Effects of short-term feed restriction on milk yield and composition, and hormone and metabolite profiles in mid-lactation Sarda dairy sheep with different body condition score

Ten Sarda dairy ewes (5 with high Body Condition Score: H-BCS, BCS>2.5; BW 48.8±5.4 kg; 5 with low BCS: L-BCS, BCS<2.5; BW 36.2±4.7 kg) were subjected, after 7-day preliminary (Prel) period, to short-term feed restriction (FR, 50% of nutrient requirements) for three days followed by refeeding (Re-Fed, 100% requirements) for three days. Milk yield and composition (protein, fat, lactose, MUN, SCC, fatty acids), and blood parameters (glucose, NEFA, BUN, insulin, GH, IGF-I, leptin) were monitored. Milk yield decreased during FR in both BCS groups: at day 3 it was 38% and 35% of Prel values in HBCS and L-BCS ewes, respectively, reaching Prel levels at Re-Fed in both groups. Milk fat concentration was influenced by BCS¥sampling, increasing in H-BCS ewes during FR, but not varying in L-BCS ewes throughout the trial. During FR, milk protein increased as milk yield decreased. There was no change in milk urea nitrogen concentration during FR, but this decreased in both BCS groups during Re-Fed. FR modified the FA profile of milk fat in both BCS groups, increasing LCFA at the expense of SCFA and MCFA. Some blood parameters (NEFA, GH and IGF-I) were influenced by BCS, whereas almost all parameters were influenced by sampling. There was a rapid return to initial levels in all parameters except milk urea, blood urea and insulin at Re-Fed.