Two trials will be carried out to assess the efficacy of a vaccine against Haemonchus contortus in sheep. Experiment 1 aims to assess the effectiveness of the vaccine in ewes during the pregnancy and lactation periods, maintained with high or low nutritional level. These ewes will be divided into four groups as follows: Group 1: immunised with the vaccine against haemonchosis and maintained with a high nutritional level; Group 2: control maintained with a high nutritional level; Group 3: immunised with the vaccine against haemonchosis and maintained with a low nutritional level and Group 4: Control maintained with a low nutritional level. The experiment 2 will evaluate the efficacy of the vaccine in commercial farms that rise different sheep breeds and presenting different management conditions to assess the contribution of the vaccine in the prophylaxis of nematode infections in "real" situations. In both trials, ewes and lambs will be trialled. Vaccinated groups will receive glycoproteins extracted from the gut of H. contortus (5 g each dose) diluted in saponin adjuvant (1 mg each dose) and the control groups will receive only the adjuvant. The ewes will be vaccinated every three weeks from the beginning of pregnancy until weaning of lambs. The lambs will be vaccinated with the same frequency from the third week until they complete five months of age. In both trials, parasitological, haematological and immunological tests will be performed.
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