Animal NutritionA Review

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Objectives

• Basic understand of nutrients, digestibility, evaluation, and composition of feeds

• Knowledge of digestibility in both the monogastric and ruminant animal

• Appreciation for nutrient function and requirements for growth, maintenance, reproduction, and lactation

• Understanding of ration formulation

Nutrients

• Any feed that functions to support life• Concentrates and roughages– What are they?– What are the differences nutritionally?

• Six basic classes1. Water2. Carbohydrates3. Fats4. Proteins5. Minerals6. Vitamins

Nutrients

• Water– Difference between water & moisture– Dry matter– Most important nutrient!– Functions• Metabolic reactions• Transport nutrients• Temperature maintenance• Physical shape of the body (cell contents)

Nutrients

• Carbohydrates– Found in plant & animal tissue– Simple carbohydrates• Starch

– Easily digested– High in energy

– Complex carbohydrates• Cellulose, lignin

– Energy source– Present in cell walls

Nutrients

• Fats– Includes oils– A.K.A. lipids– Fats are solid, oils are liquid at room temp.– 2.25x more energy/lb. than carbs.– >100 fatty acids identified• Linoleic, and α-Linolenic are essential in livestock diets

– Precursor of prostaglandins & cell structure

Nutrients

• Proteins– Simple

• Amino acids– Building blocks of the animal’s body– Ex.

– Complex• Glycoproteins• Lipoproteins• Hemeproteins

– Only nutrient class that contains nitrogen• Ave. ~16%• 6.25 multiplier

– %N X 6.25 = %protein

Nutrients

– Essential Amino Acids• Must be supplemented in the diet

– Feed– Microbial protein

– Nonessential Amino Acids are synthesized by the body

– Various absorption rates• Egg• Animal• Plant

Nutrients

• Minerals– Chemical elements other than carbon, hydrogen,

oxygen, nitrogen– Macrominerals

• Required in larger amounts• Ex.?• Important for several major bodily functions

– Micromineral• Trace minerals, required in small amounts• Ex.?• Important for vitamins, hormone synthesis

– Usually work together w/ other nutrients– Can be harmful in high levels

Nutrients

• Vitamins– Organic nutrients required for very specific bodily

functions– 16 vitamins• Fat soluble

– A, D, E, K

• Water soluble– C, B12, B1, Niacin– In ruminants, these are synthesized by the microorganisms

Feed Analysis

• Proximate Feed Analysis– Separates feed components into group according

to feed value– Accuracy of the analysis is dependent upon

accuracy of the sample• Components measured– Water– Crude protein– Crude Fat– Crude Fiber– Nitrogen-free extract– Ash (minerals)

Feed Analysis

• Determining moisture and/or DM content

• Feed Digestibility– Amount of a feed that is absorbed from the digestive tract– Great variance– Measuring digestibility

• Energy Evaluation of Feeds– Energy is available in any nutrient with carbon• Carbs., protein, fats

– Driving force in bodily function

Feed Analysis

– Measuring energy• TDN

– Not as accurate

• ME– Very accurate– NE– DE

– Calorie (cal)• Energy required to raise the temp of 1g of water 1

degree C

Feed Analysis

– Kilocalorie (kcal)• Energy needed to raise the temp of 1kg water 1 degree

C

– Megacalorie (Mcal)• =1,000 kcal or 1,000,000 cal

– Some energy is lost, and therefore not digested• Feces• Urine• Gases• Heat

Feed Analysis

• Animal uses energy in two ways– Maintenance– Production

• GE– Amount of heat (cal) released from complete burning of a

feed (Bomb Calorimeter)

• ME is what the animal actually has the opportunity to use– NE is what is available after energy used for consumption,

digestion, metabolism (heat increment)

Feed Analysis

• In diet formulation:– NEm– NEg– NEl

Figure 15.3 Measures of energy and energy utilization.

