Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2012
Publication Date: 6/1/2012
Citation: Dikmen, S., Cole, J.B., Null, D.J., Hansen, P.J. 2012. Heritability of rectal temperature and genetic correlations with production and reproduction traits in dairy cattle. Journal of Dairy Science. 95(6):3401-3405. Interpretive Summary: Selection of dairy cattle for ability to regulate body temperature may reduce the impact of heat stress on production and reproduction. Genetic parameters were estimated for rectal temperature in dairy cows under heat stress conditions. The heritability of rectal temperature was 0.21, higher than many traits routinely evaluated. Rectal temperature had positive genetic correlations with somatic cell score and negative genetic correlations with productive life, daughter pregnancy rate, and net merit. Selection for decreased rectal temperature will not result in decreased genetic merit for production and may result in improved genetic merit for other traits.
Technical Abstract: Genetic selection for body temperature regulation during heat stress might be a useful approach to reduce the magnitude of heat stress effects on production and reproduction. Present objectives were to estimate the genetic parameters of rectal temperature in dairy cows reared in free stall barns under heat stress conditions and determine the genetic and phenotypic correlations of rectal temperature with other traits. Afternoon rectal temperatures were measured in a total of 1695 lactating Holstein cows sired by 509 bulls during the summer in North Florida. Genetic parameters were estimated with GIBBS1F90 and breeding values were estimated with MTDFREML. The heritability of rectal temperature was estimated as 0.21. Cow estimated breeding value (EBV) for rectal temperature changed 0.000068 degree C/year from birth year 2002 to 2008. Genetic correlations between rectal temperature and other traits were generally low and not different from zero. Exceptions were for 305-d actual somatic cell score (SCS), which was positively correlated with rectal temperature, and productive life (PL), daughter pregnancy rate (DPR) and net merit (NM), which were negatively correlated. Phenotypic correlations between rectal temperature and production traits were often significant. In conclusion, rectal temperature during heat stress is moderately heritable and generally does not have strong genetic correlations with economically important traits. It should be possible to select for low rectal temperature without decreasing genetic merit for production and while possibly increasing genetic ability for superior SCS, PL, DPR and NM.