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Reproduction in Targhee and Finnish Landrace x Targhee Ewes¹

University of California, Davis 95616

Abstract

Targhee and Finnish Landrace x Targhee (Finn-Targhee) crossbred yearling ewes were subjected to three nutritional treatments to investigate the effects of the genetic difference and genotype x environment interaction on reproductive traits. The three treatments were adjustments in feed intake sufficient to produce mean body weights of approximately 80, 90 and 105% of initial weights. Following attainment of the treatment weights, ovulation rate was measured by laparotomy twice for each ewe prior to flushing and a third time following breeding at the end of one cycle of flushing. Other traits measured were: onset of estrus, estrous cycle length, ova success, and lambing performance.

Finn-Targhees averaged 14 days later and were somewhat more variable in onset of seasonal estrus, but had shorter (P<.01) estrous cycles and fewer missed estrous periods after cycling began. Ovulation rate was higher (P<.01) for Finn-Targhees, both before and after flushing. The significant (P<.01) pre-flushing treatment differences in ovulation rate were removed by flushing. Mean post-flushing ovulation rate was 1.89 for Targhees and 2.62 for Finn-Targhees. For all ewes lambing, 78% of the corpora lutea observed at the post-flushing laparotomy were represented by lambs born. Targhees lambing averaged 1.50 lambs per ewe compared to 2.22 lambs per Finn-Targhee ewe lambing. Although the Finn-Targhee ewes in this experiment were all sired by the same Finnish Landrace ram, the lambing results agree quite well with those from other studies of crosses with this breed.

¹ Department of Animal Science.

² Present address: Department of Genetics, University of Minnesota, St. Paul 55101.

³ The authors gratefully acknowledge the loan of a Finnish Landrace Ram by the A.R.S., U.S.D.A.; the advice and instruction of Dr. Clarence Hulet of the U.S. Sheep Experiment Station, Dubois on the laparotomy procedure; and the able assistance of Mr. R. M. Finlay for his care of the research flocks.