Rice R L, Blodgett D J, Schurig G G, Swecker W S, Fontenot J P, Allen V G, Akers R M
Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg 24061, USA.
Vet Immunol Immunopathol. 1997 Nov;59(3-4):285-91. doi: 10.1016/s0165-2427(97)00079-2.
Anecdotal reports suggest cattle with fescue toxicosis may not respond to vaccination and thus, experience increased incidence of Bovine Respiratory Disease Complex (BRDC) when shipped to feedlots. Fescue toxicosis causes hypoprolactemia in cattle. Hypoprolactemia decreases humoral immune responses in mice. Therefore, a study was conducted to compare the magnitude of primary and secondary humoral immune responses against specific antigens in cattle grazing endophyte-infected or endophyte-free fescue. Angus steers were blocked by weight and allocated into four groups. Two groups grazed endophyte-infected (EI) fescue and the other two groups grazed endophyte-free (EF) fescue. All steers were injected IM on d 0 and 21 with lysozyme without adjuvant and concanavalin. A (Con A) with sheep red blood cells (SRBC) in incomplete adjuvant of Freund. Steers were bled on days 0, 21 and 35 post-vaccination. Average daily gains (ADG), alkaline phosphatase (ALP) activity, cholesterol concentrations, rectal temperatures, and serum prolactin concentrations were measured to confirm fescue toxicosis in steers grazing EI fescue. Antibodies to Con A and SRBC were determined by ELISA and hemagglutination assay, respectively. The ADG were decreased for the EI group during the first month. Rectal temperature were elevated and serum prolactin concentrations were decreased in the EI group. Cholesterol and ALP concentrations also were decreased in the EI group. Primary and secondary immune responses against Con A tended to be increased and were increased against SRBC in the EI group. Antibodies against lysozyme were not induced in either group. In conclusion, cattle grazing EI fescue mounted similar humoral immune responses to vaccination, despite hypoprolactemia, as cattle grazing EF fescue. Increases in bovine respiratory disease in cattle maintained on EI fescue probably is not associated with lack of humoral immune response to vaccination protocols as a result of fescue toxicosis.
轶事报告表明，患有牛尾草中毒的牛可能对疫苗接种无反应，因此，当被运往饲养场时，患牛呼吸道疾病综合征（BRDC）的发病率会增加。牛尾草中毒会导致牛低催乳素血症。低催乳素血症会降低小鼠的体液免疫反应。因此，开展了一项研究，以比较放牧内生真菌感染或未感染内生真菌的牛尾草的牛对特定抗原的初次和二次体液免疫反应的强度。安格斯阉牛按体重进行分组，分为四组。两组放牧感染内生真菌（EI）的牛尾草，另外两组放牧未感染内生真菌（EF）的牛尾草。所有阉牛在第0天和第21天肌肉注射无佐剂的溶菌酶以及含绵羊红细胞（SRBC）的伴刀豆球蛋白A（Con A），使用弗氏不完全佐剂。在接种疫苗后的第0天、第21天和第35天采集阉牛血液。测量平均日增重（ADG）、碱性磷酸酶（ALP）活性、胆固醇浓度、直肠温度和血清催乳素浓度，以确认放牧EI牛尾草的阉牛是否患有牛尾草中毒。分别通过酶联免疫吸附测定（ELISA）和血凝试验测定针对Con A和SRBC的抗体。EI组在第一个月的ADG下降。EI组的直肠温度升高，血清催乳素浓度降低。EI组的胆固醇和ALP浓度也降低。EI组针对Con A的初次和二次免疫反应趋于增强，针对SRBC的免疫反应增强。两组均未诱导出针对溶菌酶的抗体。总之，尽管存在低催乳素血症，但放牧EI牛尾草的牛与放牧EF牛尾草的牛对疫苗接种的体液免疫反应相似。在EI牛尾草上饲养的牛呼吸道疾病增加，可能与牛尾草中毒导致对疫苗接种方案缺乏体液免疫反应无关。
