell-shaped inlet and the diffuser are taken into use, the consequence is higher energy con- sumption according to fan laws. Therefore, the specific volume flow was reduced after 1990 and it is still lower than in 1990. Today the fan capacity for 600-650 mm units is up to 14 000 m3/h or nearly twice the capacity of 1980, corresponding to a much higher pressure drop in the unit, so it is a real challenge to keep the specific flow above 30 000 m3/kWh.
Conclusion: Since the nineties, the maximum ventilation rate for 600-650 mm fans has been increasing, the investment has been decreasing due to bigger capacity per unit and the energy consumption is higher than in 1990.
Another factor to take into consideration is the noise from the ventilation units, which in- creases about 6 dB (A) when the capacity increases from 10 000 to 14 000 m3/h. for a 600- 650 mm unit. (Pedersen, 1998). That corresponds to one unit with a capacity of 14 000 m3/h producing the same amount of noise as four units with a capacity each of 10 000 m3/h.
A more systematic investigation of the efficiency of different exhaust types is shown in Fig- ure 17. In this case the same fan wheel and motor are used for all types, i.e. the fan wheel and motor are not optimized for each of the five types. The increase in volume flow from type 2 to type 5 is 79%, the decrease in energy consumption is 3 % and the increase in specific volume flow is 92% (Pedersen and Jensen, 1998). The performance for type 5 could probably be im- proved further, by using an optimized smaller motor.
1100
1000 1000 1000
1000
460
1000 620
320
750 1000
820
1000
Type 1. 2. 3. 4. 5.
Speed r.p.m 821 814 790 805 832
Effect W 390 390 403 401 378
Air flow m3/h 5870 6090 8620 9410 10930
Spec. flow m3/kWh 15050 15620 21390 23470 28920
Figure 17. Performance of a fan section together with different combinations of inlet open- ings and outlets
3.3 Under-floor suction from slatted floors in pig houses
The introduction of partly slatted floors in pig houses in the seventies made it possible to extract exhaust air through the slats. By means of suction from the manure pit under slatted floors it is possible to remove a considerable part of the volatile gases e.g. NH3, H2S and bad odours re- leased from animals, manure and urine before they are whirled up in the breathing zone of ani- mals and humans. Under-floor suction can be considered a special version of a negative pres- sure ventilation system. Many pig houses in the seventies were equipped with partly slatted floors ventilated by under-floor suction. With the extension of the slatted floors, from partly slatted floors to fully slatted floors in the late eighties and in the nineties, the interest for under- floor suction decreased because the air velocity through the slats became too low to ensure downwards air direction over the entire slatted floor surface.
Figure 18 shows the layout of an under-floor suction system (Pedersen, 1977 and 1978), which consists of a main air duct parallel to the manure channel and some side ducts. The main prob- lem is to obtain a homogeneous flow through slats along the main air duct, because the suction is highest nearest to the fan and lowest farthest from the fan. The larger the main air duct is, compared to the sum of the cross-area of the side ducts, the more equal the suction along the air duct will be, as shown in Figure 19. It is also important that the air velocity through slats is above 0.2 m/s to ensure a stable suction over the entire surface (Albrechtsen and Pedersen, 1978).
Therefore, the following can be concluded:
x The total side duct area has to be smaller than the cross-are of the main air duct. (If so, the velocity ratio will not be higher than 1.6, which is acceptable in most cases.) x The air velocity in the main duct should be below 3 m/s and maximum 4 m/s in order to
restrict the energy consumption concerning pressure loss.
x To ensure that the air only goes downwards in the slatted floor, the air velocity in slats must be 0.2 m/s on average or more.
Figure 18. Sketch of under-floor suction layout
Figure 19. Air velocity ratios for side channels (nearest/farthest) as a function of area ratio, (total area of side ducts/area of main duct)
3.4 Temperature stability in pig houses, 1971-1972
At DLU the experimental station ‘Ørritslevgaard’, an experimental unit for growing-finishing pigs (Figure 20) was established in the late sixties in order to improve the productivity in pig production regarding the use of labour, daily feed conversion (kg feed per kg gain) and pig health. The facilities consisted of four identical pig buildings, each with 12 pens of 8 grow- ing-finishing pigs. The house design was typical for that time, with two-row pens, consisting of a bedded lying area, a common dunging area and feeding passages for hand feeding along the outer walls.
