Variability of resistance in goats infected with Haemonchus contortus in Brazil

The variability between and within breeds with respect to nematode egg coun ts (EPG), packed cell volume (PCV) and hemoglobin (Hb) was studied in 36 ye arling female goats of the Caninde (15), Bhuj (6) and Anglo-Nubian (15) bre eds, exposed to Haemonchus contortus. Nematode-free goats were turned to a contaminated paddock in late February. From then on, fecal egg per gram cou nts (EPG), packed cell volume (PCV) and hemoglobin (Hb) were determined at 2-week intervals up to Week 18. The EPG, transformed as [log(EPG + 75)], va ried (P < 0.01) between goats within breeds and between weeks of exposure, but not between goat breeds (P > 0.05). PCV and Hb were affected by goat br eeds (P < 0.05), by goats within breeds (P < 0.01) and by weeks of exposure (P < 0.01). Anglo-Nubians had higher (P < 0.01) PCV and Hb than Caninde; B huj had intermediate values. There were two EPG rises; one between Weeks 6 and 10 and the other between Weeks 14 and 16. The within breed variability was marked during the EPG rise on Week 6, when individual egg counts ranged from 130 to 2500. The EPG rises coincided with drops in Hb. PCV presented a similar trend, though not as marked. Haemonchus was responsible for more than 95% of nematode eggs counted. Considering the goat as experimental uni t, the correlation coefficients (r) were: -0.45, P = 0.0064, between log(EP G + 75) and PCV; and -0.53, P = 0.0009, between log(EPG + 75) and Hb. The n egative correlation between egg counts and blood values suggested breed dif ferences in PCV and Hb were related to resistance to H. contortus infection and/or to its effects. (C)2000 Elsevier Science B.V. All rights reserved.