Parasitological response of hair sheep to an experimental infection with gastrointestinal nematodes

The response of Pelibuey (P), Blackbelly (BB) and Dorper x Pelibuey (DxP) lambs to an experimental infection with gastrointestinal nematodes (GIN) was studied. Twenty-one two-month-old P, 15 three-month old BB, and 14 two-month-old DxP lambs, with live weights (LW) of 12.0±3.2, 13.6±3.9, y 13.0±3.6 kg, respectively, were used. The experiment was carried out in two stages of 30 dayseach; at the first stage, the lambs were grazing, while in the second one they were confined. At both stages, the lambs were infected with 3,000 larvae of a mixture of gastrointestinal nematodes (L3). Every seven days, fecal samples were taken to count the number of eggs per gram of feces (EPG) as well as blood samples to measure packed cell volume (PCV); in addition, their LW, body condition (BC), and color of ocular mucous (COM) were assessed. The BB and DxP lambs had the highest fecal egg counts (5,259±654 and 5,515±654 EPG, respectively), while the P the lowest (3,252±515,P<0.01). For the PCV, the most affected (P<0.01) were the BB lambs (0.257±0.005), because the P and DxP lambs had higher values (0.281±0.004 and 0.275±0.005). The resistance of P lambs to GIN was superior to that of BB and DxP lambs.