Abstract
The study investigates the right size of cow in terms of both biological and economic efficiency under a typical production system in semi-arid South Africa. Cow size influences biological efficiency of individual animals, which influences herd composition and stock flow on a predetermined resource base. This in turn influences the economic efficiency of the herd. Individual cows were classified as either small, medium, or large and their individual biological efficiency determined. When similar reproduction and growth rates were assumed, large cows were the most biologically efficient, followed by medium and small cows. Income from the herd of small cattle was the lowest, as fewer kilograms of beef were available to sell. Allocated costs for the herd of small cattle were the highest, due to a large number of expenses being charged per head of cattle. Subsequently, when economic efficiency was calculated, the herd of large cattle was more profitable than its smaller counterparts. The herd of large and medium cattle would become less profitable than the herd of small cattle at lower reproduction rates, and these reproduction rates were calculated. Smaller cattle have a faster maturity rate than larger cattle. A faster maturity rate provides the opportunity for early breeding. The effect of limiting feed intake of small, medium, and large cattle was compared and yielded varying results. The study concluded that cattle size influences biological efficiency, biological efficiency influences economic efficiency however there are many more variables that influence biological and economic efficiency other than size, such as reproduction rates.