Effect of sward density and size of faecal deposit on the development and persistence of third‐stage Trichostrongylid larvae of sheep

Abstract

Ryegrass swards of low and high density were established to which lamb faeces containing nematode eggs were uniformly applied. This was done as either large or small deposits with all plots receiving the same quantity. Herbage was cut at 15 mm above ground level on five occasions over the following 29 weeks and nematode larvae extracted. The lower sward density plots produced less dry matter during the first 12 weeks after establishment but subsequently out‐yielded those sown at the high density. When assessed over 36 weeks post‐sowing, initial density had no effect on production. Overall, larval recovery equated to less than 0.5% of eggs applied. Numbers peaked between 67 and 147 days after application then declined and were extremely low by Day 200. Compared to low density, high density swards yielded the highest number of larvae overall. Sward density during the first 67 days after faeces were deposited had a greater effect on larval development, survival and persistence than subsequent differences in sward characteristics. The larger faecal deposits resulted in higher numbers of larvae. Effects of increasing sward density and faecal deposit size were cumulative.

Keywords:

• endoparasites
• larvae
• nematodes
• sward density
• faecal deposits
• microclimate
• herbage mass
• sheep