Today's Veterinary Practice

NOV-DEC 2015

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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tvpjournal.com | November/December 2015 | ToDay's VeTeriNary PracTice acVN NuTriTioN NoTes Peer reviewed 71 exception, presumably because their evolutionary prey were never limiting in protein. PROTEIN SOURCES Protein and essential amino acids can be derived from animal or plant sources. Meat Sources Meats refer to striated muscle from mammals and can contain other surrounding tissue, such as fat or skin. Muscle meat contains a large concentration of protein, but substantial amounts can also be found in other products, such as organ tissues. Most pet foods rely on parts of the animal that are not destined for human consumption, and ingredients listed as a general descriptor, such as chicken or beef, need not contain the whole animal but rather selected parts. For example, poultry or chicken, if listed on a label, refers to the clean combination of fesh and skin with or without accompanying bone, derived from parts or whole carcasses of poultry. 1 s ome more expensive canned diets are marketed as containing prime cuts of meat (eg, chicken breast, sirloin), but current labeling guidelines make such claims diffcult to evaluate. A meat meal refers to a product that contains similar inclusions as meats but is rendered and dried to contain minimal moisture. Meals are typically slightly higher in protein than meats, and generally provide more calories by weight than fresh meat; therefore, their appearance frst on an ingredient list suggests that they may provide the primary source of calories in the food, which may not be the case for meats. Plant Sources Plant proteins can provide digestible protein and amino acids. Many cereal grains are processed to produce starch, fat, and gluten. Gluten is the protein containing fraction of grains. Vegetable proteins may be benefcial for reducing nitrogenous waste, with implications for hepatic encephalopathy and urate stones. 4 Digestibility animal proteins are generally more digestible than plant proteins. However, this is not always the case; for example, corn gluten can have better availability than lamb meal. 5 Fish, casein (a dairy protein), and egg are animal proteins that often display the highest digestibility. Digestibility of animal products depends on the: • animal from which it is derived • Part(s) of the carcass used • Processing • cooking temperature and pressure. Digestibility of protein is both diffcult to assess from information found on food labels and to measure because typical methods are not able to separate digestibility by the animal versus that of intestinal bacteria. Atwater factors are used in human nutrition to predict the amount of energy in a certain mass of food. These factors assume a certain digestibility and refect the anticipated amount of energy that is actually available after energetic losses in the urine and feces. The value used for many foods consumed by humans is 4 kilocalories (kcal) per gram of protein. 2 aaFco uses a modifed factor of 3.5 kcal per gram for commercial pet foods, as it is assumed that extruded pet foods have reduced digestibility. 1 Fortunately, most foods contain excess amino acids and crude protein due to the diffculty of precisely measuring protein digestibility. PROTEIN MODIFICATION FOR LIFE STAGES requirements for dietary amino acids present in protein are well established for various life stages and types of animals: • Growth, lactation, and late gestation increase protein and amino acid requirements, primarily due to increased biosynthetic reactions (Table 2, page 72). • cats (obligate carnivores) have higher protein requirements than dogs (omnivores). • Performance animals may require elevated dietary concentrations of protein. 7 • s enior dogs have nearly double the protein turnover of younger dogs and may require increased dietary protein due to decreased muscle anabolism and, perhaps, decreased protein digestibility or conversion. 8 Concerns with g lutens While gluten free is a common label in human foods, true gluten sensitivity appears to be rare in dogs and cats, but has been documented in certain lines of Irish setters. Adverse effects from long-term gluten exposure in domestic animals have not been documented in scientifc studies. In addition, owners may express concern about plant proteins due to recalls in response to melamine contamination of wheat gluten-containing foods. 6

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