The effect of level of feeding on the response of lactating ewes to dietary supplements of fish meal

Abstract

Link to this article: http://journals.cambridge.org/abstract_S0003356100031834How to cite this article: J. S. Gonzalez, J. J. Robinson and I. McHattie (1985). The effect of level of feeding on the response of lactating ewes to dietary supplements of sh meal. ABSTRACTThirty-six individually-penned ewes (mean live weight 69 kg), each suckling two lambs, were given one of three diets containing either 128 (low), 155 (medium) or 186 (high) g crude protein (CP) per kg dry matter. All diets contained (g/kg), milled hay, 570; molasses, 95; and a barley/fish meal concentrate, 330. The three protein concentrations were achieved by adjusting the proportions of barley and fish meal in the concentrate. Each diet was given at daily metabolizable energy (ME) intakes of 19, 23 and 27 MJ. Mean daily yields of milk in weeks 3 to 8 of lactation for ewes given the diet with the low concentration of crude protein increased from 2-32 kg at 19 MJ ME to 2-53 kg at 27 MJ. Corresponding values for the medium concentration of CP were 2-49 and 2-67 kg and for the high concentration 2-52 and 3-09 kg (P < 005 for differences between ME intakes and differences between dietary protein concentrations). For milk composition, interactions between the concentration of dietary protein and level of ME intake were not statistically significant but the main treatment effects were significant, with the protein concentration in milk increasing from 49-6 g/kg for ewes given the low concentration of dietary protein to 54-1 g/kg for those given the high (P < 0-001). Corresponding values for protein concentration in milk for the lowest and highest energy intake were 51-2 and 53-4 g/kg (P < 0-05). Losses of tissue protein were variable but decreased from 26 g/day for ewes given the low-protein diet to 8 g/day for those given the high. In discussing the responses in milk yield to dietary protein and ME intake attention is drawn to the modifying influence of the energy contributed from body tissue.

Level and quality of protein in rations for lactating ewes

“…This response seems to be enhanced in ewes with high restrictions in energy intake (Robinson et al, 1974;, although positive responses have also been found with energy intake close to the theoretical requirements (Gonzalez et al, 1984). This phenomenon can be due either to a greater mobilization of body reserves (Robinson et al, 1974) or to an increase in the efficiency of utilization of these reserves for milk production (Cowan ef al, 1981 ).…”

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

“…Responses of milk yield to increased dietary protein have been observed in a number of experiments (Robinson et al 1974(Robinson et al , 1979Gonzalez et al 1984;Jaime and Purroy 1995). In the present experiment, increasing dietary protein did not increase milk yield, probably because of the high CP content of the rations.…”