Feed additives which enhance the growth rate of beef cattle during the fattening period would be of benefit to the industry. The effects of dietary supplementation with “Bio-Boost Plus”, a product containing mineral proteinates (Cu, Zn, Mn) and yeast culture on heifer growth rate and carcass characteristics were examined. The response to the inclusion of yeast culture in the diet of fattening cattle was a 7.5% increase when averaged over sixteen different studies (Wallace and Newbold, 1993). It was postulated that the response to yeast culture would be increased with the inclusion of proteinated minerals Cu, Zn and Mn to the daily diet.

Seventy two 16 month old continental cross heifers with an initial liveweight of 393 kg were assigned on a liveweight basis to one of two treatments: a) control - diet consisting of grass silage ad libitum plus 3 kg of concentrates per head per day; b) Bio-Boost Plus - control diet supplemented with 15 g of Bio-Boost Plus per head per day. Heifers were group penned according to treatment (8 pens of 9 animals) for the 131 day experimental period. The daily concentrate (rolled barley 900, soyabean meal 80 and minerals and vitamins 20 g/kg) allowance was offered in one feed each morning and the Bio-Boost Plus was added as a top dressing to the concentrate.