Department of Animal Sciences, North Florida Research and Education Center, University of Florida, Marianna, FL.
Agronomy Department, North Florida Research and Education Center, University of Florida, Marianna, FL.
J Anim Sci. 2020 Jun 1;98(6). doi: 10.1093/jas/skaa175.
An experiment was conducted during the winter of two consecutive years to evaluate the effects of feeding green-chopped cool-season forages on digestibility, ruminal fermentation, and blood parameters in beef steers. Nine ruminally cannulated Angus crossbred steers (year 1: 359 ± 79 kg; year 2: 481 ± 105 kg) received ad libitum green-chopped forages from pastures planted with one of the following mixtures: 1) OAT = Horizon 201 oats (Avena sativa L.)/Prine annual ryegrass (Lolium multiflorum Lam.) at 95 and 17 kg/ha, respectively; 2) RYE = FL401 cereal rye (Secale cereale L.)/Prine annual ryegrass (Lolium multiflorum Lam.) at 78 and 17 kg/ha, respectively; or 3) TRIT = Trical 342 triticale (X Triticosecale spp.)/Prine annual ryegrass (Lolium multiflorum Lam.) at 95 and 17 kg/ha, respectively. Intake was measured using the GrowSafe system and orts were discarded prior to subsequent feeding. After a 14-d adaptation, feed and fecal samples were collected twice daily for 4 d to determine apparent total tract nutrient digestibility using indigestible neutral detergent fiber (NDF) as an internal marker. On day 19, blood and ruminal fluid samples were collected every 3 h during a 24-h period to analyze plasma urea nitrogen (PUN) and glucose, ruminal pH, and concentration of ruminal ammonia nitrogen (NH3-N) and volatile fatty acids (VFA). Data were analyzed as a generalized randomized block design with repeated measures using the PROC MIX of SAS. No effect of treatment (P > 0.05) was observed for intake of dry matter, organic matter (OM), crude protein, NDF, or acid detergent fiber. Apparent total tract digestibility of nutrients was greater (P < 0.05) for OAT and TRIT when compared with RYE, with OM digestibility being 82.7%, 79.6%, and 69.5%, respectively. An effect of time (P < 0.01) was observed for ruminal pH. Plasma concentration of glucose was greater (P < 0.01) in steers consuming OAT, whereas steers fed RYE had greater (P < 0.05) concentrations of ruminal NH3-N and PUN, and the least concentration of total ruminal VFA (P < 0.05), despite having the greatest (P > 0.05) molar proportion of acetate, branched-chain VFA, and acetate:propionate. Increased nutrient digestibility and favorable ruminal fermentation and blood metabolites of OAT and TRIT are potentially conducive to enhanced growth performance when compared with RYE.
在连续两年的冬季进行了一项实验，以评估喂养绿色切碎的冷季饲草对肉牛干物质采食量、瘤胃发酵和血液参数的影响。9 头瘤胃切开的安格斯杂交公牛（第 1 年：359±79kg；第 2 年：481±105kg）自由采食来自种植以下混合物之一的牧场的绿色切碎饲草：1）OAT = Horizon 201 燕麦（Avena sativa L.）/普赖恩一年生黑麦草（Lolium multiflorum Lam.），分别为 95 和 17kg/ha；2）RYE = FL401 黑麦（Secale cereale L.）/普赖恩一年生黑麦草（Lolium multiflorum Lam.），分别为 78 和 17kg/ha；或 3）TRIT = Trical 342 小黑麦（X Triticosecale spp.）/普赖恩一年生黑麦草（Lolium multiflorum Lam.），分别为 95 和 17kg/ha。采用 GrowSafe 系统测量采食量，在随后的喂养前丢弃残渣。适应期 14d 后，每天两次收集 4d 的饲料和粪便样品，用不可消化的中性洗涤纤维（NDF）作为内标物测定表观全肠道养分消化率。在第 19 天，在 24h 期间每隔 3h 采集一次血液和瘤胃液样品，分析血浆尿素氮（PUN）和葡萄糖、瘤胃 pH 值以及瘤胃氨氮（NH3-N）和挥发性脂肪酸（VFA）浓度。数据采用 SAS 中的 PROC MIX 作为广义随机区组设计进行分析，采用重复测量。处理（P>0.05）对干物质、有机物（OM）、粗蛋白、NDF 或酸性洗涤剂纤维的采食量没有影响。与 RYE 相比，OAT 和 TRIT 的养分表观全肠道消化率更高（P<0.05），OM 消化率分别为 82.7%、79.6%和 69.5%。瘤胃 pH 值随时间（P<0.01）而变化。OAT 组牛的血浆葡萄糖浓度更高（P<0.01），而 RYE 组牛的瘤胃 NH3-N 和 PUN 浓度更高（P<0.05），总瘤胃 VFA 浓度最低（P<0.05），尽管乙酸、支链 VFA 和乙酸：丙酸的摩尔比例最高（P>0.05）。OAT 和 TRIT 的养分消化率提高、瘤胃发酵和血液代谢物良好，与 RYE 相比，可能有利于提高生长性能。
