UCD nutrition slide 3

what are carbs made up of?

monosaccharides

disaccarides

oligosaccharides

polysaccharides

why is starch more digestible than cellulose?

the enzymes that are in rumen can break down starch easier

how do cell walls influence nutrient digestibility?

enzymes!

more stem =

more undigestible components of the grass that the cow is eating

what is the digestive purpose of ruminants?

efficiently break down and extract nutrients from plant materials that are otherwise difficult to digest, particularly fibrous plant matter like grasses

what is the difference between hind gut fermenters and ruminants in terms of their digestive system?

hind gut: fermentation occurs in hindgut, one stomach, fermentation happens after food is digested
ruminants: fermentation occurs in rumen, four-chambered stomach, fermentation happens before food is digested, more efficient

What is the most important nutrient?

carbs

-needed for lactation, maintenance, growth, gestation and movement

how is the rumen adapted for carb digestion?

because of the presence of microorganisms

the rumen size

movement of the reticulo-rumen breaking down cellulose

what is the most important digestive process taking place in the rumen?

the breakdown of cellulose and other resistant polysaccharides

what are some sources of energy in an animal?

glucose

glycogen

propionic acid

butyric acid

acetic acid

what do ruminant diets consist of?

considerable quantities of cellulose, hemicellulose, starch and water-soluble carbs

what goes into carb breakdown?

the proportion and type of VFAs produced depend on the substrate metabolized and the species of bacteria present

what are some microorganisms present in the rumen?

ciliate protozoa

anaerobic fungi

bacteria

methanogenic archaea

what is the importance of rumen MO?

rumen bacteria responsible for digesting feed by attaching to feed particles and releasing enzymes

increasing surface area increases the rate of digestion

what is the symbiotic relationship between the ruminant and microbes?

ruminant: fiber digestion, microbial protein, synthesis of B vitamins

microbes: food source, removal of waste products, relatively stable environment

what are the two stages carb digestion is broken down into?

1. complex carbs to simple sugars

-extracellular microbial enzymes

-digestion similar to monogastrics but source of enzymes is different

2. conversion of pyruvate to VFAs in the rumen

what is cellulose digestion dependet on?

the degree of lignification

what is important about cellulose breakdown?

decomposed by one or more beta-1,4 glucosidases to cellobiose

what is step 2 in the rumen digestive process?

simple sugars --> pyruvate --> VFA + C02 + CH4

how is acetic acid used as an energy source?

it is the major product of CHO digestion in the ruminant

how is propionic acid used as an energy source?

after absorption from the rumen propionic acid is transported to the liver and converted to glucose

how is butyric acid used as an energy source?

converted to a beta blocker (BHBA) in the passage across the rumen wall, and is then used as an energy source

what are some factors that influence carb digestibility?

-the extent to which cellulose is digested

-lignin

-diet based on cereals

-pH

how do diet and VFA production connect?

-mature forages: acetic predominates

-young forages: lower acetic/higher propionic

-additional concentrates: lower acetic/higher propionic

-all concentrates: propionic equal to or greater than acetic

what are some digestive enzymes present in the cow?

-saliva (no enzymes)

-rumen (no enzymes)

-abomasum wall (hydrochloric acid, pepsinogen)

-small intestine (bile, lipases, proteases)