Udder classification based on AMS data
Since April 2023, CRV uses AMS (Automatic Milking System) data to estimate breeding values for udder conformation traits in the Netherlands and Flanders in addition to data from herd classification. AMS data is used to derive traits for udder depth, distance between the front teats, distance between the rear teats and udder balance. Three teat coordinates are determined and stored by the AMS each milking, all given in millimetres: x (measure of the width), y (measure of the length), and z (measure of the depth). Based on these three teat coordinates, the four udder traits can be derived. Traits are derived for first three parities. The heritability for respectively udder depth, distance between the front teats, distance between the rear teats and udder balance in parity 1 is 0.56, 0.60, 0.45 and 0.45. Based on herd classification, heritabilities for udder depth, front teat placement and rear teat placement are respectively 0.39, 0.31 and 0.29. The genetic correlations between these three traits and corresponding heifer traits based on AMS data are respectively 0.98, 0.98 and 0.99. Traits for later parities show comparable heritabilities and genetic correlations. The repeated records lead to an increase of the heritability and reliability compared to udder depth, front teat placement and rear teat placement based on herd classification. Furthermore, the AMS gives more objective results compared to scores given by herd classifiers. The udder conformation traits based on herd classification are still the traits that are published, while udder balance is introduced as new trait. Due to the usage of AMS data, an increase of reliability for bulls breeding values was found ranging between 0.4 and 3.0%. Adding AMS data to the breeding value estimation of udder conformation traits leads to better estimates of the breeding values for existing udder conformation traits by using more information as well as having a breeding value for the new trait udder balance.
Key words: udder conformation, herd classification, AMS data, udder balance
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