One of the first investigations carried out in these facilities was on temperature stability (Pedersen, 1974). The main parameter was the temperature stability over a cross section of the building at air velocities below 3 m/s (low wind speed) and above 10 m/s (high wind speed) perpendicular to the buildings at outdoor temperatures below 2oC (winter) and above 20oC (summer). An auxiliary interface was used to start the data recordings when the prescribed conditions about wind speed, wind direction and outdoor temperature were fulfilled. Meas- urements were carried out for growing-finishing pigs in the ranges 20-40 kg, 40-60 kg and above 60 kg.
Temperature measurements were carried out in 19 positions, with 7 at the height of 1.2 m above the floor, 7 at the height of 1.8 m and 5 at the height of 2.4 m above the floor, as shown in Figure 21. The data were collected by a data logger and punched in binary notation on a one-inch tape (Pedersen, 1972).
The goal was to compare the widely used negative pressure ventilation system with the equal pressure or balanced ventilation system developed in the sixties. The negative pressure venti- lation system was installed in two pig houses (A and B) and the equal pressure ventilation system in the two others (C and D). In Sections B and C, the ceiling follows the roof, and in A and D the roof is horizontal and lowered as shown in Figure 21. The exhaust units and the inlet units in the negative pressure system were equipped with dampers, governed by servo motors. The balanced units worked with a constant inlet flow of a mixture of fresh air and re- circulated air due to a damper system governed by a servo motor, which was again controlled by the indoor temperature.
Figure 20. To the left a plan of experimental facilities. To the right a low speed data acquisi- tion system (based on mechanical relays)
Figure 21. Cross section showing the positions of 19 temperature sensors Figure 22 shows the inlet system built on site and the exhaust fan for negative pressured ven- tilation, used in sections A and B. The opening area of inlets and the damper in the outlet were mechanical coupled with and governed by a so-called servo motor.
Figure 22. Inlet valve to the left and to the right servo motor exhaust fan (DAE), temperature and humidity sensors
Figure 23 shows the temperature distribution for the negative ventilation principle for the measuring period with the lowest temperature variation across the building (23a) and the highest temperature variation (23b) and Figure 24 shows the temperature distribution for the balanced ventilation principle for the measuring period with the lowest temperature variation across the building (24a) and the highest temperature variation (24b).
Figure 23. Temperature distributions in section A with negative pressured ventilation for the measurements with the smallest (23a) and the biggest (23b) temperature variation above the cross section
23a
23b
The figures show that very little difference was found between the ventilation principles and the temperature distribution was also nearly identical for the two systems. One of the charac- teristics is that the temperature is high above the lying area and low above the dunging area in the middle. It is also obvious that the temperature is low above the feeding passage, close to the colder outer wall.
Conclusion:
x The temperature stability using the balanced pressure system was better than when using the negative pressure system, but the differences were not as big as expected. If it is as- sumed that temperature variations of up to two degrees have no harmful effect on an ani- mal production, it may be concluded that both ventilation systems were able to create sat- isfactory temperature stability under all conditions studied.
x The greatest temperature difference measured within a cross section was 3.5oC during winter and 4.1oC during summer.
x Wind velocity has no significant effect on the temperature stability in the buildings.
x The energy consumption for supplemental heat during winter for negative pressure venti- lation and equal pressure ventilation was of the same order at wind speed below 3 m/s. At wind speed above 10 m/s during winter, the energy consumption for negative pressure ventilation was three times higher than for the balanced pressure ventilation.
24a
24b
Figure 24. Temperature distributions in Section D with balanced ventilation (Figure 9) for the measurements with the smallest (24a) and the biggest (24b) temperature variation above the cross section
3.5 Effect of indoor climate and bedding on pig performance, 1974-80
As the knowledge about the influence of indoor climate on pig performance was poor and primarily based on laboratory measurements, DLU and SBI initiated in 1974 a research pro- gramme on the influence of air velocity, temperature and bedding on pig performance under commercial production conditions.
