IMPROVING GENETIC PREDICTIONS FOR DAIRY ANIMALS USING PHENOTYPIC AND GENOMIC INFORMATION
Title: Short communication: Genetic evaluation of mobility for Brown Swiss dairy cattle
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 11, 2012
Publication Date: April 1, 2013
Citation: Wright, J.R., Wiggans, G.R., Muenzenberger, J.R., Neitzel, R.R. 2013. Short communication: Genetic evaluation of mobility for Brown Swiss dairy cattle. Journal of Dairy Science. 96(4):2657-2660.
Interpretive Summary: The Brown Swiss Cattle Breeders’ Association of the USA began scoring mobility in 2007. This trait is an overall measure to indicate movement ease and comfort while the animal is standing and is scored on a scale of 50 to 99. Heritability of mobility was estimated to be 21%, and the trait was found to be highly correlated with final score and rear legs (rear view). Mobility may increase accuracy and timeliness of predictions of productive life by giving a more accurate assessment of the structural soundness required for longevity. Genetic evaluations for mobility became official in August 2012.
Genetic parameters were estimated for mobility score and 16 linear type traits of Brown Swiss dairy cattle. Mobility is an overall assessment trait that measures a cow’s ability to move as well as the structure of her feet, pasterns, and legs. Scores from 50 to 99 were assigned by appraisers for the Brown Swiss Cattle Breeders’ Association of the USA beginning in June 2007. Only scores made before 69 mo of age were used. After edits, 32,710 records were available for 19,472 cows in 819 herds. The model included fixed effects for the interaction of herd and appraisal date (2,109 groups); appraisal age within parity (46 groups); lactation stage within parity (21 groups) as well as random effects for animal, permanent environment, and residual error. A multitrait analysis was conducted using canonical transformation, multiple diagonalization, and a decelerated expectation-maximization REML algorithm. Heritability was estimated to be 0.21 for mobility and ranged from 0.06 to 0.37 for the other 16 type traits. The traits with the highest genetic correlation with mobility were final score (0.78), rear legs (rear view) (0.74), rear udder width (0.52), and foot angle (0.51). Predicted transmitting ability (PTA) for mobility was calculated using the Brown Swiss multitrait type evaluation system but included only appraisals for which all traits had been scored. For the 1,868 bulls evaluated, PTA for mobility ranged from 1.6 to '1.8 with a standard deviation of 0.5 and was most highly correlated with PTA for final score (0.88), rear legs (rear view) (0.77), rear udder height (0.70), and rear udder width (0.69) as expected from the trait correlations. When matched with official US national evaluations from August 2011, PTA mobility had moderately high correlations with PTA for milk, fat, and protein yields as well as productive life (0.31 to 0.41). The mobility trait may provide a more accurate assessment of the structural soundness required for longevity than does the feet-legs composite.