PATHOLOGY - Flock Nutritional and Metabolic Diseases Flashcards
Why is ewe nutrition so important?
Ewe nutrition is key to both ewe and lamb health as nutrition affects susceptibility to disease, dystocia, lamb viability, colostrum and milk quality and production
What body condition score should ewes be at weaning?
Body condition score (BCS) or 2 - 2.5
What body condition score should ewes be at tupping?
Body condition score (BCS) 2.5 - 3.5
What is flushing?
Flushing is a temporary but purposeful increase in the level of nutrition at tupping to boost ewe ovulation and conception rates
What body condition score should ewes be at the second trimester?
Body condition score (BCS) 2 - 3. The placenta develops during the second trimester, and thus nutrition can have an effect on foetal size and birthweight
What body condition score should ewes be at the third trimester?
Body condition score (BCS) 2.5 - 3.5. 75% of foetal growth occurs within the third trimester so ewe nutrition is critical during this period
How should ewe nutrition be altered during the third trimester?
During the third trimester, concentrates may need to be increased for the last 6 - 8 weeks of gestation and dry matter should be reduced to 1.8 - 2% of their liveweight
Which methods can be used to monitor the nutritional status of ewes?
Body condition scoring (BCS)
Weighing
Lamb birth weights
Metabolic profiling
What are the limitations of body condition scoring (BCS) to monitor ewe nutritional status?
Subjective
Labour intensive (to palpate every ewe)
What are the limitations of weighing to monitor ewe nutritional status?
Cost of weighing equipment
Weight can vary based on urine/faeces stored, wet fleece etc.
How can lamb birth weights be used to monitor ewe nutritional status?
Lamb birth weights can be used t indicate if nutrition should be altered in the ewes still due to lamb
What is metabolic profiling?
Metabolic profiling refers to the analysis of various metabolic markers in the blood to assess the metabolic and nutritional status of an animal. Metabolic profiling can be used to monitor the nutritional status and optimise feeding strategies, as well as identify any metabolic changes that may indicate disease
When should you carry out metabolic profiling in a flock?
Take blood samples for metabolic profiling 2 - 4 weeks prior to lambing. Be aware that the earlier you take samples, the less likely you are to see metabolic changes, however if you do you have more time to rectify them. However, the closer to lambing you take samples, the more metabolic changes you are likely to see as the ewes are under more metabolic stress, however you have less time to correct it
How do you carry out metabolic profiling in a flock?
Take representative blood samples from 5 ewes, from each group (i.e. singles, twins and triplets). Or, take 10 - 15 representative blood samples if they haven’t been ultrasound scanned and split into groups based on how may lambs they are carrying. Make sure to also body conditon score (BCS) the ewes at time of blood sampling
Which blood parameters should you assess in ewes in the pre-lambing period for metabolic profiling?
β-hydroxybutyrate (BHB)
Urea
Albumin
Globulin
Magnesium
Why is it important to measure serum β-hydroxybutyrate (BHB) in ewes in the pre-lambing period?
β-hydroxybutyrate (BHB) is a ketone body released into the bloodstream when the ewe metabolises fat stores to meet their energy demands and these free fatty acids are oxidised in the liver to form ketone bodies. This occurs in periods of negative energy balance which can occur when energy intake is insufficient to meet requirements for maintenance, pregnancy and lactation. Elevated β-hydroxybutyrate (BHB) levels suggest the ewe is mobilising significant fat stores which can indicate a poor energy balance or inadequate nutrition
Why is it important to measure serum urea levels in ewes in the pre-lambing period?
Urea is a byproduct of protein metabolsim, and measuring serum urea levels allows for the assessment of protein intake and utilisation in the rumen. Decreased serum urea levels can indicate inadequate supple of rumen degradable protein, which is important for maintenance, growth, pregnany, lamb growth, milk production and fertility
Be aware low serum urea levels can also indicative hepatic disease
Why is it important to measure serum albumin levels in ewes in the pre-lambing period?
Decreased albumin levels can indicate chronic disease (such as liver fluke), reduced liver function and/or poor long term protein status
Why is it important to measure serum globulin levels in ewes in the pre-lambing period?
High globulin levels can indicate a chronic inflammatory condition
How does a ewe’s appetite change as lambing approaches?
As lambing approaches, a ewe’s appetite will decrease by 30% as the growing foetuses and increasing uterus size will put pressure on and reduce the space in the rumen. However the energy requirement for the ewe will increase
What is the maintenance energy requirement for a ewe?
8 - 11MJ per day
What is the energy requirement for a ewe in late pregnancy?
19MJ per day
What is the energy requirement for a ewe in peak lactation?
30MJ per day
What are the common periparturient diseases seen in ewes?
