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Chapter 5 Animal nutrition.

Chapter Objectives

* Learn the names and purposes of the primary nutrients

* Learn the primary sources of nutrients for animals

* Understand how the body digests foodstuffs

* Understand how the body uses nutrients

Nutrients (noo-tre-ehnts) are the compounds in food that support growth, development, and maintenance of the body. Nutrition (noo-trish-shuhn), the study of these nutrients and how the body uses them, is one of the foundations of animal management, and a primary area of focus in animal sciences. Arguably, nutrition has the greatest potential impact on an animal being able to perform the purpose for which it has been bred. The genetics of the animal give it the potential to perform to a certain level, but that potential will not be fulfilled if the animal's nutritional needs are not met. Nutrition is a complex field. It is important to understand not only the nutrients, but also the foods that provide those nutrients, and the processes in the body that change the raw foodstuffs into a form that is usable by the body. Many of the nutrients have an optimal level for feeding. Either too much or too little can have negative effects on the health of an animal. Many diseases that challenge animal scientists are nutritionally related.

The study of animal nutrition also has direct human impacts. Many of the principles of nutrition that we have learned from doing research on animals have been applied to human nutrition. Currently, many of the nutrition-related issues facing humans, such as diabetes and obesity, are being researched using animal models.

Different types of animals gain their nutrients from different food sources. Their digestive systems have evolved to best utilize the nutrients from their food source of choice. As we seek to meet an animal's nutritional needs with commercial diets, it is important to understand how their digestive systems evolved, and the components of their original diets.

One part of the digestive tract that is significantly different between species is their dentition, or teeth (see Figure 5-1). Animals are often classified into the following groups based on the primary source of food:

Carnivores (kahr-nih-vors) are animals that get most of their food from a meat source. Some species, like dogs, are preferential carnivores, whereas others, like cats, are obligate carnivores. Obligate carnivores are animals that must have meat in their diet to gain all of the nutrients they need. All carnivores are animals that we think of as predators, and have monogastric digestive systems.

Herbivores (herb-ih-vors) are animals that get most of their nutrients from plant sources. Some herbivores eat plant sources such as grass, and others are browsers, and eat plants that are woody in nature. Some herbivores are ruminants, and others are monogastrics. Examples of herbivores are horses, cattle, and sheep.

Omnivores (ohm-ne-vors) are animals that eat a combination of plant- and meat-based food sources. Examples of omnivores are pigs, humans, and some birds.



Nutrients can be divided into categories based on their chemical makeup and the purpose they serve for the body. Nutrients come from a variety of foodstuffs, and most foodstuffs contain several nutrients, although the amount of each nutrient in a particular food stuff is highly variable.


Carbohydrates (car-bo-hi-dra-ts) Made up of carbon, oxygen, and hydrogen, carbohydrates are one of the primary sources of energy in the diet. Carbohydrates are burned for energy, and excess carbohydrates are stored in the body as fat.

Cellulose (sehl-yoo-los) One of the most important carbohydrates in the diets of herbivores. Cellulose is found in most plant sources and is an important source of glucose that the body converts to energy.

Fiber A type of carbohydrate classified as a complex carbohydrate. Cellulose (sell-yoo-los) and lignin (lihg-nehn) are the specific carbohydrates that are in fiber-based feeds like grass and hay. The digestive tracts of ruminant animals can better utilize fiber than the digestive tracts of carnivores. Fiber is important in the diet to facilitate movement of feed through the digestive tract. In animals that are evolutionary herbivores, such as horses, it is important to maintain sufficient fiber in the diet to maintain the health of the digestive tract.

Sugars A type of carbohydrate classified as a simple carbohydrate. Sugars are easily digested and found in grain-based feedstuffs.

Starches A type of carbohydrate classified as a simple carbohydrate. Starches are easily digested to sugars, the other simple carbohydrate. As with sugars, starches are found in grain-based feedstuffs.


Fats are made up of carbon, oxygen, and hydrogen, and provide energy in the diet. Dietary fats can either be solid at body temperature (fats), or liquid at body temperature (oils). Fats are much more energy-dense that carbohydrates, with 2.25 times the calories per gram as carbohydrates. Fats can increase the palatability and energy density of feeds. However, excessive fat can lead to feed rancidity and make the feed unpalatable.


