Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2006
Publication Date: 12/1/2006
Citation: Wiggans, G.R., Thornton, L.L., Neitzel, R.R., Gengler, N. 2006. Genetic parameters and evaluation of rear legs (rear view) for Brown Swiss and Guernseys. Journal of Dairy Science. 89(12):4895-4900. Interpretive Summary: Improvement in structural soundness is important to the dairy producer because lame animals or those that have other locomotion difficulties often produce less milk or are less fertile. The Brown Swiss Association and the American Guernsey Association recently began recording rear legs/rear view. Cows that are severely hocked in and toed out receive a low score for this trait. Heritability estimates for rear legs/rear view were less than 8%. Moderate correlations were found with other linear traits, the highest (above 0.5) was for udder width. Rear legs/rear view may be included in the feet and legs composite, which affects net merit. Evaluations for this trait were first released for Brown Swiss and Guernsey in May 2006.
Technical Abstract: Genetic parameters for rear legs/rear view (RLRV) and 15 current linear type traits in Brown Swiss (BS) and Guernsey (GU) dairy cattle were estimated. The BS Association began scoring RLRV in 2004 and the American GU Association began in 2002. For BS, 7,522 records were available on 6,896 cows in 375 herds. Seven unknown parent groups were defined; each included 4 years of birth. The GU data included 4,666 records on 4,223 cows in 209 herds. The model included fixed effects for herd appraisal date and age within parity, and random effects for animal, permanent environment, and residual. The multi-trait analysis for RLRV and the 15 linear type traits used canonical transformation, multiple diagonalization, and a decelerated expectation-maximization REML algorithm. Heritabilities ranged from 0.073 for RLRV to 0.440 for stature in BS; and from 0.050 for RLRV to 0.384 for udder depth for GU. Heritabilities from the RLRV data set averaged 0.048 lower for BS and .052 lower for GU than previous estimates for the 15 currently evaluated traits and ranged from 0.179 lower for GU rump angle to 0.026 higher for BS rear udder height. The lowest heritabilities for currently evaluated traits were GU foot angle (0.066), BS strength (0.102), and BS udder width (0.103). The change in heritabilities may reflect the short period of data collection with very few dams being recorded, changes in parameters over time, and/or sampling errors given the limited amount of data. The highest genetic correlations for RLRV in BS with other traits were 0.58 (udder width), 0.54 (strength), and 0.38 (thurl width). The most negative correlation for BS was –0.17 with rear legs side view. For GU traits, the highest genetic correlations for RLRV were 0.52 (udder width), 0.46 (udder height), and 0.37 (dairy form), while the most negative genetic correlation was with rear legs side view (–0.46). The trait RLRV has low heritability with moderate correlations with several other traits in both breeds. It should be useful in selection for improved locomotion. It is likely to be included in the feet and legs composite and would affect net merit values. Release of the evaluation began in May 2006 for the BS and GU breeds.