Feeds and Feed Consumption

Classification of Feeds1. Dry roughages & forages

• Hay• Straw• Other

2. Range, pasture, green forage

Feeds and Feed Consumption

3. Silages4. Energy Feeds

• >18% CF, <20%CP

5. Protein supplements• >20% CP

6. Mineral supplements7. Vitamin supplements8. Nonnutritive additives

• Antibiotics• Coloring• Flavors• Medicants• Etc.

Feeds and Feed Consumption

• Nutrient Composition of Feeds– Goal of nutrient analysis is to predict the

production capability of a feed– Tables are an average, true analysis is much more

accurate• Composition can vary:

– 15% in CP– 10% in energy– 30% in minerals

Digestion & Feed Absorption

• Digestion– Mechanical– Chemical– Role is to produce feed particles the can be

absorbed and used by the body

Carnivorous, Omnivorous, & Herbivorous animals

• Which is which?• Carnivores & Omnivores are monogastric

animals– One, simple stomach– Also some herbivores (horse, rabbit)

• Herbivores– Ruminants– Stomach compartments

The Monogastric Digestive Tract

• Mouth– Mechanical chewing and swallowing of food– Salivary Glands

• Esophagus– Delivery tube from mouth to stomach– Valve controls opening

• Stomach– Primary area of reduction in feed particle size

The Monogastric Digestive Tract

• Small intestine– Duodenum– Jejunum– Ileum– Split molecules & absorb nutrients

• Large intestine– Cecum– Colon– Absorb water– Forms indigestible waste (Feces)

Figure 16.1 Digestive tract of the pig as an example of the digestive tract of a monogastric animal.

Figure 16.2 Digestive system of the horse. The posterior view shows the colon or large intestine proportionally larger than the rest of the digestive tract. Note particularly the location of the cecum at the anterior end of the colon.

Ruminants

• Rumen– Fermentation vat– Papillae– Bacteria & protozoa

• Reticulum– Aka honeycomb– Initiate mixing in rumen

Ruminants

• Omasum– Many folds (manyplies)– Grinding action?– Not a lot of digestive responsibility

• Abomasum– True stomach

• Ruminants can rechew feed already consumed for more thorough breakdown of feed particles (Cud) known as rumination

• Elimination of gases by eructation

Figure 16.4 Beef cattle digestive tract.

Figure 16.5 Lining of the four compartments of the ruminant stomach (goat). (A) Compartments intact.(B) Compartments separated. Courtesy of George F. W. Haenlein. University of Delaware.

Figure 16.7 The esophageal groove, with its location relative to the esophagus, reticulum, and rumen. Courtesy of N. J. Benevenga et al., 1969. Preparation of the ruminant stomach for classroom demonstration. J. Dairy Sci. 52:1294.

Digestion in Monogastrics

• Begins in the mouth• Enzymatic reactions– Organic catalyst that speeds a chemical reaction

without being altered by the reaction– Stomach secretions• HCl• Mucus• Pepsin• Gastrin

Digestion in Monogastrics

• Mixture and some digestion occurs, resulting in Chyme

• Amino acids, fatty acids, and monosaccharides are available for absorption

• Two methods of absorption– Passive• Molecules diffuse from high concentration area to low

concentration– Active• Engulf molecules in villi, and transport them to

bloodstream or lymph

Digestion in Monogastrics

• Liver function– Metabolizes feed particles in bloodstream– Detoxifies harmful substances

Digestion in RuminantsFermentation in rumen & reticulum

Microorganisms number in the billionsExcess are removed with feed movement and killed by acid in the

abomasumMutually beneficial relationship

Digestion is the same after feed reaches the abomasumMicroorganisms use starch and sugar for their growth and

developmentRobs the animal of valuable energy sourcesProduce Volatile Fatty Acids (VFA) which the animal absorbs and converts

to energy Acetic Propionic Butyric

Methane gas is released through eructation What if this action fails?

