Effects of Twin Birth on the Occurrence of Postpartum Disorders, Culling and Reproductive Performance, and its Risk Factors in Dairy Cows

This study determined the effects of twin birth on subsequent postpartum disorders, culling and reproductive performance, and its risk factors in dairy cows. Detailed data related to reproduction, health, and calving events, including dates of artificial insemination (AI) and calving, hormonal treatment prior to conception, cow parity, twin birth, retained placenta, metabolic disorders, and endometritis were collected from 1,717 individual calvings on 9 dairy farms. The incidence rate of twin birth was 3.4%. Gestation length was shorter in cows with twin birth ($270.6{\pm}2.0$ days) than cows giving birth to singletons ($279.5{\pm}0.2$ days, P < 0.01). The incidence of retained placenta (47.5 vs. 16.0%), metabolic disorders (18.6 vs. 3.8%) endometritis (62.7 vs. 28.2%), and culling rate (32.2 vs. 16.5%) was greater in cows with twin birth than in cows giving birth to singletons, respectively (P < 0.01). The hazard of pregnancy (adjusted hazard ratio, AHR) by 210 days in milk analyzed using Cox proportional hazards model was affected by calving season, in that the rate of pregnancy for cows calved during spring was less than for cows calved during winter (AHR = 0.80; P = 0.01); this was also true for endometritis (AHR = 0.46, P < 0.01). AHR was not affected by twin birth. Logistic analysis demonstrated that increasing the cow parity (P < 0.01) and hormonal treatment prior to conception (adjusted odds ratio, AOR = 1.84, P < 0.05) increased the risk of twin birth. These results demonstrate that twin births are responsible for severe economic losses through the increased occurrence of postpartum disorders and culling; thus, appropriate management for the deleterious impact of twin birth, and/or reducing the risk factors by herd control regarding cow parity and the use of reproductive hormones prior to conception might be necessary.

젖소에서 쌍태분만이 산후질병 발생, 도태 및 번식능력에 미치는 영향과 쌍태 위험 요인

젖소에서 쌍태분만이 이후의 산후질병 발생, 도태, 번식능력에 대한 영향과 쌍태분만에 대한 위험요인을 조사하였다. 9개 목장 1,717 분만축의 번식, 위생 및 분만관련 상세 자료가 분석에 이용되었다. 쌍태 분만율은 3.4%였으며, 임신기간은 쌍태분만 시에 단태분만 시에 비해 9일 단축되었다($270.6{\pm}2.0$ vs. $279.5{\pm}0.2$일, P < 0.01). 쌍태분만 시가 후산정체(47.5 vs. 16.0%), 대사성질병(18.6 vs. 3.8%) 및 자궁내막염의 발생(62.7 vs. 28.2%)뿐만 아니라 도태율(32.2 vs. 16.5%)이 단태분만 시에 비해 현저하게 증가되었다(P < 0.01). 쌍태분만은 분만으로부터 임신까지의 간격에 유의적인 영향을 미치지 않았으나, 분만계절이 영향을 미쳤는데, 즉 봄에 분만 시가 겨울에 분만 시에 비해 임신율이 감소되었으며(AHR = 0.80; P = 0.01), 또한 자궁내막염의 발생이 임신율의 감소를 초래하였다(AHR = 0.46, P < 0.01). 로지스틱 분석은 산차의 증가(P < 0.01)와 수태 전 번식호르몬의 사용(OR = 1.84, P < 0.05)이 쌍태분만의 위험요인임을 나타내었다. 결론적으로, 젖소에서 쌍태분만은 산후질병 발생과 도태의 증가에 의한 심한 경제적 손실을 초래하므로, 쌍태분만에 대한 적절한 관리 및 고산차 소 및 번식호르몬 사용에 대한 적절한 통제를 통한 위험요인을 감소시키는 것이 요구된다.