Some effects of diet on beef meat and fat attributes

Steers were fed for nine weeks on either ryegrass/clover pasture or maize (six animals per group), to evaluate the effects of diet on attributes of meat and fat. Feed intake was restricted in the grain-fed group with the intention of producing equivalent growth rates in the two treatment groups, but this resulted in significantly slower weight gain, reduced carcass weight, and reduced subcutaneous and intramuscular fat. Nevertheless, the glycolytic potential (an estimate of pre-slaughter glycogen) in the M. longissimus dorsi lumborum was approximately 20% higher (P < 0.05) in the grain-fed cattle, while the ultimate pH of the meat was equivalent for both groups. The results suggest that grain-based diets can increase muscle glycogen concentrations independent of the higher calorific intake normally associated with grain diets, probably in response to changes in rumen fatty acid production. Compared with grain diet, pasture diet resulted in significantly higher (P < 0.01) muscle tocopherol content, but did not influence meat colour. The dietary treatments influenced fat colour, but both carotene content and energy intake may be responsible for this effect. The microbiological profile of meat during chilled storage was not affected by diet.