Effects of parity and season on pregnancy rates to Japanese Black beef cattle
Ono, T. Yamaguchi University
Isobe, T. Cattle Breeding Development Institute, Kagoshima Prefecture
Morita, Y. Yamaguchi University
Do, L. T. K. Yamaguchi University
Tanihara, Fuminori Yamaguchi University KAKEN Search Researchers
Taniguchi, M. Yamaguchi University
Takagi, M. Yamaguchi University
Otoi, Takeshige Yamaguchi University|Tokushima University Tokushima University Educator and Researcher Directory KAKEN Search Researchers
Repeat-breeder (RB) cows are a major source of economic waste due to their decreased fertility. Embryo transfer (ET) is an alternative tool to improve the fertility of RB cows. The aims of the present study were to evaluate the effects of recipient parity and the season on pregnancy rates following ET in RB Japanese Black beef cattle. Embryos were transferred nonsurgically to recipients, consisting of 155 heifers (< 2 years old) and 172 cows (< 8 years old), which were defined as RB cattle. Of the recipients that were presented for ET, 57 recipients received a fresh embryo and 270 recipients received a frozen embryo. There were no differences in the pregnancy rates between cattle that received fresh embryos or frozen embryos. The rates of recipients with pregnancy, abortion, stillbirth, and normal calving were similar between heifers and cows. In cows, the pregnancy rates were lower (P < 0.05) in summer (June to August) than in spring (March to May) and winter (December to February). In heifers, however, there were no differences in the pregnancy rates among the seasons. Our findings indicate that in RB Japanese Black beef cattle, the parity of the recipients does not have an effect on the pregnancy rates following the transfer of fresh and frozen embryos. However, heat stress may affect reproductive performance in RB Japanese Black cows.
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This work is distributed under the Creative Commons Attribution 3.0 License (https://creativecommons.org/licenses/by/3.0/).
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Bioscience and Bioindustry