It is important to improve the energy balance (EB) of dairy cows in lactation to prevent the deterioration of health and fertility. Here, we estimate the genetic correlations between EB and days open (DO) in Holsteins in Japan. The data consisted of test-day milk records for the first lactations of Holstein cows calving in 2010–2013. The data set for analysis consisted of 2,279,906 records of 247,487 cows. EBs were estimated by using the multiple regression equations of Friggens et al. (2007) and Løvendahl et al. (2010). Genetic parameters of EBs and DO were estimated by using a random regression model. Estimated EBs were negative soon after parturition and changed to positive at about 50 days in milk (DIM). The phenotypic values of DO were greater in lower Friggens EB classes or lower Løvendahl EB classes from 36 to 65 DIM. The heritability estimates of EBs were about 0.2 and almost constant throughout lactation. The heritability estimate of DO was 0.07. The genetic correlations between EBs and DO were strongest soon after parturition, at about –0.3, and then weakened to –0.1 to 0 after 200 DIM. In conclusion, it should be possible to decrease DO—that is, to improve reproductive performance—by improving EB. Keywords: dairy cow, energy balance, random regression model, reproduction
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Electronic Poster Session - Biology - Feed Intake and Efficiency 1, , 277, 2018
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