Gas exchange and heat production in growing pigs fed different feed compounds
6.1 Gas exchange and heat production in relation to live weight and intake of metabolizable energy
The individual measurements of live weight, intake of ME, gas exchange and heat production, (RQ), will be found in the main tables. From these figures mean values and standard deviation for each period including all 6 feed com-pounds, have been calculated and the figures are shown in Table 36.
It will be found that most of the values for the relative standard deviation for the mean values of live weight and intake of metabolizable energy are between 5 and 8%. The gas exchange and heat production are strongly influenced by the live weight of the animals and their intake of energy. As demonstrated in Table 36 the relative standard variations of the mean values for gas exchange and heat production are of the same magnitude as for the mean values of live weight and intake of ME.
The values for CCh-production, Ch-consumption and heat production (RQ) in relation to live weight taken frem Table 36 have been graphically demonstra-ted in Fig. 24, 25, 26 and compared with the corresponding values obtained by Breirem (1935) and Nielsen (1970).
Table 36. Gas exchange and heat production (RQ). Series C-D-E-F. Mean of individual measurements of pigs on 6 different feed compounds
Tabel 36. Respiratorisk stofskifte og varmeproduktion (RQ). Serie C-D-E-F. Middel af individuelle målinger af svin på 6 forskellige foderblandinger
Period no.
I II III IV V VI VII VIII
n
36 46 48 47 48 48 47 47
Live weight kg
23.0 28.5 34.7 42.6 50.8 59.7 69.9 80.3
S.D.
2.7 2.4 2.7 2.9 3.5 4.3 4.8 5.4
Intake of ME Meal
2.56 3.28 3.92 4.80 5.78 6.74 7.64 8.57
S.D.
0.16 0.18 0.20 0.32 0.33 0.35 0.44 0.50
CCh-product.
litres 430 499 564 648 721 813 905 991
S.D.
28 31 28 45 51 50 62 76
Ch-product.
litres 432 494 545 613 667 716 789 858
S.D.
37 34 37 45 50 50 58 71
HP (RQ) kcal
2172 2494 2767 3127 3408 3714 4102 4470
S.D.
169 165 170 219 252 248 290 352
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20 30 40 50 60
Live weight Figure 24.
CCh-production in relation to live weight.
COi-produktion i relation til legemsvægt.
70 80 90 kg
From the work of Breirem (1935), including 5 pigs on low protein intake, measured in 26 individual respiration experiments, the mean values for gas exchange and heat production at comparable live weights have been used for comparison. From the work of .Nielsen (1970) with 80 pigs measured in 6 periods the data consisting of mean values for each of 4 pigs have been used, independently of the type of feeding.
It is clearly demonstrated that the curves for gas exchange and heat produc-tion in relaproduc-tion to live weight observed in the trials of Breirem are on a lower level than found in our investigation. In the live weight group from 20-30 kg the 24 hour CCh-production was 351 below and the 02-consumption 801 below our results, the difference increased to 125 1 CO2 and 155 1 O2 in the weight group from 80-90 kg. The difference in heat production (RQ) was 0.30 Meal in the lower weight group increasing to 0.55 Meal in the higher weight group.
The differences might be caused by the protein and energy norm used by Breirem (cf. chap. 4). The protein norm used for the pigs on »Low protein« was about 35% below our norm during the experimental time, so in spite of the ME-intake being 0.5 Meal higher in the liveweight group from 20-30 kg in the
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80 90 kg Figure 25.
02-consumption in relation to live weight.
Oi-forbrug i relation til legemsvægt.
experiments of Breirem (cf. Fig. 12) the lower protein intake may be responsi-ble for the lower heat production of 0.30 Meal. The reduced ME-intake of 1.4 Meal in the live weight group from 80-90 kg together with the lower protein intake gave a heat production 0.55 Meal below our results.
Comparing the present investigation with the results obtained by Nielsen (1970) it is striking how closely the curves for CCh-production (Fig. 24) follow each other during the growth period from 20-90 kg, considering the many different types of feed compounds in question. The curves for Ch-consumption are identical too, in the lower weight classes, but with a greater slope of the curve from the observations of Nielsen a difference of about 50102 daily was found in the weight group from 80-90 kg, thereby causing a difference in the heat production of about 0.2 Meal daily above the results obtained in the present investigation (Fig. 26).
