Five-year old Coopworth pregnant twin bearing ewes were allocated to four periods of treatment which commenced either -4, 0, 6 or 12 weeks from lambing periods 1 to 4, respectively. Within each period, pregnant ewes were further allocated to one of two groups (n+6) one receiving 4000 Ostertagia(Teladorsagia) circumcincta larvae per day for 30 days (MCI) or no infection (NIC). All ewes were housed indoors and offered a pelleted diet. Faecal egg counts, ewe liveweight, food intake, milk production and serum pepsinogen were determined weekly. Wool growth, fibre diameter and tensile strength were determined on wool grown within each experimental period. Abomasal damage, as judged by serum pepsinogen, occurred during all periods of infection. The magnitude of production losses varied with time of challenge. Parasitism reduced milk production by 10-59% (p<0.01) and wool staple strength by 29-44% (p<0.01) with greatest effects on wool staple strength being recorded during period 1. During lactation food intake (p<0.01) was reduced by 30% in period 1 by parasitic infection but little effect was seen prior to parturition. These data confirm that significant production losses do occur in breeding ewes. The effects on ewe production of any larval challenge will depend on the timing of the challenge will depend on the timing of the challenge and on the susceptibility of the ewe to infection at that time.

JA, Duckworth, and GK Barrell

Proceedings of the New Zealand Society of Animal Production, Volume 51, , 55-62, 1991
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