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Animal Breeding and Genetics
Asian-Australasian Journal of Animal Sciences 2009;22(2): 162-167.
DOI: https://doi.org/10.5713/ajas.2009.80284    Published online January 6, 2009.
Number of Calves Produced at Specified Age as a Measure of Reproductive Performance in Beef Cattle under Artificially-Inseminated Breeding Scheme
Kenji Oyama*, Shinya Fujiwara, Tomohiro Katsuta, Takeshi Honda, Fumio Mukai
Correspondence:  Kenji Oyama,
Reproductive abilities in beef cattle herds are receiving increased attention due to recent rises in production costs. To achieve more efficient management, a measure of fertility, namely the number of calves produced at k yr of age (NCPk), was developed and its genetic parameters were estimated from Japanese Black cows by restricted maximum likelihood procedures. The k examined were distributed from 2 to 10 yr of age and NCP2 averaged 1.077 calves over 43,536 cows. The averages increased by approximately 0.9 calf with each additional 1 yr increment in k. Heritabilities of NCPk were estimated to be low ranging from 0.083 to 0.162, which seemingly suggested a difficulty of genetic improvement. However, large genetic variation and high accuracy were observed in predicted breeding values of NCPk. For example, the breeding values of NCP7 were predicted between -0.303 and +0.213 with average accuracy of 0.607 for cows with observations. Genetic correlations among different k were generally high and positive (0.474 to 0.995). The analyses showed that at least NCP4 was required to maintain the genetic correlations of 0.8 or higher with subsequent NCPk. Also NCP5 maintained the genetic correlations of 0.9 or higher with subsequent NCPk. The results suggested some possibilities for NCPk to be a selection criterion considering its genetic variation, high accuracy and consistency with subsequent performance.
Keywords: Beef Cattle; Genetic Parameter; Number of Calves Produced; Reproductive Performance
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