School of Life and Environmental Sciences, Faculty of Science, University of Sydney, Camden, NSW 2570, Australia.
Sydney School of Veterinary Science, Faculty of Science, University of Sydney, Camden, NSW 2570, Australia.
J Anim Sci. 2022 Jan 1;100(1). doi: 10.1093/jas/skab361.
Bovine respiratory disease (BRD) is the primary cause of morbidity and mortality in cattle feedlots. There is a need to understand what animal health and production factors are associated with increased mortality risk due to BRD. The aim of the present study was to explore factors associated with BRD case fatality in feedlot cattle. Four pens totaling 898 steers were monitored daily for visual signs of BRD such as difficult breathing and coughing, and animals exhibiting signs of BRD were taken to the hospital shed for further examination and clinical measures. Blood samples were obtained at feedlot entry and at time of first BRD pull from animals diagnosed with BRD (n = 121) and those that died due to BRD confirmed by postmortem examination (n = 16; 13.2% case fatality rate). Mixed-effects linear regression models were used to estimate differences in animal health and production factors and the relative concentrations of 34 identified blood metabolites between animals that survived versus those that died. Generalized linear mixed-effects models were used to obtain the odds of being seronegative (at both feedlot entry and first BRD pull) to 5 BRD viruses and having a positive nasal swab result at the time of first pull in died and survived animals. Animals that died from BRD had lower average daily gain (ADG), reduced weight at first BRD pull, higher visual BRD scores and received more treatments for BRD compared with animals that survived BRD (P < 0.05). The odds of being seronegative for bovine viral diarrhea virus 1 (BVDV-1) were 5.66 times higher for animals that died compared with those that survived (P = 0.013). The odds of having a positive bovine coronavirus nasal swab result were 13.73 times higher in animals that died versus those that survived (P = 0.007). Animals that died from BRD had higher blood concentrations of α glucose chain, β-hydroxybutyrate, leucine, phenylalanine, and pyruvate compared with those that survived (P < 0.05). Animals that died from BRD had lower concentrations of acetate, citrate, and glycine compared with animals that survived (P < 0.05). The results of the current study suggest that ADG to first BRD pull, weight at first BRD pull, visual BRD score, the number of BRD treatments, seronegativity to BVDV-1, virus positive to BCoV nasal swab, and that certain blood metabolites are associated with BRD case fatality risk. The ability of these measures to predict the risk of death due to BRD needs further research.
牛呼吸道疾病（BRD）是牛饲养场发病率和死亡率的主要原因。需要了解哪些动物健康和生产因素与 BRD 导致的死亡率增加有关。本研究的目的是探讨与饲养场牛 BRD 病例死亡率相关的因素。每天监测四个围栏共 898 头阉公牛的 BRD 视觉症状，如呼吸困难和咳嗽，出现 BRD 症状的动物被带到医院棚进行进一步检查和临床措施。从被诊断患有 BRD（n = 121）的动物和因 BRD 死亡并经死后检查证实（n = 16；死亡率为 13.2%）的动物在进入饲养场时和首次 BRD 抽取时获得血液样本。使用混合效应线性回归模型估计动物健康和生产因素以及 34 种鉴定出血液代谢物的相对浓度之间的差异，这些代谢物在存活动物和死亡动物之间的差异。使用广义线性混合效应模型获得 5 种 BRD 病毒的血清阴性（在进入饲养场和首次 BRD 抽取时）和首次抽取时鼻腔拭子阳性的动物死亡和存活的可能性。与存活的 BRD 动物相比，死于 BRD 的动物的平均日增重（ADG）较低，首次 BRD 抽取时的体重减轻，视觉 BRD 评分较高，并且接受了更多的 BRD 治疗（P <0.05）。与存活的动物相比，死于 BRD 的动物的牛病毒性腹泻病毒 1（BVDV-1）血清阴性的可能性高 5.66 倍（P = 0.013）。死于 BRD 的动物的牛冠状病毒鼻腔拭子阳性的可能性比存活的动物高 13.73 倍（P = 0.007）。与存活的动物相比，死于 BRD 的动物的血液中α葡萄糖链、β-羟丁酸、亮氨酸、苯丙氨酸和丙酮酸的浓度较高（P <0.05）。与存活的动物相比，死于 BRD 的动物的乙酸盐、柠檬酸盐和甘氨酸的浓度较低（P <0.05）。本研究的结果表明，首次 BRD 抽取时的 ADG、首次 BRD 抽取时的体重、视觉 BRD 评分、BRD 治疗次数、BVDV-1 血清阴性、BCoV 鼻腔拭子病毒阳性以及某些血液代谢物与 BRD 病例死亡率风险相关。这些措施预测 BRD 死亡风险的能力需要进一步研究。