Minerals (mihn-ehr-ahls) do not contain carbon, so they are inorganic. Minerals comprise a very small percentage of the diet, but are vital for normal growth and development. Minerals are involved in regulation of body systems, as well as proper growth of bones, teeth, and other tissue. Requirements for minerals vary, and care must be taken to meet the animals' mineral requirements without exceeding them. Deficiency and excess of minerals can both lead to poor health in animals. Minerals are divided into macro- and microminerals, and important minerals are listed on next page:

Macrominerals Minerals that are needed in relatively large amounts. The following is a list of macrominerals:

Calcium (kahl-se-uhm) A mineral that is vital to the development of bones, muscle, and nerve activity.

Phosphorus (fahs-fer-uhs) A mineral that works with calcium in the skeleton, and helps with energy transfer throughout the body. It is important to keep phosphorus and calcium in proper balance in the diet.

Magnesium (mahg-nez-e-uhm) A mineral that, along with calcium and phosphorus, is involved with bone development.

Salt Sodium chloride is one of the most important minerals in the diet. Sodium and chloride are important in maintaining the proper water balance in the body. Salt is excreted through perspiration, and should always be available in the diet, or as a supplement.

Microminerals Minerals that are needed in relatively small amounts. Also knows as trace minerals. The following is a list of trace minerals:

Cobalt (ko-bahlt) Part of vitamin B12.

Copper (kahp-per) A mineral in red blood cells, skin, and hair pigment.

Iodine (i-ah-din) A mineral that is essential in the thyroid (thi-royd) hormone, which controls metabolism.

Iron A component of red blood cells that helps carry oxygen in blood. Iron deficiency is known as anemia (ah-ne-m-e-ah).

Selenium (seh-len-e-uhm) A mineral that is involved in muscle development and function.

Zinc A component of enzymes and an important mineral in normal skin and hair growth.


Proteins (pro-ten) are made up of amino acids (ah-me-no ahs-ihdz) that are derived from the diet. These amino acids are formed from carbon, hydrogen, oxygen, and nitrogen. Some amino acids contain other elements such as iron, phosphorus, and sulfur. Proteins are known as "building blocks" because of the vital role they play in the formation of everything from muscle to skin and hair and internal organs. Amino acids are classified as essential and nonessential. The following list defines which amino acids fit into each category:

Essential amino acids Essential amino acids must be provided in the diet because they cannot be metabolized in the body. There is some variation of essential amino acids with species. All animals require methionine (meh-thi-o-nihn), arginine (ahr-jih-nehn), threonine (thre-o-nihn), tryptophan (trihp-to-fan), valine (vahl-ihn), histidine (hihs-tih-dihn), isoleucine (i-so-loo-sen), leucine (loo-sen), lysine (li-sen), and phenylalanine (fehnehl-ahl-ah-nehn). Poultry also require glycine (gli-sen) and proline (pro-len), and cats also require taurine (tawr-en).

Nonessential amino acids These amino acids do not need to be provided in the diet because they can be manufactured in the body from other amino acids. Different species can synthesize different amino acids.


Vitamins (vi-tah-mihns) are organic compounds that are needed in small amounts in the diet. Vitamins are placed in the following two major classifications, fat-soluble and water-soluble.

Fat-soluble vitamins These vitamins can be dissolved in fat, and are stored in fat in the body. Care must be taken with fat-soluble vitamins to meet the needs of the animal without exceeding them. Because fat-soluble vitamins can be stored in the body, they can rise to toxic levels. The following are fat-soluble vitamins:

Vitamin A Involved in vision, skin health, and bone growth.

Vitamin D Involved in use and absorption of calcium, vital for proper bone growth and development.

Vitamin E Protects cells from damage and assists in muscle growth and immune function.

Vitamin K Essential in blood clotting.

Water-soluble vitamins These vitamins can be dissolved in water, and excesses are excreted through urine. Because the body can excrete water-soluble vitamins, toxicity is rarely seen. The following are water-soluble vitamins:

B vitamins The B vitamins include thiamin (thi-ah-mihn), riboflavin (ri-bo-fla-vehn), niacin (ni-ah-sihn), pyridoxine (per-eh-docks-en), pantothenic acid (pahn-to-thehn-ik), biotin (bi-o-tehn), folic acid (fo-lihk), benzoic acid (behn-zo-ihk), choline (ko-len), and vitamin B12.

