Browning R
Cooperative Agricultural Research Program, Tennessee State University, Nashville 37209-1561, USA.
J Anim Sci. 2004 Feb;82(2):634-43. doi: 10.2527/2004.822634x.
Poor growth often occurs in cattle consuming ergot alkaloids associated with endophyte-infected (EI) tall fescue. Hyperthermia may contribute significantly to poor growth resulting from fescue toxicosis. This study examined indicators of thermal status and growth in Hereford (n = 30; heat-sensitive Bos taurus; H) and Senepol (n = 28; heat-tolerant Bos taurus; S) steers fed EI tall fescue (TF) or orchardgrass (OG) in 2 x 2 factorial experiments. Respiration rates, daytime shade use, tail skin temperatures, and body weights were measured during the summer and fall of 2000 (Exp. 1) and 2001 (Exp. 2). Experimental diets consisted of hay and seed for 12 wk in 2000, hay for 6 wk during the summer of 2001, and hay plus seed for 6 wk during the fall of 2001. In Exp. 1, EI tall fescue increased (P < 0.01) respiration rates, shade use, and skin temperatures in both breeds. Breed x diet affected (P < 0.01) 12-wk ADG in Exp. 1. Growth rate was lower for H-TF (262 g/d) than for S-TF, S-OG, and H-OG (475, 497, and 524 g/d, respectively). In Exp. 2, Senepol had lower (P < 0.01) respiration rates, shade use, and skin temperatures compared with Hereford, but diet did not alter (P > 0.14) these indicator traits in either breed. Breed x diet affected (P < 0.01) summer growth rates. Growth rate was lower for H-TF (88 g/d) than for H-OG, S-TF, and S-OG (508, 555, and 566 g/d, respectively). Adding seed to the diets in Exp. 2 decreased (P < 0.01) ADG for both breeds on TF during the fall. Thermal status indicator traits in Senepol and Hereford steers were similarly altered by TF; however, only Hereford showed consistently poor growth. Senepol showed resilience in their capacity for growth under conditions of fescue toxicosis. Senepol influence may enhance cattle performance in production systems that use EI tall fescue as the base forage.
食用与内生真菌感染（EI）的高羊茅相关的麦角生物碱的牛常常生长不良。体温过高可能是导致高羊茅中毒引起生长不良的重要原因。本研究在2×2析因实验中，检测了给赫里福德牛（n = 30；热敏型黄牛；H）和塞内波尔牛（n = 28；耐热型黄牛；S）饲喂EI高羊茅（TF）或果园草（OG）时的热状态指标和生长情况。在2000年（实验1）和2001年（实验2）的夏季和秋季测量了呼吸频率、白天遮荫情况、尾皮温度和体重。2000年的实验日粮由干草和种子组成，持续12周；2001年夏季为干草，持续6周；2001年秋季为干草加种子，持续6周。在实验1中，EI高羊茅使两个品种的呼吸频率、遮荫情况和皮肤温度均升高（P < 0.01）。品种×日粮对实验1中12周的平均日增重有影响（P < 0.01）。H-TF组（262克/天）的生长速度低于S-TF、S-OG和H-OG组（分别为475、497和524克/天）。在实验2中，与赫里福德牛相比，塞内波尔牛的呼吸频率、遮荫情况和皮肤温度较低（P < 0.01），但日粮对两个品种的这些指标性状均无影响（P > 0.14）。品种×日粮对夏季生长速度有影响（P < 0.01）。H-TF组（88克/天）的生长速度低于H-OG、S-TF和S-OG组（分别为508、555和566克/天）。在实验2中，秋季给两个品种的TF日粮添加种子会降低平均日增重（P < 0.01）。TF对塞内波尔牛和赫里福德牛的热状态指标性状有类似影响；然而，只有赫里福德牛一直生长不良。塞内波尔牛在高羊茅中毒条件下的生长能力具有恢复力。塞内波尔牛的这种特性可能会提高以EI高羊茅为基础饲草的生产系统中牛的生产性能。
