Castor cake as organic fertilizer to control gastrointestinal nematodes in pasture-raised sheep

Abstract Gastrointestinal parasitism is one of the factors that discourages farmers from raising small ruminants in cultivated pastures. To validate a soil treatment strategy to control the free-living stages of gastrointestinal nematodes (GIN), castor cake (CC) was used as a fertilizer on a pasture where sheep grazed on guinea grass under continuous stocking. On day zero, the pasture was divided into three paddocks, contaminated by GIN and treated, respectively, with CC divided into two applications (2CC1/2), CC in a single application (CC1) and organic compost in a single application (control). On day 21, eight GIN-free sheep were placed in each paddock. On day 58, significant differences (P<0.05) were observed: reduction of up to 66.10% in larvae.g-1 of dry mass in pastures fertilized with CC, decrease of up to 60.72% in infection rates among the animals in the groups treated with CC, higher average daily weight gain (over 185 g.day-1) and packed cell volume (over 26%) in the groups treated with CC, when compared to the control (128 g.day-1; 20.9%). In view of the results, the use of CC, mainly CC1, as a fertilizer for guinea grass pastures, under continuous stocking, proved to be promising, with 63.41% effectiveness in controlling worm infestations.

摘要 胃肠道寄生虫病是阻碍农户在人工栽培牧场开展小反刍动物养殖的主要制约因素之一。为验证可管控胃肠道线虫（Gastrointestinal Nematodes, GIN）自由生活阶段的土壤处理策略，本研究以蓖麻饼（Castor Cake, CC）作为肥料，施加于采用连续放牧制度、以类蜀黍（Guinea Grass）为优势牧草的绵羊放牧牧场中。试验第0天，将该牧场划分为3个围场，所有围场均预先被GIN污染，随后分别施以两种施用方式的CC：分两次各施一半总量的分次施用方案（2CC1/2）、单次全量施用方案（CC1），以及单次施用有机堆肥的对照组方案。试验第21天，于每个围场中投放8只无GIN感染的健康绵羊。试验第58天时，观测到具有统计学意义的显著差异（P<0.05）：与对照组（平均日增重128 g·d⁻¹、血细胞比容20.9%）相比，施加CC的两组围场中，牧场每克干物质的幼虫数最高可降低66.10%，受试绵羊的感染率最高可下降60.72%，且平均日增重（超185 g·d⁻¹）与血细胞比容（超26%）均显著更高。综合上述试验结果可知，在连续放牧制度下，以CC（尤以单次全量施用的CC1为佳）作为类蜀黍牧场的肥料，对蠕虫侵染的防控效果可达63.41%，具备良好的应用前景。