absorption & energy metabolism

Question 1

mol that can transport into enterocytes

Answer 1

carbohydrates: only monosaccharides
* glucose & galactose need active transport
* fructose can use facilitated diffusion

AA: some free AA & small peptides can use facilitated & some active

minerals: co-transported with proteins

Question 2

modes of transcellular transport

Answer 2

nutrients flow through enterocytes

passive transport
* diffusion
* only free fatty acids & monoglycerides
* remade into triglycerides in ER & packaged into chylomicrons: triglycerides + cholesterol + phospholipids ➔ then enter circulation by lymph system
* fat-soluble vitamins: vit D stimulates active transport of Ca2+
* water by osmosis (paracellular transport ➞ nutrients flow between enterocytes)
* facilitated diffusion: through transmembrane proteins
* carbs: fructose
* AA, minerals

acive transport
* use of transporter proteins
* carbs: glucose & galactose
* AA, minerals

Question 3

digestibility

Answer 3

amount of nutrients in feed absorbed by GI

Question 4

nutrient digestibility equation

Answer 4

Question 5

digestibility depends on

Answer 5

• feed type
• quality/composition of ration
• animal factors
  
  • age
  • genetics
  • envir ➞ climate, facility management

Question 6

energy partitioning

Answer 6

energy lost along process of digestion

1. maintenance: minimum E necessary to sustain animal ➞ E used for basal metabolism, voluntary activity, temp regulation
2. left over goes towards production
   
   1. reproduction ➔ est & maintaining preg
   2. growth
   3. lactation
   4. stored energy (fat deposits) if fed more than requires

Question 7

gross energy

Answer 7

all energy in feed including that which cannot be used

Question 8

total digestible nutrients (TDN)

Answer 8

energy value of feed

Question 9

digestible energy (DE)

Answer 9

DE = gross E in feed − E in feces

• feed that can be broken down by animal (animal can use)

Question 10

metabolizable energy (ME)

Answer 10

ME = DE − E in urine & gaseous byproducts of digestion
* energy available to use

Question 11

net energy (NE)

Answer 11

NE = ME − E used in consumption, digestion, & metabolism of feed

• amount of energy left for animal to partition for maintenance & towards production