Genetic factors affecting antibody responses to four species of nematode parasite in Romney ewe lambs

• Published in: International journal for parasitology 1995-07, Vol.25 (7), p.823-828
• Main Authors: Douch, P.G.C., Green, R.S., Morris, C.A., Hickey, S.M.
• Format: Article
• Language: English
• Subjects: Animals; Antibodies, Helminth - biosynthesis; Antibodies, Helminth - blood; Antibodies, Helminth - genetics; antibody; Cooperia curticei; Feces - parasitology; Female; genetic correlation; Haemonchus - immunology; Haemonchus contortus; heritability; Immunogenetics; Immunoglobulin G - biosynthesis; Immunoglobulin G - blood; Immunoglobulin G - genetics; Nematoda - immunology; Nematode Infections - genetics; Nematode Infections - immunology; Nematode Infections - veterinary; Ostertagia - immunology; Ostertagia circumcincta; Parasite Egg Count; sheep; Sheep - genetics; Sheep - immunology; Sheep - parasitology; Sheep Diseases - genetics; Sheep Diseases - immunology; Sheep Diseases - parasitology; Trichostrongyloidea - immunology; Trichostrongylus - immunology; Trichostrongylus colubriformis
• ISSN: 0020-7519; 1879-0135
• DOI: 10.1016/0020-7519(94)00213-8

Serum levels of antibodies (Ab) and immunoglobulin G 1 (IgG 1) to the larval (L3) stage of the internal parasites Cooperia curticei and Trichostrongylus colubriformis and levels of Ab to the L3 stages of Haemonchus contortus and Ostertagia circumcincta were determined in 1432 Romney ewe lambs which were born on one farm in 1990 and 1991 and were the progeny of 63 rams. The objectives were to estimate heritabilities of, and genetic correlations among, the serum concentrations in newly weaned lambs under commercial conditions and to estimate genetic correlations of Ab and IgG 1 with production traits. Lambs were exposed to a natural parasite challenge on pasture, following an anthelmintic drench at weaning. Blood and faecal samples from 4- to 6-month-old lambs were then taken when the mean faecal nematode egg count of a monitor group reached 800–1500 eggs g −1. Heritabilities for the serum levels of the four Abs ranged from 0.25 ± 0.05 to 0.37 ± 0.06. Heritabilities for the level of IgG 1 developed against C. curticei was 0.19 ± 0.04 and against T. colubriformis, 0.18 ± 0.05. Genetic correlations between Abs for the 4 species were high, averaging 0.84, and between the two IgG 1s it was 0.82. The genetic correlations between Ab or IgG 1 levels and weight or gain traits were negative (for the 6 significant values out of 18), with yearling fleece weight positive (for the 2 significant values out of 6), whilst those with log e faecal egg count were all negative (average −0.15). These results show that Ab and IgG 1 traits are heritable and the data suggest that ram selection based on average serum antibody levels would lead to modest reduction in faecal egg counts (about 20% of the genetic gain achievable from selection based on faecal egg count), reduced weaning weight and weight gain, but increased yearling fleece weight and breech soiling.