Hair coat characteristics and sweating rate of Braford cows in Brazil

This paper deals with the effects of hair coat characteristics on the sweating rate of Brazilian Braford cows and estimation of heritabilities and genetic correlations of these traits. Data ( n = 1607) on hair length, coat thickness, hair diameter, number of hairs per unit area, coat reflectance and sweating rate were recorded from heifers and cows of a commercial herd managed on range under extensive system. The data were analyzed considering the following effects on the model for hair coat traits: classes of sires and contemporary groups; linear effects of month and genotype; linear and quadratic effects of age. The effect of sire was important ( P P P P P P h 2 ) and broad ( H 2 ) sense for single-trait analyzes: hair thickness ( h 2 = 0.16; H 2 = 0.26); hair length ( h 2 = 0.18; H 2 = 0.39); number of hairs ( h 2 = 0.08 ± 0.07; H 2 = 0.08 ± 0.07); hair diameter ( h 2 = 0.12 ± 0.07; H 2 = 0.12 ± 0.07); coat reflectance ( h 2 = 0.30; H 2 = 0.42); and sweating rate ( h 2 = 0.10 ± 0.07; H 2 = 0.10 ± 0.07). In general, the genetic correlations between the adaptive traits were favorable as for the direction to select for adaptation in tropical environment; however, they presented high standard errors. The results of this study imply that hair coat characteristics and sweating ability are important for the adaptability to heat stress and they must be better studied and further considered for selection for genetic progress of adaptation in tropical environment.