Results can be used to develop ‘beef’ traits in dairy indices
Take Home Message: Selecting for carcass conformation in dairy cows will reduce milk yield but improve fertility, with little effect on somatic cell count or lifespan.
Selection on an index that improves carcass conformation of Holstein Friesian beef by 0.1 of a unit will lead to a reduced rate of improvement in production traits and an improvement in fitness traits – albeit with a reduction in the rate of improvement in lifespan.
“And these results can be used to develop dairy indices that include ‘beef’ traits in the overall goal,” SAC geneticist Eileen Wall told delegates at this year’s British Society of Animal Science’s annual conference.
Sharing the findings of a study carried out to develop tools to allow Holstein Friesian dairy breeding goals to include muscling and carcass quality to help improve the value of dairy bred bull calves as beef animals, she explained that the role of the dairy herd as a provider of beef has proportionately reduced as the dairy animal has become more specialised over the years.
“High milk production per cow and a decreasing national herd has resulted in a reduction in calves born, and genetic changes have led to dairy bred bull calves being less suited to beef production.
“This has led to the market for purebred dairy bull calves being severely curtailed and, in some instances, the male purebred calf has had no value.”
She and her team looked at the predicted transmitting abilities (PTAs) for carcass traits and correlated them with those for production traits (milk, fat and protein) and fitness traits (somatic cell count, lifespan, calving interval, and non-return rate after 56 days).
“And our results showed that there is a moderate correlation between carcass traits and milk production with adjusted carcass conformation score and adjusted carcass fat score being negatively correlated with milk production traits suggesting that higher producing animals will have unfavourable carcass classification,” she said.
“There is a favourable correlation between milk production and carcass weight, suggesting that higher milk production bulls will produce heavier animals at slaughter. But there was no significant correlation between the carcass traits and lifespan and somatic cell count score.”
There was a significant low to moderate correlation between the fertility traits and adjusted carcass conformation score, suggesting that bulls producing more highly conformed carcasses will produce daughters that will have better fertility.
“But this correlation may be driven through the negative relationship between milk production and adjusted carcass conformation score,” added Dr Wall.
Summary (pdf) Presentation (pdf)
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