Factors affecting the immune response of hairy lambs on the first infection with gastrointestinal nematodes in a hot humid climate in Mexico

The objective was to determine the influence of some on faecal nematode egg counts (FEC), immunological, hematological and productive indices of Pelibuey, Blackbelly and Katahdin lambs during their first natural infection in mountain range region of Tabasco, Mexico. Every month for a year, six lambs were introduced to grazing, where they remained for 30 days and subsequently stabled for 30 days. A sampling was carried out before and after grazing (day -5 and 30), then at 45 and 60 days after stabling. The number of nematode eggs per gram of feces (EPGEPG), agglomerated cell volume (ACV) and plasma protein (PP) level were recorded, the total and differential leukocytes count was also performed and the IgA level was estimated by indirect ELISA. The data was analyzed with a repeated measures model over time. Increased infection was observed from October to December with 7933 to 13983 EPG, while from February to April the number of EPG ranged between 2300 to 2600 EPG. At 60 days post-infection, Pelibuey lambs showed higher EPG than the Katahdin and Blackbelly breeds. The Katahdin breed had highest ACV and PP (P <0.05). Subsequently, the ACV decreased due to the presence of H. contortus. There was no significant IgA response compared to the positive control (less than 6.9 %). It is concluded that immunological parameters for first-infected lambs do not allow to reduce the effects of gastrointestinal nematodes.