ANSM 321
APPLIED RUMINANT
NUTRITION
ASSIGNMENT 1
, 1. Briefly explain the chemostatic and thermostatic theories in relation to short-term
regulation of voluntary feed intake ruminant animals. [10 Marks]
The chemostatic theory of feed intake regulation in mammals postulates that the post-prandial rise
in blood metabolites stimulates chemically sensitive receptors, which somehow trigger the nervous
system to bring about the condition of satiety i.e. the excess circulating nutrients manufactured
during the digestion and metabolism of feed shortly after eating are what cause the feeling of being
“full”. In monogastric animals it has been suggested that the metabolite causing cessation is glucose
(glucostatic theory), however this theory does not apply to ruminants as they do not showcase
increased glucose levels after feeding and glucose is only produced on demand through
gluconeogenesis. Metabolites that have been considered for ruminants are non-esterified fatty acids
and serum amino acids. The predominant acids involved in the peripheral circulation which lead to
cessation in ruminants include acetic acid, propanoic acid as well as some traces of butyric acid.
These metabolites do so by stimulating the release of hormonal peptides. (Ulyatt, 1964)
In contrast, the thermostatic theory of feed intake has been proposed as the method by which the
body may thermo regulate, in part, by decreasing the insulating amount of body fat. The theory
states that animals consume food in order to keep warm and stop eating to prevent hyperthermia.
Studies performed on a number of experimental animals show cessation of eating at high
temperatures, proving that if they were to continue to eat it would cause the animal to overheating
leading to hyperthermia. Increase in body temperature due to physiological processes such as
metabolism and digestion may stimulate receptors to regulate feed intake in the short-term.
Temperatures below the thermoneutral zone cause the animal to feed more, and those below the
thermoneutral zone stimulate the opposite reaction. (Yates, 1993)
2. Write short notes on the following feed additives commonly used in ruminant animal
nutrition: [15 marks]
a. Antifungals
Probiotics are live cultures of non- pathogenic organisms administered orally often used as
antifungals, which benefit the host animal by improving its intestinal microbial balance. The
improved performance of animals due to probotics application is often as a result of improved
digestibility of nutrients. Bacterial population in the silage is also a good source of probiotics to the
ruminants. Probiotics have also been found to effective in reducing acidosis. (Deswal & Deswal,
2020)
b. Antioxidants
Antioxidants are feed additives that enhance feed intake. They are compounds that prevent
oxidative rancidity of polyunsaturated fats. Primary antioxidants can stop propagation of free radicals
while the secondary antioxidants can stop formation of free radicals. Rancidity may cause the destruction
of vitamins A, D and E and several of the B complex vitamins. The by-products resulting from
rancidity may react with lysine and thus affecting the protein value of the ration. (Deswal & Deswal,
2020)
c. Buffers
Buffers are aqueous solutions with the unique ability to resist pH changes. As feed additives, they
are used in high concentrate diets fed to ruminants to compensate for the shortcomings in saliva
APPLIED RUMINANT
NUTRITION
ASSIGNMENT 1
, 1. Briefly explain the chemostatic and thermostatic theories in relation to short-term
regulation of voluntary feed intake ruminant animals. [10 Marks]
The chemostatic theory of feed intake regulation in mammals postulates that the post-prandial rise
in blood metabolites stimulates chemically sensitive receptors, which somehow trigger the nervous
system to bring about the condition of satiety i.e. the excess circulating nutrients manufactured
during the digestion and metabolism of feed shortly after eating are what cause the feeling of being
“full”. In monogastric animals it has been suggested that the metabolite causing cessation is glucose
(glucostatic theory), however this theory does not apply to ruminants as they do not showcase
increased glucose levels after feeding and glucose is only produced on demand through
gluconeogenesis. Metabolites that have been considered for ruminants are non-esterified fatty acids
and serum amino acids. The predominant acids involved in the peripheral circulation which lead to
cessation in ruminants include acetic acid, propanoic acid as well as some traces of butyric acid.
These metabolites do so by stimulating the release of hormonal peptides. (Ulyatt, 1964)
In contrast, the thermostatic theory of feed intake has been proposed as the method by which the
body may thermo regulate, in part, by decreasing the insulating amount of body fat. The theory
states that animals consume food in order to keep warm and stop eating to prevent hyperthermia.
Studies performed on a number of experimental animals show cessation of eating at high
temperatures, proving that if they were to continue to eat it would cause the animal to overheating
leading to hyperthermia. Increase in body temperature due to physiological processes such as
metabolism and digestion may stimulate receptors to regulate feed intake in the short-term.
Temperatures below the thermoneutral zone cause the animal to feed more, and those below the
thermoneutral zone stimulate the opposite reaction. (Yates, 1993)
2. Write short notes on the following feed additives commonly used in ruminant animal
nutrition: [15 marks]
a. Antifungals
Probiotics are live cultures of non- pathogenic organisms administered orally often used as
antifungals, which benefit the host animal by improving its intestinal microbial balance. The
improved performance of animals due to probotics application is often as a result of improved
digestibility of nutrients. Bacterial population in the silage is also a good source of probiotics to the
ruminants. Probiotics have also been found to effective in reducing acidosis. (Deswal & Deswal,
2020)
b. Antioxidants
Antioxidants are feed additives that enhance feed intake. They are compounds that prevent
oxidative rancidity of polyunsaturated fats. Primary antioxidants can stop propagation of free radicals
while the secondary antioxidants can stop formation of free radicals. Rancidity may cause the destruction
of vitamins A, D and E and several of the B complex vitamins. The by-products resulting from
rancidity may react with lysine and thus affecting the protein value of the ration. (Deswal & Deswal,
2020)
c. Buffers
Buffers are aqueous solutions with the unique ability to resist pH changes. As feed additives, they
are used in high concentrate diets fed to ruminants to compensate for the shortcomings in saliva
