Exam 2- Animal Science

Ruminant stomach (IN ORDER!!!!)

4 compartments: rumen, reticulum, omasum, abomasum

What is the rumen also known as

paunch

rumen (paunch)

largest compartment

• 40-50 gallons in cattle

• 2.5-8 quarts in sheep

what does the rumen include

fermentation vat

• microbes digest cellulose and starch

  • anaerobic bacterial fermentation

what does anaerobic mean

no oxygen

what is the reticulum also known as

honeycomb

reticulum (honeycomb)

• sorts particles by size

• sends large particles back for rumination

  • chewing cud

• catches foreign objects

  • hardware stomach

what is the omasum also known as

many plies

omasum (many plies)

• multiple muscular folds

• mechanical grinding of feed

• absorbs water, VFAs, electrolytes

what is the abomasum also known as

true stomach

abomasum (true stomach)

• acidic

• functions like monogastric stomach

• produces HCl and enzymes (pepsin, rennin)

where does protein digestion begin

abomasum

rumen microbes and symbiosis

• bacteria, protozoa, fungi work in symbiosis

• digest cellulose and starch

• synthesize microbial protein and vitamins

• produce VFAs as energy source

fermentation products

volatile fatty acids (VFAs) and microbial protein

what are volatile fatty acids

main energy source (50-70%)

acetate (VFA)

from fiber fermentation → used for fat synthesis

propionate (VFA)

from starch and sugars → covered to glucose via liver

butyrate (VFA)

from fiber and starch → energy by rumen wall, fat synthesis

what is microbial protein

amino acids for growth and tissue repair

byproducts of fermentation

• gas: methane and CO2 → belching (eructation)

• heat production → rumen produces heat

• essentrial for rumen function

monogastric stomach functions

• storage and mixing of feed

• secretes acid (HCl) and enzymes (pepsin)

• begins protein digestion

what are the four regions of the monogastric stomach

esophageal, cardiac, fundic, pyloric

esophageal (monogastric)

no secretions, prone to ulcers

cardiac (monogastric)

secretes mucus to protect stomach lining

fundic (monogastric)

secretes HCl and enzymes (main digestion region)

pyloric (monogastric)

secretes mucus, controls passage to small intestine

enzyme action in monogastric: amylase

starch → sugar

enzyme action in monogastric: pepsin

proteins → peptides

enzyme action in monogastric: lipase

fats → fatty acids and glycerol

what does enzyme action in monogastric depend on

stomach pH

limitations and diet needs of monogastric

• limited fiber

• require nutrient-dense feeds (grains, protein meals)

• balanced amino acids critical (can’t synthesize all)

what does growth efficiency depend on in monogastrics

feed quality

hindgut fermenter

• horses, rabbits, and guinea pigs

  • use roughages because of active cecal bacterial population that digests fiber

hindgut fermenter: small stomach

• only 8% of capacity in entire tract (3-4 gallons)

• less muscular

  • feed arranges in layers

hindgut fermenter: large intestine

• 60% of total gut capacity

  • cecum and large colon contain bacterial population similar to ruminants

beak

prehension

the crop

• expansion of esophagus

• temporary feed storage

• softens food before digestion

• some microbial activity

proventricules

secretes HCl and pepsin → chemical digestion

gizzard

muscular, grinds feed with grit

small intestine: poultry

main site for nutrient absorption

two ceca

some fiber fermentation; limited

large intestine

very short, limited function

cloaca

single exit for feces, urine, eggs

poultry digestive system

• very fast (2-4 hours)

• nutrient-dense food required

• cannot digest fiber efficiently

• balanced amino acids essentail

feeds

delivery system for nutrients

the right feed choices impact:

cost efficiency, animal health, sustainability

nutrient composition

amount of specific nutrients, expressed as % of the dry matter

dry matter

portion of feed left after water is removed, contains nutrients

crude protein (CP)

measures nitrogen content of a feedstuff

digestibility

amount of absorbable nutrient in a feed

crude fiber (CF)

fiber contents in feeds

total digestible nutrients (TDN)

sum of digestible fiber, protein, lipid, and carbs components of a feedstuff

what value is most commonly used in simple ration balancing

Total digestible nutrients (TDN)

dry matter

the universal basis for comparison

why dry matter

• water dilutes nutrient concentration

• always compare feeds on a DM basis

• forage testing reports are DM standardized

NRC feed classifications

• dry forages and roughages

• pasture and green forages

• silages

• concentrates (energy foods) (carbs)

