Gastrointestinal nematode (GIN) parasite infections can be detrimental to not only cattle health and immunity, but also result in economic loss and poor performance. Cattle grazing in the southeast are challenged even further by the favorable environmental conditions for parasite development, especially those animals who have yet to develop an immunity to combat parasitism. To diminish potential economic and performance-based losses, many beef producers treat animals for GIN parasites with anthelmintics on a regular basis without proper diagnosis. Anthelmintic resistance(AR) develops when deworming products are overused and misused. To minimize the development of AR, selective deworming and sustainable management practices should be implemented. However, the severity of parasite burden over the production cycle needs to be better understood in beef cattle herds before recommendations can be made. Thus, the objective was to investigate the rates of GIN parasite infections through fecal egg counts (FEC) and the impact on body weight (BW) and body condition score (BCS). Angus-based cattle (6 mo-13 yr, n = 1,154) on a were utilized from five different research and educational herds across North Carolina. Cattle were categorized based on their age at the start of the project as either calves (n = 446), yearling heifers (n = 205), 2 year old (n = 260), 3-5 year old (n = 501), or 6+ year old (n = 206). Starting in September, FEC, BW, and BCS were collected and analyzed every 90 d at critical production timepoints (calving, breeding, weaning, and 90d post-weaning) to monitor the severity of GIN parasite challenge. Cattle on study were not treated with anthelmintics regardless of parasite load, with the exception of calves at four of the locations at the time of weaning. All data were analyzed using Proc MIXED in SAS with repeated measures. Statistical significance was declared at P ≤ 0.05 and a trend at 0.10 > P > 0.05. Age of cattle had an impact on FEC overall (P < 0.05), however, there was no difference between FEC of mature cattle over 3 yr (4.29 ± 4.9 eggs/gm). Calves had the greatest FEC (120.59 ± 4.2 eggs/gm) while cattle 6+ yr had the least (3.68 ± 4.5 eggs/gm). Cattle age at each location affected BCS and BW (P < 0.05). Between age groups across locations, time had an impact on FEC, BW, and BCS (P < 0.05). There was also a tendency (P = 0.6) for location to impact FEC. Calf sex did not affect (P > 0.05) FEC. Further FEC analysis of cattle under 2 yrof age is required to better understand when a natural immune response to GIN parasite infections develops.

中文翻译：

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136 北卡罗来纳州放牧肉牛在整个生产生命周期内体内寄生虫负担的评估

胃肠道线虫 (GIN) 寄生虫感染不仅会损害牛的健康和免疫力，还会导致经济损失和生产性能不佳。东南部的牛群放牧面临着寄生虫生长的有利环境条件的进一步挑战，特别是那些尚未形成抵抗寄生虫免疫力的动物。为了减少潜在的经济和绩效损失，许多牛肉生产商在没有正确诊断的情况下定期使用驱虫药治疗动物的杜松子酒寄生虫。当驱虫产品过度使用和误用时，就会产生驱虫耐药性（AR）。为了尽量减少 AR 的发生，应实施选择性驱虫和可持续管理实践。然而，在提出建议之前，需要更好地了解肉牛群中寄生虫负担在生产周期中的严重程度。因此，目的是通过粪便虫卵计数 (FEC) 调查 GIN 寄生虫感染率以及对体重 (BW) 和身体状况评分 (BCS) 的影响。使用来自北卡罗来纳州五个不同研究和教育牛群的安格斯牛（6 个月至 13 岁，n = 1,154）。根据项目开始时的年龄将牛分类为小牛 (n = 446)、一岁小母牛 (n = 205)、2 岁 (n = 260)、3-5 岁 (n = 501)、或 6 岁以上 (n = 206)。从 9 月开始，每 90 天在关键生产时间点（产犊、配种、断奶和断奶后 90 天）收集并分析 FEC、BW 和 BCS，以监测 GIN 寄生虫挑战的严重程度。无论寄生虫负载如何，研究中的牛都没有接受驱虫药治疗，但断奶时有四个地点的小牛除外。所有数据均使用 SAS 中的 Proc MIXED 进行重复测量分析。当 P ≤ 0.05 时声明有统计显着性，当 0.10 > 0.10 时声明有趋势。P＞0.05。牛的年龄对总体 FEC 有影响（P < 0.05），然而，3 岁以上的成熟牛的 FEC 之间没有差异（4.29 ± 4.9 蛋/克）。犊牛的 FEC 最高（120.59 ± 4.2 蛋/克），而 6 岁以上的牛则最低（3.68 ± 4.5 蛋/克）。每个地点的牛龄都会影响 BCS 和 BW (P < 0.05)。在不同地点的年龄组之间，时间对 FEC、BW 和 BCS 有影响（P < 0.05）。位置也有影响 FEC 的趋势 (P = 0.6)。小牛性别不影响（P>0.05）FEC。需要对 2 岁以下的牛进行进一步的 FEC 分析，以更好地了解何时对 GIN 寄生虫感染产生自然免疫反应。