Altogether, three different studies with a total of about 2300 pigs were carried out (Pedersen and Christensen, 1977, Pedersen and Christensen, 1979 and Pedersen, 1982) where each study consisted of two winter and two summer measurements. The facilities were identical with the facilities shown in Figure 20 and 21, except that the ceiling in section A and D also followed the roof.
The pigs were fed with the feed being restricted in accordance with the Danish norm of 0.85 kg feed per pig at 20 kg, increased to 3.00 kg at 90 kg. (1 kg pig feed ~ 12 900kJ metaboliz- able energy). The maximum allowed relative humidity was 85%. At higher relative humidity, supplemental heat was turned on automatically. In pens with bedding, a maximum of 0.2 kg barley straw per pig per day was used.
The measurements on pig performance include daily gain, feed conversion, animal health in respect to medical treatments, remarks from slaughterhouses and pigs removed due to illness or death.
To maintain the set values of air velocity as well as is possible in all parts of the pen, special ventilation equipment was developed as shown in Figure 25.
Figure 25. Ventilation principles. Injector system (25a), horizontal slot inlet (25b) and circu- lar inlets (25c)
Air velocities below 0.2 m/s were obtained by the injector principles shown as 25a, where a constant inlet velocity could be obtained for variable need for fresh air, by combining the fresh air through the small nozzles on the underlying duct and the fresh air via the 45o connec- tion from the overlying duct. The principle is that by low need for fresh air, only the small
25a 25c
25b
nozzles are in function and according to the injector principle, six times as much leaves the mixing chambers. In case of maximum need for fresh air, all air is supplied via the 45o bend to the mixing chamber without any injection. In case of need for ventilation between mini- mum and maximum, both supply systems begin working.
The system 25b, with a horizontal pipe with a 2 m long slot, was used for velocities at the range <0.2 to 0.5 m/s, while system 25c was used for high air velocities of 0.8 m/s
The maximum allowed relative humidity was set to 85 %. At a higher relative humidity, sup- plemental heat was automatically turned on.
Figure 26 shows the sensor for measuring air movements and the data acquisition system, comprising a 100-channel data logger and a tape-punching unit.
Figure 26. High-speed data acquisition system (based on reed-rely) and a sensor (10 mm in diameter) for air velocity/temperature measurements and a blow up of the (2 mm in diameter) sensor tip with the thermistor for measuring air velocity
This acquisition system, with a recording speed of above 10 channels per second, was an ad- vanced system at that time. Later on data acquisition systems have improved very much in speed by means of PC recordings where the scanning velocity can be 10 000 Hz or more. Be- sides, the storing media have developed over time.
Figure 27 shows the media used by the author over three decades. The punched card for “For- tran” language was used in the sixties, primarily to handle programs and datasets punched manually via a keyboard. When experimental date could be automatically punched on a 1- inch tape for treatment by a “big” computer common for many users at university level, it was a revolution in the late sixties. In the first period, the paper tape was sent to NEUCC (North- ern Europe University Computing Center) and later on to Odense Teknikum, where the data were fed directly into the computer via a tape reader. Later the data were transferred to a magnetic tape for “fast” transfer to the computer, treated by the language GIER-Algol.
Gradually it was possible to store data on diskettes for treatment on PC and later also on CD’s. The storing media became still smaller and grew in memory capacity. The diskette shown in Figure 27 has a capacity of 1.44 MB, while a USB memory stick (not shown), common since the turn of the century, can have a capacity which is 500 times bigger or more.
Figure 27. Different media used for data storing over three decades. Punched cards above to the left, punched tape above to the right, magnetic tape below to the left, plus a diskette and a CD below to the right
3.5.1 Study 1. Influence of air velocity on pig performance at two different indoor temperatures (1972-1974)
The first study (Pedersen and Christensen, 1977) comprises measurements on pig perform- ance at the four different air velocities <0.2, 0.4, 0.6 and 0.8 m/s, combined with the tempera- ture 13oC (winter) and 23oC (summer). The plan is shown in Table 2.
