ABSTRACT

Precise and continual information on the energy supply from pasture is mandatory for managing grazing ruminants. Therefore, estimating the organic matter (OM) digestibility from faecal crude protein concentration using the regression equation, OM digestibility [%] = 79.76–107.7 · e^{(−0.01515 · faecal crude protein [g/kg OM])}, is known to be a suitable tool. However, essential information regarding faeces sampling times and the required number of samples are not yet available. We therefore analysed the OM digestibility data of an experiment with dairy cows grazing two pasture types and receiving two concentrate types over 6 d in three independent runs. Both pasture type and grazing day affected the OM digestibility estimates, whereas concentrate type and intake did not, indicating that this method reliably detects small changes in OM digestibility of pasture without being interfered by moderate concentrate supplementation, selective grazing behaviour or differences in feed intake. Likewise, as sampling time did not influence OM digestibility, faeces sampling once daily can be recommended to be sufficient for an accurate estimation of OM digestibility. The variance within pasture type and grazing day amounted for 1.1 percentage units of estimated OM digestibility, which enabled to define the minimum sample number required to detect given differences in OM digestibility with adequate statistical certainty. In conclusion, estimating OM digestibility from faecal crude protein concentration is an applicable and sensitive method to reliably detect differences in the quality of ingested pasture using a limited number of animals. Therefore, instructions for faeces sample collection were provided.

摘要

牧场能源供应的精确和持续信息是管理放牧反刍动物的必要条件。因此，使用回归方程根据粪便粗蛋白浓度估算有机物质 (OM) 消化率，OM 消化率 [%] = 79.76–107.7 · e ^{(-0.01515 · 粪便粗蛋白 [g/kg OM])}, 被认为是一个合适的工具。然而，关于粪便采样时间和所需样本数量的基本信息尚不可用。因此，我们分析了奶牛在 6 天内在三个独立运行中放牧两种牧场并接受两种浓缩类型的实验的 OM 消化率数据。牧草类型和放牧日数都会影响 OM 消化率估计值，而精料类型和摄入量没有影响，这表明该方法可靠地检测了牧草 OM 消化率的微小变化，而不受中等精料补充、选择性放牧行为或采食量差异的干扰。同样，由于采样时间不影响 OM 消化率，建议每天采样一次粪便足以准确估计 OM 消化率。牧场类型和放牧日内的差异为估计 OM 消化率的 1.1% 单位，这使得能够以足够的统计确定性定义检测 OM 消化率的给定差异所需的最小样本数。总之，从粪便粗蛋白浓度估计 OM 消化率是一种适用且灵敏的方法，可以可靠地检测使用数量有限的动物摄入的牧场质量差异。因此，提供了粪便样本收集说明。从粪便粗蛋白浓度估计 OM 消化率是一种适用且灵敏的方法，可以使用有限数量的动物可靠地检测摄入的牧场质量的差异。因此，提供了粪便样本收集说明。从粪便粗蛋白浓度估计 OM 消化率是一种适用且灵敏的方法，可以使用有限数量的动物可靠地检测摄入的牧场质量的差异。因此，提供了粪便样本收集说明。