Lamb G C, Miller B L, Lynch J M, Thompson K E, Heldt J S, Löest C A, Grieger D M, Stevenson J S
Department of Animal Sciences and Industry, Kansas State University, Manhattan 66506-0201, USA.
J Anim Sci. 1999 Aug;77(8):2207-18. doi: 10.2527/1999.7782207x.
Two experiments were conducted to determine whether milking beef cows two or five times daily in the presence or absence of their own nonsuckling calves would alter postpartum interval to first ovulation. Multiparous Angus x Hereford cow-calf pairs were assigned randomly between 13 and 18 d postpartum to treatments for 4 wk. In Exp. 1, pairs were assigned to six treatments: 1) calf was weaned permanently from its dam (CW; n = 9); 2) same as CW, but dam was milked twice daily (CW+2xM; n = 9); 3) calf was present continuously with its dam but restricted from contact with the udder (CR; n = 9); 4) same as CR, but dam was milked twice daily (CR+2xM; n = 9); 5) same as CR, but calf was allowed to suckle twice daily (CR+2xS; n = 8); and 6) calf was present continuously with its dam and suckled ad libitum (CP; n = 9). The interval from onset of treatments to first postpartum ovulation was shorter (P<.05) in the CW (14.1+/-3.1 d), CR (14.2+/-3.1 d), CW+2xM (13.0+/-3.1 d), and CR+2xM (17.2+/-3.1 d) than in the CP (34.7+/-3.1 d) and CR+2xS (33.9+/-3.3 d) treatments. Daily milk yield during treatment was greater (P<.01) for CR+2xM cows (7.1+/-.6 kg) than for CW+2xM cows (3.5+/-.6 kg). In Exp. 2, cow-calf pairs were assigned to three treatments: 1) CR+2xM (n = 10); 2) same as CR+2xM but cows were milked five times daily (CR+5xM; n = 10); or 3) CP (n = 10). The interval to first postpartum ovulation was shorter (P<.05) in the CR+2xM (23.6+/-3.5 d) and CR+5xM (26.1+/-3.7 d) treatments than in the CP (37.7+/-3.7 d) treatment. Daily milk yield during treatment was greater (P<.05) for CR+5xM cows (7.7+/-.6 kg) than for CR+2xM cows (6.4+/-.6 kg) by 17%. We conclude that suckling twice daily was sufficient to prolong postpartum anestrus as much as suckling ad libitum. Furthermore, milk removal by suckling, but not by milking two or five times daily, even in the presence of the cow's own nonsuckling calf, is essential to prolong postpartum anovulation.
进行了两项试验，以确定在有或没有自己未哺乳犊牛的情况下，每天对肉用母牛挤奶两次或五次是否会改变产后至首次排卵的间隔时间。经产安格斯×赫里福德母牛犊牛对在产后13至18天被随机分配到各处理组，为期4周。在试验1中，牛犊对被分配到六种处理：1）犊牛永久性地与其母亲断奶（CW；n = 9）；2）与CW相同，但母牛每天挤奶两次（CW + 2xM；n = 9）；3）犊牛一直与其母亲在一起，但限制其接触乳房（CR；n = 9）；4）与CR相同，但母牛每天挤奶两次（CR + 2xM；n = 9）；5）与CR相同，但犊牛每天允许吸吮两次（CR + 2xS；n = 8）；6）犊牛一直与其母亲在一起并随意吸吮（CP；n = 9）。从处理开始至产后首次排卵的间隔时间在CW（14.1±3.1天）、CR（14.2±3.1天）、CW + 2xM（13.0±3.1天）和CR + 2xM（17.2±3.1天）组比在CP（34.7±3.1天）和CR + 2xS（33.9±3.3天）组短（P<0.05）。处理期间，CR + 2xM组母牛的日产奶量（7.1±0.6千克）比CW + 2xM组母牛（3.5±0.6千克）高（P<0.01）。在试验2中，母牛犊牛对被分配到三种处理：1）CR + 2xM（n = 10）；2）与CR + 2xM相同，但母牛每天挤奶五次（CR + 5xM；n = 10）；3）CP（n = 10）。产后首次排卵的间隔时间在CR + 2xM（23.6±3.5天）和CR + 5xM（26.1±3.7天）组比在CP（37.7±3.7天）组短（P<0.05）。处理期间，CR + 5xM组母牛的日产奶量（7.7±0.6千克）比CR + 2xM组母牛（6.4±0.6千克）高17%（P<0.05）。我们得出结论，每天吸吮两次足以像随意吸吮一样延长产后乏情期。此外，即使在母牛有自己未哺乳犊牛的情况下，通过吸吮而不是每天挤奶两次或五次来移除乳汁，对于延长产后无排卵至关重要。
