Multiple trait estimates of genetic parameters for juvenile growth and calving traits in Canadian Angus cattle

Abstract

Two analyses, both with three calf body weights at birth (BW), weaning (WW) and yearling (YW), one including first calving date (CD1) using a four-trait model, and the other including calving date (CD) and interval (CI) in a five-trait model, were carried out for a pooled population of beef cattle from one herd in Manitoba (n = 3,601), three herds in Alberta (n = 779, 600 and 967) and one herd in Saskatchewan (n = 495) totaling 6442 calving records for years 1984 through 2001. Multiple-trait mixed-animal model methodology was utilized in both analyses to estimate genetic parameter estimates for three juvenile growth traits with three calving traits. The direct heritability estimates for BW, WW and YW from Analyses (1, 2) were (0.51, 0.45), (0.70, 0.70) and (0.52, 0.79), respectively, and corresponding maternal heritability estimates were (0.10, 0.18), (0.20, 0.24) and (0.06, 0.12), respectively. Estimates of direct heritabilities for CD1 (Analysis 1), CD (Analysis 2) and CI (Analysis 2) were 0.18, 0.25 and 0.10, respectively. Estimates of genetic correlations among direct effects on juvenile growth traits ranged from 0.31 to 0.89, and those among maternal genetic effects ranged from 0.20 to 0.98. Estimates of direct-maternal genetic correlations within each of BW, WW and YW ranged from -0.61 to -0.06, but those between any two growth traits were variable, with positive genetic correlations shown particularly between maternal BW with direct WW and direct YW. Direct genetic correlation estimates of BW, WW and YW with CD1 were -0.01, 0.28 and 0.04, respectively. Correspondingly, estimates of genetic correlations of maternal BW, WW and YW with direct CD1 were 0.02, -0.73 and -0.75, respectively. Estimates of direct genetic correlations of BW, WW and YW with CD were -0.19, -0.31 and -0.21, respectively, and those with CI were -0.29, -0.38 and -0.65, respectively. Correspondingly, estimates of genetic correlations maternal BW, WW and YW between direct CD (CI) were -0.02 (0.00), -0.18 (0.07) and -0.36 (0.51), respectively. The genetic trends for direct BW, WW and YW were 0.167, 1.817 and 4.394 kg yr-1, respectively, and those for direct CD and CI were -1.089 and -0.088 d yr-1, respectively, and for maternal BW, WW and YW were -0.015, -0.065 and -0.952 kg yr-1, respectively. The genetic parameter estimates indicate potential merit for developing breeding strategies that permit genetic improvement of both growth and dams' calving efficiency in Canadian Angus cattle.