PDF(Sci-hub)
Abstract：
Provision of nutrients in appropriate amounts to meet nutrient requirements for growth, production, and reproduction is the basis for modern animal nutrition. Ration formulation systems predict nutrient requirements based on numerous inputs and then predict nutrient supply based on predicted intake and nutrient content of feeds. Energy systems are used to predict energy supply based on gross caloric content of feeds followed by adjustments for digestion and metabolism of ingested energy. Many models of energy supply use static coefficients of digestibility based on nutrient composition of feed. Other models partition digestion dynamically between ruminal and postruminal digestion but use static estimates of intestinal digestibility to predict energy supplied to the animal. In young calves, both ruminal fermentation and intestinal digestion are underdeveloped; therefore, existing models of energy supply might overestimate the energy available before complete gastrointestinal maturation. In a series of experiments, we reported that total-tract digestion of nutrients changes with advancing age and nutrient intake. Total-tract digestion was measured in calves from 3 to 16 wk of age when fed different amounts and types of milk replacers. Calves were also fed different types of calf starter for ad libitum consumption. Total-tract digestibility of protein, fat, neutral detergent fiber, and nonfiber carbohydrate (NFC) was used to calculate the metabolizable energy (ME) in starter. We used nonlinear regression to estimate the contribution of protein and fat from starter and milk replacer before weaning. Early in life, calculated ME of starter was low and increased with increasing intake of NFC. Cumulative intake of NFC was more highly correlated with changing ME values than other indices, including age, intake of milk replacer, or intake of other nutrients in starter. When calves consumed at least of 15 kg of NFC, ME calculated from digestibility measurements was similar to the ME calculated using National Research Council equations and indicated maturation of gastrointestinal digestion. Our data suggest that intake of NFC is critical to gastrointestinal maturation and the calf\'s ability to extract energy from calf starter.
摘要：
提供适量的营养，以满足生长所需的营养，生产,繁殖是现代动物营养的基础。口粮配方系统基于大量输入来预测营养需求，然后基于预测的饲料摄入量和营养含量来预测营养供应。能量系统用于根据饲料的总热量含量来预测能量供应，然后调整摄入的能量的消化和代谢。许多能量供应模型使用基于饲料营养成分的静态消化率系数。其他模型在瘤胃和腔后消化之间动态地划分消化，但使用肠道消化率的静态估计来预测提供给动物的能量。在小牛中，瘤胃发酵和肠道消化都不发达；因此，现有的能量供应模型可能会高估胃肠道完全成熟之前的可用能量。在一系列的实验中,我们报告说，随着年龄的增长和营养摄入量的增加，营养的全道消化会发生变化。当饲喂不同数量和类型的代乳品时，在3至16周龄的小牛中测量了总肠道消化。还饲喂了不同类型的小牛发酵剂，以随意食用。蛋白质的全道消化率，脂肪，中性洗涤剂纤维，和非纤维碳水化合物（NFC）用于计算初始代谢能（ME）。我们使用非线性回归来估计断奶前发酵剂和牛奶替代品中蛋白质和脂肪的贡献。在生命早期,计算的起始物ME较低，并且随着NFC摄入量的增加而增加。与其他指标相比，NFC的累积摄入量与ME值变化的相关性更高，包括年龄,牛奶替代品的摄入量，或摄入其他营养素。当小牛消耗至少15公斤的NFC，从消化率测量中计算出的ME与使用国家研究委员会方程式计算出的ME相似，并表明胃肠道消化成熟。我们的数据表明，摄入的NFC是至关重要的胃肠道成熟和小腿的能力，从小腿发酵剂提取能量。
