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A comparison of plasma LH concentrations in milked and suckling post-partum cows

Summary. Plasma samples were taken every 10 min for periods of 8 h on 3 occasions during the post-partum period from 8 cows milked twice daily (Groups M₁ and M₂) and from 4 cows each suckling 4 calves (Group S). All samples were assayed for LH, and ovarian activity was monitored by measurement of milk progesterone. Three of the Group M₁ cows had a delayed return to ovarian activity after calving (> 70 days) whereas all 4 Group M₂ cows resumed ovarian cycles by 25·25 ± 3·35 days post partum. Three Group S cows resumed cycles by a mean of 47·7 days post partum while the fourth had not done so by Day 100. Mean plasma LH concentrations were low pre partum (0·67 ± 0·05 ng/ml) and up to Day 5 post partum (0·80 ± 0·03 ng/ml, Group S; 0·90 ± 0·12 ng/ml, Group M₁; 0·80 ± 0·25 ng/ml, Group M₂). Concentrations then increased up to Day 12 (1·23 ± 0·20, 1·66 ± 0·16 and 1·67 ± 0·21 ng/ml in Groups S, M_, and M₂ respectively). Between Days 13 and 20 a distinct pulsatile pattern was seen in the profiles of milked but not of suckling cows. The pulse frequency was lower (approximately 2/8 h) in those milked cows in which ovarian activity was delayed and varied from 4 to 10 episodes/8 h in milked cows that commenced ovarian activity early in the post-partum period. It is suggested that the pulsatile LH pattern is a prerequisite for the onset of ovarian cycles.

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				R. P. Wettemann, C. A. Lents, N. H. Ciccioli, F. J. White, and I. Rubio Nutritional- and suckling-mediated anovulation in beef cows J Anim Sci, February 1, 2003; 81(14_suppl_2): E48 - 59. [Abstract] [Full Text] [PDF]