Table 2. Plan for experiments with different air velocity and in houses for growing-finishing pigs (1974-1976)
Indoor temperature, oC Section Air velocity
m/s
Trial 1 (winter)
Trial 2 (summer)
Trial 3 (winter)
Trial 4 (summer) A <0.2 13 23 13 23 B 0.4 13 23 13 23 C 0.6 13 23 13 23 D 0.8 13 23 13 23 Daily gain and feed conversion
At an indoor temperature of 13oC (winter) the daily gain decreased by 6%, and the feed con- sumption per kg gain increased by 4 % when the air velocity increased from < 0.2 to 0.8 m/s.
That means that at normal air velocities below 0.2 m/s, the production results were nearly identical at 13oC and 23oC, with a slightly higher daily gain and a slightly lower feed conver- sion at 13oC compared to 23oC. At an indoor temperature of 23oC (summer) the daily gain in- creased by 3%, and the feed consumption per kg gain decreased by 2% when the air velocity increased from < 0.2 m/s to 0.8 m/s. Figure 28 shows the results on daily gain and Figure 29 the results on feed conversion.
Temperature and air velocity
500 550 600 650
0,0 0,2 0,4 0,6 0,8 1,0
Air velocity, m/s
Daily gain, g 13°C Winter
23°C Sommer
Figure 28. The influence of air velocity on daily gain at different indoor climate at 13 and 23oC, 1974-76
Temperature and air velocity
3,1 3,2 3,3 3,4
0,0 0,2 0,4 0,6 0,8 1,0
Air velocity, m/s Feed conversion, kg/kg
13°C Winter 23°C Summer
#REFERENCE!
Figure 29. The influence of air velocity on feed conversion at different indoor climates at 13 and 23oC, 1974-76
Animal behavior
As to the possibility for the pigs to improve their own microclimate in hot weather, they re- sponded by showing different behaviors, e.g. by wallowing in the wet dung area. The pigs’ ly- ing behavior was investigated by regular manual observations through spot tests, where all pigs were observed at 1:00 pm. The analysis shows that 69% of the pigs lie in the resting area, when the indoor temperature is 13oC and that 90% lay there when the temperature was above 23oC and the rest were standing. At 23oC, the pigs started lying in the dung area at a weight of 35 kg at an air velocity <0.2 m/s and at 45 kg, at an air velocity of 0.8 m/s. The labor required for cleaning the lying area was about 25% higher in fouled pens than in clean pens.
3.5.2 Study 2. Influence of variations in air velocity and temperature on pig performance (1974-76)
The second study (Pedersen and Christensen, 1979) comprises measurements on pig perform- ance, when the ventilation rate is controlled by different p-bands of 0 (two step positions low/high of ventilation flow) and 4oC and 10oC, respectively. This means that for p-bands of 4oC and 10oC, the indoor temperature and air velocity drop down at night when the ventilation need is low due to low animal heat production combined with a low night temperature and vice versa. The sections with 13oC/<0.2 m/s during wintertime and 23oC/<0.2 m/s during summertime act as reference. Table 3 shows the plan.
Table 3. Plan for experiments with different p-bands for growing-finishing pigs (1976-1978)
Trial Section Temperature
oC
Air velocity m/s
A 13 <0.2
B 13 <0.2 or 0.8
C 13-17 0.15-0.8
1976/77 and 1977/88 (winter periods)
D 12-23 0.15-0.8
A 23 <0.2
B 23 <0.2 or 0.8
C 19-23 0.15-0.8
1977 and 1978 (summer periods)
D 13-23 0.15-0.8
Daily gain and feed conversion
The daily gain in the reference, section A, with an air velocity of <0.2 m/s and 13oC in the winter experiments and 23oC in the summer experiments was nearly identical with 608 g dur- ing winter and 604 g during summer.
The feed conversion in the reference, section A, with an air velocity of <0.2 m/s and 13oC in the winter experiments and 23oC in the summer experiments was 3.29 kg/kg during winter and 3.21 kg/kg during summer, which is also nearly identical.
