MDC Evaluations Ltd, Fox Talbot House, Greenways Business Park, Chippenham, Wiltshire, SN15 1BN, UK. Introduction There is growing interest in the dairy ...
Genetic parameters for locomotion and composite type traits for the Jersey and Guernsey dairy breeds in the United Kingdom (UK) M.F.Paget, G.J.T. Swanson and R.A. Mrode MDC Evaluations Ltd, Fox Talbot House, Greenways Business Park, Chippenham, Wiltshire, SN15 1BN, UK Introduction There is growing interest in the dairy industry to broaden breeding objectives by incorporating health and welfare traits into selection indices. Although these traits are difficult to measure directly, there is good evidence to show that some linear type traits are genetically correlated with certain health and welfare traits, e.g. udder-type with somatic cell count (Mrode, Swanson and Lindberg, 1999) and locomotion with lameness (Boelling, 1996). Linear and composite type traits, such as locomotion and the feet and legs and mammary system composites, have been proposed for inclusion in a future modification to the UK Profitable Life Index (PLI). The objective of this study was to estimate genetic parameters of locomotion and composite traits for application in UK national dairy genetic evaluations for Jerseys and Guernseys. Materials and Methods The data consisted of linear and composite type scores from the official classification schemes carried out by the Jersey and Guernsey Breed Societies. The traits included locomotion (LOCO), a linear type trait scored on a scale of 1 (poor) to 9 (very good), and body character (BC), dairy character (DC), feet and legs (FL) and mammary system (UDD), which are composite type traits scored on a scale of 40 (poor) to 89 (very good) (MDC Evaluations Ltd, 2002). Data used for analyses was restricted to classifications on heifers aged between 18 and 45 months and within 1 and 365 days of lactation. The data sets consisted of 6590 records for Jersey and 3838 records for Guernsey after edits. Multivariate analyses were carried out using ASREML software (Gilmour et al., 2000) to obtain genetic parameter estimates. The animal model fitted included month of calving and herd-inspection date as fixed effects and age and stage of lactation at classification fitted as linear and quadratic covariables. Results While the mean scores were higher in the Jersey breed, the lower sds reflected a more limited use of the scoring range. All heritabilities were moderate to moderately high in both breeds with the lowest found for FL and LOCO. Although the magnitude varied between the breeds, most genetic and phenotypic correlations were positive. The genetic relationships found between UDD, FL and LOCO were all moderate to strongly positive. A high genetic correlation of 0.91 was found in Guernseys between FL and LOCO. The same correlation in Jerseys was low at 0.30. Table 1. Unadjusted means, standard deviations (sd) and parameter estimates1 (s.e.) Jersey Mean sd BC DC FL 80.74 3.98 0.25 (0.04) 0.29 0.30 BC 81.40 3.69 0.23 (0.09) 0.36 (0.04) 0.18 DC 80.09 4.45 0.38 (0.11) 0.13 (0.11) 0.19 (0.04) FL 79.18 5.27 0.56 (0.09) 0.25 (0.09) 0.41 (0.11) UDD 1.17 0.15 (0.12) 0.04 (0.10) 0.30 (0.13) LOCO 5.38 Guernsey Mean sd BC DC FL 75.98 9.19 0.51 (0.06) 0.54 0.15 BC 78.50 8.24 0.82 (0.04) 0.41 (0.05) 0.22 DC 78.09 7.45 -0.09 (0.14) 0.08 (0.14) 0.14 (0.04) FL 74.50 9.58 0.46 (0.09) 0.38 (0.10) 0.35 (0.14) UDD 1.49 -0.02 (0.13) 0.03 (0.14) 0.91 (0.05) LOCO 5.28
UDD 0.25 0.28 0.22 0.31 (0.04) 0.63 (0.08)
LOCO 0.18 0.12 0.32 0.45 0.22 (0.04)
UDD 0.28 0.43 0.23 0.29 (0.05) 0.42 (0.14)
LOCO 0.12 0.16 0.75 0.23 0.17 (0.04)
1
Heritabilities on the diagonal (in bold), phenotypic correlations above diagonal and genetic correlations below diagonal
Conclusions Heritabilities found in this study suggest scope for genetic improvement for all traits considered. The heritability estimates for composite traits were in reasonable agreement to those found in Holstein-Friesians (HF), although estimates found for LOCO in this study were slightly higher (h2=0.11 in HF) (S.Brotherstone, pers.com.). The positive correlations between the feet (FL and LOCO) and mammary (UDD) traits is promising for inclusion of these traits in a revised PLI for Jerseys and supports the inclusion of FL and UDD in the Guernsey Merit Index already in use. Locomotion is widely considered as a more objective measure than the feet and leg composite and since these traits are highly correlated in Guernseys, consideration should be given to replacing the feet and leg composite with locomotion. The unexpectedly low correlation between these traits in the Jersey breed requires further investigation. References Boelling, D. 1996. The influence of phenotype and genotype on locomotion in cattle. PhD. thesis, Wye College,University of London. Gilmour, A.R., Cullis, B.R., Welham, S.J. and Thompson, R. 2000. ASREML Reference Manual. Orange Agricultural Institute, NSW, Australia. MDC Evaluations Ltd. 2002. Technical Bulletin, pp. 21-23. Mrode, R.A., Swanson, G.J.T. and Lindberg, C.M. 1999. Genetic relationship between somatic cell count and lifespan and conformation traits in some dairy breeds in the United Kingdom (UK). Proceedings of the British Society of Animal Science, p. 48. 56
