Metabolism and Negative Energy Balance

Question 1

What molecules are metabolised during severe negative energy balance?

Answer 1

Triglycerides, non-esterified fatty acids (NEFA) from adipose tissue and ketone bodies from liver

Question 2

What are triglycerides converted into?

Answer 2

Very low density lipoproteins in liver but are only available to tissues with active lipoprotein lipase in the capillary bed

Question 3

When are levels of NEFA very high in plasma?

Answer 3

During times of starvation, stress and high metabolic load

Question 4

How are ketones metabolised?

Answer 4

Converted to ketone bodies - B-OH-butyrate and acetoacetate which is used to provide energy by supplying acetyl-CoA into the TCA cycle
Acetone is mostly lost in expired air but a small amount is converted to glucose

Question 5

What is the cause of ketosis in dairy cows?

Answer 5

Hyperketonaemia resulting from severe negative energy balance and hypoglycaemia

Question 6

What increases the risk of ketosis?

Answer 6

Parity and age of cow (multiparous cows most as risk)
BCS >6 out of 8
Proximity to parturition (7 weeks prior to calving but up to 14 weeks)

Question 7

What are some of the factors that cause ketosis?

Answer 7

Decreased energy intake (CP, ME, height or mass of pasture is poor, poor supplementation)
Limited capacity to ingest and metabolism large amount of feed in early lactation (rumen and liver not adapted)

Question 8

What are the 2 types of ketosis?

Answer 8

Wasting form has a gradual onset

Nervous form has a rapid onset

Question 9

What occurs during wasting ketosis?

Answer 9

Decline in appetite over 2-5 days
Lack of interest in cereal grain-based supplement but may still eat forage
Elevated B-OH-butyrate in blood
Elevated levels in ketones in urine (ketouria)
Unsteady stance and gait with head low to the ground
Rapid reduction in milk yield
Ketone smell on breath
Disinclined to move

Question 10

What level does B-OH-butyrate have to be in the blood to cause ketosis?

Answer 10

>1.2mM = ketotic
>3mM = clinical disease

Question 11

What occurs during nervous ketosis?

Answer 11

Incessant tongue movements and unusual licking of the skin

Aimless wandering, walking in circles and bellowing for no apparent reason

Question 12

How do we treat ketosis?

Answer 12

Glucose replacement therapy (IV of dextrose short acting, drench with propylene glycol long acting, isolate and feed high quality roughage, treat for 2-4 days, reintroduce cereal grain-based supplements)
Hormonal therapy (administer a long-acting corticosteroid with glucose replacement therapy to avoid excessive muscle catabolism)
Prompt treatment will usually resolve the hypoglycaemia and hyperketonaemia but production for that lactation will be greatly reduced or lost

Question 13

How do we prevent ketosis?

Answer 13

Keep cow in BCS of 5-5.5 at calving time
Feed cereal grain supplements in the transition period leading up to calving
Identify at risk cows and drench with propylene glycol of glycerine at calving
Offer high quality pasture after calving
Feed cereal grain-based supplements during milking

Question 14

What is pregnancy toxaemia in ewes a consequence of?

Answer 14

Hypoglycaemia

Question 15

What factors predispose ewes to pregnancy toxaemia?

Answer 15

Inadequate pasture quality/quantity
In late pregnancy
Twin or triplet ewes
Undersized (maiden ewe)
Poor health (teeth and parasites)
too thin BCS under 2.5 or too fat BCS above 4 in late pregnancy

Question 16

Preg toxaemia is a response to?

Answer 16

Compromised energy intake

Acute stress from handlign or environmental factors

Question 17

What are the consequences of a decrease in glucose and an increase of ketones in plasma?

Answer 17

Weakens ewe (ketoacidosis, anorexia, ketouria, dehydration, fatty liver)
Starves the foetus
Suppresses CNS function of ewe

Question 18

What are the clinical signs of preg toxaemia?

Answer 18

Staggering, star gazing, drowsiness, convulsions, death
Signs of CNS dysfunction (blindness, muscle tremors, convulsion, death) and muscle weakness in response to hypoglycaemia and ketoacidosis

Question 19

What are the levels of B-OH-butyrate and acetone in pregnancy toxaemia?

Answer 19

B-OH-butyrate >3.0mM

Acetone >2-10+ mM

Question 20

What molecules in plasma appears in the normal range during a case of pregnancy toxaemia?

Answer 20

Glucose which can be due to the release of cortisol during stressful situations (having a clinical exam done)

Question 21

Treatment of pregnancy toxaemia?

Answer 21

Early support with glucose and electrolytes can resolve signs and prevent progression of disease
Later ewes with CNS and hyperketonaemia become unresponsive to glucose
Chemical induction of pregnancy by surgical intervention may restore normal metabolism in the ewe

Question 22

How can we prevent pregnancy toxaemia?

Answer 22

Good ME available on pasture
Ewes in good health
Actively manage at risk ewes as a separate group
BCS of 3 in late pregnancy
Supplement to support energy intake
good husbandry to avoid stress in late pregnancy