Gonzalez-Rivas Paula A, Sullivan Megan, Cottrell Jeremy J, Leury Brian J, Gaughan John B, Dunshea Frank R
Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, VIC, 3010, Australia.
School of Agriculture and Food Sciences, The University of Queensland, Gatton, QLD, 4343, Australia.
Trop Anim Health Prod. 2018 Dec;50(8):1763-1769. doi: 10.1007/s11250-018-1616-5. Epub 2018 May 23.
Feeding low-fiber and high-energy diets to dairy cows is one approach to ameliorate heat stress (HS) by reducing heat increment (HI) during digestion. However, rapidly and slowly fermentable cereal grains differ in their HI. The aim of this experiment was to quantify if feeding slowly fermentable grains ameliorated the physiological responses to HS and improved milk production (MP) in dairy cows. Holstein-Friesian lactating dairy cows were housed in shaded pens and were fed either a total mixed ration (TMR) plus wheat (TMRW), a TMR plus wheat treated with 2% of a commercial starch-binding agent (TMRB), or a TMR plus corn (TMRC) (n = 8 cows per diet) during summer in Queensland, Australia. Respiration rate (RR) and panting score (PS) were measured four times a day; rumen temperature (RuT) was recorded every 20 min, and rectal temperature (RT) and milk samples were obtained every 4 days. Cows fed slowly fermentable grains had higher milk production (MP) than cows fed TMRW, and cows fed TMRC had lower RT than those fed TMRW and TMRB (P < 0.001). Rumen temperature was positively correlated with temperature-humidity index and negatively correlated with MP (P < 0.05). In summary, feeding TMRC ameliorated HS as indicated by lower RT and improved MP in dairy cows. Milk production was improved with starch-binding agents; however, this was not associated with efficient thermoregulatory responses. Furthermore, determination of RuT enabled the prediction of changes in physiological variables and productive responses due to HS in lactating dairy cows.
给奶牛喂食低纤维和高能量日粮是通过减少消化过程中的热增耗（HI）来缓解热应激（HS）的一种方法。然而，快速和缓慢发酵的谷物在热增耗方面存在差异。本实验的目的是量化喂食缓慢发酵谷物是否能改善奶牛对热应激的生理反应并提高产奶量（MP）。在澳大利亚昆士兰州的夏季，将荷斯坦 - 弗里生泌乳奶牛饲养在有遮阳的牛栏中，分别给它们喂食全混合日粮（TMR）加小麦（TMRW）、添加2%商业淀粉结合剂处理的TMR加小麦（TMRB）或TMR加玉米（TMRC）（每种日粮8头奶牛）。每天测量4次呼吸频率（RR）和喘息评分（PS）；每20分钟记录一次瘤胃温度（RuT），每4天采集一次直肠温度（RT）和牛奶样本。喂食缓慢发酵谷物的奶牛比喂食TMRW的奶牛产奶量更高，喂食TMRC的奶牛直肠温度低于喂食TMRW和TMRB的奶牛（P < 0.001）。瘤胃温度与温湿度指数呈正相关，与产奶量呈负相关（P < 0.05）。总之，如较低的直肠温度所示，喂食TMRC可缓解奶牛的热应激并提高产奶量。淀粉结合剂可提高产奶量；然而，这与有效的体温调节反应无关。此外，测定瘤胃温度能够预测泌乳奶牛因热应激导致的生理变量和生产反应的变化。
