A brief report on the relationship between level of milk production and estrous behavior of lactating dairy cows

The objective of this study was to evaluate if there was an association between milk production and duration of estrus in lactating cows as determined by standing activity recorded by a radiotelemetry system. Holstein cows (n = 42) were fitted with a radiotelemetric transmitter that allowed continuous recording of standing activity. Cows were housed in a free-stall barn and milked twice daily. Average milk production for the 5 days before estrus was used to classify cows as low (< 35.1 kg/day) or high (greater than or equal to 35.1 kg/day) producers at the time of expression of estrus. Periods of estrus recorded during higher milk production (40.4 +/- 0.8 kg/day; 89.2 +/- 3.2 days postpartum) were shorter (6.9 +/- 0.8 versus 11.1 +/- 1.5 h; P < 0.05) than periods of estrus recorded during lower production (28.0 +/- 0.8 kg/day; 84.9 +/- 3.9 days postpartum). Increased level of milk production was associated (P < 0.05) with decreased duration of estrus. (C) 2004 Published by Elsevier B.V.