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.