Vitamin C This water-soluble vitamin is available through many forages. Although most animals gain enough vitamin C through their diet, guinea pigs must receive vitamin C in the diet.


Water is the single most important nutrient, and one that is often forgotten. Animals can live longer without food, or with inadequate food, than without water. Water is vital to allow the body to use other nutrients and for normal bodily function. All animals should have a constant supply of clean, fresh water. Animals may not consume water that is stale or dirty. Lack of water can lead to a range of disease states, such as colic in horses, and feline lower urinary tract disease in cats. Water need increases in hot weather, when animals are exercising, and during lactation. Dehydration (lack of water in the body) may also occur in cold weather, when the water supply is frozen, or the animals do not drink enough water because it is too cold.


Ruminant and Nonruminant Digestion

Digestion is the process by which the body breaks down foodstuffs into the nutrients needed by the body. Digestion has chemical phases, which are performed by enzymes, and mechanical phases, where the foodstuffs are broken down by physical movement. After the digestive tract has broken down the foodstuffs, nutrients are absorbed into the blood stream and distributed throughout the body. In most species, this absorption takes place in the small intestine. Ruminant and non-ruminant animals have different capacities to digest and use nutrients in feed, and varying capacities of feed they can consume.

Digestion begins in the mouth, with the chewing of food into a bolus (mechanical digestion), which is swallowed. In the mouth, saliva is added to the food bolus. The saliva contains the enzymes salivary amylase (ahm-ih-la-s) and salivary maltase (mahl-tas), which begin to break down the foodstuff (chemical digestion). The process of chewing breaks the food into smaller pieces, which increases the surface area and provides more opportunity for the enzymes to begin chemical digestion.

Following chewing, the food bolus is swallowed, and travels down the esophagus. The esophagus uses peristaltic (pehr-ih-stahl-tihk), or wavelike, movement to move the bolus to the stomach.

In ruminant animals, the food bolus is swallowed before it is completely chewed. Solid food matter goes to the rumen, and liquid food matter goes to the reticulum. There is no physical barrier between the rumen and the reticulum, so food matter moves freely between the areas. After consuming a quantity of feed, the ruminant animal regurgitates solid food from the rumen back up to the mouth, and rechews the bolus. This rechewing is called rumination, or chewing cud. In the rumen and reticulum, bacteria and protozoa further break down the feed. The bacteria and protozoa also produce vitamins that the animal can then absorb and use. Furthermore, as the bacteria and protozoa die, they remain in the digestive tract and are digested as sources of protein.

Maintaining a healthy population of microorganisms in the rumen is vital to proper function of the digestive system. A diet that provides adequate forage for the microbes is necessary to maintain a healthy population. Feed of larger particle sizes maximizes the efficiency of the microbes in the rumen. The presence of these microbes allows the ruminant animal to efficiently use lower quality protein and forages than animals that do not have the capacity to bacterially ferment feed. From the rumen and reticulum, the food material (digesta) moves on to the abomasum, or true stomach, of the ruminant. From the abomasum on, digestion in the ruminant is similar to digestion in the nonruminant animal. In young ruminant animals that are consuming milk, the reticular groove can contract, making a route for the milk to bypass the immature rumen, directly to the abomasum, which digests the milk.

In the stomach, the stomach muscles contract on the digesta to continue to break it down, and to mix in the hydrochloric acid and enzymes secreted by the stomach. Pepsin (pehp-sihn) is the enzyme that breaks down proteins, and lipase (li-pas) breaks down the fats. As the stomach contracts, the semiliquid parts are moved out of the stomach into the small intestine. This partially digested mass is called chyme (kim).

The small intestine is the site of the final stages of digestion and absorption of nutrients. The enzymes trypsin (trihp-sihn), pancreatic amylase, and pancreatic lipase are added to the chyme. The trypsin continues to break down proteins, the amylase breaks down starches, and the lipase breaks down any remaining fats. Bile is secreted from the gall bladder into the small intestine where it assists the lipase in breaking down fats. Horses do not have a gall bladder, so bile is secreted from the liver. The small intestine is lined with small fingerlike projections called villi (vihl-i), which are the site of nutrient absorption. The presence of villi increases the surface area of the small intestine, allowing it to absorb more nutrients.

