These determine days open and are accepted indicators of the dairyman's management ability. 11 days on average to breed each cow. DHI herds average 126 days open and 1.7 services per conception. Therefore, missed heats were much more costly than concep- tion rate. Herd conception rates were not extremely variable.
Dairymen lose twice as many days to missed heats compared to failure to conceive.
It appears reasonable to be able to reduce the 41 missed heat days to below 21 days. Female reproductive management has its major economic impact on the profitability of the cow being bred. The impact is expressed through changes in milk per day in the herd and ampules of semen per cow. An acceptable days open has been defined as 85 days. When all economic factors are considered, improved heat detection has a large beneficial economic impact.