midterm Flashcards
2 major roles of digestive tract
barrier to the environment, digestion and absorption of nutrients
what metabolism happens in rumen?
aerobic and anaerobic metabolism
rumen epithelium
stratified squamous epithelium
metabolizes SCFA ad VFAs
reticulum
allows for rumination, reason why cows can eat fast, honeycomb lining, contains undigested feed and feed that is being digested
omasum
soccer ball, lots of folds, small particle size removes moisture. involved in water and VFA absorption
abomasum
true stomach, secretes acid and pepsin, reabsorbs water w lower pH (2-4). kills the microbes from the rumen to make protein.
esophageal groove
connects esophagus to omasum, in calves. allows milk to pass reticulorumen
duodenum
releases a lot of enzymes, first part of small intestine. starts at pylorus, digestion and absorption
jejunum
all coiled up, middle part of small intestine, lots of absorption bc so long
illeum
final section of small intestine, absorption and immune responses.
mucous secretion - brunners glands
mucus rich alkaline secretion produced, neutralizes acid, to lubricate and protet
Peyers patch
immune surveillance of intestinal rumen, where immune memory gets formed. facilitates immune response
cecum
large blunt tipped tube, where fermentation, absorption and passage happens
colon
connects midgut w rectum, site of fermentation, absorption and passage
gastrointestinal epithelium
mixture of absorptive, goblet, paneth and neuoendocrine cells. richness and diversity increases throughout the lower gut. cell junction proteins are expressed differently
rumen mat
several natural divisions in the rumen, gas rises to surface, partially digested feed settles to the bottom
4 R’s of ruminating
relaxation - esophageal sphincter allows digesta in
reverse peristalsis - feed up to mouth
re-masticating
re-swallowing
ruminal epithelium type
stratified squamous
intestinal epithelium
columnar
main polysaccharides digested by dairy cows
starch, cellulose, pectin, hemicellulose
butyrate
used for energy source for the rumen wall
propionate
primary glucose precursor of the cow
acetate
used for energy throughout the cow
microbial protein synthesis
incorporates ammonia, AAs and peptide into bacterial protein
fermentable carbs influence bacterial protein synthesis
rumen bacteria
major contributor to microbial fermentation, dynamic pop w large diversity
symbiotic relationship
additional nutritional req of bacteria
NH3, CO2, acetate, branched amino acids (Va, Leu, Iso), minerals, vitamins
protozoa
50% microbial biomass an fermentation end products, uses starch, sugars and amino acids. slows rate of CHO fermentation. deanimate AAs and contributes to NH3 production in the rumen, sensitive to low pH
protozoa and microbial protein
sequester protein in the rumen, only 20-40% leave rumen.
anaerobic fungi
cellulolytic, attach and grow on plant fragments, penetrate into tissues that are inaccessible to bacteria. susceptible to low rumen pH
acetate:propionate ratio
decrease, more propionate = less methane. increases energy and glucose avail to animal.
less energy lost as methane.
methanogenesis
forming methane from microbes. symbiotic relationships involving interspecies hydrogen exchange w rumen. can be associated intercellular lily and extracellularly
monensin
alters microbiota to increase propionate production, inhibits gram positive bacteria. produces more propionate and acetate
SARA
20% of lactating dairy cattle, rumen and mucosal damage, liver abbesses, laminitis, inflammation, depressed intake, growth, fibre degradation, milk and milk fat
detecting SARA
difficult to obtain consensus on pH thresholds for SARA detection
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hingut acidosis
manure is the main indicator, more fermentable products make it through. bacteria in hindgut can’t break down as good
acidosis is associated with
- altered rumen microbes, damage of gut epithelium, whole animal inflammatory response, liver abscesses, etc
NFC -
non-fibre carbs
difference between NDF and ADF
NDF - intake, ADF - indigestible
NDF
neutral detergent fiber
ADF
acid detergent fibre
NFC
non- fibre carbohydrates
NDICP
neutral detergent insoluble protein
WSC
water soluble carbohydrates
NSC
starch and sugar
ash
dirt and mineral feed content
cellulose
harder to break down , has most structure w a lattice shape
pectin
fastest to break down
factors that impact forage quality
type and variety of forage, repro maturity, soil quality, water avail, Fert use, time of szn, enviromental temp, drying conditions, morphology (C3 vs C4)
particle size, harvest height
legume v grass
legume is higher CP, fibre higher lignin, less digestible in rumen, legume more fragile passes through faster, less rumen fill.
legumes more Ca than grass
amylose
glucose polymer bound to each other through alpha 1-4 glycosidic bonds
amylopectin
highly branched polymer of glucose containing alpha 1-4 and alpha 1-6 glycosidic bonds
most valuable metrics for feed evaluation
NDF, NDFD and starch
relative fermentability
soluble carbs get fermented at feeding, next is pectin, cellulose is much later
alpha-amylase
starch digestion beyond the rumen, secreted by the pancreas
maltase and isomaltase, and sodium dependent glucose transporter
post ruminal starch digestion in small intestine brush border
gluconeogenesis
glucose req by brain, RBCs, adipose tissue, mammary gland. ruminants synthesize glucose from propionate. also amino acids. lactate and glycerol
how much energy in 1 glucose?
38 ATP
how much energy in 1 acetate?
10 ATP
how much energy in 1 propionate?
18 ATP
mcal to increase BCS from 2-3 in cattle
500 mcal to gain 1 BCS
crude protein
NPN an true protein