Feeding systems for increasing marbling in cattle

Summary

The factors controlling the expression of the economically important fat tissue, marbling, are poorly understood and need to be studied to allow Australian producers to compete on export markets in the Asia-Pacific area. For example cattle finished to similar age, weight and fatness specifications in Australian feedlots typically have lower marbling scores than genetically similar cattle in America and Japan. It is suggestedthat diet may be a factor in this difference. Typical ruminant diets are heavily fermented in the reticulo-rumen and as a consequence acetate is a major substrate for fat synthesis rather than glucose.

Despite this, fat depots show different rates of fat synthesis from glucose versus acetate. Marbling adipocytes show a preference for glucose while subcutaneous adipose tissue uses mainly acetate for fat synthesis. Consequently dietary regimes which increase the availability of glucose are likely to increase the rate of marbling. The overall aim of this project was to use lipogenic enzymes in subcutaneous fat to assess the effects of glucose and nutrition on the capacity for fat synthesis. The approach was to use the activity of ATP citrate lyase and acetylCoA carboxylase as indices of fat synthesis from glucose and glucose plus acetate respectively. A further aim was to use the enzyme markers as an index of glucose availability within the animal under different dietary regimes.