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Journal of Dairy Science Vol. 64 No. 10 1996-2002
© 1981 by American Dairy Science Association ®
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Effects of Early and Late Breeding of Dairy Cows on Reproduction and Production in Current and Subsequent Lactation

F. Schneider1, J. A. Shelford, R. G. Peterson and L. J. Fisher2

Department of Animal Science, University of British Columbia, Vancouver V6T 2A2

ABSTRACT

Effects of early and late breeding post partum on reproduction and production were investigated in a Holstein herd. Cows were assigned randomly to two groups at calving: an early group bred at the first observed heat following 50 days postpartum and a late group bred at first observed heat 80 days postpartum. Early versus late breeding resulted in intervals to first service of 72 ± 18 or 93 ± 17 days; conception at 88 ± 33 or 121 ± 40 days postpartum; and 1.50 (range 1 to 3) or 1.96 (range 1 to 5) services per conception.

Postpartum reproductive activity was monitored with milk progesterone analyses. Average duration of first estrous cycle was 17 ± 7.5 days. The first heat detected by milk progesterone occurred 33 ± 10 days postpartum compared to the first observed heat at 48 ± 26 days postpartum. Calving problems and calving in pasture season delayed conception in the late bred group but did not influence conception in the early bred group. The late bred group produced more fat-corrected milk in 305-day lactation and in the first 150 days of the subsequent lactation. Average daily milk production from beginning of current lactation to day 150 of subsequent lactation (including the dry period) was the same for both early and late bred groups.

FOOTNOTES

1 Neuhaus, CH-3411, Biemback, Switzerland.

2 Agriculture Canada Research Station, Agassiz, British Columbia, Canada Contribution #274.






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