Postpartum reproduction in protein restricted beef cows: effect on the hypothalamic-pituitary-ovarian axis.

摘要: The influence of dietary CP on circulating LH and anterior pituitary hypothalamic function was examined. In Exp. 1, 28 cows were randomly assigned to four treatment groups: adequate (ADQ; .96 kg/d) or deficient (DEF; .32 beginning at 90, 60 30 d before parturition continued a 33% increase in feed consumption after parturition. Cows bled 15-min intervals for 8 h 20, 40 Pituitaries collected 62 analyze GnRH receptor numbers gonadotropin content. Frequency pulsatile release increased (P less than .05) from 20 ADQ cows. Basal mean not affected greater .10) by restriction days Crude protein did affect receptors .10), but it content, FSH content concentration .05). 2, groups as 1. All challenged with (.22 micrograms/kg BW) every min 6 h. Responsiveness time .07). Deficient decreased GnRH-induced 3, 12 DEF 120 received 1 mg estradiol-17 beta (E2) 19, 39 59 14 following E2. Response E2 unaffected whereas E2-induced peak Results suggest that delayed return estrus CP-deficient postpartum beef might be due reduced the responsiveness GnRH.