Sithole F, Dohoo I, Leslie K, DesCôteaux L, Godden S, Campbell J, Keefe G, Sanchez J
Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, PEI, Canada C1A 4P3.
Prev Vet Med. 2006 Aug 17;75(3-4):267-79. doi: 10.1016/j.prevetmed.2006.04.003.
The objective of this study was to investigate if treatment of cows with eprinomectin around calving had any beneficial effects on the calving to first artificial insemination interval, calving to conception interval, and number of services per conception in totally- and semi-confined dairy herds. In totally-confined herds lactating- and dry-cows were housed throughout the summer and had no access to pasture. In semi-confined herds lactating- and dry-cows had limited outdoor exposure to a small pasture or paddock but were still fed a ration that met all their nutritional requirements. The study was carried out between February 2002 and February 2003 in 35 herds (2381 cows) located in Quebec, Ontario and Minnesota (USA) participating in a larger clinical trial. The herds kept electronic reproduction records. Cows were randomly allocated to receive eprinomectin or a placebo, with treatment being administered on or close to the day of calving. Monthly bulk tank milk samples from each farm were tested with an indirect ELISA using a crude Ostertagia ostertagi antigen and these data were averaged over the study year. The optical density ratio (ODR) values were then dichotomized into high and low using a cut-point of 0.50. Treatment effects were analyzed using Cox proportional hazards survival models with herd frailty effects for calving to conception and calving to first service intervals. Aalen's linear hazards model was used to investigate time-varying effects in the Cox models. A random effects poisson regression model was used to model the number of services per conception. Other predictor variables tested in the models were lactation number, calving season, study site, peak milk production, ODR and the lactating- and dry-cow housing variables. Overall, there was no significant effect of treatment on the three indices of reproductive performance. The effect of season of calving depended on how much time had passed since calving. Presumably this effect reflected a seasonal effect at the time of breeding. Hazard of conception in younger cows was higher than in older cows. Early bred cows tended to have a higher number of inseminations per conception than those bred late. The results of the study suggested that eprinomectin treatment at calving was not beneficial to reproduction.
本研究的目的是调查在产犊前后用伊维菌素治疗奶牛，对完全圈养和半圈养奶牛场的产犊至首次人工授精间隔、产犊至受孕间隔以及每次受孕的输精次数是否有任何有益影响。在完全圈养的牛群中，泌乳牛和干奶牛整个夏天都被圈养，无法放牧。在半圈养的牛群中，泌乳牛和干奶牛在户外能有限地接触到一小块牧场或围场，但仍被喂食满足其所有营养需求的日粮。该研究于2002年2月至2003年2月在魁北克、安大略和美国明尼苏达州的35个牛群（2381头奶牛）中进行，这些牛群参与了一项更大规模的临床试验。这些牛群保存着电子繁殖记录。奶牛被随机分配接受伊维菌素或安慰剂治疗，治疗在产犊当天或临近产犊当天进行。每个农场每月采集的批量罐奶样本用粗奥斯特他加（Ostertagia ostertagi）抗原通过间接ELISA进行检测，这些数据在研究年度内进行平均。然后使用0.50的切点将光密度比值（ODR）分为高和低两类。使用Cox比例风险生存模型分析产犊至受孕和产犊至首次输精间隔的治疗效果，并考虑牛群脆弱性效应。Aalen线性风险模型用于研究Cox模型中的时间变化效应。使用随机效应泊松回归模型对每次受孕的输精次数进行建模。模型中测试的其他预测变量包括胎次、产犊季节、研究地点、产奶高峰、ODR以及泌乳牛和干奶牛的圈养变量。总体而言，治疗对繁殖性能的三个指标没有显著影响。产犊季节的影响取决于产犊后经过的时间。据推测，这种影响反映了配种时的季节效应。年轻奶牛受孕的风险高于年长奶牛。早期配种的奶牛每次受孕的输精次数往往比晚期配种的奶牛多。研究结果表明，产犊时用伊维菌素治疗对繁殖没有益处。
