Effect of gastrointestinal nematodes on ovulation rate of merino Booroola heterozygote ewes (FecB Fec+)

Abstract

Twenty-five multiparous Merino ewes, each carrying one copy of the Booroola gene (FecB Fec+), were divided into two experimental groups (Control, n = 13 and Challenged, n = 12). The treatments were applied in the autumn between 14 March and 21 May. The sheep in the Control group were dosed orally twice-weekly with 10 mL water, and dosed with Levamisole every 14 days. Each sheep in the Challenged group was dosed orally twice-weekly with 6000 nematode larvae in 10 mL water. Challenged sheep shed more eggs per gram of faeces, lost live weight (40 vs. 38.2) and lost body condition score (3.5 vs. 3.0 condition score) during the study compared with the Control sheep. While live weight, body condition and the number of developing follicles all decreased in association with a nematode larval challenge, the proportion of developing follicles which formed a corpora lutea were unaffected. Thus a larval challenge during joining with nematode larvae at doses comparable to those encountered under field conditions can be expected to affect subsequent lambing performance. © INRA, EDP Sciences, 2006.