EXAM 1

Question 1

What is photosynthesis?

Answer 1

The process plants use to convert CO2 into O2, and light into glucose energy (sugar/food)

Question 2

What is amino acid synthesis?

Answer 2

Plants take in nitrates and ammonia from the soil, and use that to synthesize amino acids (meaning amino acids contain N2)

Question 3

What is nitrogen fixation?

Answer 3

Nitrogen-fixing bacteria, that cling to the roots of plants, will absorb N2 from the air, and transform it into fixed nitrogen

Question 4

What are the parts of the plants and the functions of each?

Answer 4

1. Leaves: where photosynthesis occurs
2. Stems: provide structure and stability; transport for nutrients
3. Fruit: encloses the seed of the plant; also contains endosperm, which is used as food by the seed when it initially sprouts and is a source of nutrients for animals
4. Roots: anchor the plant; absorb water and minerals from the soil; stores food

Question 5

What are the broad classifications of plant feeds? Be able to list examples and different characteristics.

Answer 5

1. Concentrates: low levels of fiber (<18% crude fiber); high energy source; low to moderate protein levels; high density (ex. corn, oats, barley, grains and high quality by-products from cereal grains)
2. Forages/Roughages: high levels of fiber (>18% crude fiber); low levels of energy; variable levels of protein; bulky, course, low density (ex. legumes, grass, hay, wheat, corn cobs, rice hulls)

Question 6

What is the relationship between lignin, dry matter, and digestibility?

Answer 6

As lignin and DM increase, digestibility decreases; inversely proportional

Question 7

What is nutrient density?

Answer 7

The content of a specific nutrient/unit weight; increase in DM increases nutrient density because there’s less water/unit weight

Question 8

What is the relationship between the leaf: stem ratio, and its effect on the digestibility of the plant?

Answer 8

Leaves tend to be high in nonstructural carbohydrates (easily digestible), while
stems tend to be high in structural carbohydrates (including lignin); nutritive value (& digestibility, if animal can absorb nutrient) increases as the leaf:stem ratio increases due to leaves having more nutrients and less fiber

Question 9

What is the relationship between digestibility and particle size?

Answer 9

As particle size gets closer to the optimum size, digestibility increases; if size is too small, particles pass through digestive tract too quickly for enzymes to break it down; if size is large, enzymes can only interact with the particle’s outside surface

Question 10

What are the different processing techniques, and examples of them?

Answer 10

1. Chopping & Grinding: forages can be chopped to a particle size of about 2” or ground to a particle size that is <1”; helps the animal consume enough poor quality forage
2. Pelleting: occurs after the grinding of forages; costly process; useful for feeding sheep, poultry and rabbits
3. Heat Treatment: in ruminants, heat treatment decreases the solubility and
   rumen degradability of protein, leading to increased delivery of amino acids to the lower gut; in non-ruminants, the efficiency of protein digestion of legumes seeds is increased by degradation of toxic factors, specifically trypsin-inhibotors

Question 11

What are the advantages and disadvantages of heat treatment?

Answer 11

Advantage: energy value can be increased by partial gelatinization of starch within the endosperm (won’t degrade as quickly); can kill bacteria on the feed
Disadvantage: overheating may decrease the protein quality and degradation of
fat- soluble vitamins and some B complex vitamins

Question 12

What makes corn so versatile?

Answer 12

It can be processed in many different ways (ex. dry or wet milling processes), and produce a large amount/variety of products

Question 13

What are the advantages and disadvantages of silage? What types of feeds can be made into silage?

Answer 13

Advantages: can be made from many different sources; very palatable feed; can be stored for a long time (if made and processed correctly)
Disadvantages: high-protein forages (i.e., alfalfa) are more difficult to ensile because it requires more lactic acid to lower the pH; final product will be variable with silage coming from different parts of the silo having different nutrient compositions; if you do something wrong during the ensiling process, you can ruin the entire
400 ton contents; bulky to store/handle and has no resale value (only used for your property)
Green forages (ex. grass hay, alfalfa, or a grain); corn silage is the most common

Question 14

What are the components of a proximate analysis and how do you calculate each part?

Answer 14

1. Crude fiber: (g fiber/g AF) x 100= CF%
2. Crude protein: (g protein/g AF) x 100= CP%
3. Ash (mineral, ie. Ca & P): (g mineral/g AF) x 100= mineral%
4. Ether extract (lipid): (g lipid/g AF) x 100= lipid%
5. NFE (nitrogen free extract): [(AF - everything added together)/AF] x100

Question 15

What is the concept of CP?

Answer 15

Proteins are 16% nitrogen (Kjeldahl method is used to find the amount of nitrogen in a sample), meaning you can be given the nitrogen weight and use that to solve for the CP weight: g nitrogen x (1/0.16)= g protein

Question 16

What is the difference between ADF and NDF and how is the Van Soest method is used to analyze these factors?

Answer 16

The %NDF is a measure of the percent structural carbohydrates in the
sample, while ADF only consists of cellulose and lignin because the hemicellulose goes into the acid solution; as %ADF increases, digestibility/fermentability decreases because there is more lignin in the sample
Van Soest method helps separate the different fiber components to measure the fermentable components within the fiber

Question 17

What is a digestion trial? Why is it performed and how do you to run it?

