Changes

==Roles in the Body==  

==Roles in the Body==  

Both essential and non-essential amino acids are required to form the structural components of the body, such as muscle, connective tissue, and blood cells. Adequate amounts of protein are necessary for proper growth in puppies and kittens<ref name="NRC">National Research Council (NRC). Protein and Amino Acids. In Nutrient Requirements for Dogs and Cats. 2006 Washington, DC: National Academies Press p.111-120.</ref>. Protein is also required for maintenance of lean body mass in adult dogs and cats<ref name="NRC"/>. The fate of metabolised protein is to serve as a source of nitrogen for incorporation into other compounds in the body, such as heme, catecholamines, and neurotransmitters while the carbon is used in gluconeogenesis and energy production.

Both essential and non-essential amino acids are required to form the structural components of the body, such as [[Muscles - Anatomy & Physiology|muscle]], connective tissue, and blood cells. Adequate amounts of protein are necessary for proper growth in puppies and kittens<ref name="NRC">National Research Council (NRC). Protein and Amino Acids. In Nutrient Requirements for Dogs and Cats. 2006 Washington, DC: National Academies Press p.111-120.</ref>. Protein is also required for maintenance of lean body mass in adult dogs and cats<ref name="NRC"/>. The fate of metabolised protein is to serve as a source of nitrogen for incorporation into other compounds in the body, such as heme, catecholamines, and neurotransmitters while the carbon is used in gluconeogenesis and energy production.

==Consequences of Protein Deficiency==  

==Consequences of Protein Deficiency==  

#'''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="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"/>.  

#'''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|hepatic lipidosis]] during periods of starvation'''<ref name="Biourge"/>.  

==Toxicity==

==Toxicity==

There are no reports of toxicity associated with high intake of protein in healthy dogs and cats. Animals with compromised hepatic function (i.e., liver failure) may have impaired metabolism of proteins; compromised renal function may result in decreased tubular clearance of urea.  

There are no reports of toxicity associated with high intake of protein in healthy dogs and cats. Animals with compromised hepatic function (i.e. [[Liver Failure|liver failure]]) may have impaired metabolism of proteins; compromised renal function may result in decreased tubular clearance of [[urea]].  

==Dietary Sources==

==Dietary Sources==

Protein is found in animal and plant protein sources, such as muscle and organ meats, eggs, dairy protein (e.g., casein), cereal grains, and pulses (i.e.,legumes). Animal sourced proteins are generally more highly digestible than plant sourced proteins for both dogs and cats<ref>Neirinck K, et al. Amino acid composition and digestibility of four protein sources for dogs. J Nutr 1991;121:S64-S65.</ref><ref>Funaba M, et al. Evaluation of meat meal, chicken meal, and corn gluten meal as dietary sources of protein in dry cat food. Can J Vet Res 2005;69:299-304.</ref>. Processing of proteins can affect their digestibility; heat processing can increase digestibility for some proteins, while rendering and drying can decrease digestibility<ref>Murray SM, et al. Raw and rendered animal by-products as ingredients in dog diets. J Anim Sci 1997;75:2497-2505.</ref><ref>Johnson ML, et al. Effects of species raw material source, ash content, and processing temperature on amino acid digestibility of animal by-product meals by cecectomized roosters and ileally cannulated dogs. J Anim Sci 1998;76:1112-1122.</ref><ref>de-Oliveira DL, et al. Digestibility for dogs and cats of meat and bone meal processed at two different temperature and pressure levels. JAPAN(Berl) 2012;96:1136-1146.</ref>. Presence of soluble fibres and carbohydrates within a diet can also decrease protein digestibility<ref>Muir HE, et al. Nutrient digestion by ileal cannulated dogs as affected by dietary fibers with various fermentation characteristics. J Anim Sci 1996;74:1641-1648.</ref><ref>Silvio J, et al. Influences of fiber fermentation on nutrient digestion in the dog. Nutr 2000;16:289-295.</ref><ref>Harper EJ. The effect of fiber on nutrient availability in cats of different ages. Vet Clin Nutr 1995;3:114.</ref>. In dogs, digestibility varies with size, breed, and age, with older dogs experiencing a decrease in digestive capacity<ref name="Wannemacher"/><ref>Hannah SS, et al. Digestibility of diet in small and large breed dogs. Vet Clin Nutr 1995;2:145.</ref>. '''Cats have a shorter small intestinal length to body size ratio which may limit their ability to digest protein, and may explain why protein digestibility is lower in cats compared to dogs'''<ref name="NRC"/>.

Protein is found in animal and plant protein sources, such as muscle and organ meats, eggs, dairy protein (e.g. casein), cereal grains, and pulses (i.e.legumes). Animal sourced proteins are generally more highly digestible than plant sourced proteins for both dogs and cats<ref>Neirinck K, et al. Amino acid composition and digestibility of four protein sources for dogs. J Nutr 1991;121:S64-S65.</ref><ref>Funaba M, et al. Evaluation of meat meal, chicken meal, and corn gluten meal as dietary sources of protein in dry cat food. Can J Vet Res 2005;69:299-304.</ref>. Processing of proteins can affect their digestibility; heat processing can increase digestibility for some proteins, while rendering and drying can decrease digestibility<ref>Murray SM, et al. Raw and rendered animal by-products as ingredients in dog diets. J Anim Sci 1997;75:2497-2505.</ref><ref>Johnson ML, et al. Effects of species raw material source, ash content, and processing temperature on amino acid digestibility of animal by-product meals by cecectomized roosters and ileally cannulated dogs. J Anim Sci 1998;76:1112-1122.</ref><ref>de-Oliveira DL, et al. Digestibility for dogs and cats of meat and bone meal processed at two different temperature and pressure levels. JAPAN(Berl) 2012;96:1136-1146.</ref>. Presence of soluble fibres and carbohydrates within a diet can also decrease protein digestibility<ref>Muir HE, et al. Nutrient digestion by ileal cannulated dogs as affected by dietary fibers with various fermentation characteristics. J Anim Sci 1996;74:1641-1648.</ref><ref>Silvio J, et al. Influences of fiber fermentation on nutrient digestion in the dog. Nutr 2000;16:289-295.</ref><ref>Harper EJ. The effect of fiber on nutrient availability in cats of different ages. Vet Clin Nutr 1995;3:114.</ref>. In dogs, digestibility varies with size, breed, and age, with older dogs experiencing a decrease in digestive capacity<ref name="Wannemacher"/><ref>Hannah SS, et al. Digestibility of diet in small and large breed dogs. Vet Clin Nutr 1995;2:145.</ref>. '''Cats have a shorter small intestinal length to body size ratio which may limit their ability to digest protein, and may explain why protein digestibility is lower in cats compared to dogs'''<ref name="NRC"/>.

Crude protein as listed on a pet food label is a measure of dietary nitrogen and does not reflect the source or quality of protein in a commercial diet.  

Crude protein as listed on a pet food label is a measure of dietary nitrogen and does not reflect the source or quality of protein in a commercial diet.