ansc314 - carbohydrates pt 2

monosaccharide absorption

amylase

• in saliva & small intestine

  • starts breaking down carbohydrates

notes to remember

• results in oligo-, tri-, or disaccharides

• intestinal wall (duodenum, jejunum)

  • maltase, lactase, sucrase, & oligoglucosidase → all MONOsaccharides

• only MONOsaccharide forms absorbed

  • digestion of disaccharides happen on surface of brush border of s. intestine

glucose transport

glucose absorbed w/ active transport & diffusion

• active transport uses ATP (Na-K-ATPase pump)

• diffusion occurs when concentration of glucose is bigger outside mucosal cell compared to inside

glucose conversion

fructose & galactose are converted to glucose in the liver

carbohydrate digestion

carbohydrate metabolism

• carbs make fats & non-essential amino acids (AA)

  • excessive glucose → fat

• propionate → glucose

• most AA converted → carbs

  • break own glucogen when need energy

• acetate & butyrate DO NOT make glucose

story line: humming bird

extreme nutritional adaptations in a humming bird

• Metabolism 77 times faster than human’s

  • equivalent of ~150,000 calories/ day

• Extreme hyperglycemia

  • Fed glucose ~42 mM (740 mg/dL)

  • fasted ~17 mM (300 mg/dL)

• Specialized evolution to handle high sugar loads

  • extreme mechanisms to sustain high rates of glycolysis

• human glucose lvl: ~82 mg/dL

organ glucose metabolism

carbohydrate functions

• provide energy

  • Brain and CNS (can use ketones too)

  • Mammary (lactose) of non-ruminants

    • e.g. humans

  • Fetal tissue

• quick source of fuel

  • used energy in muscle (sprinting)

• energy currency

  • sugars convert → glucose → used in muscle when available → made → glycogen & fat

• part of DNA/RNA (ribose)

• plant structure (cellulose)

glycemic response

effect of a food on the extend and/or duration of the rise in blood glucose levels

glycemic index (GI)

measured based on the extent to which a food containing 50g of carbohydrates increases blood glucose concentrations

fiber

• nutritional

• dietary components resistant to mammalian enzyme digestion

• chemical

  • cellulose, hemicellulose, lignin, pectin

• botanical

  • plant cell wall material

measure fiber

• Plant cell wall

  • Structural carbohydrates

    • Cellulose, hemicellulose

• Lignin

• Pectin (soluble fiber)

• NDF: cellulose, hemicellulose, lignin (no pectin)

• ADF: cellulose, lignin (ADF increases digestibility decreases)

• CF: cellulose, lignin, some hemicellulose, some pectin

  • There is a little protein & ash in both as well

fiber analysis

• crude fiber

• neutral detergent fiber (NDF)

• acid detergent fiber (ADF)

crude fiber

• not accurate estimate of nutritional fiber

• legally required on food & feed labels

  • lignin, cellulose, some hemicellulose, some pectin

• obtained by defatting sample (ether) and boiling in 1.5% H₂SO₄ for 30 min, and 1.5% NaOH for 30 min

neutral detergent fiber (NDF)

• Used in accurate animal diet formulation

  • Lignin, cellulose and hemicellulose

  • Boil in pH-7 detergent solution for 60 min

    • Dry residue is NDF

acid detergent fiber (ADF)

• Lignin and cellulose (dissolves hemicellulose)

• Boil in pH-2 detergent solution for 60 min

alfalfa ADF/NDF

• ↑ maturity → ↑ fiber content in general

fiber functions

• insoluble fiber (NDF)

• soluble fiber (pectin)

insoluble fiber

NDF

• Energy for ruminants and hindgut fermenters

• Hydrate food and regulate passage

• Gut fill, regulate intake

• Increases rumination

• Increases intestinal cell turnover, growth

• Improves gut health

soluble fiber

pectin

• Decrease blood sugar spikes

• Decreases LDL by trapping cholesterol

fiber sources

• Forages (grass, legume, whole-plant material)

• Legume seeds (pectins)

• Beans, peas

• Bran (insoluble)

  • e.g. oatmeal, whole-wheat bread

  • Byproducts (cotton seed hulls, soy hulls)

• Fruits

  • Apples, pears, plums

• Vegetables

  • Artichoke, broccoli

ruminant fiber deficiency

• Low milk fat

• Decreased rumination

• Low feed intake

• Off feed

• Low rumen pH, acidosis, laminitis

• Displaced abomasum – death

horse fiber deficiency

• colic

• diarrhea

• hunger

human fiber deficiency

• Constipation

• Irritable bowel

• Weight gain (?)

• Blood sugar fluctuations

• Nausea and tiredness

excess fiber

• Decreased energy intake

• Weight loss

• Decreased production and growth rate

• Lower feed digestibility

• Discomfort

effective fiber

• Finely chopped fiber has less effect on passage and digestion

• High fiber digestibility has less fiber effect

• Low fiber digestibility can decrease DM and energy intake

• If less than 20% of cows are ruminating, effective fiber may be low

• Ruminants should have 1/3 fiber from source with particle length > 1.5” (not soy hulls)