The effect of selection of both sire and dam on the response of F1 generation lambs to vaccination with irradiated Trichostrongylus colubriformis larvae

Windon R. G. and Dineen J. K. (1981). The effect of selection of both sire and dam on the response of F₁ generation lambs to vaccination with irradiated Trichostrongylus colubriformis larvae. International Journal for Parasitology11: 11–18. Rams and ewes, tested for responsiveness to vaccination with irradiated T. colubriformis larvae at an early age, were mated on the basis of responder × responder and non-responder × non-responder. Progeny were vaccinated at 8 and 12 weeks of age with 20,000 irradiated larvae, treated with anthelmintic at 16 weeks and challenged with 20,000 normal larvae at 17 weeks. Faecal egg counts of progeny from responder matings were significantly lower than progeny from non-responders, and within each mating type, ewe lambs had markedly lower egg counts than ram lambs. The level of circulating complement-fixing antibodies to T. colubriformis larval extract were inversely related to egg counts. Thus, ewe progeny from responder matings had the highest serum antibody levels, non-responder ram progeny had the lowest levels and responder rams and non-responder ewes had similar intermediate levels. In vitro responses of cells stimulated with T. colubriformis L₃ antigen were greater in progeny from responder matings, whereas responses to bacterial lipopolysaccharide were higher in progeny from non-responder matings. The results confirm that the response to vaccination at an early age is genetically determined, and show that the response of progeny is most vigorously expressed when both sires and dams have been selected.