In this section:
Parasite Control in Prime Lambs Flocks
In recent years the number of meat sheep raised under broad scale pivot irrigation systems in winter rainfall areas of South Australia has dramatically increased. Pivots operate in the hot, dry summer months (November–March) to enable prime crossbreed lambs to be grown out at a time of market shortage. Substantial capital investment dictates that the system must be highly intensive and efficient; failure to meet market requirements or deadlines has severe financial penalties. The greatest constraint to the viability of this farming system is heavy infections with Trichostrongylus vitrinus, a problematic parasite in winter and spring, but hitherto unrecognised as a summer pathogen.
Starting December 1998 three irrigation systems were studied to determine whether summer parasitism in lambs can be economically and sustainably controlled. Each system was destocked of sheep for at least 3 months before lambs were introduced. In December at the beginning of summer. Immediately prior to entering the system lambs were drenched and held for 2 days for worm eggs to 'clean out'. Cattle grazed the area concurrently or following the sheep. Sheep were replaced by cattle by mid-year. Levels of cattle and sheep larval worms (larvae per kg dry matter) on pasture were estimated monthly. Faecal worm egg counts were regularly monitored.
Pasture larval counts and worm egg counts remained consistently low throughout two summers demonstrating the importance of restricting contamination in the previous spring and ensuring that lambs carry no residual infection on to the pasture. This work provides strong encouragement that sustained production of prime lambs under pivot irrigation over summer is possible, given strict attention to pasture preparation and flock sanitation.
Publications:
Carmichael, I.H. (2002). Influences on internal parasitism of sheep in South-east Australia: studies of (1) Internal parasite control on pivot irrigation systems and (2) Cobalt nutrition and internal parasite interactions, Wool Tech. Sheep Breed., 50(4), 518-533.
Carmichael, I.H., Martin, R.R. & O'Callaghan, M.G. (2002). Parasite control in lambs on spray (pivot) - irrigated pastures in an Australian winter rainfall climate, Proc. Aust. Sheep. Vet. Soc., 12, 53-59.
Further information contact:
Dr Ian Carmichael
