Phenotypic and genetic factors of twinning rate in Japanese Holsteins

概要

論文の詳細を見る
The objective of this study was to investigate phenotypic and genetic factors of twinning rate, using records from first to third parity of Holsteins calved in Hokkaido from 2000 to 2007. Phenotypic analysis was conducted by logistic regression analysis for each parity and the whole dataset. Genetic analysis was carried out by using threshold repeatability animal model. Twinning rate of all parities tended to increase from 2004 in calving year. Summer calving was a high risk factor for twinning. The risk of twinning birth increased in the older age in first parity. The association between twinning rate and calving age was little in second parity and none in third parity. However, the risk of twinning birth increased as parity increased. For second and third parity, 305-day milk yield, days open and condition of calf in previous parity were significant factors for twinning rate. Heritability and repeatability for twinning rate were 0.18 and 0.19, respectively. This result suggests that genetic improvement of twinning rate by direct selection is feasible.