Abstract
Reproductive data collected from more than 20,000 Japanese Black cows of Hyogo and Shimane Prefectures were analyzed. Averages of age at first calving, gestation length, days open and calving interval were 25.1 mo, 289 d, 112 d and 401 d, respectively. Variance components were obtained by REML procedure and the heritability estimate of age at first calving was 0.22. In gestation length the heritability estimate was 0.40 and no permanent environmental effect was estimated. Estimated variance components of calving interval were similar to those of days open and the heritability and repeatability of calving interval were 0.05 and 0.09, respectively. Random farm effects accounted for approximately 10% of phenotypic variations in all traits. Genetic and farm correlations between age at first calving and calving interval were 0.27 and 0.39, respectively. It was found that temporary environment was an important source of variation for calving intervals of Japanese Black. (Asian-Aust. J. Anim. Sci. 2002. Vol 15, No. 12 : 1680- 1685)
Highlights
GENETIC PARAMETER OF REPRODUCTIVE TRAITS intentional decision by producers
Shimane cows registered after October 1990 were chosen in countries where year-round artificial insemination (AI) is for analysis because of changes in body condition scoring taken place for the majority, calving interval (CI) seems to system
At first calving and if her AFC was within 3 SDs, her AFC was treated as a valid record
Summary
In the present study DO was required to be greater than 20 d but less than 365 d. This data edit might remove some genetically worst cows from analyses. The GL records shorter than 241 d, of twins, abortion and stillbirth were eliminated. The CI of a cow was the sum of DO and following GL. The CI of a cow was eliminated if any of individual records of DO or following GL was not a valid record. If a cow had valid GL at first calving and if her AFC was within 3 SDs, her AFC was treated as a valid record. The farm owning only one cow was excluded from the analyses of AFC, DO and CI to achieve robust analyses and to avoid confounding between random farm and permanent environmental effects in the repeatability models
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