Assessment of genetic variability of resistance to gastrointestinal nematode parasites in Creole goats in the humid tropics

Goat production is widespread in the tropics. Goats are very susceptible to gastrointestinal nematode infection, but there is less evidence of their g enetic resistance. Genetic resistance of Creole goats to gastrointestinal n ematodes has been studied at Guadeloupe in the French West; Indies since 19 95. The objective of this research was to investigate genetic variation for resistance to gastrointestinal nematode infection, in order to introduce t his trait into breeding schemes. Genetic variability was assessed within a Creole experimental flock. Forty-nine sire groups were characterized at wea ning and 55 during fattening after weaning. Kids were naturally infected,ma inly by Haemonchus contortus and Trichostrongylus colubriformis. Fecal egg counts were determined once at weaning and every 6 and 7 wk after drenching during fattening. Blood samples were collected every 7 wk during fattening for determination of packed cell volume. Live weights were recorded at wea ning and at the beginning and middle of every infection period during fatte ning. Genetic parameters were estimated using the REML for multivariate ani mal models. The heritability estimate for transformed fecal egg count was 0 .31 +/- 0.06 at weaning. During fattening, it increased from 0.14 +/- 0.05 at 4 mo to 0.33 +/- 0.06 at 10 mo. Heritabilities of packed cell volume ran ged from 0.10 to 0.33. At weaning, maternal heritability of fecal egg count reached 0.26 and direct heritability 0.20. After 6 mo of age, maternal eff ects were found to be unimportant for fecal egg count and packed cell volum e. Live weights presented significant genetic variability. Genetic relation ships between fecal egg counts and live weight in infected pastures were ne ver significant. Genetic correlations between packed cell volume and live w eight decreased from 0.47 to 0.10 from weaning to 10 mo of age. These resul ts demonstrated the feasibility of breeding far improved resistance to nema todes in Creole kids.