READJUSTMENT OF THE SUPPLY OF COBALT IN T HE RUMINANT - A CRITICAL APPROACH

Cobalt is an essential oligo-element in ruminants for two reasons: fir stly, for the ruminal micro-population and in particular for the cellu lytic flora and secondly for the animal itself by the supply, via micr obial activity, of cobalamine (or vitamin B12). It seems that the clas sic recommendation of 0.1 ppm of cobalt in the diet needs to be revise d considering recent research conducted both in vitro and in vivo. In order to optimise the digestibility of the cellulose found in forages a level of 0.3-0.5 ppm seems reasonable. As for the production of vita min B-12, vital for the host and for the ruminal protozoa, it increase s with the level of cobalt available for bacterial synthesis. Therefor e, the author recommends an increase in the amount of cobalt to a leve l of 0.3-0.5 ppm, with a minimum of 0.25 ppm in a soluble form (chlori de or sulphate) and therefore easily extractable.