Missing half the cows in first heat after calving, because of their silent estrus or other reasons, will translate into an eventual conception rate of no greater than a costly 60 percent, even when insemination takes place by 51 days after calving and everything else works perfectly. Heat detection accuracy on many of our farms is only 50 percent, and many farms do not yet breed all their cows back after calving by 51 days. At least eight parameters have a bearing on how well we can reduce reproductive costs. A short dry period does not provide enough time for mammary regeneration and results in less milk yield in the next lactation. Your goal should be no more than 90 days open after calving.
Any excess days are costly.
The number of services are directly related to conception rate. Conception rate influences days open, because every missed heat period adds 21 days to days open. The goal per herd should be no more than 1.5 services per conception. At 1.5 services per conception, the average conception rate would be about only 64 percent. With good heat detection and with proper feeding at peak production, the first estrus should show at 30-50 days after calving.