Bowley F E, Green R E, Amer P R, Meier S
AbacusBio Limited, Dunedin 9058, New Zealand.
AbacusBio Limited, Dunedin 9058, New Zealand.
J Dairy Sci. 2015 Mar;98(3):2005-12. doi: 10.3168/jds.2014-8266. Epub 2015 Jan 15.
The fertility of dairy cattle in New Zealand is well below industry targets, and the current New Zealand fertility breeding value (BV) could potentially be improved using additional information and traits. Data from 169 herds were analyzed to determine the benefits of using alternative phenotypic measures in the calculation of the fertility BV. The heritability of calving season day (CSD; calving season day as an integer day of the year) and the probability of an animal calving within 42 d of the planned start of calving (CR42) increased modestly (from 0.0206 to 0.0213 and 0.0087 to 0.0092, respectively) after accounting for the use of intravaginal progesterone-releasing devices for treatment of anestrous cows (anestrum treatment) and induced calvings. Incidence of either anestrum treatment or calving induction as a single binomial trait (AT/IND) had a heritability of 0.0223 and showed moderate genetic correlation with the probability of an animal being mated within 21 d of the planned start of mating (PM21; -0.4473), but much higher with CSD (0.8445). The use of pregnancy diagnosis data allowed fertility information that would otherwise be discarded to be included in analyses; when used to assign a prolonged CSD and a value of 0 for CR42 to animals that failed to calve, it increased the heritabilities of both of these traits (to 0.0278 and 0.0114, respectively). Because CSD was found to be more than twice as heritable as its binary counterpart, it shows potential to replace CR42 as the calving trait used in the fertility BV. Postpartum anestrous interval (PPAI), derived using incomplete premating estrous recording in some herds, had a heritability of 0.0813 and hence has potential as a trait to be included in genetic improvement programs but would require more rigorous recording of estrous during the premating period to be an effective trait. Based on selection index theory, the modifications made to current selection criteria using novel fertility traits increased the accuracy of prediction of fertility merit by more than 12%. Because of the increasing economic importance of fertility traits, and low heritabilities requiring large numbers of recorded daughters to get accurate fertility BV predictions on sires, data recorded on farm will become increasingly important in the genetic improvement of fertility.
新西兰奶牛的繁殖力远低于行业目标，利用额外信息和性状有可能提高当前新西兰的繁殖力育种值（BV）。对169个牛群的数据进行了分析，以确定在繁殖力BV计算中使用替代表型测量方法的益处。在考虑使用阴道内孕酮释放装置治疗乏情母牛（乏情期治疗）和诱导产犊后，产犊季节日（CSD；一年中的整数日产犊季节日）和动物在计划产犊开始后42天内产犊的概率（CR42）的遗传力略有增加（分别从0.0206增加到0.0213，从0.0087增加到0.0092）。将乏情期治疗或诱导产犊作为单一二项性状（AT/IND）的发生率的遗传力为0.0223，与动物在计划配种开始后21天内配种的概率（PM21；-0.4473）显示出中等遗传相关性，但与CSD的相关性更高（0.8445）。使用妊娠诊断数据可将原本会被丢弃的繁殖力信息纳入分析；当用于将延长的CSD和CR42值0分配给未产犊的动物时，这两个性状的遗传力均有所提高（分别提高到0.0278和0.0114）。由于发现CSD的遗传力是其二分类对应性状的两倍多，它显示出有潜力取代CR42作为繁殖力BV中使用的产犊性状。在一些牛群中，利用不完整的配种前发情记录得出的产后乏情间隔（PPAI）的遗传力为0.0813，因此有潜力作为一个性状纳入遗传改良计划，但需要在配种前期更严格地记录发情情况才能成为一个有效的性状。基于选择指数理论，使用新的繁殖力性状对当前选择标准进行的修改使繁殖力优劣预测的准确性提高了12%以上。由于繁殖力性状的经济重要性日益增加，且遗传力较低，需要大量记录女儿才能准确预测公牛的繁殖力BV，农场记录的数据在繁殖力的遗传改良中将变得越来越重要。
