Studies have shown that reducing energy intake by restricting dry matter intake (DMI) at a constant forage: concentrate (F:C) ratio is more effective at increasing carcass lean and reducing carcass fat content than is reducing energy intake by increasing the F:C ratio (1). Research at this Institute has also shown that, per megajoule of digestible energy (DE), diets restricted in this manner are 45 % more efficient at producing carcass lean.
The mechanism by which these methods of restriction result in these differences in carcass composition has previously been assumed to be that of rumen fermentation. More recently however, the significance of rumen fermentation in controlling the carcass composition of beef cattle has been questioned (2,3).
The aim of this experiment was to examine the effect of decreasing the F:C ratio, at constant DE and DMI, on both rumen and endocrinological parameters, in particular the hormones insulin and insulin like growth factor-1 (IGF-1), in finishing beef steers.