– Insoluble in H2O, susceptible to digestive enzymes
– Muscle protein
• Structural proteins in animals – Collagen – toughness in meat
– Elastin – rubbery; ligaments and arteries
– Keratins – hair, feathers, horns, hooves
What are Conjugated proteins?
– Contain non-protein compounds
What are the functions of proteins
Transport and metabolism
How do proteins provide structure?
-collagen ( toughness in meat)
-elastin (rubbery and ligaments & arteries)
-keratins (hooves, feathers, horns and hooves
How do proteins provide movement?
- Myofibrillar proteins - sacroplasm of muscle
- contractile proteins - actin, myosin, tyromyosin B
How do proteins help in transportation and metabolism?
-Albumin in blood
-Hormones (insulin, growth hormone, PTH)
When is a time that the body can absorp protein?
Right after birth when drinking colostrum
What does cooking do to protein? Is it necessary?
It denatures protein by disrupting the tertiary structure. It is not necessary for the digestion of protein.
What does the stomach due in digestion?
Very acidic environment.
- disrupts tertiary structure (protein folding)
-Allows access to peptide bonds by pepsin in stomach'
-endopeptidase, cleaves peptide bonds within the main structure
-peptide chain broken into smaller chains
What does the SI do in digestion and absorption?
- PH is buffered to neutral
-Activity of pancreatic proteases
-peptidases secreted as zymogens ( they are inactive precursors and help prevent self digestion)
-Entrokinase - secreted by intestinal mucosa and cleaves trypsinogen to trypsin
See chart page 6
Examples of endopeptidases - from within chain.
Make lots of smaller chains
Exopeptidases example? Where do they come from?
They come from the end of chains, example is carboxypeptidase
What do active enzymes in the SI do? Examples?
they cleave specific bonds.
-Chymotrypsin - basic amino acids
-Elastase - small amino acids
-carboxypeptidase - works at the carboxyl end
What is the action of proteases?
- release of tri and dipeptides, free amino acids in the lumen of the small intestine
- brush border membrane reduces di and tri-peptides to AA
- Must be heat treated to prevent trypsin inhibition
- very good animal feed has lots of amino acids
-has a trypsin inhibitor which will stop trypsin which will leave lots of long polypeptides lead to digestion ineffeciency
Protein Requirements in mongastrics?
No protein requirements but needs esssential AA and Nitrogen usaully in the form of protein)
Protein Requirements in ruminants?
- Can depend totally on microbial protein synthesis
- high producing animals may need pre-formed dietary AA
When are protein requirement the highest
Highest at birth and decline with age. This is related to the growth rate
What are some factors that affect protein requirements
-Higher in stages of growth then maintenace
-Sex dependent usually higher for males
-Affected by physiological state (gestation, lactation, growth work ect...
Is calorie to protien ratio imprtant?
yes! Most animals will eat to meet energy requirements so it is important to have protein balanced depending on that
Defeciency signs of protein?
– Reduced growth
– Negative N balance
– Decreased feed efficiency
– Reduced serum protein
– Fatty liver
– Reduced birth weight
– Reduced milk production
– Reduced synthesis of enzymes, hormones
What is a sign of protein defency in humans?
Kwashiorkor- Edema will cause ppl to have extended belly because of fluid buildup in belly.
Liebig’s Law of the Minimum
• "A crop ́s yield is restricted by the lack of a single element, even though there may be sufficient quantities of all other essential nutrients.”
What is protein synthesis limited by?
Protein synthesis can only occur untill the limiting AA is used up. Doesnt matter if all other AA acids are in excess. If protein synthesis is defiecent in one AA then the other AA are oxidized leads to fat desposition. Once that limiting AA is replace protein synthesis can continual at optimal level
What are signs of AA defeciencies (similiar to protein synthesis)?
- specific lesions.
- trypotophan leads to cataracts
-thereonone or methionine leads to fatty livers.
Why do you have combos of feed stuffs in rations?
Because most feedstuffs are deffecient in at least one amino acid. Example Corn is low in Lys and Trp and Soy is high in Lys and Trp. Thus they will make a good combo
What is a viable option if you are low on a certain AA in a diet?
- Supplement with synthetic amino acids.
- D,L-Met, L-Lys, L-Thr, L-Trp available
- L-Arg, L-Ile on the way
Amino acid interactions. Antagonism?
– Reduction in performance that can be overcome by supplementation of a structurally similar amino acid
• Effects of lysine excess overcome by supplementation by arginine
• AA need not be limiting
AA interactions. Toxicity?
– Adverse effects of an AA in excess can not be overcome by supplementation of other AA
- you have to reformulate the diet
AA interactions. Imbalance
– The dietary proportions of indispensible AA do not meet the needs of the animal
• 1 or more AA are limiting
• Can be overcome by relatively small supplementation of the limiting amino acid or acids