Kl. Shaw et al., EFFECTS OF WEANING, SUPPLEMENTATION AND GENDER ON ACQUIRED-IMMUNITY TO HAEMONCHUS-CONTORTUS IN LAMBS, International journal for parasitology, 25(3), 1995, pp. 381-387
This study was designed to investigate whether delaying the age of wea
ning, or feeding a protein-rich supplement alters the rare at which la
mbs develop immunity to Haemonchus contortus and whether there is any
interaction between nutrition, stress of weaning, and gender and the d
evelopment of this immunity. Ninety-six Merino lambs were allocated to
one of four treatment groups: supplemented-unweaned; supplemented-wea
ned; unsupplemented-unweaned; unsupplemented-weaned. There were approx
imately similar numbers of male and female lambs in each group. Supple
mented lambs received 80 g/head/day of a protein-rich pellet from 16 t
o 23 weeks of age. Over the same period the lambs were drenched with 3
00 H. contortus larvae twice per week, Faecal worm egg counts were det
ermined every week, and PCV and liveweight every 2 weeks for each lamb
, Neither weaning nor sex had any effect on PCV (P > 0.05) but from da
y 50 after the start of infection, the decline in PCV was more pronoun
ced in unsupplemented than in supplemented lambs, Faecal worm egg coun
ts were higher (P < 0.001) in unsupplemented-weaned than in supplement
ed-weaned lambs and in females when compared with castrates (P < 0.03)
. There was a weaning x supplementation x age interaction (P < 0.03) w
ith unsupplemented-weaned lambs developing a higher faecal egg count t
han supplemented-weaned lambs. There was also a significant (P < 0.02)
sex x weaning x age interaction with weaned-female lambs having a hig
her faecal egg count than weaned-castrate lambs; egg counts increased
more rapidly in unweaned-female lambs than in weaned-female lambs. Tog
ether, these data suggest that protein supplementation of lambs enhanc
ed the development of immunity to haemonchosis, whereas weaning at 4 m
onths of age bad no significant effect.