The effect of constant dietary energy supply during late gestation and early lactation on performances of prolific D'man ewes

A total of 42 prolific D'man ewes were used to study the effect of the dietary energy supply on their performances during the last 45 days of pregnancy and the first 60 days of the suckling phase. The ewes were fed 1 kg of hay and supplemented with either 200 (treatment L), 570 (treatment M) or 840 g (treatment H) of a barley and soyabean-based concentrate. The proportion of soyabean was adjusted so that the crude protein (CP) content of the three diets was similar (120 g CP.kg(-1)). The energy contents of the diets were 1.2, 1.8 and 2.2 of the daily net energy requirements for maintenance in respectively the L, M and H treatments. Daily hay intake averaged 829 +/- 18 g dry matter (DM) per ewe and was not affected by the level of the concentrate distributed. The body condition score of the ewes in all treatment groups was low at the beginning of the experiment (1.9 +/- 0.3) and continued to decline throughout the period of treatment application. Nevertheless, the rate of decline was higher for the L and M ewes (P < 0.05). The live weight of the ewes after lambing was higher (P < 0.05) for ewes in the H treatment group (43.2 +/- 6.9 kg) in comparison to the other ones (37.7 +/- 7.8 and 40.0 +/- 7.3 kg for the L and M groups respectively). Daily milk production over the first 40 days of lactation (959 +/- 399 g.day(-1)) was not affected by the energy level of the diet. Similarly, fat (8.9 +/- 2.4%) and protein (4.5 +/- 0.9%) contents of the milk were not affected by the diet energy content. The weights of the lambs at birth, at 10, 30 and 50 days of age were not influenced by the diet energy content. In contrast, average daily growth (ADG) between 10 and 30 (ADG10-30) and also between 30 and 50 days of age (ADG30-50) were significantly affected by energy allowances in the diet (95 +/- 23, 133 +/- 25, and 152 +/- 27 g.day(-1) for ADG10-30 and 76 +/- 22, 135 +/- 24 and 136 +/- 24 g.day(-1) for ADG30-50 in L, M and H groups respectively). It is concluded that the energy requirements of prolific D'man ewes during late gestation and early lactation are likely to be higher than the levels attempted in this study.