Late-Breaking: The Varying Relationship Between Packed Cell Volume And Fecal Egg Count In Different Breeds Of Hair Sheep And Meat Goats Artificially Infected With Haemonchus Contortus

Packed cell volume (PCV) and fecal egg count (FEC) have been used as indirect and direct indicators of haemonchosis, respectively. The relationship between PCV and FEC was evaluated with growing hair sheep and meat goats in 3 central sire performance tests. There were 52 Dorper (3.9 ± 0.13 mo old; initial BW 28.2 ± 0.74 kg), 96 Katahdin (3.8 ± 0.05 mo; 31.0 ± 1.12 kg), 49 St. Croix (4.3 ± 0.06 mo; 19.0 ± 0.77 kg), 48 Boer (3.9 ± 0.08 mo; 19.4 ± 0.78 kg), 55 Kiko (3.6 ± 0.06 mo; 19.1 ± 0.46 kg), and 57 Spanish (4.0 ± 0.09 mo; 18.0 ± 0.44 kg) males used. A 50% concentrate pelleted diet was consumed ad libitum in confinement. Animals were dewormed then dosed with 10,000 infective Haemonchus contortus larvae, with PCV and FEC determined 21, 28, 35, 42, and 49 d later. The PCV and FEC were correlated (P=0.509). A mixed effects model for each species included fixed effects of breed, year, breed×year, day as a repeated measure, and log transformed FEC (lnFEC) and lnFEC×breed as covariates. Breed affected (P=0.004) PCV in goats (24.9, 27.1, and 25.9% for Boer, Kiko, and Spanish, respectively; SEM=0.42) but not in sheep (P=0.40; 30.2, 26.6, and 31.2% for Dorper, Katahdin, and St. Croix, respectively; SEM=0.29). There were effects of lnFEC×breed (P≤0.01) for Dorper, Katahdin, St. Croix, Boer, and Kiko (-0.0011, -0.0005, -0.0006, -0.0005, and -0.0009% per egg) but not Spanish (-0.0002% per egg; P=0.87). In conclusion, PCV does not appear highly reflective of FEC in Spanish goats infected with H. contortus, and the nature of the relationship varied among other breeds of sheep and goats. Based on the magnitude of the lnFEC×breed coefficient, Dorper sheep and Kiko goats incurred relatively greater reduction in PCV as FEC increased, and correlations indicate strongest relationships for Katahdin sheep and Boer goats.