The role of cysteine in the increased parasite susceptibility of Romney sheep
selected for hogget fleece-weight.
F.M. Miller, H.T. Blair, G.W. Reynolds and D.K. Revell
Department of Animal Science, Massey University, Palmerston North
Proceedings of the New Zealand Society of Animal Production. 1998,
58: 150-153
To investigate the potential role of cysteine in the increased
parasite susceptibility of sheep selected for increased wool production,
ten sheep from both fleece-weight-selected (FW) and randomly-selected
(C) Romney lines received either 2g of supplemental cysteine per day, or
saline, via abomasal infusion. Following drenching to remove any
pre-existing parasites, all sheep were dosed with Haemonchus contortus
and Trichostrongylus colubriformis infective larvae. Cysteine infusion
elevated plasma cysteine levels by an average of 65% (P<0.0001).
Off-pasture faecal egg counts (FEC) were higher in FW than C sheep (645
versus 200 eggs/g, P<0.01). No significant effects of line or infusion
treatment on FEC were observed following the trial infection, though on
days 52, 57 and 58, FEC in sheep receiving saline were at least twice
those of sheep receiving cysteine. Total H. contortus counts were
greater in FW than C lines of sheep (1208 versus 1055, P<0.05), while
total numbers of T. colubriformis did not differ between lines or
infusions. This study confirms the greater susceptibility of FW sheep to
internal parasites, and suggests cysteine may influence certain aspects
of immunocompetency in sheep.
Keywords: NZSAPAB;
helminths; sheep; wool production; cysteine; immunocompetency
Last Updated 12-09-1998
