Hatfield P G, Clanton D C, Eskridge K M, Sanson D W
University of Nebraska, North Platte 69101.
J Anim Sci. 1989 Nov;67(11):3018-27. doi: 10.2527/jas1989.67113018x.
Two feeding trials (early and late lactation) were conducted to measure ad libitum forage intake by beef cows from three breed groups of similar mature weight, but with different milk production potential. Twenty-four cow-calf units, eight from each milk production level (low, medium and high) were grouped (two/pen) based on similarity of cow weight and previous weigh-suckle-weigh and calf weaning weight data. Each pair of cow-calf units was confined to separate pens and allowed ad libitum access to chopped native Sandhills meadow hay. Dry matter intake, cow and calf BW and calf milk consumption were determined. Daily DMI (kg/hd) and milk consumption showed a positive linear response (P less than .05) among low, medium and high milk-producing cows. When cow DMI was expressed as g/unit mean cow BW during the trial, both a positive linear (P less than .05) and a quadratic response (P less than .01) expressed the relationship among production levels during early and late lactation. Calf forage intake, birth weight and adjusted 181- and 205-d weaning weight had no linear or quadratic relationship (P greater than .10) to milk production levels. However, June 1 calf weight, actual calf weaning weight and calf rate of gain (birth to weaning) had a positive linear (P less than .07) relationship. Best fit regression models with DMI as the dependent variable were developed for each trial based on R2 and CV values of the potential models. The best fit model (R2 = .94, SE = .33) for early lactation included production level as a class variable with cow BW.75 and calf birth weight as independent variables. The best fit model (R2 = .92, SE = .53) for late lactation included actual weaning weight in addition to the variables used during early lactation.
进行了两项饲养试验（泌乳早期和晚期），以测量来自三个成熟体重相似但产奶潜力不同的品种组的肉牛母牛的随意采食量。根据母牛体重以及之前的称重-哺乳-称重和犊牛断奶体重数据的相似性，将24个母牛-犊牛单元（每个产奶水平8个）进行分组（每栏2个）。每对母牛-犊牛单元被关在单独的栏中，并允许随意采食切碎的本地沙丘草甸干草。测定了干物质摄入量、母牛和犊牛体重以及犊牛的牛奶消耗量。低、中、高产奶母牛的每日干物质摄入量（千克/头）和牛奶消耗量呈正线性反应（P小于0.05）。当将母牛的干物质摄入量表示为试验期间每单位平均母牛体重的克数时，在泌乳早期和晚期，正线性反应（P小于0.05）和二次反应（P小于0.01）均表示了生产水平之间的关系。犊牛的采食量、出生体重以及校正后的181天和205天断奶体重与产奶水平无线性或二次关系（P大于0.10）。然而，6月1日的犊牛体重、实际犊牛断奶体重和犊牛增重率（出生至断奶）呈正线性关系（P小于0.07）。根据潜在模型的R2和CV值，为每个试验建立了以干物质摄入量为因变量的最佳拟合回归模型。泌乳早期的最佳拟合模型（R2 = 0.94，SE = 0.33）包括将生产水平作为分类变量，以及母牛体重0.75和犊牛出生体重作为自变量。泌乳晚期的最佳拟合模型（R2 = 0.92，SE = 0.53）除了包括泌乳早期使用的变量外，还包括实际断奶体重。
