Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK S7N 5A8, Canada.
J Anim Sci. 2013 Aug;91(8):3815-26. doi: 10.2527/jas.2012-5677. Epub 2013 May 8.
The objective of this study was to determine how harvest maturity of whole-crop cereals commonly used in swath grazing systems in western Canada affects yield, chemical composition, and in situ digestibility. We hypothesized that the increase in yield with advancing maturity would not offset the decline in digestibility and, thus, the yield of effectively degradable DM (EDDM) would decline with advanced stages of maturity. Four replicate plots of barley (Hordeum vulgare L.; cv. CDC Cowboy), millet (Panicum milliaceum; cv. Red Proso), oat (Avena sativa L., spp.; CDC Weaver), and wheat (Triticum aestivum L.; cv. 07FOR21) were grown, with a subsection in each replicate harvested at 4 different maturities: head elongation, late milk, hard dough, and fully mature. At each stage of maturity, the wet and DM yields, and chemical composition (DM, OM, NDF, crude fat, and nonfiber carbohydrates; NFC) were determined. Whole-crop samples were ground (2-mm screen) and weighed into nylon bags (pore size of 53 ± 10 µm), and duplicate incubation runs were conducted by crop type. For each incubation run, nylon bags were randomly allocated (randomized by field replication, stage of maturity, and incubation time) to 1 of 7 heifers (32 bags/heifer during each run). Degradation rates were determined using a first-order kinetic model and data were analyzed with stage of maturity as a fixed effect and plot as a random effect. The DM, OM, and NFC yields increased linearly for barley and oat (P < 0.001), and increased quadratically for millet and wheat (P ≤ 0.025). Neutral detergent fiber yield increased linearly for barley (P = 0.005) and quadratically for millet, oat, and wheat (P = 0.044). There were no changes in CP yield observed for barley, millet, or oat with advancing maturity, but there was a linear increase observed for wheat (P = 0.002). The NFC concentration increased linearly for barley, millet, and oat (P < 0.001), and quadratically for wheat (P < 0.001), whereas the EDDM concentration decreased quadratically for millet, oat, and wheat (P = 0.003). The degradation rate of NDF decreased linearly with advancing maturity (P ≤ 0.014) for millet, oat, and wheat, but was not affected for barley (P = 0.13). The yield EDDM increased linearly for barley and oat (P < 0.001), and increased quadratically for millet and wheat (P ≤ 0.025). These findings suggest that harvesting whole-crop annual cereals at the hard dough and mature stages may maximize the yield of EDDM.
本研究旨在确定在加拿大西部条播放牧系统中常用的全谷物的收获成熟度如何影响产量、化学成分和原位消化率。我们假设，随着成熟度的提高，产量的增加不会抵消消化率的下降，因此有效可降解 DM（EDDM）的产量将随着成熟度的提高而下降。在每个重复中，种植了 4 个大麦（Hordeum vulgare L.；cv. CDC Cowboy）、黍（Panicum miliaceum；cv. Red Proso）、燕麦（Avena sativa L.， spp.；CDC Weaver）和小麦（Triticum aestivum L.；cv. 07FOR21）的重复小区，每个重复小区的一个小区在 4 个不同的成熟度阶段进行收获：头部伸长、晚期牛奶、硬面团和完全成熟。在每个成熟度阶段，测定湿重和 DM 产量以及化学成分（DM、OM、NDF、粗脂肪和非纤维碳水化合物；NFC）。将全谷物样品粉碎（2 毫米筛）并称重到尼龙袋中（孔径为 53 ± 10 µm），并按作物类型进行两次重复培养。对于每个培养运行，将尼龙袋随机分配（按田间重复、成熟度阶段和培养时间随机分配）给 7 头奶牛中的 1 头（每个运行期间每个奶牛 32 个袋子）。使用一阶动力学模型确定降解率，并使用成熟度阶段作为固定效应和小区作为随机效应进行数据分析。大麦和燕麦的 DM、OM 和 NFC 产量呈线性增加（P <0.001），黍和小麦的产量呈二次增加（P ≤0.025）。大麦的中性洗涤剂纤维产量呈线性增加（P = 0.005），黍、燕麦和小麦的产量呈二次增加（P = 0.044）。随着成熟度的提高，大麦、黍或燕麦的 CP 产量没有观察到变化，但小麦的产量呈线性增加（P = 0.002）。大麦、黍和燕麦的 NFC 浓度呈线性增加（P <0.001），小麦的 NFC 浓度呈二次增加（P <0.001），而黍、燕麦和小麦的 EDDM 浓度呈二次减少（P = 0.003）。随着成熟度的提高，NDF 的降解率呈线性下降（P ≤0.014），对大麦、燕麦和小麦均有影响，但对大麦无影响（P = 0.13）。大麦和燕麦的 EDDM 产量呈线性增加（P <0.001），黍和小麦的 EDDM 产量呈二次增加（P ≤0.025）。这些发现表明，在硬面团和成熟阶段收获全谷物一年生谷物可能会最大限度地提高 EDDM 的产量。