The cecum (se-kuhm) is located where the small intestine meets the large intestine (see Figure 5-2). In most species, the cecum has no clear role; however, horses have the capacity to bacterially digest forages in the cecum. Although less efficient in regard to maximizing the value of the roughage than the rumen, the cecum allows the horse to benefit from a primarily roughage diet. In fact, a high-roughage diet is important to maintaining the gastrointestinal (GI) tract health of the horse.

The large intestine is the final part of the GI tract. The primary role of the large intestine is to absorb the water remaining after the digestion of the foodstuff. Because horses digest feed in the cecum after it has been through the small intestine, nutrients resulting from that digestion are absorbed in the large intestine. Unused feed material is moved through the large intestine to the rectum (rehck-tuhm), the distal portion of the large intestine. It is then excreted from the large intestine as feces through the anus (a--nuhs), which is the exterior opening at the end of the digestive tract. Significant feed matter in the feces indicates that the animal is not digesting the food properly. In these cases, steps should be taken to determine the source of the problem.


Digestion in Poultry

The digestive tract of poultry has some different aspects when compared to mammals. Poultry do not have teeth, so chewing and addition of saliva are not part of the digestive process. Feed is consumed, swallowed, and stored in the crop. The crop is a thin-walled organ and is not a site of digestion. From the crop, food goes through the glandular stomach where enzymes and hydrochloric acid are added. Food then moves to the gizzard, a heavily muscled organ that contracts and grinds the food into smaller particles. Sometimes grit, a stone-type product, is added to the diet of birds to facilitate this grinding process in the gizzard. After leaving the gizzard, digestion is similar to that in the previously discussed species. Additional enzymes are added in the small intestine, which is the site of nutrient absorption. Feed material that is not digested is excreted as feces.


Feedstuffs must be analyzed to determine what nutrients they can provide. Although certain feedstuff will have average amounts of nutrients, the amount of nutrients in any particular feedstuff can vary. For example, forages that are harvested at different points in maturation will contain different nutrients. Storage and handling can also impact the nutrients available in feed. Understanding the components of feed analysis is also important in evaluating commercial feeds that are available for livestock and companion animals. Proximate analysis (see Figure 5-3) is the chemical analysis of foodstuffs. Proximate analysis quantifies the water, ash, crude protein, ether extract, crude fiber, and nitrogen-free extract in a feedstuff. The following list defines each of these components of proximate analysis:


Ash The mineral content of feed.

Crude fiber Cellulose, hemicelluclose, and insoluble lignin in the feed.

Crude protein The total amount of nitrogen in a feed. This includes the nitrogen that is in the form of protein, and other nitrogen that is not incorporated into protein. Care must be used when evaluating the usefulness of crude protein in monogastric animals. Although ruminants can utilize most forms of nitrogen, monogastric animals need amino acids to provide for their protein requirement.

Dry matter (DM) The portion of the feed that is not water. The percentages of nutrients in a feed are based on dry matter, which gives the most accurate measurement of the amount of the nutrient the animal is receiving. Percentages may also be reflected in an as-fed basis. It is especially important to understand dry matter and "as fed" when evaluating processed feeds that are marketed in different ways, such as canned versus dry dog foods. As-fed refers to the foodstuff in the form in which it is fed to the animal, with the water included. The relationship between as-fed and dry matter will vary depending on the foodstuff, and how it has been processed.

Ether extract The dissolving of the fat-based components in the feedstuff with ether. Ether extracts not only nutritional fat, but also other lipid-based materials in the plant. The value of this analysis varies with the type of plant tested.
Nutrient digestibility (%) = nutrient consumed - nutrient excreted/
nutrient consumed x 100


Nitrogen-free extract (NFE) Carbohydrates that are not fiber. NFE is calculated by subtracting all of the other components determined by proximate analysis from the total amount of feed at the onset of the test. The result is the estimated NFE.

Fiber in feed can be analyzed with the Van Soest analysis. This form of analysis is best used with forages. This chemical analysis determines the acid detergent fiber and the neutral detergent fiber in the forage:

Acid detergent fiber The part of the feed that is most undigestible. This includes cellulose and lignin, as well as undigestible protein.

Neutral detergent fiber The material found in the cell walls of plants that does not break down during digestion in the simple stomach, but can be somewhat utilized by ruminant animals.

