Animal Science- Exam 2 Flashcards

Energy

The ability to do work

2 forms of energy in diets

• Carbohydrates: 4Kcal/g(slow burning)

• Fats: 9Kcal/g(fast energy) 2.25x greater than carbs

Utilization of energy influences:

• Energy requirements

• Nutrient requirements

What are the required nutrients?

• Water

• Protein

• Energy (CHO & fats)

• Vitamins

• Minerals

What 2 cycles are powered by ATP?

• Kelvin Cycle

• Krebs Cycle

What factors affect nutrient requirements?

• Species

• Weight

• Age

• Sex

• Production use (gain, work, lactation)

• Health

• Environment

• Genetics

Dry matter

Everything not water

• Always feed on a dry matter basis

Canine teeth

Carnivores:

• Used for piercing, gripping, and tearing

Herbivores:

• Reduced or absent due to lack of necessity 

Incisors

Used for cutting, gnawing, and grooming

• Cattle, sheep, and goats don’t have a top set of incisors, they have a dental pad

Molars and premolars

Carnivores:

• Allows interlocking when chewing like scissors

Horses

• Molars and premolars are flattened in order to grind up plants

Ruminant feeding strategies

Cattle: non-selective grazers

Sheep: selective grazers

Goats: selective browsers

Ruminant Stomach

• Four compartments

• Reticulum→ rumen→ omasum→ abomasum

Reticulum

• Serves as a gateway to the rumen and omasum

• Known as the “metal catcher” or “honeycomb”

  • traps foreign objects

• Gathers feed for rumination

• Creates a bolus 

Pre- Ruminants

• Esophageal (reticular) groove

  • Allows milk to bypass the reticulum and rumen in young ruminants

Rumen

• The “paunch’

• Fermentation occurs

• Microbe lining produces cellulase enzymes to break down cellulose

• Creates its own microbiome→ can turn low quality forage into high quality protein

• Absorption of microbial fermentation products: volatile fatty acids (VFAs) and ammonia

Omasum

• Contains “leaves” or folds

  • Known as the “butcher’s Bible” 

• Absorbs 30-60% of water

  • Slows down the rate of passage to the abomasum

Abomasum

• “True stomach” similar to a monogastric stomach

• Only glandular compartment

  • Secretes enzymes and hydrochloric acid (HCl) for digestion

Functions of the abomasum

• Storage

• Mixing

• Breakdown

What happens after the abomasum

• Feed flows through the same path as in monogastrics

  • Small intestine→ Cecum→ Large intestine

What is the purpose of any digestive system?

• To take in, break down, and absorb nutrients

• 3 main digestive tracts

  • Monogastric

  • Ruminant

  • Non-ruminant herbivores

What is prehension?

• The process of seizing, grasping, otherwise getting food into the mouth

• Organs of prehension

  • Cattle→ tongue

  • Horses, sheep, goats→ lips and teeth

  • Chickens→ beak

  • Pigs→ lower lip, teeth, and tongue

What is the mouth’s purpose?

• Digestion starts here

• Two kinds of breakdown occur here

  • Chemical: amylase

  • Physical: mastication, teeth

What is the purpose and function of the esophagus?

• Function: transportation

• Peristalsis: rings of smooth muscle that contract to push food down

  • Ruminants and monogastric also have reverse peristalsis or regurgitation

  • Horses DO NOT have reverse peristalsis

Functions of the stomach

• Mixing

• Storage

• Breakdown

What are the functions of the small intestine?

• 2 primary functions

  • Chemical breakdown: enzymes are secreted by the pancreas, gallbladder, and lining of the small intestine

  • Pepsin- secreted by the small intestine, breaks down proteins

What are the 3 segments of the small intestine?

• Duodenum

• Jejunum

• Ileum

What are the functions of the gallbladder and pancreas?

Gallbladder

• Ties into the digestive tract through the duodenum

• Secretes enzymes necessary for digestion

• Secrets bile for emulsification of fats

Pancreas

• Lipase- lipids(fats)

• Trypsin and chymotrypsin- proteins

• Amylase- starch (carbohydrates)

What is the cecum and its function?

