Food restriction in ewes during different pregnancy periods affects milk production and lamb growth

Abstract Text: This study assessed the effect of food restriction during different periods of ewe pregnancy on milk production and lamb growth. Thirty-five adult pregnant ewes were assigned to four treatments (7-10 animals/treatment), which varied in the period when food restriction (removal of a supplement fed at 150 g/Kg BW/day) was applied: 1^st third period of pregnancy (T1); 2^nd third period of pregnancy (T2); 3^rd third period of pregnancy (T3), or no supplement restriction (Control; T4). All ewes grazed together in a Bermuda grass cv. Tifton-85 pasture of low biomass (below 1000 kg DM/ha), and once a day they received the supplement [14% CP; 3.5% EE; 16% ADF], or not, according to treatment. Ewes were weighed every 14 days during pregnancy. Lamb birth weight (LBW) and placenta weight (PW) were assessed at lambing. Daily milk production (MP) and lamb daily gain (LDG) were recorded until weaning. The experiment was carried out in a completely randomized design, and the data were analyzed by a Decision Tree multivariate analysis. Treatments explained 23% of MP, with greater milk production per day for T2 and T4 (3423 g ± 1047.7 g SD) than for T1 and T3 (2294 g ± 1091.1 g SD). LBW was best explained by the number of lambs per ewe (R² = 0.52), and PW had a positive correlation (R² = 0.72) with LBW, independent of the number of lambs per ewe. When the LDG was lower than 359 g, the lowest LDG and the lamb weight at weaning were observed in T1 (Figure 1). Despite the relatively low nutrient requirements from ewes during early pregnancy, these results point to the importance of avoiding dietary restriction during this period in order to enhance MP and LDG. On the other hand, nutrient restriction during mid-pregnancy had no consequences on milk production or lamb growth. Keywords: sheep nutrition, sustainability, fetal development