Innovation Center, Ferdowsi University of Mashhad, Mashhad 9177948974, Iran.
Department of Animal Science, Faculty of Agriculture, Ferdowsi University of Mashhad, PO Box 9177948974, Mashhad 9177948978, Iran.
J Dairy Sci. 2021 Jun;104(6):6756-6767. doi: 10.3168/jds.2020-19202. Epub 2021 Mar 25.
This study aimed to evaluate the effects of feeding ground, steam-flaked, or super-conditioned corn on production performance, rumen fermentation, nutrient digestibility, and milk fatty acid (FA) profile of lactating dairy cows. Twenty-four lactating Holstein cows (130 ± 12 d in milk) in a completely randomized block design experiment were assigned to 1 of 3 treatments that contained 31% of one of the following corn types: (1) ground corn; (2) steam-flaked corn; and (3) super-conditioned corn. Actual milk yield was greater in the super-conditioned corn diet than in the steam-flaked and ground corn diets. Dry matter intake, 3.5% fat-corrected milk and energy-corrected milk remained unaffected by treatments; however, milk fat concentration decreased in the super-conditioned corn diet compared with the ground and steam-flaked corn diets. The molar proportion of ruminal acetate decreased in the super-conditioned corn diet compared with the ground and steam-flaked corn diets, whereas the molar proportion of propionate spiked in the super-conditioned corn diet. Ruminal pH dropped in cows fed super-conditioned corn compared with the other 2 diets. A similar pattern was observed for ruminal NH-N and acetate-to-propionate ratio. Total-tract starch digestibility increased the most in the super-conditioned corn diet followed by the steam-flaked and ground corn diets (96.8, 95.1, and 92.5%, respectively). The neutral detergent fiber digestibility declined in cows fed the super-conditioned corn diet as opposed to other diets (~3.9%). The concentrations of 16:0 and mixed-FA in milk fat dropped in the super-conditioned corn-based diet compared with the ground corn diet. Milk trans-10 18:1 FA increased, whereas trans-11 18:1 FA decreased in cows fed the super-conditioned diet. We concluded that super-conditioned corn has the potential to increase milk yield and starch digestibility in lactating dairy cows; however, reduced milk fat output caused by altering ruminal pH and ruminal FA biohydrogenation pathways may not be desirable in certain markets. Future research is warranted to investigate how super-conditioned corn affects feed efficiency.
本研究旨在评估饲粮中使用地面玉米、蒸汽压片玉米还是超高温处理玉米对泌乳奶牛生产性能、瘤胃发酵、养分消化率和乳脂肪酸（FA）组成的影响。24 头荷斯坦泌乳奶牛（泌乳 130±12 天）采用完全随机区组设计试验，分为 3 个处理组，每个处理组含有 31%的以下 3 种玉米类型之一：（1）地面玉米；（2）蒸汽压片玉米；（3）超高温处理玉米。超高温处理玉米组的实际产奶量大于蒸汽压片玉米组和地面玉米组。干物质采食量、3.5%校正乳和能量校正乳不受处理影响；然而，与地面玉米和蒸汽压片玉米组相比，超高温处理玉米组的乳脂浓度降低。与地面玉米和蒸汽压片玉米组相比，超高温处理玉米组瘤胃乙酸摩尔比例降低，丙酸摩尔比例升高。与其他 2 种饲粮相比，饲喂超高温处理玉米的奶牛瘤胃 pH 降低。瘤胃 NH-N 和乙酸/丙酸比也呈现出类似的模式。超高温处理玉米组的总肠道淀粉消化率最高，其次是蒸汽压片玉米组和地面玉米组（分别为 96.8%、95.1%和 92.5%）。与其他饲粮相比，超高温处理玉米组奶牛中性洗涤纤维消化率下降（~3.9%）。与地面玉米组饲粮相比，超高温处理玉米组奶牛乳脂中 16:0 和混合 FA 的浓度降低。超高温处理玉米组奶牛乳中转 10 18:1 FA 增加，而反式 11 18:1 FA 减少。我们得出结论，超高温处理玉米有可能提高泌乳奶牛的产奶量和淀粉消化率；然而，改变瘤胃 pH 和瘤胃 FA 生物氢化途径可能会降低乳脂产量，这在某些市场可能不受欢迎。需要进一步的研究来调查超高温处理玉米如何影响饲料效率。
