Effect of insulin on feed intake and reproductive performance of well-nourished nulliparous ewes.
Eighty-four nulliparous ewes were used to examine the effect of short-term insulin treatment on feed intake and reproductive performance. Following estrus synchronization, ewes were observed for estrus (= Day 0) and were penned individually beginning on Day 7. Ewes were fed twice daily and feed intake was recorded. On Days 9 through 13, ewes were treated s.c. with 1 IU/kg BW insulin (n = 44) or an equivalent volume of saline (n = 40). On Day 14, ewes were placed with fertile rams and number of ewes in estrus (bred) was recorded. Thirty days post-breeding, ewes were checked for pregnancy via ultrasonography. Feed intake and percentage of ewes in estrus did not differ between saline- and insulin-treated ewes. Similarly, neither pregnancy rate (69 +/- 8.7% vs. 80 +/- 8.1%, respectively) nor lambing rate (61 +/- 8.9% vs. 78 +/- 8.4%, respectively) differed between treatments. The number of lambs born per ewe was, however influenced by a breed-group effect (P < 0.0002). Romanov ewes had more (P < 0.001) lambs than the other breed groups in the study. Therefore, treating well-nourished, nulliparous ewe lambs with insulin did not increase reproductive efficiency, possibly because the ewes were already at a maximal nutritional and/or reproductive state.
Whitley
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NC
Department of Animal Sciences, University of Missouri, Columbia 65211, USA.
McFadin-Buff
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EL
Keisler
D H
DH
D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D004435:Eating / Q000187:drug effects*; D004973:Estrus Synchronization; D005260:Female; D007328:Insulin / Q000494:pharmacology*; D011247:Pregnancy; D012098:Reproduction / Q000187:drug effects*; D012756:Sheep / Q000502:physiology*; D013045:Species Specificity
D007328:Insulin