homeostasis and metabolic challenges Flashcards
what is homeostasis?
regulation of a stable internal environment
- constant challenge of change
- maintaining functions within tolerable limits
- adjustments made by by negative feedback
explain how a negative feedback loop works
change detected by body sensors + controlled by brain. adjustments through effectors: endocrine system (hormones) and nervous system (nerve cells + signals)
what is an inherited homeostatic imbalance/failure?
diabetes
what percentage of the body’s calcium is in the bones?
99%
what is the normal mass of calcium in blood?
8-12g
how are calcium levels in blood regulated (if not by diet)?
- kidney filtration and reabsorption
- bone formation and resorption (via osteoclasts)
what happens if the blood Ca level is low?
- Parathyroid hormone stimulated
- Cholecalciferol in liver activated
- Hydroxycholecalciferol is formed
- activated in kidneys to dihydroxycalciferol
- Ca - binding protein synthesized: acts on gut, kidneys and bones to raise blood Ca
what is milk fever?
hypocalcaemia: low blood Ca
what percentage of dairy herds have milk fever?
5-8%
how much calcium does a dry cow need per day?
15g
how much calcium does a cow in early lactation need per day?
50-60g
what measures can be taken to prevent milk fever?
- calcium infusion + vit D when calving, low Ca diet when dry
- diet balanced for cations and anions
what percentage of Mg is found in bones?
70%
what is dissolved Mg needed for?
enzyme activity for carbohydrate + lipid metabolism
what symptoms arise from Mg deficiency?
nervous irritability, convulsions, hypomagnesaemic tetany
what are high vs low Mg foods?
high in vegetable protien feeds
low in rapidly growing grass
What are the grass staggers?
hypomagnesaemic tetany
in what season is there a higher risk of grass staggers?
spring/autumn
what is Mg absorption affected by?
K (potassium), protein, low fibre
how much Mg do cows need per day?
20-30g
how much Mg do ewes need per day?
2-3g
what is hyperlipaemia (fatty liver) induced by?
increased energy requirements coinciding with reduced energy intake
when are dairy cows most susceptible to hyperliaemia?
at calving
when are alpacas and llamas most susceptible to hyperliaemia?
in late preganancy
when are ponies and donkeys most susceptible to hyperlipaemia?
during pregnancy + lactation
what is hyperlipaemia?
fatty liver
what is urolithiasis?
stones in kidney and bladder
what are salt precipitates that form crystals in kidney/bladder made of?
usually Mg, NH4, also Ca oxalate
which animals are most susceptible to urolithiasis?
dogs, cattle, sheep
what can happen to animals with urolithiasis?
bladder ruptures
what are predisposing factors (risk factors) for urolithiasis?
- males
- diet with high levels of P + Mg, excess
- infection
- alkaline urine
what are changes that can be observed in animals with urolithiasis?
- wide leg posture to relieve pain
- straining when passing urine
- small volumes of blood stained urine
- crystals around penis
how do you prevent urolithiasis?
- suitable and balanced diet (Ca supplementation: Ca:P 2-2.5:1)
- minimise Mg and P in diet
- risk reduced by low pH urine -> add 0.5-1% NH4Cl
- maximise urine volume: add 1.4% salt
- avoid breeding from recurrent cases
