Factors Associated with Shortened Estrous Cycles after Abortion in Beef Heifers

Abstract

Forty-six crossbred Hereford heifers were allotted into five experimental groups. Fenprotalene, a prostaglandin analogue, was administered to induce abortion and (or) to regress the corpus luteum (CL) in four groups of heifers about 75 d after conception. The four groups were 1) pregnant heifers, 2) pregnant heifers with the ovary contralateral to the gravid uterine horn removed 24 h after fenprostalene injection, 3) same as Group 2 but with the ipsilateral, rather than the contralateral, ovary removed and 4) heifers with uterus removed (ovaries intact) about 35 d after conception. A fifth group of nonpregnant heifers received implants containing norgestomet from 10 to 76 d after estrus and were given fenprostalene 24 h before removal of the implant. Average length of the first estrous cycle after the fenprostalene injection was 11.2, 8.3, 9.7 and 19.1 for Groups 1, 2, 3 and 5, respectively. Estrous cycles were longer (P less than .05) in norgestomet-treated heifers. Hysterectomized heifers (Group 4) did not exhibit a second estrus by 50 d after fenprostalene treatment; otherwise, all first estrous cycles after the fenprostalene injection were either "short" (7 to 13 d) or "normal" (17 to 23 d). Twenty-two of 24 heifers that aborted had short estrous cycles and two had normal estrous cycles. Short estrous cycles occurred after abortion regardless of whether the ovary ipsilateral or contralateral to the previously gravid uterine horn ovulated. Early regression of the CL (short luteal phase) did not occur in nonpregnant heifers after long-term progestogen stimulation or after hysterectomy, but it did occur in heifers with a previously gravid uterus.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma fatty acids, prostaglandin F2alpha metabolite, and reproductive response in postpartum heifers fed rumen bypass fat.

“…Preceding estrous cycles of normal length, the first postpartum estrus is frequently associated with a cycle of short duration, generally 8 to 10 d in length, with P 4 ≥ 1 ng/mL (Odde et al, 1980;Peters and Lamming, 1984;Wright et al, 1988). An improperly steroid-conditioned uterus is thought to be the cause of premature release of PGF 2α and an early demise of the corpus luteum.…”

Endocrine changes and ultrasonography of ovaries in suckled beef cows during resumption of postpartum estrous cycles.

“…We have shown that patterns of follicular than preceding so. (Kesler et al, 1985;Copelin et al, 1987;Wright et al, 1988). Whether the mechanism causing premature luteal regression after FO is triggered by a preovulatory follicular determinant is unknown.…”