Developing a continuous adjustment factor for dry matter intake of gestating and lactating ewes

ABSTRACT: Intake is a multifactorial process that is influenced by animal type, environmental factors, and diet characteristics. Sheep, especially, have specific eating habits, with a greater selection of ingested feed compared to cattle. Thus, predictive equations for dry matter intake (DMI) must constantly be reviewed. The objective of this study was to combine different adjustment factors to develop one continuous adjustment factor for predicting the DMI of pregnant, dry, and lactating ewes. The equations evaluated for non-lactation ewes accounts for metabolic body weight and weight gain, and the equation for lactating ewes includes milk production and its fat content. The database used in this study was pooled from hair sheep ewes, two to four years old, with controlled feeding, during the pregnancy and lactating physiological phases. For the overall predictions (gestating and lactating ewes), the adjusted DMI prediction had greater accuracy but lower precision than the unadjusted DMI prediction. However, adjusting DMI increased the adequacy of the prediction as the mean square error of prediction difference (ΔMSEP) decreased (p = 0.0328). Similarly, for gestating ewes, the adjusted predicted DMI had a lower ΔMSEP than the unadjusted predicted DMI (p < 0.001). For lactating ewes, no difference was detected between the adjusted and unadjusted predicted DMI based on the ΔMSEP statistics (p = 0.3672), but the assumption that peak milk was 28 days (default) worsened the predictability of the adjusted predicted DMI as it had lower precision and accuracy. Adjustments for predicted DMI of dry and lactating ewes are necessary to increase adequacy and precision.

摘要：采食量是一个受动物品种、环境因素及日粮特性共同影响的多因子过程。其中，绵羊具有独特的采食习性，相较于牛类，其对采食饲料的选择性更强。因此，干物质采食量（dry matter intake, DMI）的预测方程需持续进行审核与更新。本研究旨在整合多种校正因子，构建统一的连续校正因子，用于预测妊娠母羊（gestating ewes）、干奶母羊（dry ewes）及泌乳母羊（lactating ewes）的干物质采食量。本研究评估的非泌乳母羊预测方程纳入了代谢体重（metabolic body weight）与体增重（weight gain）两项指标，而泌乳母羊的预测方程则包含产奶量（milk production）及其乳脂率（fat content）两项参数。本研究所用数据集汇集自2~4岁毛用绵羊（hair sheep）母羊，涵盖其妊娠与泌乳两个生理阶段，且饲喂管理均处于可控状态。针对妊娠与泌乳母羊的整体预测结果显示，经校正的干物质采食量预测值相较于未校正预测值，具有更高的准确性，但精确性稍低。不过，通过校正干物质采食量可提升预测的适宜性，表现为预测均方误差差（mean square error of prediction difference, ΔMSEP）显著降低（p=0.0328）。同样地，针对妊娠母羊，经校正的干物质采食量预测值的ΔMSEP显著低于未校正预测值（p<0.001）。而就泌乳母羊而言，基于ΔMSEP统计指标，校正与未校正的干物质采食量预测值之间未检测到显著差异（p=0.3672）；但当默认泌乳峰值出现在第28天的假设被采用时，经校正的预测模型的预测性能出现下降，表现为精确性与准确性均有所降低。为提升预测的适宜性与精确性，对干奶母羊与泌乳母羊的干物质采食量预测模型进行校正是十分必要的。