Under winter conditions (13oC), the daily gain decreased by 3% and the feed consumption per kg gain decreased by 1 % when the air velocity stepped between <0.15 m/s and 0.8 m/s (p- band = 0) For a climate control with temperatures of 13 - 23oC and air velocities of 0.15 - 0.8 m/s (p-band = 10oC), the daily gain increased by 1% and the feed consumption decreased by 1%.
Under summer conditions (23oC), the daily gain increased by 2% and the feed consumption per kg gain decreased by 2 %, when the air velocity stepped between <0.15 m/s and 0.8 m/s (p-band = 0). For a climate control with temperatures of 13 - 23oC and air velocities of 0.15 - 0.8 m/s compared to a p-band of 4 or 10oC (p-band = 10oC), the daily gain increased by 3%
and the feed consumption decreased by 2%. Figures 30 and 31 show the results.
p-band
500 550 600 650
0 2 4 6 8 10 12
p-band
Daily gain, g
Winter Summer
13 oC 23
13-17 oC
13 - 23 oC
13 - 23 oC 19-23 oC
Figure 30. The influence of variations in air velocity and temperature on the daily gain for growing-finishing pigs (1976-1978)
p-band
3,1 3,2 3,3 3,4
0 2 4 6 8 10 12
p-band
Feed conversion, kg/kg WinterSummer13
oC
23oC
13-17 oC
19-23 oC
13 - 23 oC
13 - 23 oC
Figure 31. The influence of variations in air velocity and temperature on the feed conversion for growing-finishing pigs (1976-1978)
Animal behavior
Table 4 shows manual observations of animal behavior for pigs of 20-50 kg and 50-90 kg, re- spectively, as to lying in the dung area when it is hot.
Table 4. Percent of pigs lying in the dung area under different indoor climatic conditions.
Pigs lying in the dung area at 1.30 pm
% Animal
house
Temperature
oC
Air velocity m/s
p-band
oC
May-June (20-50 kg)
July-August (50-90 kg)
A 23 <0.2 (0) 3.3 11.6
B 23 0.2 or 0.8 0 3.0 8.0
C 19-23 0.1- 0.8 4 1.5 7.3
D 13-23 0.1- 0.8 10 0.2 3.5
The table shows that the animals used the lying area for resting purposes as intended until they obtained a body weight of 50 kg. Fewer than 4 pigs out of 96 were lying in the dung area. For pigs above 50 kg 11.6 % were lying in the muddy dung area at 23oC and <0.2 m/s, which can be interpreted as if it was too hot for the pigs. At a colder indoor climate (via a combination of lower temperature and air velocity), the percentages dropped to 3.5, indicating better welfare.
3.5.3 Study 3. Influence of variations in air velocity and temperature on pig performance with and without bedding (1975-1978)
Studies 1 and 2 comprise measurements for pigs in bedded pens. The third study (Pedersen, 1982) comprises measurements on pig performance with and without bedding (barley), com- bined with different combinations of indoor temperatures and air velocities. One row of pens in each section was with bedding and the other half without bedding. Table 5 shows the ex- perimental plan
Table 5. Plan for experiments with different combinations of temperature and air velocity for pens with and without bedding.
Section Type of climate control
Temperature
oC
Air velocity m/s
A 1 13 <0.2
B 2 13 0.8
C 3 13-17 0.1-0.5
1978/79 and 1979/80, Winter
D 4 13-23 0.1-0.5
A 1 23 <0.2
B 2 23 0.8
C 3 19-23 0.1-0.5
1979 and 1980, summer
D 4 13-23 0.1-0.5
Daily gain and feed conversion
For all examined combinations of temperatures and air velocities, the effect of using bedding was on average about 1.5% higher in daily gain and about 1.5% lower in feed consumption per kg gain. The highest deviation from the average daily gain and feed consumption was measured for the coldest combination in respect to chilling, namely with an air temperature of 13oC and an air velocity of 0.8 m/s, in combination with no bedding. The daily gain was 7.5%
lower and significant (P < 0.001) and the feed consumption was 9.1% higher and also signifi- cant (P < 0.001). Figure 32 shows the influence of air velocity, temperature and bedding on the production results (1978-80).
