A study on the role of body fatness in the control of voluntary feed intake in sheep

Abstract

The role of body fatness in the control of the voluntary intake of concentrate diets was studied using the 1 normal obese sheep as a model to be compared with the ’normal lean' sheep.

Five experiments were carried out to investigate the effect of body fatness on voluntary intake, feeding behaviour and metabolic concomitants of feeding.

When diets containing 0.4, 10.0 and 12.2 M..J. of metabolizable energy per kg. dry matter were fed. to sheep in fat and lean body conditions for a twenty-four hour period dry matter intakes were significantly lower in fat animals. Behavioural studies indicated intake differences to be due mainly to differences in meal size rather than number of meals consumed. dry matter intake decreased linearly with increased energy concentration in both fat and lean animals indicating an ability to regulate energy consumption.

Under a restricted feeding regime of five hours per day it was found that lean animals consumed 88% and fat animals 63% of their ad libitum intake. An ability to adjust feed intake according to the metabolizable energy content of the diet was also shown under restricted access conditions.

Under a restricted feeding regime of five hours per day it was found that lean animals consumed 88% and fat animals 63% of their ad libitum intake. An ability to adjust feed intake according to the metabolizable energy content of the diet was also shown under restricted access conditions.

In metabolism studies plasma insulin levels reflected an effect of body fatness and diet type and an association with feeding patterns. Concomitant observations on plasma glucose, α-amino nitrogen and free fatty acids suggested a reduced response to insulin action in fat compared with lean sheep. No relationships between either these plasma constituents or rumen volatile fatty acids and insulin were evident.

In a second series of experiments intravenous insulin, glucose and acetate tolerance tests were carried out on fat and lean sheep. It was found, that the response to exogenous insulin was lower in the fat animals.

The findings are discussed in the light of other data and a possible role for insulin in feed intake control in the ruminant postulated.