Lecture 3 - Macronutrients (CHO) Flashcards
What are the three macronutrients?
Carbohydrates, fat, protein
What is a carbohydrate?
A combination of carbons and hydrogens - chemical structure can be open chain or closed ring
What are monosaccharides?
Stand-alone simple sugars that also act as building blocks
What are polysaccharides?
A carbohydrate whose molecules consist of a number of simple sugar molecules bonded together
What is the difference between STARCH and FIBER?
STARCHES are natural carbs that can be broken down by the mammalian body to create glucose (a primary energy source), while FIBERS are carbs from plants that are not digestible by mammalian enzymes
Name some examples of simple carbohydrates that can be consumed in the diet
Sugars, grains, and fruit
Name some examples of fiber that can be consumed in the diet
Legumes, vegetables, wheat bran, and grass/roughage
True or False: Carbohydrates (including fiber) are NOT essential nutrients for dogs and cats
True
What is the role of the “mouth” in monogastric carb digestion?
Secreting salivary amylase
What is the role of the “pancreas” in monogastric carb digestion?
Secreting pancreatic amylases, converting STARCHES to MALTOSE and GLYCOGEN to GLUCOSE
What is the role of the “small intestines” in monogastric carb digestion?
Brush border enzymes (maltase/isomaltase, lactase and sucrase) further break down carbs into simple sugars (monosaccharides)
True or False: While cats and dogs can digest and absorb carbohydrates, and they are often added into pet foods, carbohydrates are not considered essential nutrients for them
True
True or False: Cats can easily metabolize high sugar loads and will actively seek out sweet flavored foods for their taste
False; cats have a limited ability to metabolize high sugar loads, and they are unable to taste sweet flavors
True or False: Cats are constantly converting amino acids from protein to glucose in order for their body to maintain proper energy levels
True
When forestomach fermenters consume fiber (cellulose and hemicellulose) from hay, forage, and silage, how does the rumen break it down?
(Name the enzyme and whether the process is fast or slow)
Microbial cellulase, slow process
What is produced when a forestomach fermenter breaks down fiber in its rumen?
Gases (CH4 and CO2), volatile fatty acids/VFAs (acetate, propionate, butyrate), and microbial sugars
When forestomach fermenters consume starches and sugars from grain, how does the rumen break it down?
(Name the enzyme and whether the process is fast or slow)
Microbial amylase, fast process
What is produced when a forestomach fermenter breaks down starch and sugar in its rumen?
Gases (CH4 and CO2), volatile fatty acids/VFAs (acetate - LESS than in fiber digestion, propionate - MORE than in fiber digestion, butyrate), and microbial sugars
Why is the production of acetate much lower and the production of propionate much higher in ruminant starch/sugar digestion?
Propionate is the most energy efficient for the animal and helps with weight gain, while acetate is the building block for milk-fat (produces more lipids than glucose)
Compounds that aid in the efficiency of converting feed energy into usable energy by altering the rumen microfloral population to favor propionate production
Ionophores
True or False: Gaseous energy losses (like CH4 and CO2) are increased with ionophore feeding
False; gaseous energy losses are reduced with ionophore feeding
Ionophores are considered to be ______________ because they suppress growth of certain microbes in the forestomach
Antimicrobials
True or False: Ionophores are safe for ruminants, but toxic to camelids and horse
True
What effect does increased propionate have on milk production in ruminants?
Increases lactose production in the udder, which increases milk volume
What effect does increased acetate (a result of high fiber fermentation) have on milk production?
Increases milk fat production in the mammary gland
A drop in rumen pH caused by excessive production and accumulation of VFAs in the rumen, typically the result of a diet too high in concentrate (grains)
Rumen Acidosis
High-concentrate diets require ______ chewing time, leading to ______ saliva production, and thus ______ salivary bicarbonate to buffer acids produced by fermenting these diets
(One word for all three blanks)
Less
The physical burn, pain, and discomfort caused by rumen acidosis can cause…
(3 physical symptoms)
- Anorexia (from indigestion)
- Bloat (from rapid gas build-up in rumen)
- Bacteremia (from bacteria invading through burned rumen wall)
True or False: Many carbs in brewer’s and distiller’s grains bypass the rumen rather than being degraded
True
What happens to carbs that bypass the rumen?
Pancreatic amylase completes the digestion in the small intestine, and any remaining undigested carbs that reach the colon are fermented by gut microbes
Where in the body does fermentation occur for sugars/starches and fibers, respectively, in hindgut fermenters?
