GENETIC-RESISTANCE TO GASTROINTESTINAL NEMATODE PARASITES IN POLISH LONG-WOOL SHEEP

A study was undertaken from 1991 to 1994 on a farm in southern Poland to evaluate the genetic parameters of resistance to gastrointestinal n ematodes. The predominant species were Teladorsagia circumcincta and H aemonchus contortus. A total of 32 sires were evaluated, around 15 per year. Faecal egg counts were measured twice during the 4-month grazin g season for lambs (total 659 lambs) and three times for their mothers (total 327 ewes). Infection levels were high during the first 2 years and low during the last 2 years. Using an animal model, the heritabil ity of log(10)(epg + 25) increased from 0.20 in August to 0.33 in Sept ember for lambs, and from 0.18 in May to 0.25 in September for ewes. T he repeatability of ewe faecal egg count between years was 0.25. A gen etic correlation of 0.58 was found between faecal egg count in ewes an d in 6-7-month-old lambs. A negative genetic correlation (-0.61) was e stimated between faecal egg count in September and daily weight gain o f lambs from 70 days of age to the end of grazing season (7 months of age). The results confirm the feasibility of genetic selection of shee p for resistance to nematode parasites in an environment where T. circ umcincta and H. contortus are the dominant species. (C) 1998 Australia n Society for Parasitology. Published by Elsevier Science Ltd. All rig hts reserved.