Provision of additional trace elements to cattle at grass by means of free-access mineral mixtures, feed blocks or molassed liquid feeds results in both wide variation and unpredictable individual intakes. Frequently, more than one trace element may be required and sometimes, for example, animals may individually receive combinations of selenium (by injection or rumen bolus), copper (by injection or as copper oxide needles) and cobalt (by rumen bolus or vitamin B12 injection).

This communication describes the use of a multi-trace element/vitamin bolus system (“Alltrace”, Agrimin Ltd.) in situations where dietary selenium intakes were very low over extended periods. The bolus is a dietary supplement composed of normal trace element salts such are used in mineral mixtures, vitamin sources and copper oxide powder. It is in the form of a compressed cylinder (2·5 cm diameter × 7·5 cm length) coated, apart from one exposed end, with an impervious polymer. Two boluses, by a process of solution and mutual erosion in the reticulum, release nutrients at mean rates (estimated by the use of rumen-fistulated cows) over about 240 days of 2 mg Se and 9 iu vitamin E with (mg/day) Cu 138, Mn 71, Zn 113, Co 2,1 2·1 with (lu/day) vitamin A 4644 and vitamin D 929. An end weight is included to increase the overall density. This disperses to leave no permanent residue in the rumen.