Lecture 11/12 - Ruminants protein and lipids Flashcards
What does microbial fermentation break down proteins into?
- ammonia which is utilized for microbial protein synthesis
What is microbial protein a primary source of?
amino acids absorbed in the small intestine
What does urea recycling provide rumen bacteria with?
Nitrogen (low quality protein), which ruminant animals can convert into microbial protein (high quality protein)
- even during starvation
What can ruminant animals convert low quality protein (N) into?
Microbial protein = high quality protein
What are 2 cons of ruminant protein digestion?
1) Protein is extensively degraded to ammonia, especially with deficiency of energy from CHO fermentation (relying on AA as energy source)
2) Efficiency of N utilization is lower compared to non-ruminant animals
- if a cow is given high quality protein, it is being wasted; could feed a lower quality protein and get the same outcome
5 factors affecting microbial protein synthesis
- ruminally degradable N (related to amount of protein in the diet)
- Energy from CHO fermentation
- Quality of ruminally degradable N
- fiber-digesting bacteria utilize ammonia to make protein whereas start bacteria need aa and peptides to make microbial protein - Passage rate of digesta
- microbial turnover in the rumen and predation by protozoa can result in excessive loss of microbial protein before it reaches the small intestine - Factors affecting rate of passage
- feed intake
- particle size
- digestibility of fiber
What is ammonia toxicity induced by?
- excessive urea or protein in the diet results in too much ammonia being released; microbes from that forage are not getting enough energy from CHO to replicate and create microbial protein
- when there is insufficient microbial VFA production ammonia isn’t used up for microbial protein production
- cellulolytic fermentation
What deaminates urea to ammonia?
Ruminal urease
How does cellulolytic fermentation induce ammonia toxicity?
- VFA production rate is lower so less substrate available for protein synthesis
- rate of microbial division is slower so microbial requirement for protein is less
- higher ruminal pH favours ruminal absorption of ammonia = impacts CNS
- toxicity is associated with CNS ammonia intoxication
How can ammonia toxicity induced by cellulolytic fermentation be countered?
- by VFA administration (feeding grain and molasses)
- lower pH = reduces absorption
- increases microbial protein synthesis
What is the most important lipid fraction?
- Fatty acids
- High energy/ some are essential/ impact rumen
- majority of fatty acids are bound to glycerol as simple or compound lipids
- majority of FAs are unsaturated
What are most triglycerides degraded into in the rumen?
- FFA and glycerol
- glycerol ferments in the rumen to VFA
Are fatty acids degraded by ruminal microbial organisms?
- no
- free fatty acids are extensively biohydrogenated in the rumen (PUFA to saturated FA)
- saturated fatty acids are absorbed in the duodenum
What are the 3 rumen transformations of lipids?
- Lipolysis
- simple (triglyceride) & compound (glycolipid) converted into FFA/NEFA - Biohydrogenation
- PUFA & MUFA converted into saturated FA - Microbial Lipid Synthesis
- VFA into branched
How are FA transformed in the rumen?
- intake: highly unsaturated FA
- outflow: saturated FA
When we consume beef, we are consuming much more saturated fat bc there is this biohydrogenation process where UFA are converted into SFA
What is the goal of biohydrogenation?
- remove double bonds which have antimicrobial properties; if too high in the rumen, they will reduce microbial activity
- not a direct process, intermediates are formed during the process and some of these are absorbed
What impacts do intermediates of biohydrogenation have?
- can have major effects on animal performance and health
- trans-10, cis-12 results in suppressed milk fat production; inhibits lipogenesis in the mammary
2 CLA’s to know (intermediates of biohydrogenation)
1) cis-9, trans-11
2) trans-10, cis-12 (bad)
Why are humans concerned with rumen lipid metabolism?
Affects human health
- meat and milk higher in saturated fat
- bioactive metabolites: anti-carcinogenic, anti-atherogenic, enhance immune system
Affects animal performance
How does rumen lipid metabolism affect animal performance?
- biohydrogenation reduces supply of essential fatty acids (PUFA)- impacts reproductive performance or immune system
- fatty acid antimicrobial effects (PUFA are antimicrobial so have to monitor how many we give since they will impact microbial ability to ferment and make SCFA)
- produces bioactive metabolites
What are the major fatty acids consumed in dairy cows?
- any cis isomers (from plants)
What increases FFA in rumen contents?
lipolysis
What is the best substrate for the synthesis of CLA in the rumen?
essential fatty acids
Microbiota
the ecological community of commensal, symbiotic, and pathogenic microorganisms that literally share our body space
What are the most abundant rumen microbes?
bacteria>archaea>protozoa>fungi>bacteriophages
Why are mammals “superorganisms”?
Our metabolic capability is a product of our own genetic potential plus that of our inhabitants
How were bacterial traditionally classified versus how are they classified now?
Traditional
- morphology
- energy source
- fermentation end-products
New
- molecular characterization
How do we study the population of microbes?
- hard to culture since there are so many bacteria
- DNA sequence can tell us who they are and what they do
- Ribosomal RNA gene is used as a phylogenetic marker bc of its genetic stability and composition of conserved and variable regions
What are the main fxns of microbes?
1) Provide nutrients
- SCFA and microbial protein
2) Detoxify the diet
What are most GI bacteria?
