The 2014 and 2018 Farm Bills defined hemp (Cannabis sativa L.) as an agricultural commodity and removed it from the controlled substances list, developing a pathway for commercialization and increasing interest in cultivating hemp in the United States. Demand for therapeutic, cannabinoid-based hemp products is increasing, and, as not all of the plant components are utilized for these products, there will likely be significant quantities of hemp by-products created. As these by-products are cellulosic, they may be marketed as livestock feed, especially for ruminant animals. There have been limited studies into hemp as cattle feed. Accordingly, the objective of this study was to determine the in-situ degradability of different hemp components in beef cattle. We conducted an in-situ trial with three ruminally cannulated steers (IACUC #8497) and 16 unique hemp samples: leaves, flower, stalk, or whole plant cultivated with four different seed inoculants. Samples were incubated in the rumen for 0, 4, 6, 12, 24, 48, and 72 h and replicated across each steer. After samples were removed, they were rinsed and analyzed for partial dry matter (DM), DM, organic matter (OM), and crude protein (CP). Solubility fractions [immediately soluble (IS), potentially soluble (PS), and not soluble [NS]), rate of degradation (kd), and rumen degradability was determined for OM and CP. Rate of passage (kp) was set at 4.7%. As there were not differences across seed inoculant method, data were combined across plant components. For OM, the NS fraction was greatest for hemp stalks (12%) and least for leaves (7%). The PS fraction ranged 72-75% across plant components with the least value for stalks and greatest for leaves. Of the PS fraction, ruminal OM degradability was lowest for stalks (51%) and highest for leaves (72%). For CP, the NS fraction of hemp stalks (16%) was greater than other fractions, which ranged from 6-8%. The PS fraction was approximately 76% for both whole plant and leaves, a vast majority of which (71-73%) was degradable, indicating these plant components provide a good source of rumen degradable protein. The IS fraction was largest (20%) for hemp flower. Although hemp flower may be easily digested by ruminants, it does not have practical value because this plant component competes in the human market as the flower contains an increased percentage of cannabinoids which have therapeutic properties. Ultimately, our data indicate that hemp leaves have nutritional and practical value as feed for beef cattle and that hemp stalks would likely not be well-utilized as a forage source. Before hemp can be integrated into the beef cattle industry as feed, additional research is required to determine the effects of feeding hemp on animal performance and evaluate uptake and retention of cannabinoids in body tissues.

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156 大麻 (Cannabis sativa L.) 植物成分在牛体内的原位降解性

2014 年和 2018 年农业法案将大麻 (Cannabis sativa L.) 定义为农产品，并将其从受控物质清单中删除，开辟了商业化途径并增加了美国种植大麻的兴趣。对基于大麻素的治疗性大麻产品的需求正在增加，并且由于并非所有植物成分都用于这些产品，因此可能会产生大量的大麻副产品。由于这些副产品是纤维素的，因此它们可以作为牲畜饲料销售，特别是反刍动物饲料。关于大麻作为牛饲料的研究有限。因此，本研究的目的是确定肉牛中不同大麻成分的原位降解性。我们对三头瘤胃插管牛 (IACUC #8497) 和 16 个独特的大麻样品进行了现场试验：用四种不同种子接种剂培育的叶子、花、茎或整株植物。样品在瘤胃中孵育 0、4、6、12、24、48 和 72 小时，并在每头公牛中重复。取出样品后，对其进行漂洗并分析部分干物质 (DM)、DM、有机物 (OM) 和粗蛋白 (CP)。确定 OM 和 CP 的溶解度分数 [立即可溶 (IS)、潜在可溶 (PS) 和不可溶 [NS]）、降解率 (kd) 和瘤胃降解性。通过率(kp)设定为4.7%。由于种子接种方法之间没有差异，因此将不同植物成分的数据合并。对于 OM，大麻茎的 NS 分数最大 (12%)，叶子最小 (7%)。植物各部分的 PS 分数范围为 72-75%，其中茎的值最低，叶的值最高。在 PS 部分中，茎的瘤胃 OM 降解性最低（51%），叶最高（72%）。对于 CP，大麻秆的 NS 部分 (16%) 高于其他部分，范围为 6-8%。整个植物和叶子的 PS 分数约为 76%，其中绝大多数 (71-73%) 可降解，表明这些植物成分提供了瘤胃可降解蛋白的良好来源。大麻花的 IS 比例最大（20%）。尽管大麻花可能很容易被反刍动物消化，但它没有实用价值，因为这种植物成分在人类市场上竞争，因为大麻花含有较高比例的具有治疗特性的大麻素。最终，我们的数据表明，大麻叶作为肉牛饲料具有营养和实用价值，而大麻秆可能不会被充分利用作为饲料来源。在大麻作为饲料融入肉牛行业之前，需要进行额外的研究来确定喂养大麻对动物性能的影响，并评估身体组织中大麻素的吸收和保留。