Factors Affecting Reproductive Performance in High Milk-producing Holstein Cows

Abstract

Abstract. Although the number of dairy farms is decreasing, that of large farms is increasing in Japan. Milk production in Japanese dairy cows has increased from 62 kg/ year to 88 kg/ year over the last 2 decades. However, Japanese dairy cows are experiencing a sustained decline in reproductive performance, calving intervals, and days open; further, the number of inseminations required for conception have increased, and the conception rate has decreased. In order to improve fertility in high milk-producing dairy cows, it is necessary to evaluate their reproductive characteristics. In this study, the postpartum body condition score (BCS) was remarkably low, and the functional recovery of reproduction was consequently delayed. Moreover, the results indicate that the estrus duration varies among individual cows. However, it is possible to improve the conception rate by inseminating cows 8-12 h after the onset of estrus. Reproductive management systems suitable for the current dairy farming system with large herd sizes are required. Key words: Artificial insemination, Body condition score, Conception rate, Dairy cows, Reproduction (J. Reprod. Dev. 56: S61-S65, 2010) lthough milk production per dairy cow has dramatically increased over the last 2 decades, the reproductive performance of dairy cows has declined worldwide [1][2][3][4][5][6]. The cause of this low reproductive performance may vary considerably across countries and is probably multifactorial. The factors that contribute to the decrease in the reproductive performance of dairy cows are increase in milk production per cow, concrete flooring, confined housing, and increase in herd size.According to the latest livestock statistics reported by the Ministry of Agriculture, Forestry and Fisheries, in July 7, 2009 (http:// www.maff.go.jp/toukei/sokuhou/data/siyou_doukou09/ siyou_doukou09.pdf), the total number of dairy farms in Japan is 22,300. This number is decreasing; however, the number of farms with more than 100 cows (aged above 24 months) is increasing, and this number is 1,860 (8.3%). The number of dairy farms with more than 300 cows is 173. This trend in the increase in herd size in Japan is the same as that in other countries such as the USA [2].According to data presented by the Livestock Improvement Association of Japan (http://liaj.lin.gr.jp/japanese/kentei/ kentei.html), over the last 2 decades, milk production (305 d) in Japanese dairy cows has increased by approximately 62 kg/year in Hokkaido and 88 kg/year all over Japan, except in Hokkaido (Fig. 1). This trend in the increase in milk production in Japan is the same as that in other countries [2,4]. However, a sustained decline in reproductive performance has been observed in Japanese dairy herds (Table 1) The Hokkaido Artificial Insemination Technician Association Inc. conducts annual surveys and reports the conception rates at the first artificial insemination (AI) in dairy cattle in the Hokkaido district. The conception rate in dairy cows was found to decrease from 53.4% in 1989 to 41.2% ...

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Effect of the Temperature-Humidity Index on Body Temperature and Conception Rate of Lactating Dairy Cows in Southwestern Japan

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