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EDGAR L. PIPER and WARREN C. FOOTE

Summary.

Two experiments designed to measure the influence of oestradiol on ovulation and cl maintenance in cycling ewes are reported. All oestradiol-treated ewes were given a single injection of oestradiol on the 4th day of their oestrous cycle ; in addition, some ewes were given continuous daily injections of progesterone or oestradiol. Ovarian condition was determined by gross observations in Exp. 1 and by gross and histological observations in Exp. 2. Oestradiol induced ovulation in 72 and 73% of the ewes in Exps. 1 and 2, respectively. Progesterone blocked the ovulatory response to oestradiol. Continued daily injections of oestradiol were effective in maintaining the cl and inhibiting follicular development. The oestrous behaviour exhibited by oestradiol-treated ewes was not associated with ovulation. Induction of ovulation by oestrogen is probably due to a release of lh. The luteotrophic nature of oestrogen in the ewe may be caused by an increase in prolactin secretion. lh as a luteotrophic factor is suggested.

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C. V. HULET, WARREN C. FOOTE and R. L. BLACKWELL

Summary.

In 1960 the U.S. Sheep Experiment Station flock was used to test the relationship of semen quality and fertility (percentage of ewes lambing) in the ram to fecundity (percentage of lambs born of ewes lambing) in the ewe. The rams were unselected for semen quality and fertility.

Six semen traits were significantly correlated with ewe fecundity. The multiple correlation of these six semen traits with fecundity was 0·49. The within age group correlation between fertility and fecundity was 0·23 (P<0·01). The correlation was highest in the mature ewes (0·30, P<0·01).

This study suggests that fecundity in addition to fertility may be affected by the ram.