A blind sack located at the junction of the small and large intestines

• The appendix in humans

• Little to no digestive function for most species

• Extremely important in horses

What are the functions of the large intestine?

• Absorption

  • Water

  • Phosporus

What animals are considered non-ruminant herbivores?

• Horses

• Rabbits

What makes non-ruminant herbivores special?

• No rumen

  • Same bacterial population in the cecum/ large intestine as the rumen— necessary for fiber digestion→ breakdown of cellulose

• Cellulose: not broken down by mammalian enzymes, only by cellulase

What is the esophagus and its functions?

• 50-60 inches long in mature horses

• Horses can’t vomit and survive for 2 reasons:

  • Extreme muscle tone at the lower end of the esophagus (esophageal/ cardiac sphincter)

  • No reverse peristalsis

• The stomach will most likely rupture before vomiting will occur, typically along the curve of the stomach

What are the functions of the stomach in non-ruminant herbivores?

• About 8.5% of the total GI tract capacity

• Small particle size moves quickly

• Very little, if any bacterial fermentation

• Little to no nutrient absorption

What are the functions of the small intestine in non- ruminant monogastrics?

• Compromise about 30% of the GI tract capacity

• About 60 inches long in a mature horse

• 3 segments

  • Duodenum

  • Jejunum

  • Ileum

Digestion and absorption in the small intestine

• Carbohydrates:

  • Starch is broken down into glucose and absorbed

  • Cannot break down cellulose in small intestine

• Proteins, fats, vitamins, and minerals digested and absorbed as in monogastrics

  • Bile required for the emulsification of fats, BUT horses have no gallbladder

  • Steady dribble of bile into SI through bile duct from liver limit inclusion of fat into diet

Function of the cecum in non-ruminant monogastrics

• Also called the hind- gut fermenters in horses

  • 50-60% of the total GI tract

• Functions like the rumen- microbial fermentation of forage occurs here

Digestion and absorption in the cecum

• Protein

  • Degraded in cecum just like in rumen of cattle— no small intestine after to absorb

• Carbohydrates

  • Fermented in cecum just like in the rumen of cattle—VFA’s produced and absorbed

• Vitamins

  • Bugs make water-soluble vitamins and E and K, no small intestine to absorb

What are nutrients

• A substance that provides nourishment essential for growth and the maintenance of life

• Without nutrients, our animals cannot survive

How much do they really need?

• Have to meet they’re minimum daily requirements (MDR) in order to perform

• Different daily requirements depending on the physiological state or stage of production

What are the six classes of nutrients?

1. Water

2. Carbohydrates

3. Proteins

4. Fats (lipids)

5. Vitamins

6. Minerals

Water

• Most vital nutrient ingested!

• Does not need to be digested- absorbed

• Supplemented in the diet in two forms:

  • Drinking water

  • Free water- moisture fraction of feeds

• Factors impacting water consumption:

  • Environment: temperature

  • Stage of production: lactating cows vs. dry cows

  • Dietary water- Moisture content of feeds

• Feeds high in moisture:

  • Silage

  • High moisture corn

Carbohydrates

• Composition

  • Carbon (40%)

  • Hydrogen (7%)

  • Oxygen (55%)

• Energy value- 4kcal/g

• Structural component in plants

  • Largest parts of the animal’s food supply

• Can be in simple or complex forms

  • Sugars→ simple → readily digestible

  • Starches and fiber → complex → poorly digestible

• Function as a:

  • Source of energy

  • Source of bacterial fermentation

  • Building block for other nutrients

  • Stored by converting to fats

Sugars

• Simplest form of carbohydrate, most easily digestible

• Monosaccharides- single sugar molecules

  • Glucose, fructose, and galactose

• Disaccharides- two sugar molecules

  • Sucrose (glucose+ fructose)