• protein supplements

• mineral supplements

• vitamin supplements

• nonnutritive additives

right feed for the need

• start with animal’s requirement, not the feed

• identify which nutrient is limiting production

• choose the feed class that supplies it most efficiently

right feed: energy

concentrate

right feed: protein

protein supplement

right feed: bulk/fiber

forage or roughage

right feed: vitamin/mineral

supplement/additive

dry forages and roughages

• higher in cellulose, hemicellulose, lignin

• lower energy density than other feeds (high in fiber)

• required for rumen health, stimulates chewing and saliva

maturity at harvest

more mature = high fiber, low protein

weather damage

leaches nutrients

soil fertility

impacts proteins and mineral levels

plant species

legumes > grasses for protein

harvest method

mold, spoilage

pasture and green forages (seasonal nutrition)

• most common global feed source

• young, fertilized pasture = high protein, highly digestible

• mature, overgrazed pasture = low protein, high fiber

rational grazing

allows rest and regrowth, maintains plant health

fertilization and soil health

improves protein content and yield

weed control

reduces competition for nutrients

avoid overgrazing

prevents pasture degradation

silage

preserving nutrients through fermentation

what is silage

• anaerobic fermentation: beneficial bacteria lactobacillus produce lactic acid

• preserves forage by decreasing pH

• does not increase nutrients- fermentation consumes some energy

• risk of mycotoxins if storage is poor

corn silage

most common, increase energy from starch

haylage

fermentation grass or alfalfa, increase protein

by-product silages

cannery waste, root crops, beet pulp

concentrate

high energy, high risk, low fiber

how much concentrate in crude fiber

< 18%

how much concentrate in crude protein

< 20%

concentrates

• increase in starch → rapid energy release

• risk digestive upset if fed to quickly or in excess

  • rumen acidosis

where do most concentrates come from

corn, barely, molasses

protein supplements

building blocks for growth

protein supplement in plants

SBM, cottonseed meal, peanut meal

protein supplement in animal

fish meal, blood meal, feather meal (cannot be fed to ruminants)

protein supplement in nonprotein nitrogen (NPN)

urea - ruminants only!

nonnutritive additives - beyond nutrition

• growth promo: ionophores, hormones

• health: anti- and pro- biotics

• palatability: flavors, coloring agents

• controlled by FDA and USDA

Modern feeding challenges: sustainability focus

• reduce methane emissions

• decrease carbon footprint of feed production

Modern feeding challenges: precision feeding

AI-driven systems to tailor diets to individual animals

Modern feeding challenges: alternative proteins

insects, algae, fermentation-based feeds

why ration balancing matters

• prevents deficiencies → poor health and reproduction

• avoids excesses → waster and cost

• meets animals performance goals efficiently

Pearson Square

• developed in late 1800s

• 1st simple visual method for balancing livestock rations

Pearson Square- simple configurations

• balances 2 feeds to reach a target nutrient level

• works for protein, energy, or minerals

• goal value must be between 2 feed values

impact of farm animal reproduction

• essential for species survival and livestock production

• primary driver for profitability in animal agriculture

• efficiency gains in repro increase impact than most other measures

3% increase in birthrate yields

• ~ +1 million beef calves/year

• ~ +900K pigs/year

• ~ +6.8 billion gallons of milk/year

endocrinology

study of glands and hormones

main control center

• reproduction controlled by Hypothalamic-Pituitary-Gonadal (HPG) Axis

• central neuroendocrine system

• brain and reproductive organs must coordinate

why neuroendocrine control matters

• nutrition and body condition

• stress and health

• photoperiod (day length)

hypothalamus = headquarters

• brain region controlling homeostasis

  • physiological and behavioral functions

    • appetite and energy balance, body temp, stress responses, repro

What does the hypothalamus release

GnRH (Gonadotrophin-Releasing Hormone → signal pituitary