- obligate anaerobes; bc there is not very much O2 in the rumen
Do bacteria have different fermentative capabilities?
YES
- ex. cellulolytic, hemicellulolytic
What are the growth requirements and end products of cellulolytic and hemicellulolytic bacteria?
Growth requirements
-pH 6-7
-NH3 (for protein synthesis)
End products
-acetic and butyric acid
-CO2, H2
Example of amylolytic bacteria?
Streptococcus bovis
- present in low numbers when on forage, or after adaptation to grain diets
- bloom in response to rapid infusion of starch aka produces a lot of lactic acid when we change to a high concentrate diet
- ferments starch to lactic acid, resulting in lactic acidosis
What microbe causes lactic acidosis?
Streptococcus bovis
What is lactic acidosis?
- lactic acid accumulation in the rumen
What causes lactic acidosis?
- overfeeding or quick change to high concentrate diet
- associated with a bloom of amylolytic bacteria such as Streptococcus bovis, which produce lactate
- once pH drops acid tolerant bacteria take over
Why is lactic acid accumulation in the rumen bad? What happens?
- lactic acid in the rumen draws water from the circulation into the rumen causing dehydration
- results in lysis of gram-negative bacteria = inflammation of rumen wall
How can an animal with lactic acidosis be cured?
By a rumen transplant from a healthy animal
How can acidosis be prevented?
- introduce concentrate slowly (microbes have time to adapt) and don’t overfeed concentrate
- other amylolytic bacteria have time to compete with strept bovis and make propionate instead of lactate - rumen microbial population will adapt to high concentrate diets
- bacteria and protozoa capable of UTILIZING lactate increase in number - target the culprits (streptococcus bovis)
What are the fermentation end products of amylolytic bacteria other than Streptococcus bovis?
- acetic acid
- propionic acid
- butyric acid
- CO2
What do acid-utilizing bacteria turn lactate into?
Fermentation endproducts
- acetic acid
- propionic acid
- valeric acid
- caproic acid
Proteolytic bacteria
- only use protein as their sole energy source
Lipolytic bacteria
- hydrolyze triglycerides, phospholipids, galactolipids, sulfolipids
- What are the 2 classes of archaea?
- free-living
- associated with protozoa
What are the 2 negative effects of archaea?
- energy waste
- greenhouse gas
Rumen fungi
- more prevalent on grasses than legumes
- important in fiber digestion
What does frothy bloat prevent?
- recognition of fluid/foam in cardia prevent eructation
What is legume bloat?
- rapid release of proteins results in rapid production of gas by bacteria leading to froth
What is feedlot bloat?
- due to dextran slime generated by amylolytic bacteria
How can frothy bloat be prevented?
- use antifoaming agents or ionophores that reduce gas production
Nitrite toxicity
- excess nitrates accumulate in plants when they are stressed; drought or hot dry winds put forage under water stress
- bacteria in rumen normally reduce nitrate to nitrite then ammonia; dependent on hydrogen availability
- due to excess nitrate (and not enough H), nitrite binds to hemoglobin preventing it from carrying O2
- if the increase in nitrates is gradual the rumen bacteria will adapt and remove it
Why are protozoa beneficial?
All protozoa store soluble CHOs (glucose) as an amylopectin-like storage polysaccharide
- for protozoa, this maintains a constant energy source
- for the animal, this stabilizes fermentation
- animal would be more prone to acidosis w/o protozoa competing for glucose (CHO) coming in
How do protozoa reduce efficiency of protein use?
Protozoa engulf and lyse bacteria which contributes to rumen protein turnover reducing efficiency of protein use and increase rumen NH3
Advantages of protozoa
- increased cellulose digestion
- slower fermentation of starch and sugars
- greater VFA production
- increased transport on conjugated linoleic acid and trans-11 fatty acid to duodenum and meat and milk
Are protozoa necessary?
No!
- have advantages and disadvantages
What are the 7 net effects of defaunation (removing protozoa)?
- increase daily gains due to increased protein efficiency
- improved feed efficiency
- decreased cellulose digestion
- increased total and microbial protein flow to the duodenum
- decreased pH on high concentrate diets, but increased pH on high
- increased production of propionic acid and decreased production of butyric acid
- shifting balance of SCFA
- propionic acid is more efficient - increased rumen volume and liquid outflow rate
What are 4 ways the rumen microbes can be manipulated?
- diet
- probiotics
- antibiotics
- protozoa elimination
How can diet manipulate the rumen microbes?
High forage = high pH
- increase cellulolytic bacteria, methanogens and protozoa
High concentrate = low pH
- increase amylolytic bacteria
- reduce methanogens and protozoa = less greenhouse gases
How can antibiotics manipulate rumen microbes?
- ionophores such as monensin are the most commonly used; creates pores in membranes of gram + bacteria
- inhibit methane production, proteolysis and AA degradation = overall improves animal efficiency
- increase propionate
How can eliminating protozoa manipulate rumen microbes?
- reduces protein degradation
Results of feeding ionophores
- increased propionate
- reduced protein degradation
- reduced deamination
- reduced methane production
- reduced lactate production
What is the composition of microbes predictive of?
- how efficient an animal is
