Chapter 6: GI Tract and Nutrition

Question 1

Reticular/Esophageal Groove

Answer 1

• alignment of esophagus such that milk in young ruminants bypasses rumen and reticulum and goes straight to the omasum and abomasum
• rumen undeveloped in the young
• otherwise, milk rots in the rumen/becomes cheese-like
• as animal starts eating plants, rumen develops into fermenting factory

Question 2

Eructation

Answer 2

• belching
• removing gas from rumen via esophagus
• occurs when ruminants chew the cud/ruminate

Question 3

Forage

Answer 3

• collective grouping of plant material that animals can eat

Question 4

Fresh Forage

Answer 4

• grazing fresh grass; pasture
• or cut and carry food to animals

Question 5

Conserved Forage

Answer 5

• storing fresh material for use at a later time
• hay
• silage (fermented plant material)
• harvest grain (stored in silos/storage containers)
• varies animals’ diets
• different nutrient profiles than conserved forage –> nutrient mixes
• can sell or buy this, or just keep some in reserve
• allows control over food intake
• can get feeds grown in different places if you can’t grow them where you are (alfalfa grown in CA –> TX; hay in CA –> China or Middle East)

Question 6

Concentrates

Answer 6

• grain
• very high in nutritive value
• not necessarily higher in energy than forages

Question 7

Supplements

Answer 7

• supplement animals’ rations w/ vitamins and minerals

Question 8

Nutrient Classes

Answer 8

• carbs
• fats
• proteins
• water

Question 9

Carbs (CHO)

Answer 9

• complex: starch
• simple: glucose, lactose
• 4.1 kcal/g of DM

Question 10

Proteins

Answer 10

• made up of amino acids
• meat and eggs are high in protein
• plant protein comes from peas, alfalfa, beans, lentils
• 4.1 kcal/g of DM

Question 11

Lipids/Fats

Answer 11

• made up of fatty acid chains (3 fatty acid tails to one glycerol = triglyceride)
• vegetable oils, dairy fats, meat fats, butter
• 8.8 kcal/g of DM

Question 12

Water

Answer 12

• most essential nutrient
• plants have water in them and wilt when they evaporate water

Question 13

Teff Plant

Answer 13

• can be dried to make hay
• vegetative growth (leaves) and reproductive growth (flowers, seeds)

Question 14

Oat Plant

Answer 14

• mostly leaves
• highly nutritious

Question 15

Alfalfa

Answer 15

• legume
• high in protein, like soybeans and peas
• nitrogen-fixing because of symbiosis w/ rhizobium
• high in protein because high in nitrogen –> nitrogen is part of amino acids

Question 16

calories

Answer 16

• amount of energy needed to raise temperature of 1 g H2O by 1 degree C
• bomb calorimeter to measure number of calories in food

Question 17

Corn

Answer 17

• 100 days from seed to mature plant with fruit
• as size and volume increase, DM will increase
• young, leafy plants are high in protein but low DM%
• mature plants are lower in protein but higher DM%
• young plants have starch, mature plants have structure carbs (cellulose, lignin)

Question 18

Digestibility

Answer 18

• what goes in vs. what goes out
• what is used as energy, used for bodily processes
• % DM digestibility = (DM in - DM out)/(DM in)

Question 19

Plants

Answer 19

• oats = 20% DM, 80% water
• hay = 90% DM, 10% water
• grains = 95% DM, 5% water

Question 20

Ruminant Stomach

Answer 20

• 4-chambered stomach
• rumen, reticulum, omasum, abomasum
• bolus of food enters

Question 21

Rumen

Answer 21

• bolus of food enters rumen
• large particles digested by microbial digestion (cellulose digestion done by microbes)
• active fermentation chamber

Question 22

Reticulum

Answer 22

• used to regurgitate food and redigest the large particles that can’t make it to the omasum

Question 23

Rumination/Chewing the Cud

Answer 23

• brings food up from rumen into mouth to chew cud and make particles easier to digest
• allows microbes to access nutrients and food particles to move through the tract
• animal might eructate

Question 24

Rumen Walls

Answer 24

• lined w/ papillae

Question 25

Reticulum Walls

Answer 25

• looks like honeycomb
• catches large particles of plant matter –> can be pushed into esophagus
• small particles pushed further thru digestion

Question 26

Omasum

Answer 26

• tripe meat
• small particles in reticulum go to omasum
• purpose is to absorb water
• folds of walls are sites of water absorption back into body

Question 27

Abomasum

Answer 27

• “true stomach”
• acidic environment
• chemical breakdown of digester (stuff to be digested)
• breaks down proteins into AAs, triglycerides into fatty acids, and carbs

Question 28

What Enters Rumen?

Answer 28

• starch (grains esp rich in starch)
• structural carbs (cellulose, hemicellulose)
• proteins (made of AAs - nitrogen)
• non-protein nitrogen (soluble nitrogen compounds, nitrogenous compounds)
• soluble carbs
• water
• salts, buffer

Question 29

Rumen Contents

Answer 29

• gasses, fibrous mat of long particles that float to the top, small particles in liquid suspension at the bottom
• lot of physical movement of particles (washing machine)
• largest volume chamber
• particles of food and dead microbes leave rumen

Question 30

Microbes

Answer 30

• in each mL (1/5 tsp) there are
• 100s of thousands yeast/fungi
• billions of protozoa
• millions of bacteria
• dead microbes have AAs and are source of nutrition for cow, since the microbes are constantly dying and replenishing
• microbes hit abomasum’s acidic environment and fall apart
• animal can reabsorb nutrients given to microbes
• many microbes only found in rumen of ruminants

Question 31

Symbiosis Between Microbes and Ruminant

Answer 31

• rumen provides: optimal temperature, anaerobic, gas exchange, pH buffering, water, nutrients
• microbes provide: access to range of unique forages and feedstuffs, temperature (internal hot water bottle as microbes cook and digest food), flexible intake pattern (slow release dinner from food in rumen), flexible mixture of feedstuffs

Question 32

Rumen Enzymes

Answer 32

• catalyze reactions to break down long chains of carbs
• end in “-ase”
• cellulose, starch, sugars = inputs
• enzymes: cellulase, hemicellulase, amylase, maltase
• sugars broken into hexose (6-C sugar)
• carbs broken down to CO2, CH4 (methane), hydrogen, and volatile fatty acids (VFAs)

Question 33

Volatile Fatty Acids (VFAs)

Answer 33

• acetate
• butyrate
• propionate
• enter blood and can be used by animal as source of energy in other organs
• taken into liver and turned into glucose

Question 34

Gas Fates in Ruminants

Answer 34

• rumen full of gasses that leave through rumen wall and enter blood supply
• CO2 and CH4 through eructating
• ammonia leaves rumen and animal uses this nitrogen to make proteins
• anaerobic fermentation produces many gases, which can be deadly if too much

Question 35

Bloat

Answer 35

• gas is produced too rapidly to escape
• can be deadly
• based on nutrition and diet and amount of food consumed

Question 36

Nitrogen

Answer 36

• ammonia enters blood as nitrogenous gas to be used in other organs
• microbes use N to multiply

Question 37

Summary

Answer 37

• rumen: food enters, large particles digested
• reticulum: larger particles pushed back into rumen for rumination
• omasum: absorbs water
• abomasum: acidic, digestion, true stomach
• small intestine; absorbs nutrients across gut wall back to blood for use by other organs
• large intestine: absorbs water across wall back to blood for use by other organs

Question 38

Why use mixed rations?

Answer 38

Balanced all nutrients, reduces waste from local industry, helps monitor biological state, feed is typically portable