Genetic analysis of body condition score in Canadian Holsteins
This thesis is preliminary research working toward a genetic evaluation of body condition score (BCS) in Canada using a random regression animal model, which would allow each animal to possess, and be ranked according to, a unique BCS lactation curve. Valacta, a milk recording agency based out of Que?bec, Canada, has been collecting several BCS records per cow since 2001. Using a multiple-lactation random regression animal model, it was determined that many of the same genes control BCS in each of the first three parities. Thus, collection of first-lactation BCS records would be sufficient for genetic evaluation. Additionally, this thesis investigated the change in BCS's relationship with various milk production traits over the lactation with a multiple-trait random regression animal model. Early lactation was when the genetic relationships between BCS and milk production traits were most favorable. Hence, early lactation BCS shows potential for selection. Because Valacta's BCS data was only available for Que?bec herds, other traits that were potentially strongly genetically correlated with Valacta's BCS, that were recorded nation-wide, were investigated. Holstein Canada collects records for type traits once at classification. Although Holstein Canada collects BCS, only 1 record is available per cow, such that a genetic evaluation of each animal's BCS curve would not be possible. Holstein Canada's BCS, angularity, and chest width were moderately to strongly genetically correlated with Valacta's BCS. Using all 4 traits in conjunction will allow for a genetic evaluation of each animal's unique BCS curve for Holsteins across Canada.