Carbohydrate and Protein Requirements for Lactation and Metabolic Diseases Flashcards
What has the most influence on milk composition?
Nutrient requirement of the offspring
Discuss kanagroo lactation
They are unique in nursing two joeys at once and will make different milk compositions for newborn vs. older joeys
i.e. milk is matched to individual requirements
Discuss lactation in the Northern Elephant Seal
These seals do not eat during lactation
The dam loses 42% of their body weight during lactation, roughly equivalent to 58% body fat and 14% lean tissue
The mother tries to rapidly transfer body fat to her young
The mother does not make much lactose because it requires different body reserves
Describe net nutrient requirements for lactation
Net nutrient requirements for lactation = milk yield x milk nutrient concentration
How does milk composition vary?
It varies greatly by species
How are carbs classified?
Carbs are classified by the number of sugars in them
monosaccharides are simple sugars like glucose and fructose
disaccharides are two simple sugars bound together such as sucrose or lactose
trisaccharides are three simple sugars; cannot be broke down by most animals due to lack of proper enzymes
Polysaccharides have more than three simple sugars; ex. starch, cellulose, chitin
What is needed for lactose synthesis in the cow?
A large amount of glucose because lactose, a disaccharide, is composed of glucose and galactose
Ruminants don’t absorb much glucose because of their rumen microbe populations, but they still need it to make lactose
Cows also need a considerable amount of essential amino acids
How does metabolism in different tissue adapt to support lactation?
There is a dramatic increase in nutrient requirements during early lactation that is met by …
- rapid mobilization of endogenous reserves, especially fat (also calcium, some protein)
- slower increase in maximum voluntary feed intake in many animals
Discuss lipid catabolism
Lipid stores make up for deficits in dietary energy supply
Caused by low feed intake or too high demand
Net release of nonesterified fatty acids (NEFA; not bound to glycerol) from adipose tissue represents balance between rates of lipid synthesis and breakdown (lipolysis)
Discuss the three major processes of lipolysis
- Lipolysis of adipose tissue triglycerides to glycerol and NEFA
- transport of NEFA to other tissues
- fatty acid uptake and oxidation by these tissues
Discuss the movement of NEFA
NEFA released from adipose tissue are transported in blood bound with plasma albumin
Plasma NEFA is directly related to rate of fatty acid mobilization and can vary from <100 to >1500 mol/L
Turnover is very rapid and concentrations reflect the extent to which body fat is being mobilized
Discuss tissue utilization of NEFA
Most tissues can take up and oxidize NEFA for energy (exceptions: brain, red blood cells, testes)
Uptake increases as plasma concentration increases
Complete oxidation of long-chain fatty acids to CO2 and H2O occurs in the mitochondria by a two stage process called beta-oxidation
Discuss beta-oxidation
fatty acids are transported into the mitochondria for oxidation
fatty acids are activated to fatty acycl-CoA
The two carbon acetyl-CoA is formed in each round of the cycle
Complete oxidation occurs after acetyl-CoA enters the TCA cycle
Describe ketone synthesis
Ketone synthesis occurs in the liver when TCA does not run
Ketone synthesis uses acetyl-CoA that is exported from the liver; it is originally converted to acetoacetate
The acetoacetate is then broken down to 2CoA, acetone, and 3-hydroxybutyrate (aka a ketone body)
How does acetone cause sweet smelling breath?
After the breakdown of the intermediate acetoacetate, acetone is one of the products formed
It enters the bloodstream and travels to the lungs, where it evaporates and makes the breath smell sweet