Answer 17

A digestion trial observes how digestible a certain nutrient is for an animal. The amount of feed intake is measured, followed by collection of all the feces produced, without the urine. The nutrient of interest must also be measured in the feed and feces. Should be 5 or more animals tested for 7 days or longer

Question 18

Why are production trials so important?

Answer 18

It is important to evaluate how well animals produce on the ration they are eating. A production trial compares diets to determine which will give the best performance

Question 19

What is a feed:gain ratio? Why is it so important when assessing feeds and animals?

Answer 19

Feed:gain ratio shows how effectively the feeds are used by the animal. This allows producers to make economically (cost) and biologically (production) efficient decisions.

Question 20

Name the anatomical parts of the gastrointestinal tract and know the function of each organ.

Answer 20

1. Mouth: selection, chewing, saliva, swallowing; teeth incisors shear forage, molars grind food
2. Esophagus: propels the food, liquids and saliva from the mouth down into the stomach (peristalsis)
3. Stomach: reservoir, mechanical breakdown (gastric motility), hydrolytic digestion of protein components via acid and enzymes
4. SI: duodenum breaks down the food via secretion of digestive enzymes and bile, jejunum and ileum absorb nutrients and send them into the bloodstream (responsible for the chemical digestion of carbohydrates and fats as well as the absorption of protein, carbohydrates and fats)
5. LI (colon): fiber fermentation, the absorption of water and feces formation, flora aided fermentation of unabsorbed material occurs, vitamin absorption
6. Cecum: important for fiber fermentation while in others it is non functional (human; reduced in obligatory carnivores)
7. Rectum & Anus: feces are temporarily held in the rectum just prior to elimination; the opening at the end of the digestive tract that controls the expulsion of feces
8. Accessory Organs (liver, pancreas, gallbladder): process the nutrients absorbed from the SI (produces bile to help digest fat); secrete pancreatic enzymes that aid in digestion of carbs, fats & proteins after they left the stomach (exocrine); stores and concentrates bile and then releases it into the duodenum to help absorb and digest fats

Question 21

Compare and contrast the simple and complex stomach.

Answer 21

Simple: 1 compartment; monogastrics (horses, humans, cats, etc.)
Complex: 4 compartments (rumen, reticulum, omasum, abomasum); ruminants; microbes found in rumen

Question 22

What are the functions of the microbes in digestion and fermentation?

Answer 22

Bacteria: fermentation- fiber fermentation
Protozoa: fermentation- prey on bacteria
Fungi: fermentation- prey on bacteria, digest fiber

Question 23

What is meant by the term rumen “ecosystem”, and why is it important?

Answer 23

The rumen ecosystem is made of microbes that must interact to keep a healthy balance; improper nutrition and feeding can throw the ecosystem out of balance

Question 24

What are the environmental requirements of the microbes?

Answer 24

1. Constant temp. of ~39℃ (internal body temp.)
2. pH between 6.5-6.8
3. Gas emitted into rumen by microbes must be expelled
4. Anaerobic environment
5. Constant supply of nutrients (energy and nitrogen)

Question 25

What is a by pass protein and what are some other names for this type of protein? Which animals would be fed a by pass protein?

Answer 25

By pass protein is a protein that escapes degradation by the microbes and enters the abomasum (digested by the animal); aka a protected protein; fed to ruminants

Question 26

What are benefits and costs of fermentation?

Answer 26

Benefits: ruminant consumes pasture-> microbes use pasture as feed source-> produce ATP-> release VFAs as waste product-> VFAs become feed source to
produce ATP for cell survival; microbes provide a source of protein to the ruminant; microbial presence allows ruminant to utilize fiber and non-protein nitrogen
Costs: microbes must be fed (supply of nutrients must be enough to keep ecosystem in balance); difficult to adjust ruminant rations to meet amino acid requirement; less efficient than monogastrics because of carbon lost as methane and carbon dioxide by the microbes; microbes also lose nitrogen when amino acids are deaminated and ammonia is produced

Question 27

What is the difference between pre and post gastric fermentation?

Answer 27

Pre-gastric: before the stomach; ruminants, kangaroos, hippos, hamsters
Post-gastric: after the stomach (either in cecum or colon); less feed available to microbes (meaning fewer microbes), and less regulated than pre-gastric; colonic fermenters- horses and elephants (important), pigs and humans (importance depends on diet); cecal fermenters- small herbivores and rodents

Question 28

What is rumen acidosis?

Answer 28

When the rumen pH drops to very low levels; rumen balance isn’t maintain; can occur by a diet that’s very high is soluble carbs; buffers and change in diet (back to high fiber) can reestablish balance

Question 29

How does the feeding behavior in different animals compare and contrast?

Answer 29

• Elephants grab feed with their trunk and bring it to the mouth
• Cows have a barbed tongue they use to sweep feed into the mouth and bring it back into the throat
• Sheeps incisors on the jaw (dental pad on top) to nip off the grass, and an center-split upper lip that allows for independent control of both sides (allows for selective feeding)
• Pigs use rooting to find feed

Question 30

What is pre-hension?

