immune mechanisms of resistance. A negative correlation with bodyweight makes it unsuitable in a breeding scheme. The FEC estimated at 11 months of age is thus best suited to be included in a breeding scheme as there is no conflict with any performance trait and the absence of maternal genetic effects makes its selection favourable. This criterion reflects several mechanisms of resistance, making difficult the adaptation of the parasites against the increasing resistance of the host. In

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... , this selection could also be optimized using genetic markers of resistance. Genes of resistance The study performed on Creole goats for quantitative trait loci (QTL) associated with GIN is the only one available in this species (de la Chevrotiè re et al., 2009). A total of 13 genomic regions associated with GIN resistance were detected. Five QTL were significant at the 1% chromosome-wide threshold and the average effect of most QTL exceeds one phenotypic standard deviation. Many QTL were found on chromosomes known to carry candidate genes such as the interferon gamma or the IgE gene. The use of SNP chip will complement these first results and provide a more powerful detection of QTL. Over the past several years there has been an increased interest in using Dorper sheep in crossbreeding programs with local sheep breeds in the Caribbean. The Dorper breed was chosen for its heavy muscling in an attempt to increase the growth rate and size of lambs produced for the local market. It has been shown that Dorper 3 St. Croix White lambs grow faster and yield heavier carcasses than St. Croix White lambs when they are raised on either a concentrate or forage ration after weaning (Dodson et al., 2005; Godfrey and Weis, 2005) . The Dorper was developed for an arid environment and is not known for prolificacy, unlike the indigenous hair sheep in the Caribbean that have been selected for a humid environment and are prolific. There is little information on how Dorper 3 St. Croix White crossbred ewes will perform under tropical conditions found in the Caribbean. The objective of this study was to compare production traits of St. Croix White and -