
TY  - JOUR
A1  - Albers, GAA 
A1  - Gray, GD 
A1  - Le, Jambre LF 
A1  - Piper, LR 
A1  - Barger, IA 
A1  - Barker, JSF 
T1  - The effect of <I>Haemonchus contortus</I> on liveweight gain and wool growth in young merino sheep
JF  - Australian Journal of Agricultural Research
JO  - Aust. J.  Agric. Res.
Y1  - 1989
VL  - 40
IS  - 2
SP  - 419
EP  - 432
KW  - 
UR  - https://doi.org/10.1071/AR9890419 
N2  - Results of three crossover experiments on a total of 1078 Merino lambs were used to estimate the effect of a single infection of 11 000 Haernonchus contortus larvae on liveweight gain, clean wool growth and wool fineness. Estimates were obtained by direct comparison of six groups of infected and matched uninfected iambs under field conditions. Infections were terminated after 5 weeks, at which stage some mortality had occurred and haematocrits had in five out of six cases declined to less than 24%. Over an 8-9 week period, beginning at the time of infection, liveweight gains of infected lambs were reduced by on average 1.29 kg (range 0.83-1.71 kg) amounting to 38% (12-64%) of liveweight gain in uninfected controls. The detrimental effect of infection was most severe towards the end of the infection period. There was a lag phase of 3-6 weeks between larval administration and the onset of wool growth depression. The reduction of wool growth persisted for at least 14 weeks after termination of infection. The size of this reduction was very variable. Over a 4 month post-infection period, reductions ranged from 11 to 97 g clean wool (mean 46 g) or 1.4 to 157% (mean 6.8%) of clean wool grown by uninfected lambs. Estimates of reduction of fibre diameter over the same period ranged from 0.39 to 0.79 8m (mean 0.57 8m). 
ER  -

