Ruakura Research Centre, AgResearch Limited, Hamilton, New Zealand.
Invermay Agricultural Centre, AgResearch Limited, Mosgiel, New Zealand.
J Anim Sci. 2020 Mar 1;98(3). doi: 10.1093/jas/skaa055.
The reproductive performance of a sheep flock is dependent on a multitude of complex interacting factors. Achieving optimal flock performance requires knowledge of the reproductive steps and how these are linked and related to available measurements of the state and performance of the flock. The goal was to use previously collected data from a research flock that had undergone selection for fecundity (11,369 lambing records), to model the key reproductive steps affecting flock reproductive performance. The model was used to investigate how changes in liveweight, age, ovulation rate, number of fetuses at midpregnancy, number of lambs born, and birthweight affect the number of lambs weaned and the weaning weight of each lamb in this flock. The data available from the research flock were used to parameterize models of each reproductive step and assess the role of ewe age and premating liveweight on each reproductive step. These models were then linked together as a simulation tool to assess the role of different parameters on flock reproductive performance, which was defined as the total weight of lambs weaned per ewe exposed to the ram. Flock elasticities were calculated that characterize the relative importance of the effect of average premating ewe liveweight (0.81), average ovulation rate (0.33), variance in ovulation rate (-0.095), embryo survival (0.72), lamb survival (1.03), conception failure (0.35), and average ewe age (0.056) on the total kilograms of lamb liveweight at weaning per ewe exposed to the ram. The largest elasticity for lamb survival indicated that a 1% increase in lamb survival is expected to have a 1.03% increase in the total kilograms of lamb liveweight at weaning per ewe exposed to the ram in this flock. Assuming similar costs, interventions to increase lamb survival for this flock will provide the largest increase in the total kilograms of lamb liveweight at weaning per ewe exposed to the ram, which is a key metric of flock performance.
绵羊群的繁殖性能取决于许多复杂的相互作用因素。要实现最佳的羊群性能，就需要了解繁殖步骤，以及这些步骤如何相互关联，并与羊群的状态和性能的可用测量值相关联。目的是利用已经进行了繁殖力选择的研究羊群中收集到的先前数据（11369 次产羔记录），对影响羊群繁殖性能的关键繁殖步骤进行建模。该模型用于研究活重、年龄、排卵率、妊娠中期胎儿数量、产羔数和初生重的变化如何影响断奶羔羊数量和每只羔羊的断奶体重。研究羊群中可用的数据被用于对每个繁殖步骤的模型进行参数化，并评估母羊年龄和配种前活重对每个繁殖步骤的作用。然后，这些模型被链接在一起作为一个模拟工具，以评估不同参数对羊群繁殖性能的作用，该性能被定义为每只接触公羊的断奶母羊所产羔羊的总重量。计算了羊群的弹性，这些弹性特征描述了平均配种前母羊活重（0.81）、平均排卵率（0.33）、排卵率变异（-0.095）、胚胎存活率（0.72）、羔羊存活率（1.03）、配种失败率（0.35）和平均母羊年龄（0.056）对每只接触公羊的断奶母羊所产羔羊活重总公斤数的相对重要性。羔羊存活率的最大弹性表明，在该羊群中，羔羊存活率增加 1%，预计每只接触公羊的断奶母羊所产羔羊活重总公斤数将增加 1.03%。假设成本相似，为提高该羊群的羔羊存活率而采取的干预措施将使每只接触公羊的断奶母羊所产羔羊活重总公斤数增加最多，这是羊群性能的一个关键指标。
