United States Department of Agriculture, Agricultural Research Service, Forage-Animal Production Research Unit, Lexington, KY 40506, USA.
Department of Animal and Food Sciences, University of Kentucky, Lexington, KY 40506, USA.
J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skad036.
Red clover produces isoflavones, including biochanin A, which have been shown to have microbiological effects on the rumen while also promoting growth in beef cattle. The objective was to determine if supplementation of biochanin A via red clover hay would produce similar effects on the rumen microbiota and improve growth performance of lambs. Twenty-four individually-housed Polypay ram lambs (initial age: 114 ± 1 d; initial weight: 38.1 ± 0.59 kg) were randomly assigned to one of three experimental diets (85:15 concentrate:roughage ratio; N = 8 rams/treatment): CON-control diet in which the roughage component (15.0%, w/w, of the total diet) consisted of orchardgrass hay; 7.5-RC-red clover hay substituted for half (7.5%, w/w, of the total diet) of the roughage component; and 15-RC-the entire roughage component (15.0%, w/w, of the total diet) consisted of red clover hay. Feed intake and weight gain were measured at 14-d intervals for the duration of the 56-d trial, and rumen microbiological measures were assessed on days 0, 28, and 56. Red clover supplementation impacted growth performance of ram lambs. Average daily gains (ADG) were greater in ram lambs supplemented with red clover hay (7.5-RC and 15-RC) than for those fed the CON diet (P < 0.05). Conversely, dry matter intake (DMI) was lower in 7.5-RC and 15-RC than for CON lambs (P = 0.03). Differences in ADG and DMI resulted in greater feed efficiency in ram lambs supplemented with red clover hay (both 7.5-RC and 15-RC) compared to CON (P < 0.01). Rumen microbiota were also altered by red clover supplementation. The total viable number of hyper-ammonia-producing bacteria in 7.5-RC and 15-RC decreased over the course of the experiment and were lower than CON by day 28 (P ≤ 0.04). Amylolytic bacteria were also lower in 15-RC than in CON (P = 0.03), with a trend for lower amylolytic bacteria in 7.5-RC (P = 0.08). In contrast, there was tendency for greater cellulolytic bacteria in red clover supplemented lambs than in CON (P = 0.06). Red clover supplementation also increased fiber utilization, with greater ex vivo dry matter digestibility of hay for both 7.5-RC and 15-RC compared to CON by day 28 (P < 0.03). Results of this study indicate that low levels of red clover hay can elicit production benefits in high-concentrate lamb finishing systems through alteration of the rumen microbiota.
红三叶草产生异黄酮，包括开环异落叶松脂素 A，已被证明对瘤胃具有微生物学作用，同时促进肉牛生长。目的是确定通过红三叶草干草补充开环异落叶松脂素 A 是否会对瘤胃微生物群产生类似的影响，并提高羔羊的生长性能。24 只单独饲养的 Polypay 公羊羔羊（初始年龄：114 ± 1 天；初始体重：38.1 ± 0.59 公斤）被随机分配到三种实验饮食中的一种（85:15 浓缩物：粗饲料比；N = 8 只公羊/处理）：CON-对照饮食，粗饲料成分（总饮食的 15.0%，w/w）由果园草干草组成；7.5-RC-红三叶草干草代替总饮食的一半（7.5%，w/w）的粗饲料成分；15-RC-整个粗饲料成分（总饮食的 15.0%，w/w）由红三叶草干草组成。在 56 天试验期间，每隔 14 天测量一次饲料摄入量和体重增加，在第 0、28 和 56 天评估瘤胃微生物学指标。红三叶草的补充影响了公羊羔羊的生长性能。补充红三叶草干草的公羊羔羊（7.5-RC 和 15-RC）的平均日增重（ADG）高于喂食 CON 饮食的羔羊（P < 0.05）。相反，7.5-RC 和 15-RC 羔羊的干物质摄入量（DMI）低于 CON 羔羊（P = 0.03）。ADG 和 DMI 的差异导致补充红三叶草干草的公羊羔羊的饲料效率更高（7.5-RC 和 15-RC 均高于 CON）（P < 0.01）。红三叶草的补充还改变了瘤胃微生物群。7.5-RC 和 15-RC 中产生高氨细菌的总活菌数在实验过程中下降，到第 28 天低于 CON（P ≤ 0.04）。15-RC 中的淀粉分解菌也低于 CON（P = 0.03），7.5-RC 中的淀粉分解菌呈下降趋势（P = 0.08）。相比之下，补充红三叶草的羔羊中纤维素分解菌有增加的趋势（P = 0.06）。红三叶草的补充还提高了纤维利用率，到第 28 天，7.5-RC 和 15-RC 的体外干物质消化率均高于 CON（P < 0.03）。本研究结果表明，低水平的红三叶草干草可以通过改变瘤胃微生物群，在高浓缩物羔羊育肥系统中产生生产效益。
