Heritability and repeatability of resistance to nematode parasites in commercial beef cattle

摘要

Faecal egg count (FEC) is used commonly as a guide to nematode parasite burdens in animals in vivo. The objective of this study was to estimate the heritability and repeatability of FEC in commercial beef calves, along with breeding values for FEC inthe calves and their sires, for future quantitative and molecular analyses. In 2008-2011, faecal samples from 4,621 weaned beef calves were obtained for FECI from 11 herds (mainly Angus or Hereford). FECI represented the first sample after weaning (generally between May and July); a second sample (for FEC2) was taken by September from all calves in some herds, with FECI and FEC2 samplings separated by an effective anthelmintic drench. Calves were sired by a total of 325 and 57 separate Angus and Hereford sires, respectively. Heritability estimates for log_e(FEC+50) in Angus at Times 1 and 2 were 0.28 ± 0.05 (standard error) and 0.11 ± 0.09, respectively, with a genetic correlation of 0.89 ± 0.22 between them. Treating FECI and FEC2 as repeated measurements of the same trait, the repeatability estimate for log_e(FEC+50) was 0.38 ± 0.04. The parameters estimated for log_e(FEC+50) in weaned beef calves under commercial grazing conditions were similar to those from experimental beef calves.