Roughage Ruminants consume a considerable volume of roughage, and the rumen may be filled before energy requirements are satisfied. Normally, however, feeding behavior changes to accomodate differences in the energy content of the feed. Control signals may be transmitted by acetate and propionate sensors in, or near the rumen. But there is also a complex interaction between diet and the growth of the gut itself, such that diets with high levels of complex carbohydrates and inadequate protein may cause extra growth of the gastrointenstinal tract. Stress Behavioural factors also are involved in the animal's growth responses to long-term stress.
Stress diminishes live weight gains, mainly because of a decrease in fat deposition.
Competition between tissues Body tissues may compete for circulating nutrients. In ruminants, for example, the energy flow to skeletal muscle is increased by STH while the flow to adipose tissue is increased by insulin. In other words, circulating factors such as hormones may govern the energy distribution system by switching on and off the energy assimilation systems of each type of tissue. Insulin is particularly important in controlling the distribution of nutrients from the blood stream since it turns on the whole energy catching system of a cell. Receptors on the cell membrane recognize insulin molecules and bind them, although some insulin does enter the cell, perhaps to exercise its long-term control functions.