Mutsvangwa T, Kiran D, Abeysekara S
Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK, Canada, S7N 5A8.
Department of Animal and Poultry Science, University of Saskatchewan, Saskatoon, SK, Canada, S7N 5A8.
J Dairy Sci. 2016 Feb;99(2):1216-1227. doi: 10.3168/jds.2015-9991. Epub 2015 Dec 17.
The objective of this study was to determine the effects of feeding canola meal (CM) or wheat dried distillers grains with solubles (W-DDGS) as the major source of protein in diets varying in crude protein (CP) content on ruminal fermentation, microbial protein production, omasal nutrient flow, and production performance in lactating dairy cows. Eight lactating dairy cows were used in a replicated 4×4 Latin square design with 29-d periods (21 d of dietary adaptation and 8 d of measurements) and a 2×2 factorial arrangement of dietary treatments. Four cows in 1 Latin square were ruminally cannulated to allow ruminal and omasal sampling. The treatment factors were (1) source of supplemental protein (CM vs. W-DDGS) and (2) dietary CP content (15 vs. 17%; DM basis). Diets contained 50% forage and 50% concentrate, and were fed twice daily at 0900 and 1600 h as total mixed rations for ad libitum intake. Dry matter intake and milk yield were unaffected by dietary treatments; however, milk yield in cows that were fed CM was numerically greater (+1.1 kg/d) when compared with cows fed W-DDGS. Feeding CM increased milk lactose content compared with feeding W-DDGS. Milk urea nitrogen and ruminal NH3-N concentrations were greater in cows fed the high-CP compared with those fed the low-CP diet. The rumen-degradable protein supply was greater in cows fed the high-CP when compared with those fed the low-CP diet when diets contained CM, whereas rumen-degradable protein supply was lower in cows fed the high-CP when compared with those fed the low-CP diet when diets contained W-DDGS. Total N flow at the omasal canal was not affected by diet; however, omasal flow of NH3-N was greater in cows fed CM when compared with those fed W-DDGS. The rumen-undegradable protein supply was greater in cows fed the low-CP when compared with those fed the high-CP diet when diets contained CM, whereas rumen-undegradable protein supply was lower in cows fed the low-CP when compared with those fed the high-CP diet when diets contained W-DDGS. Omasal flow of fluid-associated bacteria was greater and that of particle-associated bacteria tended to be greater in cows fed CM when compared with those fed W-DDGS; however, omasal flow of total microbial nonammonia N was unaffected by dietary treatment. Omasal flows of threonine and tryptophan were greater, whereas that of histidine and lysine tended to be greater in cows fed CM when compared with those fed W-DDGS. Our results show that when dairy diets are formulated to contain 15 or 17% CP, CM or W-DDGS can be used as the major source of protein and achieve similar levels of milk production.
本研究的目的是确定在粗蛋白（CP）含量不同的日粮中，以油菜籽粕（CM）或小麦干酒糟及其可溶物（W-DDGS）作为主要蛋白质来源，对泌乳奶牛瘤胃发酵、微生物蛋白产生、瘤胃营养物质流量和生产性能的影响。八头泌乳奶牛采用重复的4×4拉丁方设计，每期29天（21天日粮适应期和8天测量期），日粮处理采用2×2析因安排。1个拉丁方中的4头奶牛安装了瘤胃瘘管，以便进行瘤胃和瘤胃内容物采样。处理因素为：（1）补充蛋白质的来源（CM与W-DDGS）和（2）日粮CP含量（15%与17%；以干物质计）。日粮中粗饲料和精饲料各占50%，每天0900和1600时各投喂1次，以全混合日粮形式自由采食。干物质采食量和产奶量不受日粮处理的影响；然而，与饲喂W-DDGS的奶牛相比，饲喂CM的奶牛产奶量在数值上更高（+1.1千克/天）。与饲喂W-DDGS相比，饲喂CM可提高牛奶乳糖含量。与饲喂低CP日粮的奶牛相比，饲喂高CP日粮的奶牛牛奶尿素氮和瘤胃NH₃-N浓度更高。当日粮含CM时，与饲喂低CP日粮的奶牛相比，饲喂高CP日粮的奶牛瘤胃可降解蛋白供应量更大；而当日粮含W-DDGS时，与饲喂低CP日粮的奶牛相比，饲喂高CP日粮的奶牛瘤胃可降解蛋白供应量更低。瘤胃通道处的总氮流量不受日粮影响；然而，与饲喂W-DDGS的奶牛相比，饲喂CM的奶牛瘤胃NH₃-N流量更大。当日粮含CM时，与饲喂高CP日粮的奶牛相比，饲喂低CP日粮的奶牛瘤胃不可降解蛋白供应量更大；而当日粮含W-DDGS时，与饲喂高CP日粮的奶牛相比，饲喂低CP日粮的奶牛瘤胃不可降解蛋白供应量更低。与饲喂W-DDGS的奶牛相比，饲喂CM的奶牛瘤胃内容物中与液体相关的细菌流量更大，与颗粒相关的细菌流量也有增加的趋势；然而，日粮处理对瘤胃总微生物非氨氮流量没有影响。与饲喂W-DDGS的奶牛相比，饲喂CM的奶牛瘤胃内容物中苏氨酸和色氨酸的流量更大，组氨酸和赖氨酸的流量也有增加的趋势。我们的结果表明，当日粮CP含量为15%或17%时，CM或W-DDGS均可作为主要蛋白质来源，并实现相似的产奶水平。
