BREED AND SEASON EFFECTS ON THE PERI-PARTURIENT RISE IN NEMATODE EGG OUTPUT IN INDIGENOUS EWES IN A COOL TROPICAL ENVIRONMENT

A study was carried out at the International Livestock Research Instit ute (ILRI) Debre Berhan Research Station in Ethiopia from 1992 to 1995 to compare the peri-parturient rise (PPR) in faecal nematode egg coun ts (FEC) in ewes of two indigenous sheep breeds. A total of 1439 Menz and 1347 Horro ewes were single sire mated following oestrus synchroni zation to lamb in the wet and dry season. Three ewe treatment groups w ere constituted as mated/lactating/undrenched; mated/lactating/drenche d; unmated/undrenched for three wet and three dry lambing seasons. All ewes grazed naturally contaminated pasture. Levels of faecal egg outp ut were monitored at mating, 3 months after mating, 2 weeks before lam bing, 4, 8 and 12 weeks post-lambing, A significant PPR in FEC occurre d 2 weeks before lambing and peaked at 4 weeks post-parturition in ewe s lambing just before the beginning of the dry season (October/Novembe r). There was no significant increase in FEC when lambing occurred bef ore the onset of the long rainy season (May/June). The PPR in this stu dy was associated with both lactation and seasonal availability of thi rd-stage infective larvae on pasture. There was no consistent breed di fference in FEC during the six sampling periods from mating to weaning . Faecal cultures and worm counts from both breeds confirmed the prese nce of Longistrongylus (Pseudomarshallagia) elongata, Trichostrongylus spp. land Haemonchus contortus. The role of the peri-parturient rise of EEC in ewes in gastrointestinal nematode transmission is discussed. (C) 1998 Elsevier Science B.V. All rights reserved.