Poudel Sanjok, Fike John H, Wright Lee, Pent Gabriel J
School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, VA 24061, USA.
Southwest Agriculture Research and Extension Center, Virginia Tech, Glade Spring, VA 24340, USA.
Animals (Basel). 2023 Jul 21;13(14):2373. doi: 10.3390/ani13142373.
Cattle grazing tall fescue () infected with wild-type endophytes (WE) leads to a syndrome commonly known as fescue toxicosis. Replacing WE tall fescue with a novel endophyte-infected (NE) tall fescue can mitigate this problem but adoption of this technology has been limited. This study measured and determined the physiological and behavioral responses of heifers that grazed either WE or NE tall fescue, utilizing relatively non-invasive techniques including hair cortisol, thermography (for extremity temperatures), small loggers for intravaginal temperature, and remote observation of in-field behavior. Heifers that grazed WE had greater ( < 0.0001) hair cortisol levels, lower extremity temperatures ( ≤ 0.0075), and 0.3-0.9 °C greater ( ≤ 0.02) intravaginal temperatures (particularly during the daytime) than heifers that grazed NE. From 1200 h-1700 h each day, heifers on WE pastures spent 1.5 more ( = 0.0003) hours standing up and 0.9 fewer ( = 0.0402) hours lying down than heifers on NE pastures. Differences ( = 0.0160) in ADG were small (0.1 kg d) and were only observed in the first year of these 8-week studies. However, even in the mild environment of the study site, grazing NE tall fescue provided clear welfare benefits as evidenced by heifer behavioral changes, temperature differentials, and hair cortisol levels. This study underscores the potential utility of non-invasive techniques, such as thermographic imaging and hair cortisol analysis, for evaluating animal responses to stress in extensive grazing systems.
放牧感染野生型内生真菌（WE）的高羊茅会导致一种通常被称为高羊茅中毒的综合征。用新型内生真菌感染（NE）的高羊茅取代感染WE的高羊茅可以缓解这个问题，但这项技术的采用一直很有限。本研究利用相对非侵入性的技术，包括毛发皮质醇、热成像（用于测量四肢温度）、用于阴道内温度的小型记录仪以及对田间行为的远程观察，测量并确定了放牧感染WE或NE的高羊茅的小母牛的生理和行为反应。与放牧NE的小母牛相比，放牧WE的小母牛毛发皮质醇水平更高（P<0.0001），四肢温度更低（P≤0.0075），阴道内温度高0.3 - 0.9°C（P≤0.02）（特别是在白天）。每天12:00 - 17:00，放牧在感染WE牧场的小母牛比放牧在NE牧场的小母牛多站立1.5小时（P = 0.0003），少躺卧0.9小时（P = 0.0402）。平均日增重的差异（P = 0.0160）很小（0.1 kg/d），且仅在这些为期8周研究的第一年观察到。然而，即使在研究地点的温和环境中，放牧NE高羊茅也带来了明显的福利益处，这从小母牛的行为变化、温度差异和毛发皮质醇水平中得到了证明。本研究强调了非侵入性技术，如热成像和毛发皮质醇分析，在评估粗放放牧系统中动物应激反应方面的潜在效用。
