The study compares the parasitological and productive traits of Criollo lambs native to the central Mexican Plateau (CNCMP) and Suffolk (SU) lambs experimentally infected with Haemonchus contortus. CNCMP lambs (n= 20) and SU lambs (n= 15) were infected with L3 of H. contortus while five lambs of each genotype were kept as controls. Fecal egg count (FEC), packed cell volume (PCV), blood eosinophil number (BEN), ocular mucous membrane color (as measured by the FAMACHA index), changes in body condition score (BCS) and cumulative live weight gain (CLWG) were measured weekly during a 20-week period. On week 20, all animals were euthanized and the number of adult worms (AW) in the abomasum was counted. Infected SU lambs had higher (p< 0.05) FEC and AW mean values compared to CNCMP lambs, which had a higher mean BEN count (p< 0.05). Infected lambs had lower PCV values than controls, regardless of genotype, and had a negative correlation (r= -0.84, p< 0.05) with the FAMACHA index. BCS tended to decline for infected SU lambs and increased slightly for infected CNCMP lambs. CLWG differed in all groups (p< 0.05); infected SU lambs gained 12.1 ± 1.9 kg, infected CNCMP lambs gained 18.8 ± 0.7 kg, control SU lambs gained 34.6 ± 1.6 kg, and control CNCMP lambs gained 26.9 ± 0.8 kg. In conclusion, CNCMP lambs had a smaller worm burden, a better ability to maintain their productive traits, and were less affected by infection with Haemonchus contortus. © 2010 Elsevier B.V.
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