Fertility Performance

The aim of the High Forage Herd breeding programme is to produce replacement heifers which will have the capacity to produce relatively high milk yields from the consumption of large quantities of forage under Northern Ireland grazing and housing conditions. Animal type is also taken into account. The aim is to breed a cow with longevity. That requires animals with good legs and feet, good udders, and a strong frame with plenty of rumen capacity. The selection criteria for bull semen is reviewed annually. The calving season for the High Forage Herd runs from November to March. Inseminations start during the second half of January.

The most important criteria determining the success of the High Forage Herd breeding programme are the herd submission rate and conception rate.

Submission rate - is calculated as the percentage of cows eligible for first service at the start of the 21 day period, which are inseminated by the end of the period. Animals not inseminated in the first period of eligibility are not counted as eligible in subsequent periods. The heat detection routine applied at the college involves observing cows 3 times each day for 20-30 minutes with a target of 80% submission rate.

Conception rate - is calculated as the percentage of animals inseminated 42 days or more, which have not received a subsequent insemination or service or which have been pregnancy diagnosed as in calf.

The overall measure of herd fertility performance which takes both of these criteria into account is the 100-day in-calf rate. The 100-day in-calf rate is simply the proportion of cows intended for rebreeding which are settled in calf within 100 days of calving. This performance measure can be calculated either during the breeding season or at the end of the breeding season giving an early indication of overall herd fertility performance.

Other more traditional measures of dairy herd fertility performance are also calculated for the High Forage Herd including calving index, days to first service and services per conception.