Department of Animal Science, North Carolina State University, Raleigh, NC.
Department of Animal and Veterinary Sciences, Clemson University, Clemson, SC.
J Anim Sci. 2019 Apr 3;97(4):1456-1467. doi: 10.1093/jas/skz024.
Fescue toxicosis is a multifaceted syndrome common in cattle grazing endophyte-infected tall fescue. The objective of this study was to evaluate the impact of the slick hair trait on physiological and reproductive parameters in heifers experiencing fescue toxicosis. Angus × Senepol heifers (n = 31) were blocked by weight (393.5 ± 17.3 kg) and phenotype relative to hair coat at birth, and randomly fed novel endophyte fescue (EN) or endophyte-infected fescue (EI) haylage in a total mixed ration for 91 d. Weekly measurements were collected to monitor heifer growth and response during ergot alkaloids exposure. Following 28 d of treatment, estrus was synchronized and heifers were inseminated. Ovary mapping and AI pregnancy rate were examined via transrectal ultrasonography. Blood samples were taken for genotyping: slick (S) or wildtype (W). Data were analyzed using repeated measures in PROC MIXED of SAS including fescue treatment (EN vs. EI), genotype (S vs. W), and sample collection time as main effects. Body condition scores were decreased for W heifers compared with S heifers (5.48 vs. 5.66, respectively; P < 0.0001). Surface temperature was greater for EI-W heifers (37.2 °C) compared with other groups (36.4, 36.6, 36.7 °C for EN-S, EN-W, EI-S, respectively; P < 0.05). Serum PRL concentrations were reduced for EI heifers compared with EN heifers (133.5 vs. 163.1 ng/mL, respectively; P < 0.05). The average number of 2 to 4 mm follicles were greater in EI-W heifers (13.8 follicles) compared with other groups (12.2, 10.6, and 11.1 for EN-S, EN-W, and EI-S, respectively; P < 0.0001). However, the average number of preovulatory follicles (≥9 mm) were reduced in EI-W heifers (0.52 follicles) compared with other heifer groups (0.94, 0.88, and 0.85 ± 0.04 for EN-S, EN-W, and EI-S, respectively; P < 0.05). Ovulatory follicle size was smaller in EI-W heifers compared with EN-W heifers (9.14 vs. 11.57 mm, respectively; P = 0.05). Corpus luteum area was reduced in EI-W heifers (235.1 mm2) compared with other heifer groups (297.2, 272.7, and 276.8 mm2 for EN-S, EN-W, and EI-S, respectively; P < 0.05). Concentrations of P4 were greater for EN heifers compared with EI heifers (2.7 vs. 1.8 ng/mL, respectively; P < 0.05). Pregnancy was not established in EI-W heifers (0%) compared with other heifer groups (37.5%, 57.1%, and 62.5% for EN-S, EN-W, and EI-S, respectively; P < 0.05). Overall, the slick hair mutation appears to aid in offsetting the physiological symptoms associated with fescue toxicosis and helps to improve reproductive performance.
糙皮病是一种常见于采食感染内生真菌高羊茅的牛的多方面综合征。本研究的目的是评估光滑毛性状对内毒素中毒牛生理和繁殖参数的影响。 Angus × Senepol 小母牛（n = 31）按体重（393.5 ± 17.3 kg）和出生时的表型（相对于毛被）进行分组，并在总混合日粮中随机饲喂新型内生真菌羊茅（EN）或内生真菌感染羊茅（EI）干草，共 91 天。每周进行测量，以监测小母牛在麦角生物碱暴露期间的生长和反应情况。治疗 28 天后，同步发情并对小母牛进行授精。通过直肠超声检查检查卵巢定位和 AI 妊娠率。采集血液样本进行基因分型：光滑型（S）或野生型（W）。数据使用 SAS 中的 PROC MIXED 程序进行重复测量分析，包括羊茅处理（EN 与 EI）、基因型（S 与 W）和样本采集时间作为主要效应。与 S 小母牛相比，W 小母牛的体况评分降低（5.48 对 5.66，分别；P < 0.0001）。与其他组相比，EI-W 小母牛的体表温度更高（37.2°C；EN-S、EN-W、EI-S 分别为 36.4、36.6、36.7°C；P < 0.05）。与 EN 小母牛相比，EI 小母牛的 PRL 浓度降低（133.5 对 163.1 ng/mL，分别；P < 0.05）。与其他组相比，EI-W 小母牛的 2 至 4 毫米卵泡数量更多（13.8 个卵泡）（EN-S、EN-W、EI-S 分别为 12.2、10.6、11.1；P < 0.0001）。然而，与其他小母牛组相比，EI-W 小母牛的排卵前卵泡数量（≥9 毫米）减少（0.52 个卵泡）（EN-S、EN-W、EI-S 分别为 0.94、0.88、0.85 ± 0.04；P < 0.05）。与 EN-W 小母牛相比，EI-W 小母牛的排卵卵泡更小（9.14 对 11.57 毫米，分别；P = 0.05）。与其他小母牛组相比，EI-W 小母牛的黄体面积较小（235.1 毫米 2）（EN-S、EN-W、EI-S 分别为 297.2、272.7、276.8 毫米 2；P < 0.05）。与 EI 小母牛相比，EN 小母牛的 P4 浓度更高（2.7 对 1.8 ng/mL，分别；P < 0.05）。与其他小母牛组相比，EI-W 小母牛未怀孕（0%）（EN-S、EN-W、EI-S 分别为 37.5%、57.1%、62.5%；P < 0.05）。总体而言，光滑毛突变似乎有助于缓解糙皮病相关的生理症状，并有助于提高繁殖性能。
