Calving age determines lifetime performance
Calving animals at less than two years of age does not reduce reproductive performance or productivity and, therefore, it could increase herd profit through reduced heifer rearing costs.
That was just one of the findings of a study, examining the factors affecting heifer survival and fertility on commercial dairy farms, presented to delegates at the British Society of Animal Science’s international conference entitled: Fertility in dairy cows – bridging the gaps.
The work, completed by researchers at London’s Royal Veterinary College, also revealed that heifers showing poor fertility before their first calving continue to have poor reproductive performance and poor productivity.
“But careful reproductive management of nulliparous [never calved] animals can influence productivity and profitability,” Claire Wathes told delegates.
Juvenile predictors of adult performance were assessed by taking newborn heifer calves and measuring their size and metabolic parameters during rearing. These heifers were monitored from birth through to the end of their second or third lactation.
The effect of genotype, heifer rearing system and age and weight at the start of their first lactation on fertility, productivity and longevity were then assessed.
The research highlighted, for example, that maiden heifers that failed to conceive were significantly smaller, in both weight and height, at nine months old than there more fertile herd mates.
Heifers that calved at between 22 and 23 months old required fewer services per conception compared to heifers that calved for the first time at between 24 and 25 months old – 1.1 services and 1.4 respectively. And 93% of heifers calving at between 22 and 23 months old were PD positive to first service, compared to 73% of heifers calving at between 24 and 25 months old.
“Heifer rearing methods are very variable on UK farms and many potential replacement heifers never become productive,” adds Professor Wathes.
“There is often little veterinary input during the rearing process and, in practice, growth rates of individual animals on a farm vary considerably.”
