Analyses involved fertility records of U.S. Holsteins. A bivariate model was for conception rate at the first insemination treated as a categorical trait, and days open treated as a linear trait. Data sets included all insemination records or only of cows with the next calving dates. The heritabilities of both traits were similar, and the genetic correlations were -0.96 to -0.98. A threshold-random regression model was used to analyze all sequential service records for the same data sets. The heritabilities were from 1.5 to 1.6% with the both data sets. The repeatability was approximately level for different days postpartum at 5.1% for the uncensored data set and increased from 5% to 12% for all insemination records. Fertility may be analyzed more accurately using all service records; however, data editing is a critical factor.

Shogo Tsuruta, C. Huang, Ignacy Misztal, Thomas J Lawlor

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 01.86, 2006
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