  • Lactose (glucose+ galactose

Starch

• More difficult to digest than sugars

• C-C bonds, broken by amylase

• Plant cell components, can be solubilized with heat

  • Steam rolled corn flakes

Fiber

• Cellulose and hemicellulose

  • Associated with plant cell walls

  • Cannot be digested by monogastrics

  • Cellulase required for digestion- synthesized by microbes in ruminant animals

• Lignin

  • Undigestible

  • Structural component of plants, increases with maturity

Feeds with high levels of these nutrients

• Sugar

  • Molasses

• Starch

  • Corn, any kind of grain

• Cellulose

  • Forages

• Lignified

  • Wheat straw, more mature forages

Proteins

• Composition:

  • Corbo

  • Hydrogen

  • Oxygen

  • Nitrogen

• On average, proteins contain 16% Nitrogen

  • Can multiply N content by 6.25 to estimate protein

• Fulfill

  • Structural role→ muscles and cell membranes

  • Regulatory

  • Enzymes- amylase, lipase, etc.

  • Hormones- FSH (follicle stimulating hormone), LH, ACTH

• 4kcal/g of energy- not used as an energy source

• Structure- made up of long chains of amino acids

  • Broken down into amino acids in order to be absorbed

Amino Acids

• Both essential and non- essential amino acids

• Essential amino acids:

  • Required in the diet in order for the animal to synthesize the other amino acids

• Non- essential amino acids:

  • Produced in the body and primarily found in glucose

Essential Amino Acids

• PVTTIMHALL

  • Phenylalanine

  • Valine

  • Threonine

  • Tryptophane

  • Isoleucine

  • Methionine

  • Histidine

  • Arginine

  • Leucine

  • Lysine- (first limitin

What do protein requirements depend upon?

• Species

• Sex

• Size

• Body composition

• Physiological state (stage of production)

• Deficiency- decreased growth rate and efficiency, anemia, infertility, etc.

Fats (lipids)

• Composition:

  • Carbon

  • Hydrogen

  • Oxygen

  • More C & H relative to O than carbohydrates

• Typically 3 fatty acids attached to a glycerol backbone

  • Broken down into fatty acids in order to be absorbed- bile (gallbladder) and lipase (pancrease)

What are the forms of fats?

• Saturated and unsaturated

• Saturated

  • Single bonded carbons

  • Solid at room temperature 

• Unsaturated

  • One or more double bonded carbons

  • Liquid at room temperature

What are the functions of fats?

• Energy

  • 9kcal/g of energy- 2.25 times more than carbohydrates

• Form of stored energy

• Solvents for some nutrients- vitamins

• Precursors for hormones- prostaglandin

• Structural component of cells

• Improve feed characteristics- dust, mixing, etc.

Fats as an energy source

• Inexpensive form of energy

  • More energy than carbohydrates or proteins

  • Included in diet to increase energy density

• Inclusion limited due to palatability

  • less than 10% in diet

  • High fat feeds require additional storage and handling considerations

Sources of fat

• Rendered animal fat (tallow)- not commonly used today

• Oilseeds

• By- products from food processing- yellow grease (corn/ sunflower oil)

Vitamins

• Organic compounds- do not need to be digested

• Essential for development of animal tissue

• Required in small amounts for normal metabolism

• Classified based on their solubility

  • Fat soluble or water soluble

Fat soluble vitamins

• Soluble in fat

  • Vitamins A, D, E, and K

• Vitamin A

  • Maintenance of vision and epithelial things of the body- bone formatting/ growth

• Vitamin D

  • Bone formation, regulation of Ca and P absorption

• Vitamin E

  • Antioxidant, cell membrane stability

• Vitamin K

  • Blood clotting

Water soluble vitamins

• Soluble in water

  • Vitamins Bs and C

• Play a role in metabolic and immune functions

  • Energy metabolism

  • Cofactors for enzymes (B₁, B₂, B₃, B₆, and B₁₂)

  • Increase disease resistance and recovery (C)

