New Zealand Journal of Agricultural Research abstracts

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Parasitological characteristics of fleece-weight-selected and
control sheep

J. F. WILLIAMSON
H. T. BLAIR
D. J. GARRICK

Department of Animal Science
Massey University
Palmerston North, New Zealand

W. E. POMROY

Department of Veterinary Pathology and
Public Health
Massey University
Palmerston North, New Zealand

P. G. C. DOUCH
R. S. GREEN

AgResearch
Wallaceville Animal Research Centre
P.O. Box 40 063
Upper Hutt, New Zealand

Abstract  Male sheep (aged 15 months) from a Massey University flock selected for increased fleece weight for 37 years (FW, n = 13) and unselected controls (C, n = 13), were infected with larvae of Haemonchus contortus (n = 4000), Ostertagia circumcincta (n = 22750), and Trichostrongylus colubriformis (n = 25000). Some FW sheep (n = 7) and C sheep (n = 5) had previously been treated with an albendazole controlled release capsule (CRC), at 6 months of age. Faecal egg counts (FEC) were higher in FW than C sheep (4204 versus 300 eggs/g, P < 0.0001), as were the numbers of adult H. contortus (1151 versus 249, P < 0.01) and O. circumcincta (2268 versus 600 eggs/g, P < 0.05), when slaughtered at Day 28. Numbers of T. colubriformis (5838 versus 5266 eggs/g) did not differ between lines but were higher in previously CRC-treated sheep than in untreated sheep (7585 versus 3810 eggs/g, P < 0.05). Thymus weights (corrected for liveweight) were higher in FW sheep than C sheep (P < 0.01) and lower in CRC-treated sheep than in untreated sheep (P < 0.01). Numbers of mast cells were inversely related to number of parasites in FW sheep, but not C sheep. The level of circulating antibodies to H. contortus did not differ between groups. This study confirms that higher FEC in FW sheep are a result of decreased resistance to establishment of internal parasites (of some species).

Keywords  sheep; selection; internal parasites; faecal egg count; mucosal mast cells; thymus weight; antibodies; albendazole controlled release capsule

New Zealand Journal of Agricultural Research, 1995, Vol. 38: 389-397

0028-8233/95/3803-0389 $2.50/0 (c) The Royal Society of New Zealand 1995

PDF file of entire paper: medium quality (649K); (scanned from paper original: notes about this process)

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