Effect of different dietary energy level intakes on efficiency of estrus synchronization and fertility in Mashona goat does

The objective of the study was to determine the effects of three dietary en ergy levels: 0.27 (low level: LL); 0.53 (medium level: ML), and 1.06 (high level: HL) MJ ME kg(-1) W-0.75 On estrus synchronization and fertility in M ashona goat does. Forty-five multiparous Mashona goat dues of average bodyw eight 19.9 +/- 2.5 kg were randomly allocated in equal numbers to the three dietary energy levels, The diets were made from a complete feed ration pro viding 9.83 MJ ME kg(-1) DM and 15.5% CP hg-l DM. Dues were fed initially d uring a 60-day pre-synchronization period, and blood samples were collected twice a week for the determination of plasma progesterone concentrations t o ascertain ovarian activity. Intramuscular injections of cloprostenol ( 10 0 mug each) were administered 11 days apart. Immediately after the second i njection of cloprostenol, three fertile bucks were introduced to the does a nd were left with the does for 21 days. The does were maintained on their d ietary treatments throughout gestation except for those does in the LL trea tment. Pregnancy was diagnosed 90 days post-mating using an ultrasound scan ner. After pregnancy diagnosis, does on the LL treatment were randomly allo cated to ML (n = 7) and HL (n = 8) treatments. During the pre-synchronizati on period, does on the LL treatment lost 12.35 whereas those on ML and HL t reatments gained 2.1 and 28.8% of their initial bodymasses, respectively. T he proportion of does exhibiting overt estrus within 96h after the last clo prostenol injection was significantly lower (P < 0.05) for does on the LL t reatment (60%) than for those on ML (93%) or WL (100%) treatments, respecti vely. However, based on plasma progesterone concentrations, the percentage of does on the LL treatment that exhibited ovarian cycles was numerically l ower than that of does that were bred (40 versus 73%). Conception, fecundit y and twinning rates were significantly lower (P < 0.05) on the LL treatmen t than on the ML and WL treatments. These results indicate that feeding Mas hona goat does 0.27 MJ ME kg(-1) W-0.75 compared to 0.53 and 1.06 MJ ME kg( -1) W-0.75 reduces the expression of estrus, conception, fecundity and twin ning rates, and that feeding 0.53 MJ ME kg(-1) W-0.75 suffices for optimum reproduction. In addition, the results suggest that cloprostenol administra tion may induce ovarian cycles in reproductively quiescent does on dietary energy restriction. (C) 2001 Elsevier Science B.V. All rights reserved.