Digestion and absorption

• Vitamins do no need to be digested

• Some do not need to be supplied in the diet

  • Most mammals can synthesize vitamin C

  • Ruminants can synthesize vitamin Bs, C and K

• Absorbed through the small intestine

• Excess stored if fat (fat soluble vitamins) or excreted in urine (water soluble vitamins)

Digestion of carbohydrates in ruminants: mouth and esophagus

• Carbohydrates enter the mouth

  • Mechanical digestion- mastication

  • Saliva moistens and softens feed

• Feed moves down the esophagus- peristalsis

  • Sore of these feed particles are large and not chewed well 

• Bi carbonate in the rumen wants a neutral pH

Digestion of carbohydrates in ruminants: reticulum and rumen

• Feed enters the reticulum/ rumen

  • Large particles are assembled in the reticulum (bolus)

  • These large particles are regurgitated back up (reverse peristalsis) the esophagus for continued mastication

    • This whole process is called rumination

  • The reticulum also initiates rumen contractions to mix feed in the rumen

• Rumen

  • Carbohydrates in the rumen can either bypass the rumen (not as common) and go to the omasum or be degraded by rumen microbes (most common)

Digestion of carbohydrates in ruminants: rumen

• When microbes digest carbohydrates in the rumen they produce:

  • Volatile fatty acids (VFAs)

    • Acetate

    • Butyrate

    • Propionate- (the most efficient VFA)

  • Methane

    • Lost to the environment due to eructation (burping)

  • Carbon Dioxide

    • Lost to the environment due to eructation

Over production of gas in the rumen

• If CO₂ and methane cannot escape through eructation, bloat occurs AKA acute tymphany

  • Enlargement of rumen

  • Occurs on left side of the animal

  • Causes discomfort

  • Can cause death if not treated

  • Two main types

    • Free gas bloat

    • Frothy bloat

VFA’s

• Absorbed through the rumen papillae

  • Taken to the liver via the hepatic portal vein

  • Metabolized in the liver

  • In the liver the VFA’s are metabolized into glucose and other energy sources 

  • After metabolism, glucose enters the bloodstream and is used for tissue metabolism

VFA overproduction in the rumen

• VFAs are acidic so an overproduction can lead to a condition called ruminal acidosis

Carbohydrates that are not fermented by microbes

• These carbohydrates pass into the omasum then into the abomasum and are digested very similar to monogastrics in the small intestine

  • Enzymatic breakdown in small intestine into sugars that go to the liver then to the bloodstream

• Undigested carbohydrates

  • Pass into the large intestine then out through the feces

Protein Digestion in ruminants: Mouth and esophagus

• Protein is mechanically digested in the mouth

• If protein is in a large feed particle it is ruminated

• No protein digestion in the mouth

Protein digestion in the rumen

• Fed protein is degraded by the rumen microbes and converted to ammonia

• Ammonia is used by the microbes as a protein source for the microbes

  • Some of the protein fed to a ruminant is used for microbe growth

• The dead microbes, which contain protein, pass through the rest of the digestive tract

  • Dead microbes are high in protein

  • Microbes synthesize essential amino acids

Protein digestion in the abomasum

• Two types of protein enter the abomasum

  • Dead microbes

  • Proteins that are degraded by the microbes

    • These are called by-pass proteins

• In the abomasum HCl unfolds proteins and pepsin starts enzymatic breakdown

Protein digestion in the small intestine

• Enzymatic breakdown of protein chains into amino acids

  • Trypsin

  • Chymotrypsin

• Absorption of amino acids occurs in the small intestine

• As amino acids are absorbed, they go to the liver and can go two different ways

  • Into the bloodstream

  • Converted to ammonia, then to urea and incorporated into saliva

Nitrogen recycling in ruminants

• Nitrogen in a ruminant can either be excreted in the urine or sent to the saliva

• During a protein deficiency, nitrogen instead of being excreted is recycled into the saliva

• The saliva enters the rumen and that nitrogen is converted to ammonia and used as a proteins source for the microbes

Ruminant protein digestion: large intestine

• Protein that is undigested is excreted through the feces