The intake of nitrogen (NI) and digested nitrogen (ND) was determined for each pig in each balance period and the individual figures will be found in the main tables (p. 159). From these figures the mean values for intake of digestible protein in the 6 different rations have been calculated (ND x 6.25) and will be found in Tables 21, 22, and 23 together with the intake of lysine and methionine + cy stine. The concentrations of the amino acids in the different feedstuff s in question are determined by the courtesy of Bjørn O. Eggum of this institute, according to the method of Moore, Spackman & Stein (1958).
From the tables it will be found that in the first period the intake of digestible protein started at 120 g for the compounds with skim-milk powder, and about 130 g for the protein mixture compounds, ending in period VIII with 280 g and 300 g respectively. The protein norm has been established according to previous investigations (Møllgaard (1955), Ludvigsen & Thorbek (1955)) to ensure a maximal protein retention. From the investigations mentioned it was found that the curve for nitrogen retention was fairly constant in the live weight group from 40 to 90 kg. For barrows the nitrogen retention was about 18-20 g daily, on the assumption that no lack of protein intake had occured in the previous periods. According to these findings the norm used in series C-D-E-F is charac-terized by a rather high and increasing intake of digestible protein in the live
Table 21. Daily intake of digestible protein, lysine and methionine + cystine in the experi-ments with barley. Series C-D-E-F, Mean of 12 pigs in each group
Tabel 21. Daglig optagelse af fordøjeligt protein, lysin og methionin + cystin i forsøgene med byg. Serie C-D-E-F. Middel af 12 svin i hver gruppe
Period
no.
I II . . HI IV V VI VII VIII
Barley and skim-milk powder Live
weight kg . . . . 23.7
. . 29 3 . . . 35.7 43.6 . . . 52 3 . . . 61.4 . . . 71.9 . . . 83.1
Dig.
protein g 119 149 176 198 223 246 266 283
Lysine g 9.5 12.0 14.3 15.1 16.4 17.6 18.7 19.6
Methionine + cystine
g 4.9 6.2 7.3 8.4 9.7 10.9 12.1 13.0
Live weight
kg 23.4 28.7 34.7 42.8 50.9 59.6 69.6 80.2
Barley and protein mixture Dig.
protein g 133 168 198 218 243 263 283 299
Lysine g 9.7 12.2 14.4 15.5 16.7 17.9 18.9 19.9
Methionine + cystine
g 5.2 6.5 7.7 8.8 10.0 11.3 12.4 13.3
Table 22. Daily intake of digestible protein, lysine and methionine + cystine in the experi-ments with maize. Series C-E. Mean of 6 pigs in each group
Tabel 22. Daglig optagelse af fordøjeligt protein, ly sin og methionin + cystin i forsøgene med majs. Serie C-E. Middel af 6 svin i hver gruppe
Period
lize and skim-milk powder Dig. + cystine
g
Maize and protein mixture Dig. + cystine
g
weight group from 20-50 kg, while in the last period from 50-90 kg the rate of increase is slowed down.
Using feed compounds with a constant composition during the whole period of growth very often implies that the nitrogen intake in the lower weight classes is below the requirement for maximal protein gain, and above the requirement in the later periods of growth, causing an excessive loss of nitrogen through the urine.
In the trials described here, the amount of skim-milk powder or protein mixture constituted about 30% of the total ration in period I, decreasing to
Table 23. Daily intake of digestible protein, lysine and methionine + cystine in the experi-ments with sorghum. Series D-F. Mean of 6 pigs in each group
Tabel 23. Daglig optagelse af fordøjeligt protein, ly sin og methionin + cystin i forsøgene med milo. Serie D-F. Middel af 6 svin i hver gruppe
Period Sorghum and skim-milk powder Sorghum and protein mixture Live Dig. Lysine Methionine Live Dig. Lysine Methionine weight protein + cystine weight protein + cystine no. kg g g g kg g g g
I 24.0 124 9.0 4.6 23.9 131 8.7 4.7 II 29.0 156
III 35.3 184 IV 43.0 206 V 50.6 224 VI 60.1 250 VII 70.6 271 VIII 80.4 281
11.0
about 13% in period VIII. Expressed in terms of digestible protein, the feed compounds contained 15-17% in the first period and 11-12% in the last period.
Comparing the intake of digestible protein (Tables 21, 22 and 23) with the intake of metabolizable energy (Tables 16,17 and 18) for the respective rations, it will be found, that the ratio g digestible protein: Meal metabolizable energy for the rations containing skim-milk powder decreased from 44 to 32, while the ratio decreased from 53 to 35 for the rations with protein mixture, according to the somewhat higher intake of protein and lower intake of energy in these rations.
As discussed in section 4.2 the energy loss in urine, closely related to the excretion of nitrogen, has been rather low in the present investigation, indica-ted by the regression coefficient of ME on DE being 0.972 (Tables 19) for all rations in question. This indicates, that the norm used for intake of digestible protein in relation to intake of metabolizable energy, is not above the require-ment, as an excess of nitrogen intake would have caused a higher excretion of nitrogen in the urine, thereby lowering the ratio ME:DE. The question remains whether the protein norm and the intake of amino acids combined with the energy norm used is sufficient to secure a maximum protein gain during the growth period, a problem which will be discussed later in relation to protein-and fat gain.
The daily intake of digestible protein in relation to daily intake of metabol-izable energy is demonstrated graphically in Figure 15, indicating the mean
ü°300
200 100
Present invest.(Ml) ., - (PR) Nielsen (1970)
2,0 3,0 4,0 5,0 6,0 7,0 8,0 9[0 Meal Daily intake of ME
Figure 15.
Daily intake of digestible protein in relation to daily intake of metabol-izable energy (ME).
Daglig optagelse af fordøjeligt protein i relation til daglig optagelse af omsættelig energi (ME).
curves for the rations containing skim-milk powder or protein mixture, respec-tively, compared with the rations used by Nielsen (1970). The intake of dige-stible protein in relation to metabolizable energy has been calculated from the trials of Nielsen for the 56 pigs not receiving screenings from U.S. 5 barley in their rations. As commonly used in practical feeding, different kind of pellets, each with a constant composition were used in the experiments of Nielsen, and for the six different feed compounds investigated the protein mixture varied from 14 to 24% of the total compound. Expressed in relation to intake of me-tabolizable energy only small variations existed between the different feed compounds. The mean curve, being linear, is demonstrated in Figure 15, and the ratio of digestible protein to metabolizable energy was found to be fairly constant, around 47, which probably caused the somewhat greater energy loss in urine, found by Nielsen in the last balance periods, as discussed in section 4.2.