What about bacterial fermentation?
Sugars/starches = small intestine
Fibers = large intestines
Bacterial fermentation = cecum and/or colon
True or False: In hindgut fermenters, fermentation products such as VFA are absorbed through the gut wall while other products (like sugars and gases) are simply passed through or used by bacteria
True
What happens physiologically when a hindgut fermenter consumes excess sugars?
Starch and sugar not absorbed by the small intestine reaches the large intestine, where it ferments and supports lactic acid bacteria (reduces gut pH)
Bacterial translocation, enterotoxaemia, and endotoxemia are all possible consequences of reduced gut pH in hindgut fermenters caused by…
Excess simple sugars reaching the large intestine (promoting lactic acid bacteria growth)
Glucose enters cells via a transporter molecule and is facilitated by ___________.
Insulin
Glucose can be polymerized to ____________ and stored in the cell, mostly in muscle and the liver, to be used when extra energy is needed (like in fight or flight responses).
Glycogen
Which hormones promote glycogenolysis?
(3 hormones)
Epinephrine, glucagon, and cortisol
Which type of metabolism is described here?
- Glycolysis produces pyruvate
- Pyruvate only enters the mitochondria if sufficient O2 is present
- 1 glucose produces 38 ATP
Aerobic metabolism
Which type of metabolism is described here?
- Pyruvate is metabolized to lactic acid
- 2 ATP are formed
- When O2 is restored, lactate can be metabolized back to pyruvate in the liver
Anaerobic metabolism
What causes lactic acidosis?
Prolonged hypoxia
What effects can lactic acidosis have on the body?
Negatively impacts cardiac function and enzyme function (effects can be life threatening)
What is gluconeogenesis?
The process of making new glucose in the body
What is the main hormone responsible for the shift from glycolysis to gluconeogenesis? What are two additional hormones that may be involved during stress-induced gluconeogenesis?
Glucagon = main hormone
Cortisol and epinephrine are also involved in times of stress
When is gluconeogenesis needed?
Stress, physical activity, lactation, gestation
(Normal state for some species, like cats)
What is the main thing all of these have in common?
Pyruvate/pyruvic acid, oxaloacetate/oxaloacetic acid, lactate/lactic acid, most amino acids, glycerol, and propionic acid
They are all important glucogenic precursors used to generate glucose
Neoplasm of alpha pancreatic islet cells; rare overall and reported primarily in dogs (not seen in cats); clinical signs are similar to DM due to excess glucagon antagonizing insulin; may also cause superficial neurological dermatitis (SND)
Glucagonoma
How is glucagonoma diagnosed?
High BG and liver enzymes, high plasma glucagon levels, honeycomb liver on US, skin lesions (often appearing on foot pads) with edema present (SND)
How is glucagonoma treated?
- Surgery
- Amino acid supplementation (enteral or parenteral) to treat skin lesions (from SND)
Beta islet cell tumor of the pancreas; primarily reported in dogs and ferrets (rarely in cats, horses, and cattle); may be malignant (dogs) or benign (sometimes in ferrets); associated with hypoglycemia due to excess insulin
Insulinoma
What are some possible clinical signs of insulinoma?
Lethargy, pawing at mouth, weakness, weight loss, tremors/seizures, collapse, abnormal behavior
How is insulinoma diagnosed?
Hypoglycemia, elevated insulin levels, US/CT/MRI
How is insulinoma treated?
- Glucocorticoids (pred)
- Diet that has high fat/protein, low in simple carbs, and consists of multiple small meals to reduce insulin secretion
Absolute/relative deficiency of insulin; reported primarily in dogs and cats (rarely in other species); characterized by abnormal BG and persistent, fasting hyperglycemia; three recognized types
Diabetes mellitus
Insulin-dependent DM; lack of insulin production, very common DM seen in dogs
DM Type I
Non-insulin-dependent DM; peripheral insulin resistance, found in cats but not dogs
DM Type II
DM results from diabetogenic hormones (progesterone, cortisol, epinephrine, growth hormone, glucagon)
DM Type III
What does insulin target?
Liver, muscle, adipocytes
Insulin promotes __________ synthesis and decreases gluconeogenesis
Glycogen
What are clinical signs of diabetes mellitus?
PU/PD, weight loss, polyphagia, lethargy, cataracts (in dogs)
How is diabetes mellitus treated?
Insulin replacement, dietary therapy, weight loss if overweight
Dog dietary therapy = high fiber, low fat, food before insulin
Cat dietary therapy = low carb
