The effect in ewes of source and level of dietary protein on milk yield, and the relationship between the intestinal supply of non-ammonia nitrogen and the production of milk protein

Abstract

Individually penned Finnish Landrace × Dorset Horn ewes in early lactation, and each suckling two lambs, were used to test the effects on milk yield, milk composition and the concentrations of some plasma constituents of supplementing a basal diet with either urea, groundnut, soya bean, linseed, fish, meat and bone, or blood meal. The basal diet contained 94 g crude protein and 10 MJ of metabolizable energy per kg dry matter and supplied daily 0·3 MJ of metabolizable energy per kg body weight. Except for urea, which was tested at an inclusion rate that increased the protein (nitrogen × 6·25) content of the basal diet by 43 g/kg, the remaining sources were tested at three levels, corresponding to increases in protein content of 34,60 and 86 g/kg. Daily milk yields were 1·92 and 2·08 kg for ewes given the basal diet and the basal diet supplemented with urea. For the high inclusion rates of each protein source the following daily yields were obtained (kg): groundnut, 2·26; soya bean, 2·45; meat and bone, 2·49; linseed, 2·68; fish, 2·84; and blood meal, 2·91. The daily yields of true protein in milk were (g): basal diet, 76; basal diet plus urea, 80; groundnut, 104; soya bean, 107; meat and bone, 105; linseed, 112; fish, 136; and blood meal, 125. Plasma concentrations of free fatty acids did not appear to support the hypothesis that the milk yield response to protein is accomplished solely by increases in tissue energy loss.The increment in the amount of non-ammonia nitrogen reaching the abomasum as a result of the low levels of inclusion of the protein sources in the basal diet was used for the production of true protein-nitrogen in milk with an efficiency of 0·58.

Kikuyu (Pennisetum clandestinum) pasture for sheep. 2. Production and nutritional status of ewes with or without lupin (Lupinus albus) supplementation

“…The lack in wool growth response may be primarily attributed to the high protein degradability of lupins (Brand et al 1992), accompanied by a low sulphur (S) content, which may result in poor utilisation of available NH3-N for microbial growth due to a poor N:S ratio (Murray et al 1991). The low methionine content of lupins together with a low S content may have prevented a response in wool growth, since it is well known that wool growth is particularly sensitive to the supply of sulphur amino acids (Reis (Gonzales et al 1982;Robinson 1990). Seen in relation to the high degradability of lupins (Brand et al 1992), it appears that the already high CP degradability (c. 85%) of the pasture (Corbett 1987) might have compounded the problem.…”

Level and quality of protein in rations for lactating ewes

“…On the other hand, as the degradability of dietary protein in the rumen decreases, the amount of milk produced by the ewe increases (Robinson et al, 1979;GonzAlez et al, 1982 (Penning et al, 1988;Ngongoni et al, 1989;Hadjipanayiotou, 1992 production as a covariate to correct the total milk production. On the 8th day after lambing, they were distributed into 6 homogeneous treatments in terms of live weight (LW = 40.4 ± 5.28) and body condition score (BCs = 2.4 ± 0.32) at lambing (Russel et al, 1969), following a 2 x 3 factorial model, with 2 levels of CP in the ration and 3 main protein sources of different degradability in the concentrate.…”

Effects of maturity of silage and protein content of concentrates on milk production of ewes rearing twin or triplet lambs

“…In previous experiments, milk protein has been proven to respond to increases in dietary protein when fish meal supplement was used (Robinson et al 1979;Gonzalez et al 1982;Penning et al 1988) and also when soybean meal was increased (Gonzalez et al 1982). Since milk fat concentration was not affected by treatments, the difference in fat yield between EB and FB silages was mainly explained by a higher milk yield and could be caused by the higher daily protein intake with EB compared with FB silage.…”

“…Generally, with enough metabolizable energy in the diet to sustain a milk production of 3 kg ewe -1 d -1 , microbial proteins alone are not sufficient to fulfill protein requirements (Gonzalez et al 1982). Indeed, milk production in ewes varies with the percentage of CP in the diet (Robinson et al 1974(Robinson et al , 1979Gonzalez et al 1982).…”

“…Indeed, milk production in ewes varies with the percentage of CP in the diet (Robinson et al 1974(Robinson et al , 1979Gonzalez et al 1982). Ewes receiving 340 g d -1 or 415 g d -1 of protein produced 21 and 28% more milk, respectively, than ewes receiving 273 g d -1 (Robinson et al 1974).…”