As discussed in chapter 4 and demonstrated in Figure 12 the energy norm used by Nielsen was about 0.7 Meal ME lower in the weight group from 80-90 kg than in the present investigation. With a lower ME-intake one would have expected a correspondingly lower heat production, but instead a somewhat higher heat production was found. This may be caused by the higher protein intake for the heavier pigs in the experiments of Nielsen. With the ratio of g digestible protein to Meal metabolizable energy being fairly constant around
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Live weight
80 90 kg Figure 26.
Heat production (RQ) in relation to live weight.
Varmeproduktion (RQ) i relation til legemsvægt.
47, the norm apparently was above the requirement for maximum protein gain in the later weight classes, thereby causing a somewhat greater energy loss in urine. An excess of nitrogen intake above the requirement for maximum nitrogen retention will result in an excretion of the superfluous nitrogen as urea and this, being an oxygen consuming process, will increase the 02-consump-tion and thereby increase the heat loss, as found from the trials of Nielsen.
In order to discuss the heat production found in the present investigation with figures commonly used for planning the ventilation in pigsties values for ME-in-take, gas exchange and heat production have been estimated from Fig. 12, 24, 25 and 26 and compiled in Table 37.
Table 37. CCh-production, O2-consumption and heat production (RQ) in different live weight classes, estimated frem Fig. 12, 24, 25 and 26
Tabel 37. COi-produktion, Oi-forbrug og varmeproduktion i forskellige vægtklasser, aflæst fra Fig. 12, 24, 25 og 26
Live weight kg
20-30 30-40 40-50 50-60 60-70 70-80 80-90
Intake of ME Meal 2.75 4.05 5.25 6.30 7.30 8.15 8.90
CO2-product.
litres 450 570 675 770 860 940 1015
O2-consumption litres 460 545 620 695 790 820 870
RQ
0.98 1.05 1.09 1.11 1.13 1.15 1.17
Heat product. (RQ) Meal 2.25 2.80 3.20 3.60 3.95 4.25 4.55
On the basis of the work of Cords-Parchim (1947), indicating a unit for heat production in milking cows of 775 kcal per hour for a body weight of 500 kg (GVE = Grossvieheinheit), Korsgaard (1951) proposed a unit for heat produc-tion (Vpe = Varmeprodukproduc-tionsenhed) of 800 kcal per hour. Based on the existing measurements of heat production in pigs Korsgaard calculated for an
»average« pig at 45 kg a heat production of 0.15 Vpe corresponding to 120 kcal per hour or 2.88 Meal per 24 hour. Since that time it has been a commonly used procedure to calculate the heat production which could be expected in pigsty proportionally with the live weight of the pigs, based on 0.15 Vpe for a pig at 45 kg.
In an earlier investigation (Ludvigsen & Thorbek, 1955) a heat production of about 2.76 Meal per 24 hour was found at an average live weight of 45 kg, being quite near the value of 2.88 Meal. In the present investigation as well as in the trials of Nielsen (1970) the heat production is now found to be about 3.20 Meal daily for pigs at 45 kg live weight (Table 37). The increment of about 10% above the former »norm« may be explained by the genetic development of the Danish Landrace and by a greater intake of energy and protein causing a higher heat production.
As clearly demonstrated in Fig. 26 and Table 37 the heat production at different live weight classes is not proportional to the live weight and the relation between heat production and live weight is not even a straight line.
Therefore calculations of expected heat production based on proportional values will lead to erroneous results. In sties housing younger pigs the heat production would be underestimated, while it would be overestimated in sties with heavier pigs, as discussed by Ludvigsen & Thorbek (1955) and Mathes &
Bergner (1963).
In conventional »mixed« sties with pigs in all weight classes the figures from the under- and overestimation of the expected heat production from the diffe-rent weight group of pigs would balance each other, and no great error would occur by calculating the heat production proportional to live weight as has been done hitherto.
In »all in - all out« sties the estimated heat production would be too high when all the pigs are in the heavier weight group. At 40 kg the heat production would be around 3.0 Meal daily, but doubling the live weight to 80 kg would not double the heat production to 6.0 Meal daily, but only 4.4 Meal could be expected.
Calculating with proportional values for heat production in that type of pigsty would therefore give rather erroneous results. A better way of calculating the expected heat production in that type of sty would be to use values proportional to metabolic live weight as discussed in the next section.
6.2 Gas exchange and heat production in relation to metabolic live weight