Department of Animal and Dairy Science, The University of Georgia, Tifton, Georgia 31793, USA.
J Dairy Sci. 2011 Sep;94(9):4616-22. doi: 10.3168/jds.2010-3984.
A study was conducted to evaluate the effects of a direct-fed microbial (M) and dietary glycerol (G) on milk yield, efficiency of yield, and nutrient digestibility during hot weather. Sixty Holstein cows averaging 120 d in milk (DIM) and 36.2 kg/d of milk were used in a 12-wk 2×2 factorial design trial from June through September 2008. Cows were fed a common diet during the 2-wk standardization period and were blocked by milk yield, DIM, parity, and dry matter intake. Diets were based on corn and ryegrass silages and balanced to be isocaloric and isonitrogenous. Treatments included a negative control (M- or G-), 4 × 10(9) cfu/head of a combination of Lactobacillus acidophilus NP51 and Propionibacterium freudenreichii NP24 (M+), control plus 400 g/h per day of 99% pure food-grade glycerol (G+), and 4×10(9) cfu/h per day of a combination of Lactobacillus acidophilus NP51 and Propionibacterium freudenreichii NP24 plus 400 g/h per day of 99% pure food-grade glycerol (MG++). No interactions were observed between direct-fed microbials and dietary glycerol in the study except on apparent nutrient digestibility. No differences were observed in dry matter intake, which averaged 22.7, 23.1, 23.4, and 22.9 for M-, G-, M+, and G+, respectively. Milk yield was increased for M+ compared with M- at 34.1 and 31.7 kg/d, but G+ had no effect on yield. No treatment effect was noted for milk fat percentage or milk protein percentage among diets. Milk protein yield was higher for M+ compared with M- at 0.93 versus 0.87 kg/d. Energy-corrected milk was improved for the M+ versus M- groups at 33.5 and 31.6 kg/d, respectively. No differences in respiratory rate, skin temperature, body temperature, or concentrations of serum glucose or urea N were observed among treatments. Improvement in apparent digestibility was observed with M+ and G+ compared with M-/G- in this experiment. The addition of a direct-fed microbial alone improved milk and protein yield, energy-corrected milk, and apparent digestibility of crude protein, neutral detergent fiber, and acid detergent fiber, and the inclusion of glycerol (G+) had a positive effect on apparent dry matter and acid detergent fiber digestibility compared with M-/G-. The addition of a direct-fed microbial and dietary glycerol may improve yield and digestibility for cows subject to heat stress.
一项研究旨在评估直接饲喂微生物（M）和日粮甘油（G）对热应激期间产奶量、产奶效率和养分消化率的影响。2008 年 6 月至 9 月期间，采用 2×2 析因设计试验，选用 60 头平均泌乳 120 天（DIM）和 36.2kg/d 产奶量的荷斯坦奶牛，进行为期 12 周的试验。在 2 周的标准化期间，奶牛饲喂基础日粮，根据产奶量、DIM、胎次和干物质采食量进行分组。日粮以玉米和黑麦青贮料为基础，平衡为等能量和等氮。处理包括负对照组（M-或 G-）、4×10（9）cfu/头的嗜酸乳杆菌 NP51 和丙酸杆菌 NP24 的混合物（M+）、对照组加每天 400g 纯度为 99%的食品级甘油（G+）、每天 4×10（9）cfu 的嗜酸乳杆菌 NP51 和丙酸杆菌 NP24 混合物加每天 400g 纯度为 99%的食品级甘油（MG++）。研究中除了表观养分消化率外，未观察到直接饲喂微生物和日粮甘油之间存在相互作用。干物质采食量无差异，M-、G-、M+和 G+分别为 22.7、23.1、23.4 和 22.9kg/d。与 M-相比，M+组的产奶量分别提高 34.1kg/d 和 31.7kg/d，但 G+对产奶量没有影响。日粮中脂肪和蛋白质百分率无处理效应。与 M-相比，M+组的乳蛋白产量分别提高 0.93kg/d 和 0.87kg/d。与 M-组相比，M+组的校正能量奶分别提高 33.5kg/d 和 31.6kg/d。呼吸率、皮肤温度、体温或血清葡萄糖或尿素氮浓度在处理组之间无差异。与 M-/G-相比，M+和 G+组的表观消化率提高。单独添加直接饲喂微生物可提高产奶量和产奶量、校正能量奶和粗蛋白、中性洗涤纤维和酸性洗涤纤维的表观消化率，与 M-/G-相比，添加甘油（G+）对表观干物质和酸性洗涤纤维消化率有积极影响。添加直接饲喂微生物和日粮甘油可能会提高热应激奶牛的产奶量和消化率。
