G.R. Wiggans1, L.L.M. Thornton*,1, and R.R. Neitzel 2
1Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350; 2Brown Swiss Association, Beloit, WI 53511-5456
2006 J. Dairy Sci. (?)
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Genetic parameters for rear legs/rear view (RLRV) and the 15 current linear type traits in Brown Swiss cattle were estimated. Appraisers record linear traits on a 1 to 9 scale. Reported scores were multiplied by 5 to make them compatible with earlier scores that were on a 1 to 50 scale. The Brown Swiss Association began scoring RLRV in 2004 so only two years of data with all traits recorded were available. These 7,511 records were on 6,896 cows in 375 herds. Pedigree data included 14,168 ancestors and seven unknown parent groups, each including four years of birth. The model included fixed effects for herd appraisal date, and age within parity effects, and random effects animal, permanent environment, and error. The multitrait analysis for the 16 linear type traits used canonical transformation, multiple diagonalization with the F-G algorithm and the expectation-maximization REML algorithm. Heritabilities ranged from 0.073 for RLRV to 0.438 for stature. They averaged 0.046 lower for the 15 currently evaluated traits and ranged from 0.114 lower for teat placement to 0.030 higher for udder height. Strength and udder width had heritability 0.102, the lowest of the currently evaluated traits. The highest genetic correlations for RLRV with the other traits were 0.55 with udder width, 0.47 with strength, and 0.35 with thurl width. The most negative correlation was –0.15 with rear legs side view. The lower heritabilities may reflect the short period of data collection and change in parameters over time. The trait RLRV has the lowest heritability and relatively high correlations with several other traits, but may still be useful in the type program because of the importance of locomotion traits. It is likely to be included in the feet and legs composite. This would affect net merit values.
(Key words: locomotion, type traits, genetic evaluation)