Gastrointestinal nematode infection in Purunã heifers raised in conventional and integrated livestock forest systems

ABSTRACT The objective of the study was to evaluate the resistance of Purunã heifers to nematode infection in two different production systems. In this study, 29 heifers were divided into eight pickets, four in an integrated livestock forest system (ILF) and four in a conventional pasture system (CPS). Feces were collected monthly to perform the fecal egg count (FEC), evaluate the degree of infection caused by gastrointestinal nematodes in cattle, and carry out coproculture, to identify the genus of the parasites. In addition, animal body weight was determined to evaluate performance. On the same day as the measurements, forage samples were collected to determine the number of infective larvae per kilogram of dry matter (L3/kg DM) in each picket. There were no statistical differences in FECs between the treatments. Although no significant differences were observed in the recovery of L3/kg DM, the contamination was higher in the ILF compared to CPS in December (344 and 37.7 L3/kg DM, respectively) and January (312 and 0 L3/kg DM, respectively). In March, the CPS (321 L3/kg DM) presented higher contamination than the ILF (80.7 L3/kg DM), but with no statistical difference. The weight of the animals was higher for the CPS compared to the ILF treatment throughout the whole experimental period, with a significant difference in December (343.30 kg and 314.08 kg, respectively). The present study demonstrated numerically that greater numbers of L3 were recovered from pasture of the ILF, which could have resulted in higher contamination and lower performance of the animals.

摘要
本研究旨在评估普拉纳（Purunã）青年母牛在两种不同生产体系下的线虫感染抗性。试验共选取29头青年母牛，将其划分为8个牧栏，其中4个牧栏采用林牧复合系统（integrated livestock forest system, ILF），另外4个采用传统牧场系统（conventional pasture system, CPS）。
每月收集粪便样本，开展粪便虫卵计数（fecal egg count, FEC）以评估牛胃肠道线虫感染程度，并通过粪便培养（coproculture）鉴定寄生虫属类。此外，测定动物体重以评估其生产性能。在采样当日同步收集牧草样品，测定每个牧栏中每千克干物质（dry matter, DM）所含感染性幼虫（infective larvae, L3）的数量（记为L3/kg DM）。
两组处理的粪便虫卵计数无统计学差异。尽管两组的L3/kg DM回收量未呈现显著差异，但在12月与1月，林牧复合系统组的牧草污染程度均高于传统牧场系统组：12月时两组分别为344 L3/kg DM与37.7 L3/kg DM，1月时分别为312 L3/kg DM与0 L3/kg DM。3月时，传统牧场系统组（321 L3/kg DM）的牧草污染程度高于林牧复合系统组（80.7 L3/kg DM），但该差异无统计学意义。
整个试验周期内，传统牧场系统组的动物体重均高于林牧复合系统组，其中12月的组间差异具有统计学意义（传统牧场系统组：343.30 kg，林牧复合系统组：314.08 kg）。本研究的数值结果显示，林牧复合系统牧场的感染性幼虫回收量更高，这可能导致该体系下动物的污染程度更高、生产性能更低。