When used correctly, the growth stimulant Zilmax could be the best way to beef up beef cattle, according to veterinarian Dr Danie Odendaal. He discussed the safety of this product at the recent annual congress of the Limpopo Red Meat Producers’ Organisation in the Baltimore Farmers’ Hall. Dr Odendaal contended that Zilmax, with the active ingredient zilpaterol, held positive short-term spin-offs in the last part of the feeding phase in feedlots, but there were negative perceptions about the use of such products in other countries. South Africa is the second country in the world to register Zilmax, Mexico being the first. In August 2006 it was registered by the FDA in America, but is not yet commercially available. Apparently the fact that zilpaterol is also used in human asthmatic medication makes people wary.
Dr Odendaal explained that the relatively small dosages used in feedlots were harmless. Studies on the safety of Zilmax in food were made public last year and, based on these, Dr Odendaal considered it safe as long as it was used according to directions, and people could eat around 300g of meat without negative effects. Only at 10 times this amount, eaten almost immediately after slaughtering, could it become dangerous. Within 48 hours of terminating feeding with the product, none can be detected in the meat.
Zilmax has been registered to promote weight gain. Animals receiving it show a weight gain increase of about 27% over untreated animals. It also improves feed conversion efficiency and increases carcass leanness. Dr Odendaal said the physiological effects of Zilmax were similar to those of adrenaline. “It opens the lungs and blood vessels, as well as stimulating more effective utilisation of protein to build muscle mass.” Farmers should, however, not believe Zilmax only has positive qualities. Dr Phillip Strydom of the Agricultural Research Council said Zilmax could be seen as positive in the feedlot, but could negatively affect eating quality. Meat from Zilmax-fed cattle needed to mature for a longer period, and short-changing on the maturing process could increase the risk of a dissatisfied customer. Dr Strydom added that the electrical stimulation used by some abattoirs to improve tenderness has a further positive effect on zilpaterol-treated meat, with some muscles more affected than others.
Dr Strydom and Dr Odendaal agreed that Zilmax-fed cattle must not receive Zilmax for at least two days before slaughtering for human consumption and be slaughtered on the third day, but recommended a withdrawal period of three days before slaughtering. Zilmax (4,8%) should be mixed into feed at 125g per ton – around 60mg of the stimulant per animal daily. Zilmax is already used extensively in this country. Dr Odendaal estimated most feedlots with more than 5 000 cattle used Zilmax. – Susan Botes