Changes

==2. Why is it Important?==

==2. Why is it Important?==

Protein is required to provide both nitrogen and essential amino acids. There are no protein stores in the body and dietary protein intake replenishes nitrogen and amino acids that are lost during normal cellular turnover in the body. Dietary nitrogen is used to synthesise non-essential amino acids and other nitrogen containing compounds. Essential (indispensable) amino acids are those that cannot be synthesized by the animal and must be consumed each day; non-essential (dispensable) amino acids can be made in the liver if adequate levels of nitrogen and carbon are available. Amino acids are the building blocks of structural proteins, and other proteins that can have enzymatic, transport, regulatory, contractile or defensive functions.  

Protein is required to provide both nitrogen and essential amino acids. There are no protein stores in the body and dietary protein intake replenishes nitrogen and amino acids that are lost during normal cellular turnover in the body. Dietary nitrogen is used to synthesise non-essential amino acids and other nitrogen containing compounds. Essential (indispensable) amino acids are those that cannot be synthesized by the animal and must be consumed each day; non-essential (dispensable) amino acids can be made in the liver if adequate levels of nitrogen and carbon are available. Amino acids are the building blocks of structural proteins, and other proteins that can have enzymatic, transport, regulatory, contractile or defensive functions.  

Protein requirements increase during growth and reproduction to meet the additional demands for tissue deposition and milk production. Cats and dogs have a relatively high protein requirement which is thought to be due to diet induced evolutionary adaptions<ref>Morris, J.G. Idiosyncratic nutrient requirements of cats appear to be diet-induced evolutionary adaptations. Nutr Res Rev 2002;15; 153-168.</ref>; both species have evolved on high protein meat based diets and this may explain why they have a relatively high metabolic set point for protein catabolism and higher urinary nitrogen loss  compared with herbivores, or other omnivores<ref>Hendricks WH, et al. Urinary excretion of endogenous nitrogen metabolites in adult domestic cats using a protein-free diet and the regression technique. J Nutr 1997;127:623-629.</ref>.2 Cats have a particularly high protein requirement, because unlike the dog and most other animals, they are unable to down regulate urea cycle enzymes in response to low protein diets<ref>Biourge V, et al. Nitrogen balance, plasma free amino acid concentrations and urinary orotic acid excretion during long-term fasting in cats. J Nutr 1994;124:1094-1103.</ref>.  

Protein requirements increase during growth and reproduction to meet the additional demands for tissue deposition and milk production. Cats and dogs have a relatively high protein requirement which is thought to be due to diet induced evolutionary adaptions<ref>Morris, J.G. Idiosyncratic nutrient requirements of cats appear to be diet-induced evolutionary adaptations. Nutr Res Rev 2002;15; 153-168.</ref>; both species have evolved on high protein meat based diets and this may explain why they have a relatively high metabolic set point for protein catabolism and higher urinary nitrogen loss  compared with herbivores, or other omnivores<ref>Hendricks WH, et al. Urinary excretion of endogenous nitrogen metabolites in adult domestic cats using a protein-free diet and the regression technique. J Nutr 1997;127:623-629.</ref>. Cats have a particularly high protein requirement, because unlike the dog and most other animals, they are unable to down regulate urea cycle enzymes in response to low protein diets<ref>Biourge V, et al. Nitrogen balance, plasma free amino acid concentrations and urinary orotic acid excretion during long-term fasting in cats. J Nutr 1994;124:1094-1103.</ref>.  

#'''Growth''': Inadequate protein intake as well as deficiencies in any single essential amino acid will result in poor growth in puppies and kittens or failure to gain weight<ref name="NRC"/>.

#'''Growth''': Inadequate protein intake as well as deficiencies in any single essential amino acid will result in poor growth in puppies and kittens or failure to gain weight<ref name="NRC"/>.

#'''Maintenance''': Inadequate protein intake will result in weight loss in adults due to an inability to maintain a positive nitrogen balance and replace amino acids lost during whole body protein turnover<ref name="Bourse">Biourge V, et al. Long-term voluntary fasting in adult obese cats: nitrogen balance, plasma amino acid concentrations and urinary orotic acid excretion. J Nutr 1995;124:2680S-2682S.</ref><ref name="Wannemacher">Wannemacher RW and McCoy JR. Determination of optimal dietary protein requirements in young and old dogs. J Nutr 1966;88:66-74.</ref>. Dogs are able to down-regulate hepatic enzymes used in amino acids metabolism, gluconeogenesis, and urea production and can adapt to low protein intakes. Cats are unable to adapt to low protein or protein-free diets and can develop hepatic lipidosis during periods of starvation<ref name="Biourge"/>.  

#'''Maintenance''': Inadequate protein intake will result in weight loss in adults due to an inability to maintain a positive nitrogen balance and replace amino acids lost during whole body protein turnover<ref name="Biourge">Biourge V, et al. Long-term voluntary fasting in adult obese cats: nitrogen balance, plasma amino acid concentrations and urinary orotic acid excretion. J Nutr 1995;124:2680S-2682S.</ref><ref name="Wannemacher">Wannemacher RW and McCoy JR. Determination of optimal dietary protein requirements in young and old dogs. J Nutr 1966;88:66-74.</ref>. Dogs are able to down-regulate hepatic enzymes used in amino acids metabolism, gluconeogenesis, and urea production and can adapt to low protein intakes. Cats are unable to adapt to low protein or protein-free diets and can develop hepatic lipidosis during periods of starvation<ref name="Biourge"/>.