In addition to chemical analysis, feeds can be analyzed through feeding trials. A basic feeding trial involves feeding the feedstuff to the animal, and evaluating parameters such as growth, lactation, production, and so on. A digestion trial is conducted to determine how much of the nutrients in the feed the animal is using. After completion of a chemical analysis, the feed is given to the animal. Fecal material is collected and tested for the nutrient component of interest. The difference between the nutrients fed, and those excreted can be divided by the total intake and multiplied by 100 to give the digestibility of a nutrient (see Figure 5-4).


Anabolism (ahn-nahb-o-lihzm) The process of building complex compounds from simple compounds.

Body condition scoring A systemic process of evaluating the amount of fat on an animal's body. The scoring system varies with species. Body condition scoring is important to maintain the animal at the optimal condition. Higher numbers on the scale indicate more fat deposits; lower numbers indicate less fat deposits. The scoring ranges from emaciated (e-mas-e-a-tehd), or extremely thin, to obese (o-be-s), or extremely fat.

Calorie (cahl-oh-re) A measurement of the amount of energy in a feed.

Catabolism (kah-tahb-o-lihzm) The process of breaking down complex compounds into their constituent parts.


Deficiency (de-fihsh-ehn-se) An inadequate amount of a nutrient provided in the diet.

Dry matter intake The calculation of how much dry matter an animal can consume based on the animal's body weight. In most species, dry matter intake is based on 3-4 percent of the animal's weight.

Energy The portion of the feed available to power the body and its functions, and to generate body heat. Energy consumed in feed is used by the body in a variety of ways (see Figure 5-5). Dietary energy is classified in the following ways, based on how it is used:

Gross energy The total amount of energy in the feed or ration.

Digestible energy The gross energy minus the amount of energy that is not utilized in the body and is excreted through the feces.

Metabolizable energy (meh-tahb-oh-liz-ah-bl) The gross energy minus all other energy lost through urinary, fecal, or gaseous excretion.

Net energy Metabolizable energy minus the amount of energy expended to produce body heat. Net energy can further be defined by its use by the body, maintenance, production, lactation, and so on. An animal with a positive energy balance is consuming more energy than it is using; an animal with a negative energy balance requires more energy than it is consuming.

Feedstuffs Food.

Metabolism (meh-tahb-oh-lihzm) The process of converting food into the energy needed to maintain the body and perform bodily functions.

Palatability (pahl-ah-tah-bihl-ih-te) The tastiness of the food. If the food is palatable, the animal will eat it. The most nutritious ration is of no value if the animal will not consume it.

Ration (rah-shuhn) The combination of feedstuffs that are provided to an animal, also may be called diet. A balanced ration is one that has the appropriate amounts of all of the nutrients that the animal needs.

Total digestible nutrients The total amount of nutrients in a feed that an animal can use.

Toxicity (tock-sihs-ih-te) The presence of a chemical that leads to damage and destruction of cells. Toxicity can occur through overfeeding of some nutrients, from ingestion of plants that contain unhealthy components, or from consumption of contaminated feed.


Feedstuff are divided into two major categories: concentrates (kahn-sehn-trats) and forages (for-ehj-ehs).


Concentrates are feed products that are relatively low in fiber and high in energy. Concentrates either provide energy in the form of carbohydrates, fats, or protein to the diet. Simple-stomached animals, such as swine and poultry, need high-carbohydrate diets because they cannot fully utilize the nutrients in high-forage diets. Feeds are often classified into the following groups based on the nutrients that they primarily provide in the diet:

Energy feeds These feeds have less than 20 percent protein, and provide energy through carbohydrates and fats. Most grains are energy feeds. Corn, oats (see Figure 5-6), and barley (see Figure 5-7) are common energy feeds. Energy feeds that are used in a particular region may vary depending on what grains are commonly raised in that area. Corn and oats are commonly used throughout the country, but other grains may be used in regions where they are commonly raised.



Protein supplements Feeds that are high in protein, usually more than 20 percent. Protein supplements can either be from animal sources (meat, milk products, and so on), or plant sources (soybean oil meal, cottonseed oil meal, and so on). Soybean oil meal is one of the most often used protein supplements in animal feeds.


Forages are high-fiber feeds, and are also known as roughage. Silage (si-lahj) is a type of forage that is commonly used for feed. Silage is a fermented form of a plant. Forages also include pasture and hay (see Figure 5-8), and are divided into legumes (lehg-yooms) and grasses:

Grasses A class of forages that is relatively low in protein. Common grasses used for animal feed are timothy, orchard grass (see Figure 5-9), and Bermuda grass.



