Wang C, Liu Q, Guo G, Huo W J, Pei C X, Zhang S L, Yang W Z
College of Animal Science and Veterinary Medicine, Shanxi Agricultural University, Taigu, China.
Research Centre, Agriculture and Agri-Food Canada, Lethbridge, AB, Canada.
J Anim Physiol Anim Nutr (Berl). 2018 Jun;102(3):611-619. doi: 10.1111/jpn.12797. Epub 2017 Nov 2.
The objective of this study was to evaluate the effects of dietary crude protein (CP) levels and 2-methylbutyrate (MB) supplementation on ruminal fermentation, bacterial populations, microbial enzyme activity and urinary excretion of purine derivatives (PD) in Simmental steers. Eight ruminally cannulated Simmental steers, averaging 18 months of age and 465 ± 8.6 kg of body weight (BW), were used in a replicated 4 × 4 Latin square design by a 2 × 2 factorial arrangement. Low protein (98.5 g CP/kg dry matter [LP] or high protein (128.7 g CP/kg dry matter [HP]) diets were fed with MB supplementation (0 g [MB-] or 16.8 g steer day [MB+]). Steers were fed a total mixed ration with dietary corn straw to concentrate ratio of 50:50 (dry matter [DM] basis). The CP × MB interaction was observed for ruminal total VFA, molar proportions of acetate and propionate, acetate to propionate ratio, ammonia-N, effective degradability of neutral detergent fibre (NDF) and CP, microbial enzyme activity, bacterial populations and total PD excretion (p < .05). Ruminal pH decreased (p < .05), but ruminal total VFA concentration increased (p < .05) with increasing dietary CP level or MB supplementation. Acetate molar proportion increased (p = .043) with MB supplementation, but was not affected by dietary CP level. Propionate molar proportion decreased (p < .05) with increasing dietary CP level or MB supplementation. Consequently, acetate-to-propionate ratio increased (p = .001) with MB supplementation, but was not affected by dietary CP level. Ruminal ammonia-N content increased (p = .034) with increasing dietary CP level, but decreased (p = .012) with MB supplementation. The effective degradability of NDF and CP increased (p < .05) with increasing dietary CP level or MB supplementation. Microbial enzyme activity, bacterial populations and total PD excretion also increased (p < .05) with increasing dietary CP level or MB supplementation. The results indicated that ruminal fermentation, nutrient degradability, microbial enzyme activity, ruminal bacterial populations and microbial protein synthesis improved with increasing dietary CP level or MB supplementation in steers.
本研究的目的是评估日粮粗蛋白（CP）水平和添加2-甲基丁酸（MB）对西门塔尔阉牛瘤胃发酵、细菌种群、微生物酶活性及嘌呤衍生物（PD）尿排泄量的影响。选用8头装有瘤胃瘘管的西门塔尔阉牛，平均年龄18个月，体重465±8.6千克，采用2×2析因排列的重复4×4拉丁方设计。低蛋白（98.5克CP/千克干物质[LP]）或高蛋白（128.7克CP/千克干物质[HP]）日粮分别添加MB（0克[MB-]或16.8克/头·天[MB+]）。给阉牛饲喂全混合日粮，日粮中玉米秸秆与精料的比例为50:50（以干物质[DM]计）。观察到CP×MB互作对瘤胃总挥发性脂肪酸（VFA）、乙酸和丙酸的摩尔比例、乙酸与丙酸比值、氨氮、中性洗涤纤维（NDF）和CP的有效降解率、微生物酶活性、细菌种群及总PD排泄量有影响（P<0.05）。随着日粮CP水平的提高或MB添加量的增加，瘤胃pH值降低（P<0.05），但瘤胃总VFA浓度升高（P<0.05）。添加MB后乙酸摩尔比例增加（P=0.043），但不受日粮CP水平影响。随着日粮CP水平的提高或MB添加量的增加，丙酸摩尔比例降低（P<0.05）。因此，添加MB后乙酸与丙酸比值增加（P=0.001），但不受日粮CP水平影响。随着日粮CP水平的提高，瘤胃氨氮含量增加（P=0.034），但添加MB后降低（P=0.012）。随着日粮CP水平的提高或MB添加量的增加，NDF和CP的有效降解率增加（P<0.05）。微生物酶活性、细菌种群及总PD排泄量也随着日粮CP水平的提高或MB添加量的增加而增加（P<0.05）。结果表明，随着日粮CP水平的提高或MB添加量的增加，西门塔尔阉牛的瘤胃发酵、养分降解率、微生物酶活性、瘤胃细菌种群及微生物蛋白合成得到改善。
