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Centre for Genetic
Improvement of Livestock Like Father, Like Son |
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Understanding the
heritability of lactation breeding values from sires to their sons will
help dairy producers make better breeding decisions.
Prof. Larry Schaeffer of the Centre for the Genetic Improvement of Livestock and Marc Rutten, a visiting scientist from the Wageningen Agricultural University in the Netherlands, have found that changes in the estimated breeding values (EBVs) of sires over lactations are heritable. They say this could change the use of breeding values in selection decisions. "This new interpretation of EBVs will help us make better breeding decisions and is a major step in estimating the genetic potential of animals over lactations," says Schaeffer. In February 1999, the Canadian Test Day Model (CTDM) - used to evaluate the genetic merit of dairy cows and their sires - was implemented in Canada. The CTDM uses the test day records for a cow's first three lactations to calculate the contribution of its genetics to milk, fat and protein yields. These values are expressed as EBVs. |
All progeny of a bull inherit half of the sire's
EBV. The researchers looked at changes in EBVs across lactations to
determine if similar patterns were observed for sires and their sons. For
example, the EBV of a sire could increase from the first to second
lactation and increase, decrease or remain constant from the second to
third lactation. But, the researchers wondered, would a similar pattern be
expected for the son of this sire?
Schaeffer and Rutten discovered that if a sire's breeding value increased from the first to second lactation, then the son did indeed follow a similar breeding pattern. That suggests the change of EBVs across lactations is hereditary. To further examine this trend, they determined how changes in breeding values between sires and sons correlated. From first to second lactation, they found a high correlation in EBV changes...but it tailed off from second to third lactation. Ideally, dairy producers want the EBV to be high for all lactations, or increase over lactations. If a producer was aiming for higher milk production, using bull EBVs to predict the progeny EBVs would be a useful breeding strategy -- plus, it offers a new way of using breeding values for future selection decisions. This research was sponsored by DairyGen (formerly the Cattle Breeders Research Council). |
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