In search of tropically adapted cattle: does size matter?

Abstract

The body size of individuals of a species of herbivore in the tropics can be half that of individuals of the same species in temperate zones. This occurs because the tropics do not have the large quantities of high quality, young, green grass leaves needed by large herbivores for growth, gestation, lactation and replenishment of weight lost during the dry season. Instead, the tropics have large quantities of tall grasses containing high levels of fibre and lignin. Herbivores take a long time to masticate and ruminate this, and they take a long time to digest it. This limits their dry matter intake, and consequently the energy and nutrients available to them.
Tropical environments select for cattle with small frame size, while industry selects for large frame size. Industry maintains large cattle through a range of management practices, sometimes with very high costs. It is proposed that smaller framed cows will more regularly achieve condition scores needed for high weaning rates. Higher weaning rates should increase the amount of beef produced per hectare, and smaller framed cows may have lower production costs.