A monitoring study to explore gastrointestinal helminth burdens of ewes of different fecundities in the periparturient period and effects on lamb growth rates

As a result of the periparturient relaxation of immunity(PPRI) in ewes and subsequent rise in parasite burdens it has become common for sheep farmers to worm all ewes prior to lambing. However, with increased prevalence of anthelmintic resistance it is necessary to find more sustainable worming strategies. In this study, the faecal egg counts (FECs) of untreated ewes in different fecundity groups (single-, twin- and triplet-bearing ewes) in the periparturient period, together with lamb FECs and lamb growth rates were monitored on a commercial organic lowland sheep farm in Oxfordshire, UK. Triplet-bearing ewes were supplemented with a high-protein concentrate ration and molasses prior to lambing. All ewe groups showed a relaxation in immunity against gastro-intestinal helminths from the week lambing began until eight weeks later. Twin-bearing ewes had a significantly higher overall worm burden as compared to single- and triplet-bearing ewes. Single lambs had the highest daily live weight gains (DLWGs) during the period from tagging to shearing of their mothers. Faecal egg counts of lambs were performed from six weeks after lambing. A general trend towards increased Trichostrongyloidea FEC with litter size was seen in the lambs. As a result, recommendations for an effective, practical and sustainable nematode control programme for the periparturient period in ewes of different fecundity for UK sheep farmers have been devised. The core recommendations are to not treat single-bearing ewes unless a high parasite burden is detected by FEC, to treat a proportion of twin- and triplet-bearing ewes, and to supplement triplet-bearing ewes with protein prior to lambing and wet foster the third lamb, if practical in indoor-lambing units.