Heritability, repeatability and environment effects in Hereford cattle. II. Calving interval, producing ability and cow productivity index

Abstract

Paternal half-sib analyses and least-square procedures were used to compute heritability estimates for calving intervals (IEP), mean calving interval (IMEP), most probably producing ability of the cow (HMMP), and cow productivity index (IMP) of two Hereford herds in Rio Grande do Sul. Year of previous calving accounted for a highly significant (P < 0.01) variation in IEP, in both herds, while age of dam at calving was not significant in herd B (P > 0.05). Sex of previous calf was not significant for IEP (P > 0.05) in either herds. The sex by age of dam interaction was a significant source of variation (P < 0.01), only in herd A. Least-squares means for both herds were: A = 437 ± 6.3 and B = 480 ± 15.3. Heritability estimates for all traits in both herds were: IEP = 0.01 ± 0.06 and 0.12 ± 0.16; IMEP = 0.06 ± 0.19 and 0.28 ± 0.26; HMMP = 0.31 ± 0.28 and 0.20 ± 0.16 and IMP = 0.10 ± 0.12 and 0.22 ± 0.25. Repeatability estimates for IEP in herd A and B were 0.18 ± 0.06 and 0.17 ± 0.05 respectively. These values obtained for IEP were low. Therefore, selection will result in little genetic progress.