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Virginia Cooperative Extension - Knowledge for the CommonWealth

Tail painting an economical and effective heat detection system:

Dairy Pipeline: July 2004

-- Ray L. Nebel
Extension Dairy Scientist,
Reproductive Management
(540) 231-4432 email:

A major factor limiting optimum reproductive performance on many farms today is the failure to detect estrus in a timely and accurate manner. Increases in herd size and milk yield have been implicated as contributors to the decreased reproductive efficiency experienced today. For example, during the past ten years the average Virginia DHI dairy herd has experienced a 35% increase in milking cows and a 20% increase in milk yield per cow without the same increase in additional labor force. During this same time period the average calving interval has increased from 13 to 14.5 months. This decrease in reproductive efficiency conservatively cost $12,000 per year per herd if one assumes a $2 loss per each day open over 115 days and an average herd size of 135 cows. This is not even taking into consideration the additional losses of fewer replacements, increased labor, fewer cull cows, and increased drug and veterinary expenditures. Our research, with the electronic heat detection system HeatWatch, has reported that the "average" Holstein cow is mounted 7 times during the 7 hours of "standing" heat. During the summer months mounting activity decreases to 5 standing events and high producing cows express shorter and less intense standing activity than lower producers.

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