EXAM QUESTIONS Flashcards
What are the metabolic fates of glucose?
- Aerobic metabolism slow twitch
• Oxygen available
• Glycolysis
• Conversion of pyruvate to Acetyl Co – A
• Enter TCA cycle
• 38 ATP produced
• SLOW MUSCLE MOVEMENT A LOT OF ENERGY - Anaerobic metabolism fast twitch
• Oxygen limited
• Conversion of pyruvate to lactic acid
• 2 ATP produced
• Lactic acid returns to liver to pyruvate
• FAST MUSCLE MOVEMENT NOT MUCH ENERGY - Glycogen synthesis
• Short-term energy store
• Excess glucose stored in muscle for later use
• Glucose homeostasis
• Glycogen glucose = Energy - Fat synthesis
• Long-term energy store
• Excess glucose stored as fat (triglycerides)
• Through the pentose phosphate pathway
• Fat mobilised when required
LOW QUALITY FEEDS ADD NON-PROTEIN NITROGEN (UREA)
In a ruminant, describe how the digestibility of a feed constrains feed intake
Intake is impeded when the rumen is full and this is influenced by the clearance rate of the rumen.
Clearance rate= (Outflow rate (L/hr))/(Rumen digesta size)
Outflow rate is the rate of digestion or onward passage
This is influenced by the digestibility of the feed: Less than 8% fiber can be digested per hour
Describe how environmental temp can affect feed intake
- Cold weather increases voluntary feed intake (VFI) to increase heat production
- Hot weather decreases VFI to decrease heat production
- Effects are acute but animals do acclimatise.
- Night feeding
- Differences for concentrates versus roughages
- Also influenced by photoperiod – larger meals or more often during day – and distance to water which affects number of drinks per day. VFI decreases if drinks/day decreases.
Magnesium is an esential mineral. Describe the functions of MG in the body
Body f(x)s of Magnesium: • Enzyme activator Inv.d in 300+ biochem Rns in body • Maintain normal muscle & nerve f(x) Control of nervous tremors • Keeps heart rhythm steady • Supports healthy immune syst • Keeps bones strong • Helps reg. blood sugar levels • Promotes normal blood pressure • Inv.d in E metab. & protein synth
List 4 symptoms of an Mg deficiency and describe how potassium and sodium levels in feed may induce a MG defiency in ruminants
Symptoms of rapid onset hypomagnesia (grass tetany) in rum.s:
• Hyperexcitability, twitching, staggers
• Reduced appetite
• Incoordination & recumbency (w. pedalling)
• Convulsions & death
Potassium & Sodium levels:
• K content of pastures reduces plant uptake of Mg. This reduces Mg absorption (K increases the potentional difference across rumen epithelium) – sheep are more sensitive
• Na is required (3g/kgDM) for Mg absorption. Therefore reduced Na uptake in plants can cause Mg deficiency. Also when K is low is it substituted w. Na in saliva further reducing Mg absorption.
Vitamin E and Selenium are both essential nutrients. Describe why this is (4 marks).
Selenium & Vit E:
• Act together to protect body tissue from oxidation
• Vit E prevents formation of lipid peroxidases & Se is part of the glutathione peroxidase enzymes that remove lipid peroxidases that are formed
• Both also have a role in immune f(x)
• Vit E also:
o Enhances Vit A absorption
o Is inv.d in Vit C & DNA synth
• Selenium also:
o Is a selenoenzyme that are responsible for conversion of T4 to T3 for correct sperm dev
Describe 2 symptoms of a deficiency of Vitamin E/Se, and list a good source of vitamin E
Deficiency symptoms:
• Nutritional muscular dystrophy (white muscle disease)
o Striated muscle damage by free-radicals
o Young ruminants experience stiffness & abnormal heartbeat
• Lowered disease resistance – greater susceptibility to mastitis
Green forage is the best sources of Vit E
Discuss metabolic roles of thiamin
Thiamin is involved in CHO metabolism:
• Oxidative decarboxylation of pyruvate to acetyl CoA
• TCA cycle
• Pentose phosphate pathway
• Synth of BCAAs (branched chain AAs)
*Thiamin triphosphate is also involved in nerve transmission
2 good sources of thiamin and list 2 symptoms of a deficiency
Sources of Thiamin: • Green leaves • Cereal grains • Yeast Deficiency symptoms: • Anorexia • Inappetite
Define basal and fasting metabolism
Basal metabolism – The Energy expended (heat) for a fasting animal with no activity This is physiologically impossible to measure because you can’t stop an animal from moving
We measure Fasting metabolism – The same as basal metabolism but accepts that an animal will undergo some activity
What is meant by heat increment in relation to feed energy and describe 2 factors contributing to heat increment
• Food ingested increase heat
• Increased heat produced as result of energy in feed = Heat increment
• Causes of heat increment
o Eating
o Microbial metabolism (78% of ME intake)
o Nutrient metabolism
o Facilitated transport across liminal wall (high low)
o Energy required for Low High (ATP)
What is meant by k values and calculate the k value
o K value = Efficiency of animal to utilise energy (energy lost/energy consumed)
E.g. 10M/D and retains 6 MJ NE K= 6/10 = 0.6
List 2 characteristics of a feed which influences its degradability in the rumen (1 mark).
Degradability is influenced by:
• Surface area available for microbial attack
• Presence of protective layers
• Physical and chemical nature of protein
The metabolisable energy content of a cereal grain is generally lower for ruminants than monogastrics. Briefly explain why this is the case
Gross Energy of a feed depends is measured as the heat of combustion. It depends on the degree oxidation (C + H:O ratio).
Digestible Energy = GE – Faecal energy
Metabolisable Energy = Digestible Energy – (urine + gas losses)
• Urinary E losses are through N containing compounds
• Gas losses are mostly only seen ruminants – mainly as CH4 (11-20% of DE depending on feeding level and digestibility)
• For this reason, because gas losses will be greater for the ruminant, ME content is generally higher for monogastrics
Briefly describe why simple relationships predicting microbial protein yield from metabolisable energy intake can lead to errors in microbial protein yield estimates (4 marks).
Microbial Protein is a mix of bacteria and protozoa. It consists of true protein, nucleic acids and cell wall proteins. Microbial crude protein (MCP) is dependent on fermentable Energy supply however simple relationships predicting yield from ME intake can be erroneous because MCP yield is also affected by:
• Level of fiber (increases microbial E requirements)
• Rumen pH (low reduces microbial E req.s)
• Variation in form of N required by microbes