Answer 30

How an animal gets feed into its mouth.

Question 31

What is the interrelationship between pre-hension and saliva, NPN, and urea?

Answer 31

Pre-hension gets the feed in the mouth (chewing occurs; breakdown particle size) -> saliva moistens, lubricates, and begins starch digestion (salivary amylase) -> NPN can come from saliva (look at card 32) -> urea is brought to the kidneys, through the blood, and excreted as urine

Question 32

Regarding the recycling of urine, who does in benefit and why?

Answer 32

Benefits ruminant animals because the ammonia that is converted to urea by the liver gets into the blood, reaches the salivary glands, and put into the saliva, going back into the rumen and becoming a source of NPN for the microbes.

Question 33

What are the types of cells and hormones involved in gastric digestion?

Answer 33

Chief cells produce protein pepsinogen (turns into pepsin, responsible for protein digestion, when pH is <5; parietal cells secrete HCl (maintains acidic pH), and intrinsic factor (protein that binds to vitamin B12 at ileum); pyloric cells secrete gastrin

Question 34

What organs are involved in post gastric digestion and what are their functions?

Answer 34

1. & 2. Pancreas & Liver: secrete bicarbonate buffer to neutralize the acid (protects SI lining, and provides correct pH of the postgastric digestive enzymes)
2. SI: secretes water and salt to keep the contents fluid and mucus for lubrication of the feed

Question 35

Describe the post-gastric digestion of lipids, carbs, and proteins.

Answer 35

Lipids: emulsified into water-soluble lipid droplets called micelles by bile salts (produced by liver and store in gallbladder); then digested by the enzyme pancreatic lipase
Carbs: digested into disaccharides -> monosaccharides by enzymes in the SI (or mouth and SI for starch)
Proteins: begins in the stomach and continues in the lumen of the SI via pancreatic enzymes; large chains are broken down by the pancreatic enzymes (either amino acids or short peptide chains)

Question 36

Describe the absorption process of lipids, carbs, proteins, vitamins, and minerals.

Answer 36

Lipids: monoglycerides and FFA are absorbed across the intestinal villi and enter the intestinal epithelial cell; triglycerides are re-synthesized within the cell (not the same as feed triglycerides; have to be broken down because they’re too large to enter the cell); enclosed in a portion of ER membrane and bud off producing a lipid droplet called chylomicron. Chylomicrons are released into the lymph circulation through capillaries called lacteals. The lymph eventually empties into the portal vein
Carbs: monosaccharides are actively transported from SI lumen into the epithelial cell; then into interstitial fluid through facilitated diffusion; then into the capillary cell and then out into the
blood is by passive diffusion
Proteins: AAs or small peptides are actively transported across the SI by processes which vary among groups of AAs
Vitamins: fat-soluble vitamins are absorbed along with the triglycerides and enter the circulation through the lymph; water-soluble vitamins are absorbed by diffusion, except B12
Minerals: Na and K are passively absorbed across the intestinal tract, but once within body cells, Na transport is
active and highly regulated (Na/K pump); Ca is actively transported across the SI and is highly regulated because it’s important for nerve impulse transmission and muscle contractions; nucleic acids are actively transported after being digested to bases and sugars; water is co-transported with osmotic solutes

Question 37

Compare positive and negative energy balance, and give examples of animals in each state.

Answer 37

Positive: animal consumes more energy than it uses; hypothalamus tells body to decrease feed intake and/or increase
energy expenditure; ex. weight gain, late stages of pregnancy, wool production
Negative: animal uses more energy than it consumes; hypothalamus tells body to increase feed intake and/or
decrease energy expenditure; ex. weight loss, starvation, early stages of lactation

Question 38

What are the physical, chemical, and endocrine signals of short term intake?

Answer 38

Physical: gut fill/distension of gut wall (presence of feed in the gut activates stretch receptors in the rumen, SI and stomach, and sends a signal to the hypothalamus)
Chemical: pH (receptors in splanchnic tissue), VFAs (receptors in rumen wall), glucose (receptors in liver)
Endocrine: insulin and glucagon control blood glucose levels (pancreas); neuroendocrine hormones are produced within the brain and usually act directly on the hypothalamus

Question 39

Compare long-term regulation to short-term.

Answer 39

While feed is homeostatically regulated in the short-term, intake is increasing in the long-term

Question 40

What is homeorhesis?

Answer 40

The coordinated changes in metabolism of body tissues to support a physiological state; chronic regulation of feed intake , above homeostasis, that affects many tissues; occurs from major shifts of energy demand (ie. pregnancy)

Question 41

How does energy balance and intake differ between ruminants and mongastrics?

Answer 41

Ruminants can consume lower quality, high-fiber diets and extract more energy from them, resulting in a different energy balance and intake compared to monogastrics; essentially, ruminants can utilize a wider range of feed sources due to their microbial fermentation process in the rumen, while monogastrics typically require higher quality, more digestible feeds to meet their energy needs.