The effect of restricted suckling on LH and ovarian steroids after induced ovulation in Bos Taurus and Bos indicus cows

Author: B.P. Louw, A.W. Lishman, A. van Niekerk, J. Grobbelaar & S.F. Lesch
Year: 1984
Issue: 2
Volume: 14
Page: 91 - 96

A total of 37 first-calf cows and their calves, comprising 19 Drakensbergers and 18 Hereford x Simmentalers, were subjected to either normal or once-daily suckling for 15 days, commencing at either day 35 or 60 post-partum in a 2 x 2 x 2 factorial experiment. All cows received common hormone therapy during the normal or restricted suckling periods. A Norgestomet ear implant was inserted in conjunction with an oestrogen injection on the first day, and removed on the tenth  day of the variable suckling periods. The cows were injected with gonadotropin releasing hormone (GnRh)30 h after the removal of the ear implants, and inseminated 18 and 42 h after the GnRh injection. There was a tendency for a greater (P ≥ 0,05) proportion of the cows suckled once daily to ovulate than those suckled normally, and this effect was most marked in the Drakensberger cows treated between days 60 and 75 postpartum. In the Drakensbergers, restricted suckling tended to increase the proportion of cows which conceived to the fixed time inseminations, and to decrease the incidence of 'short' oestrous cycles following GnRh. Tonic luteinizing hormone (LH) levels, the release of LH in response to GnRh and oestrogen secretion were not affected by any of the variables studied.



Keywords: beef cows, breed, LH steroids, Restricted suckling
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