Cabrita Ana R J, Carvalheira Júlio, Fonseca António J M
REQUIMTE, LAQV, ICBAS, School of Medicine and Biomedical Sciences, University of Porto, Rua Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal.
CIBIO, ICBAS, School of Medicine and Biomedical Sciences, University of Porto, Rua Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal.
Vet Sci. 2025 Aug 22;12(9):791. doi: 10.3390/vetsci12090791.
High temperature typically decreases feed intake, milk production, and efficiency and increases metabolic disorders and health problems, greatly impacting farm economics. Supplements based on have been suggested to benefit cows under heat stress, but effects on dairy cow performance are contradictory. This study aimed to evaluate the influence of heat stress on the effects of live yeast supplementation on the performance of dairy cows. Environmental temperature parameters were compared to two thermal humidity indices (THI1 and THI2) using wet bulb or dew point temperatures, as explanatory variables of dairy cow performance during the hot season. The experiment followed a randomized complete block design with 12 Holstein cows blocked by lactation number, days in milk, and milk production (two cows per block) and within each block, each cow was randomly assigned to a maize silage-based TMR with a concentrate mixture containing no yeast culture (Control) or 1 g/kg concentrate dry matter of a live yeast culture based on (Yeast) for 35 days. The experiment lasted for 35 d. Dry matter intake (DMI) was significantly higher for Yeast than it was for Control for all classes of temperature and THIs studied with an average increase of 2 kg DM per day, except for mean THI1 (from 54 to 60), for which the DMI was similar between treatments. Yeast promoted significantly higher milk yield than Control for all classes of daily maximum and mean temperature, averaging an increase of 4 kg of milk per day. Results suggest a more marked effect of temperature and indicate that yeast supplementation improved lactation performance of dairy cows exposed to hot weather.
高温通常会降低采食量、产奶量和效率，并增加代谢紊乱和健康问题，对农场经济效益产生重大影响。有人建议基于[具体物质未给出]的补充剂对热应激下的奶牛有益，但对奶牛生产性能的影响存在矛盾。本研究旨在评估热应激对添加活酵母对奶牛生产性能影响的作用。将环境温度参数与两个温湿度指数（THI1和THI2）进行比较，使用湿球温度或露点温度作为炎热季节奶牛生产性能的解释变量。试验采用随机完全区组设计，选取12头荷斯坦奶牛，按泌乳次数、泌乳天数和产奶量进行区组（每个区组2头奶牛），在每个区组内，每头奶牛随机分配到以玉米青贮为基础的全混合日粮（TMR），其精料混合物中不含有酵母培养物（对照组）或含有基于[具体物质未给出]的1 g/kg精料干物质的活酵母培养物（酵母组），为期35天。试验持续35天。在所有研究的温度和温湿度指数类别中，酵母组的干物质摄入量（DMI）显著高于对照组，平均每天增加2 kg干物质，但平均THI1（从54到60）除外，该温度下处理间的DMI相似。在所有日最高温度和平均温度类别中，酵母组的产奶量显著高于对照组，平均每天增加4 kg牛奶。结果表明温度的影响更为显著，并且表明添加酵母可改善处于炎热天气下奶牛的泌乳性能。