Digestion in Ruminants

• Esophageal groove– Pathway directing milk to abomasum

• Complete function of digestive tract is not complete until:– Sheep ~2 mos.– Cattle ~3-4 mos.– Influenced by feed type

• Energy Pathways– End products of glucose and fatty acids supply body

tissues with energy, and become milk fat and lactose in the lactating ruminant

Digestion in Ruminants

– Primary organs and tissues in energy metabolism• Rumen• Abomasum• Small intestine• Liver• Blood vessels• Mammary gland• Body tissue

– Undigested energy products• Complex carbos. (lignin) and other (ex. Ketone bodies)• Excreted through large intestine or kidneys

Figure 16.8 Energy pathways in the ruminant. Source: J. Bryant and B. R. Moss, Montana State University.

Digestion in Ruminants

• Protein Pathways– End products of protein and NPN:• Amino acids• Ammonia

– Excess formed into urea in liver and excreted in the urine– Some is returned to the rumen

• Synthesized amino acids

Figure 16.9 Protein pathways in the ruminant. Source: J. Bryant and B. R. Moss, Montana State University.

Nutrient Requirements for Body Maintenance

• No gain/loss of weight or production• High priority for nutrients

1. Body tissue repair2. Temp control3. Energy for vital organ function4. Water balance maintenance

• Takes ~½ of all ingested feed

Nutrient Requirements for Body Maintenance

• Examples– Feedlot steers ~30-40% for maintenance– Breeding animals ~90%– 100# dairy cow eat 4-5x their daily maintenance

requirement• Body size & Maintenance– Increased body size means increased nutrient

requirement– But, not at a linear rate

Nutrient Requirements for Growth

• Occurs when:– Protein synthesis is > protein breakdown– Cells increase in number & size– Both

• Building of muscle, bone, connective tissue• Nutrients needed for growth– Energy, protein, minerals, vitamins

• Muscle growth is due to protein

Nutrient Requirements for Growth

• Ca, P, & NaCl– Ca usually plentiful in legume forage– P plentiful in grain

• I & Se– Deficiency in I results in goiter– Se deficiency-white muscle disease

Nutrient Requirements for Growth

• Vitamin D– Needed for proper use of Ca & P– Can get from sunshine (conversion of cholesterol

in the skin), unless raised inside• Vitamin A– Can be lost during drying in the sun, or extended

dry storage

Nutrient Requirements for Fattening

• Storing surplus feed in and around body tissue• Desirable for quality meat production and

energy storage• 2.25x more energy to produce 1# fat as

opposed to 1# protein• Due to excess:– carbos, fats, protein

Nutrient Requirements for Reproduction

• 2 categories– Gamete production• Nothing above normal maintenance• Body condition affects fertility

– Fetal growth• Greatest in last trimester of pregnancy• Requirements of the fetus are the same as those after it

is born• Healthy females can withdraw nutrients from their

body for the fetus

Nutrient Requirements for Lactation

• Requires protein, minerals, vitamins, energy• Protein is greatest– >3% protein in milk– Body protein can be mobilized in deficient times

• Ca & P are critical– Hypocalcemia

Nutrient Requirements for Lactation

• Energy– Based on amount of milk produced– Production can be limited by intake• High producing dairy cow may need 3-4x the energy of

non-lactating cow of same size

– Why do some cows continue to lose weight?– What is the ideal forage to concentrate ratio in

dairy cows?

Energy Requirements for Work

– Primary requirement is energy– Regular exercise schedule is necessary for good

health• Perspiration removes nitrogenous wastes

Ration Formulation

• Objective is to economically match the animal’s nutrient requirements with available feeds

• Things to consider:– Palatability– Physical form– Other

Diet Modification to Minimize N & P Pollution

Impacts air & water qualityN

By-product of protein digestion What does it affect?

P Mineral nutrient Will be excreted if fed in excess

Two concerns Volatility of N in the form of ammonia Distribution of manure nutrients

P contaminates surface water N contaminates groundwater