Genetic correlations among fertility traits within and across Holstein herds with different milk-production during the first three lactations T. Yamazaki1, H. Takeda2, T. Osawa3, S. Yamaguchi4 & K. Hagiya5 1 Hokkaido Agricultural Research Center, NARO, Sapporo, 062-8555, Japan; 2 Institute of Livestock and Grassland Science, NARO, Tsukuba, 305-0901, Japan; 3 National Livestock Breeding Center, Fukushima, 961-8511, Japan; 4 Livestock Improvement Association of Japan, Tokyo, 135-0041, Japan; 5 Obihiro University of Agriculture and Veterinary Medicine, Obihiro, 080-8555, Japan Genotype by environment interaction (G×E) effects for lactating cows’ fertility traits with regard to herd production levels may differ with lactation number. Our objective here was to investigate the genetic correlations among several fertility traits in cows within and across herds with different milk-production levels by using lactation records of Japanese Holstein cows (475,446 records for first lactation, 378,540 for second, and 265,560 for third). Herds with data were categorized into three groups (LOW, MID, and HIGH) based on the average herd-year effects in each herd for 305-day milk yield at the first lactation. The fertility traits evaluated were conception rate at first insemination (CR); number of inseminations (NI); and days open (DO). Genetic parameters were estimated within each lactation by using a multiple-trait animal model that considered the traits of different herd milk-production groups (HPGs) as separate traits. The genetic correlations among fertility traits were strong; values did not differ greatly among HPGs or lactations. Some of the genetic correlations of CR or NI among different HPGs for the second and third lactations were lower than those for the first lactation. These findings suggest that G×E effects on a cow’s ability to conceive with respect to herd production level are larger in later lactations than in the first lactation. Keywords: dairy cattle, fertility, genotype by environment interaction, herd milk production
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume Electronic Poster Session - Challenges - Genotype by Environment Interactions, , 86, 2018
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