Ratnayake D R, Berglund B, Bertilsson J, Forsberg M, Gustafsson H
Department of Obstetrics and Gynaecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Acta Vet Scand. 1998;39(2):215-28. doi: 10.1186/BF03547794.
Effects on reproduction in a total of 135 dairy cows managed for calving intervals of 12, 15 or 18 months (72, 38 and 25 cows respectively) were studied. The cows were of the Swedish Red and White Breed (SRB) and the Swedish Freisian Breed (SLB) and were housed in 2 different herds with 3 different management systems (tied, loose, and tied but milked in a milking parlour; mixed). The cows in one of the herds (48 cows) were assigned for milking either 2 times or 3 times a day. When comparing conception rate at 1st insemination (AI) and the percentage of cows finally pregnant, we found no significant differences between the 3 calving interval groups, however, a tendency for a higher conception rate with a 15 months' interval compared with a 12 months' interval was found in one of the herds (50% vs 41.5%). The percentage of finally pregnant animals varied between 81% and 100%, but this variation was mainly attributed to the herd rather than calving interval group. A significantly higher percentage of cows was treated for anoestrous in the 12-month group than in the 15-month group in one of the herds (28.6% vs. 5.3%). The frequency of ovulations with external heat signs increased with ovulation number up to the 4th ovulation and thereafter remained stable. No significant difference was found in number of AIs required per conception with respect to calving intervals, breeds, or milking frequency groups. However, cows milked 3 times a day had a significantly longer interval from the 1st AI to conception compared with cows milked 2 times a day (45.8 days vs 17.6 days, p < .01). Cows kept loose exhibited 1st ovulatory oestrous, approximately 2 weeks earlier (55.9 days vs 69.7 days, p < .05) than their herd mates kept tied. In conclusion, our study shows that lengthening the calving interval to 15 or 18 months may have a positive influence on reproduction in terms of less need for treatments of ovarian disorders and higher conception rates. Our results also indicate that milking 3 times a day may have negative effects, and keeping cows in a loose-housing management system may have positive effects on ovarian function.
研究了产犊间隔为12、15或18个月（分别为72头、38头和25头奶牛）的总共135头奶牛的繁殖情况。这些奶牛为瑞典红白花牛品种（SRB）和瑞典弗里生牛品种（SLB），饲养在2个不同牛群中，采用3种不同的管理系统（栓系饲养、散栏饲养，以及栓系饲养但在挤奶厅挤奶；混合管理）。其中一个牛群中的奶牛（48头）每天挤奶2次或3次。在比较首次人工授精（AI）时的受孕率和最终怀孕奶牛的百分比时，我们发现3个产犊间隔组之间没有显著差异，然而，在其中一个牛群中发现，产犊间隔为15个月时的受孕率有高于12个月间隔的趋势（50%对41.5%）。最终怀孕动物的百分比在81%至100%之间变化，但这种变化主要归因于牛群而非产犊间隔组。在其中一个牛群中，12个月组中因发情异常接受治疗的奶牛百分比显著高于15个月组（28.6%对5.3%）。有外部发情迹象的排卵频率随着排卵次数增加至第4次排卵而上升，此后保持稳定。在受孕所需的人工授精次数方面，产犊间隔、品种或挤奶频率组之间未发现显著差异。然而，与每天挤奶2次的奶牛相比，每天挤奶3次的奶牛从首次人工授精到受孕的间隔时间显著更长（45.8天对17.6天，p < 0.01）。散栏饲养的奶牛出现首次排卵发情的时间比栓系饲养的同群奶牛早约2周（55.9天对69.7天，p < 0.05）。总之，我们的研究表明，将产犊间隔延长至15或18个月可能对繁殖有积极影响，即减少卵巢疾病治疗需求并提高受孕率。我们的结果还表明，每天挤奶3次可能有负面影响，而将奶牛饲养在散栏管理系统中可能对卵巢功能有积极影响。
