紀要論文 Characteristics of dairy cows with a pronounced reduction in first milk yield after estrus onset

Koyama, Keisuke  ,  Koyama, Takeshi  ,  Matsui, Yoshitaka  ,  Sugimoto, Masahito  ,  Kusakari, Naohito  ,  Osaka, Ikuo  ,  Nagano, Masashi

65 ( 2 )  , pp.55 - 63 , 2017-05 , Faculty of Veterinary Medicine, Hokkaido University
ISSN:0047-1917
内容記述
Some dairy cows display a pronounced reduction in first milk yield after estrus onset. The objective of this study was to evaluate the usefulness of the pronounced reduction in milk yield as an indicator of the optimal time for artificial insemination (AI). We confirmed that the frequency of a pronounced reduction in first milk yield after estrus onset in our dairy cows was 21.6%. We subsequently examined the differences in estrus intensity, feed intake, the timings of ovulation and fertility between cows with (cows with milk reduction) and without (cows without milk reduction) a pronounced reduction in first milk yield after estrus onset. Compared to cows without milk reduction, the percentage of cows that were milked actually during estrus tended to be higher in cows with milk reduction. However, the dry matter intake 1 day before the first milking after estrus onset was similar in both the groups of cows. In cows with milk reduction, the percentage of cows that ovulated 22-24 hr after the first milking following estrus onset was higher than that in cows without milk reduction. The pregnancy rate in cows with milk reduction that were inseminated 3-8 hr after milking during which the pronounced reduction in milk yield was exhibited was significantly higher than that in cows with milk reduction inseminated during other periods. These results indicate that the optimal time for AI can be narrowed by detecting a pronounced reduction in first milk yield after estrus onset.
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https://eprints.lib.hokudai.ac.jp/dspace/bitstream/2115/66474/1/65-2%20055-063.pdf

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