The influence of breed on the susceptibility of sheep and goats to a single experimental infection with Haemonchus contortus
Preston, J.M.; Allonby, E.W.
Veterinary Record 103(23): 509-512
1978
ISSN/ISBN: 0042-4900 PMID: 741614 Document Number: 136019
Four breeds of sheep and 3 breeds of goat (12 animals/breed), maintained on high or low planes of nutrition, were given a single infection of 350 Haemonchus contortus larvae/kg live weight, and faecal egg counts were made twice weekly for 14 or 15 wk after infection. Egg counts in the Hampshire Down (HD) sheep exceeded 10 000 eggs/g of faeces (e.p.g.) for most of the experimental period, whereas the Red Masai (RM) sheep did not exceed 800 e.p.g. on the high nutritional plane and 2000 e.p.g. on the low plane; the Corriedales and Merinos had intermediate values. Galla [Somali] and East African (EA) goats had counts of about 10 000 e.p.g. v 1700 for Saanens.For HD, Corriedale, Merino and RM sheep and EA, Galla and Saanen goats (4/group) infected with 350 larvae/kg and killed 4 wk later, the number of worms recovered as a percentage of the larval dose averaged 22.8 (range = 20.4-25.6), 15.2 (14.0-18.0), 13.0 (10.5-17.3), 3.5 (2.1-4.8), 28.9 (20.0-33.6), 19.4 (17.6-23.2) and 14.6 (10.7-19.5). Differences between the HD and Corriedale, Merino and RM, and EA and Galla breeds were significant. Four breeds of sheep and 3 of goats maintained on high or low planes of nutrition were infected with 350 Haemonchus contortus larvae/kg body-weight. Animals on a low-protein diet developed much higher faecal egg counts than did those on a diet high in protein. Irrespective of diet, Red Masai had consistently lower counts than the other sheep breeds, Hampshires had the highest, and the egg counts of Corriedales and Merinos were intermediate. The Saanen goats had consistently lower egg counts than the East African and Galla goats. These breed differences in egg counts in sheep and goats were reflected in autopsy worm recoveries (from those animals on a high-protein diet only). The animals on a low-protein diet developed a more severe clinical disease and, unlike those on a high-protein diet, did not show a sharp decline in egg counts (self-cure) towards the end of the period of observation (16 weeks).