In this section:
Worm Infections & Cobalt Defiency in Grazing Sheep
Cobalt deficiency can impair the immune function of sheep and this may increase vulnerability to infection with worms. This interaction has not been previously studied. The lease by SARDI of a coastal farm in a recognised cobalt deficient area provided an opportunity to conduct a field study on this interaction in weaners, which is the class of sheep most susceptible to both problems.
Ninety Merino cross weaners were artificially infected with a standard low dose of the commonest local worms. Ninety other weaners were kept worm free. Within both groups of infected and worm-free sheep 30 animals were given cobalt bullets, 30 received a monthly injection of Vitamin B12 and 30 had no cobalt supplementation. The study was from October 1999 - May 2000. Animals were weighed monthly and fleece measurements were done at the end of the trial. Plasma Vitamin B12 levels confirmed the development of cobalt deficiency in animals which did not receive supplementation.
Cobalt deficient animals had lower bodyweights than supplemented animals. Sheep with low levels of worms had lower body weights than worm free sheep in both cobalt deficient and adequate groups. There was also a marked cobalt/worm interaction. Fleece weights showed similar tendencies. Fleece measurements have been done.
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., Judson, G.J., O'Callaghan, M.G. & Martin, R.R. (2002). Worm infections and cobalt deficiency interactions in grazing Merino cross weaners. Proc. Aust. Sheep Vet. Soc., 12, 41-45.
Further information contact:
Dr Ian Carmichael
