Page 172 - Small Animal Clinical Nutrition 5th Edition

174 Small Animal Clinical Nutrition

protein contents are listed in Table 8-5 (Box 8-6). Protein
Table 8-4. Common grain ingredients and their carbohydrate ingredients vary widely in the levels of protein and other nutri-
VetBooks.ir or nitrogen-free extract (NFE) concentrations (as fed). ents they deliver to a formulation. For example, ash represents
NFE (%)*
Grain
Barley 76 the total mineral element of the formula (the sum of calcium,
Corn 81 phosphorus, magnesium, potassium, sodium, etc.). Ash is the
Corn flour 85 material that remains after combustion or hydrolysis of the
Cornstarch 88 organic material.The protein-to-ash ratio is a good indicator of
Grain sorghum 80
Oat groats 70 an ingredient’s efficiency in providing protein and the ingredi-
Rice 90 ent’s DM digestibility. The higher an ingredient’s ash content,
Rice bran 46 the lower its digestibility.
Rice flour 90
Wheat 78 The ratios of total protein content to total ash content
Wheat flour 82 described in Table 8-6 are critical to formulating dry pet foods.
Wheat middlings 66 This is especially true for cats, which require a higher propor-
*NFE is the nonfiber carbohydrate fraction and is calculated as
follows: % NFE = 100% – % moisture – % crude protein – % tion of protein from animal tissue and which have higher pro-
crude fat – % crude fiber – % ash. tein requirements than dogs. A protein ingredient choice that
has a low protein-to-ash ratio will make it difficult to meet a
cat’s protein requirement without delivering excessive levels of
magnesium and phosphorus. Dogs and cats readily accept
poultry by-product meal. Because it contains viscera, it provides
Table 8-5. Dry protein sources used in commercial pet foods
and their typical protein ranges (as fed). an excellent source of protein with lower mineral levels than
chicken meal, which is composed primarily of rendered chick-
Ingredient Protein (%)
Poultry by-product meal 65-70 en necks and backs. Thus, poultry by-product meal is an excel-
Meat and bone meal 50-55 lent choice for feline foods to avoid excess mineral levels.
Chicken meal 63-67
Lamb meal 48-55
Fish meal 60-65 Nutritional Characteristics
Soybean meal 46-50 Dogs are omnivorous and have lower protein requirements
Corn gluten meal 60-64 than cats. Therefore, formulations for dogs are more flexible
Rice gluten meal 40-50
Dried egg product 43-48 and may include more vegetable proteins. Vegetable proteins
typically have higher protein-to-ash ratios and contain some
fiber. Soybean meal is an excellent source of the amino acids
lysine and tryptophan. However, because dogs prefer animal
tissues to vegetable meals, it is advantageous to add animal
Table 8-6. Protein-to-ash ratios of dry protein sources used in
commercial pet foods. source proteins to the formulation. A blend of animal tissue
meals and vegetable meals is appropriate and often optimal.
Ingredient Protein:ash
Poultry by-product meal 6:1
Meat and bone meal 2:1 Wet Protein Ingredients
Chicken meal 4:1 Wet protein ingredients are classified as fresh or frozen meats
Lamb meal 2.5:1
Fish meal 3:1 and meat by-products. These ingredients generally have mois-
Soybean meal 10:1 ture contents above 60%. Table 8-7 lists the typical protein
Corn gluten meal 25:1 ingredients used in canned pet foods. Controlling excess min-
Rice gluten meal 20:1
Dried egg product 8:1 erals in moist foods is easier because the protein-to-ash ratio for
fresh meat ingredients is higher overall (i.e., they contain less
bone) than that of rendered meat meals used in dry pet foods.

The choice of a carbohydrate in a moist formulation can Process Characteristics
markedly affect processing characteristics.The starch will gelat- Protein ingredients provide structural integrity to kibbles, but
inize in moist products and combine with the denaturing pro- not nearly as much as that provided by carbohydrates. The
tein to give the loaf structure.This structure will maintain even exception to this is textured vegetable protein (TVP), which is
distribution of the formulation. However, the textural charac- made from wheat or soy flour. Sulfur is usually added to give
teristics of the structure will vary widely among carbohydrates, the matrix more structure by increasing the disulfide bonding
especially if the starch is in purified form, because each reacts between protein strands.TVP absorbs moisture readily and has
uniquely to cook temperature and time. a texture similar to that of meat when hydrated. The meat tis-
sues used in moist pet foods contribute greatly to the firmness
Dry Protein Ingredients and structure of the finished product. Overheating or adding
Protein ingredients contain higher levels of protein (>20%). strong acids will cause the structure to degenerate, affecting the
Protein ingredients typically used in dry pet foods and their finished product.