Legumes A type of plant that can convert nitrogen into protein, using nodules (nohd-uls) on their roots. Because they can do this, they are high in protein, up to 18 percent in some plants. Common legumes used for animal feed are alfalfa (see Figure 5-10), clover, and soybeans.


All animals do not have the same nutritional needs. Nutritional needs vary based on the type of activity the animal is involved in, and what the current demands are on the animal. The following terms are used to describe different levels of nutritional needs in animals:

Maintenance The amount of nutrients needed to maintain basic bodily functions. All other categories of nutritional need are based on maintenance. The animal will use nutrients first to meet its maintenance requirements, and then additional nutrients will be used for other needs.


Growth The amount of nutrients needed to maintain basic bodily functions, plus provide the nutrients needed for growth. The need for nutrients for growth is greatest in younger animals.

Lactation The production of milk demands tremendous amounts of certain nutrients. A lactating female has one of the highest nutritional needs of any animal. In addition to an increased need for energy, lactating animals need more calcium and phosphorus than nonlactating animals.

Reproduction Females need to be in optimal health to successfully become pregnant. As the fetus grows, there may be increases in the need for specific nutrients. In most species, the nutritional need does not increase until the last third of the pregnancy, when the majority of the fetal growth occurs. Cats are an exception, as they have increased nutritional needs from the beginning of the pregnancy. Females in early pregnancy that are lactating need to be fed to meet the lactational need, not fed to the reproductive need.

Work This category primarily affects dogs and horses. Animals that use energy and are involved in physical work will have an increased nutritional need when compared to animals that are not working. Energy for work will come after the animal has met its needs for maintenance; therefore, environmental characteristics such as temperature, can affect how much energy is needed for the working animal. For example, sled dogs in the Arctic will have a higher need for energy than dogs doing similar work in a temperate climate.


Food and nutrition of animals is a primary area of focus in animal science. Understanding how the digestive tract of each species functions is important to maintain their well-being, as well as to maximize their production. All animals use the same basic nutrients; however, variations in the digestive tract lead to variations in feedstuffs used for individual animals.

1. What are the five classes of nutrients?

2. In what part of the digestive tract is pepsin added to the digesta?

3. In what part of the digestive tract do horses ferment roughages?

4. -- are the forage source with the highest protein.

5. -- is the classification for energy need on which all other
classifications are based.

6. List three feedstuffs that qualify as concentrates.

7. What nutrient is the most energy dense?

8. What part of the ruminant stomach is the site of bacterial

a. Rumen

b. Reticulum

c. Omasum

d. Abomasums

9. What is a balanced ration?

10. Call a local feed provider and learn the cost of some common
feedstuffs. What class of feeds is most expensive per pound,
forages or concentrates?

11. Select a species of interest and research what amino acids
are essential and nonessential for that species.

Capacity of the digestive tract in livestock species

                           Swine                   Equine

Organ                 (qts)     (liters)      (qts)     (liters)





stomach                 8         7.57         8-19      7.6-18

Small intestine        10          9.5        27-67    25.5-63.4

Cecum                 1-1.5     0.95-1.4      14-35    13.2-33.1

Large intestine       9-11      8.5-10.4      41-100   38.8-94.6

Total                28-30.5   26.5-28.87     90-221   85.1-209.1

                           Bovine               Ovine/Caprine

Organ                 (qts)     (liters)      (qts)     (liters)

Rumen                80-192    75.7-181.6       25        23.6

Reticulum             4-12      3.8-11.4        2         1.9

Omasum                8-20      7.6-18.9        1         0.9

Abomasum              8-24      7.6-22.7        4         3.8


Small intestine       65-69     61.5-65.3       10        9.5

Cecum                  10          9.5          1         0.9

Large intestine       25-40     23.6-37.8      5-6      4.7-5.7

Total                200-367   189.3-347.2    48-49    45.2-46.2

Ranges indicate different ages, breeds, and sizes.
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Author:Brady, Colleen
Publication:An Illustrated Guide to Animal Science Terminology
Geographic Code:1USA
Date:Jan 1, 2008
Previous Article:Chapter 4 Animal anatomy.
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