FLUSHING WITH SOYBEAN-MEAL CAN IMPROVE REPRODUCTIVE PERFORMANCES IN LACTATING SARDA EWES ON A MATURE PASTURE

The effect of different flushing techniques on reproductive performanc e in Sarda ewes mated while grazing a mature pasture of Italian ryegra ss (herbage allowance, 2700 g DM per head per day) was assessed. Sixty adult ewes were allotted to four groups (n = 15). Estrus of ewes in t he control group (C) was synchronised, using the ram effect and proges terone administration, but they received no dietary supplement before the introduction of intact rams. Ewes in the other groups were offered a supplement of soybean-meal (SBM), from Day 7 before, through day of ram introduction (short-term flushing, SF); from Day 14 before, throu gh Day 2 after entire ram introduction (medium-term flushing, MF); or from Day 14 before, through Day 21 after ram introduction (long-term f lushing, LF). Estrus was not synchronised in the LF group. The amount of SBM offered was 270 g day(-1), but actual average intake was 180-21 0 g day(-1). Synchronisation did not affect date of first observed est rus. Flushing resulted in greater ovulation rate (OR) than C: 1.70, co mpared with 1.29 CL per ewe ovulating, (P < 0.03) and OR was greater i n MF than in control ewes (1.80 vs. 1.29 CL per ewe ovulating, P < 0.0 1). The ovulation rates in the SF and LF groups (1.70 and 1.57 CL per ewe ovulating) did not differ from C and MF. Prolificacy subsequent to the first estrus tended to be increased by flushing (1.66 vs. 1.36, P < 0.15). Fecundity (number of lambs born per ewe exposed, after 34 da ys with intact rams) ranked MF > LF > SF > C, and tended to differ bet ween MF and C (1.60 vs. 1.14, P < 0.13). Flushing did not result in hi gher intake of energy or crude protein, because intake of pasture was decreased in flushed ewes, but was related to greater (P < 0.03) intak e of digestible protein in the pre-mating period. Under current market conditions, medium-term flushing can be profitable for Sardinian shee p farmers. (C) 1997 Elsevier Science B.V.