Abortion
Pregnancy toxaemia
Hypocalcaemia
Hypomagnesaemia
Septicaemia
When does pregnancy toxaemia typically occur in ewes?
Pregnancy toxaemia typically occurs during late gestation in ewes
What is pregnancy toxaemia?
Pregnancy toxaemia is a metabolic disorder that occurs in pregnant ewes. It occurs due to inadequate nutrition, often when the ewe is carrying multiple foetuses, which leads to a state of negative energy balance
Describe briefly the pathophysiology of pregnancy toxaemia
During late gestation, the energy requirements for ewes increase to facilitate foetal growth and to prepare for impending lactatuon, however the rumen capacity decreases as a result of foetal growth. If the ewe does not intake enough dietary energy/has insufficient nutrition, she will end up in a state of glucose insuffiecient and hypoglycaemic encephalopathy (which is reversible). The ewe will mobilise fat stores to meet the energy requirements (mobilisation of fat results in hepatic lipidosis) and these free non-esterified fatty acids released into the blood will be oxidised by the liver into ketone bodies, resulting in ketosis which can progress to ketoacidosis. This process is exacerbated by insulin resistance as a result of increased prostaglandin levels and other counter-regulatory hormones such as adrenaline, growth hormone and cortisol (released due to physiological stress) and glucagon (which is released to try and increase glucose levels). Furthermore, gestation decreases the ability to metabolise ketones.
What are the risk factors for pregnancy toxaemia in ewes?
Late gestation
Multiple foetuses
Older ewes
Excessive or inadequate body condition score (BCS)
Concurrent disease
What are the clinical signs of pregnancy toxaemia in ewes?
Inappetence
Depression
Neurological signs
Death
What are the neurological signs associated with pregnancy toxaemia in ewes?
Blindness
Head tilt
Star gazing
Head pressing
Tremors
Convulsions
(T/F) Pregnancy toxaemia has a sudden onset in ewes
FALSE. Pregnancy toxaemia typically progresses slowly however the more subtle signs are often not noticed and thus it can seem like it has presently suddenly
How do you treat pregnancy toxaemia in ewes?
Parenteral glucose
Oral propylene glycol
Oral fluid therapy
Parenteral calcium
Remove the lambs (induce abortion or caesarean)
Treat concurrent disease
Beneficial to give calcium as pregnancy toxaemia and hypocalcaemia can have a similar presentation
What is the dose rate for oral propylene glycol when treating ewes with pregnancy toxaemia?
120ml oral propylene glycol twice daily for the first 24 hours, then 60ml of oral propylene glycol twice daily from then on
What is the prognosis for pregnancy toxaemia in ewes?
Often the response to treatment for pregnancy toxaemia in ewes is poor and affects many ewes within the flock
What are the consequences of subclinical pregnancy toxaemia?
Decreased lamb birthweight
Decreased lamb vitality
Decreased mothering abiloty
Decreased colostrum and milk quantity and quality
How do you prevent pregnancy toxaemia?
Good quality roughage
Adequate feed face space
Appropriate feeding of concentrates 6 - 8 weeks before lambing
Control concurrent disease
Ultrasound scanning (to allow you to split groups based on number of foetuses and manage them appropriately)
Body condition scoring (BCS)
Metabolic profiling
When does hypocalcaemia typically occur in ewes?
Hypocalcaemia typically occurs 1 to 3 weeks pre-partum (late gestation) in ewes
What is hypocaelcamia?
Hypocalcaemia is a metabolic disorder that can be seen in sheep in late gestation due to increased calcium demand for foetal bone development and decreased availability of dietary calcium
What are the risk factors for hypocalcaemia in ewes?
Decreased feed intake
Increased cereal and/or root crops
Stress
Why does increased cereal and/or root crop grazing increase the risk of hypocalcaemia in ewes?
Cereals and root crops contain high levels of oxalates in their leaves which bind to calcium in the gastrointestinal tract, reducing the amount of free calcium available in the bloodstream resulting in hypocalcaemia
What are the early clinical signs of hypocalcaemia in ewes?
Staggering gait
Weakness
Tremors
Tachycardia gh
Slow pupillary light reflex (PLR)
Remember that hypocalcaemia will likely affect several ewes in the flock
What are the late clinical signs of hypocalcaemia in ewes?
Tachypnoea
Collapse/recumbent
Death
(T/F) Hypocalcaemia has a sudden onset in ewes
TRUE.
How do you treat hypocalcaemia?
Intravenous 50ml 40% calcium borogluconate
Supportive care
Pregnancy toxaemia prevention (may want to adminster some propylene glycol)
What are the potential benefits of administering magnesium and phosphate in addition to calcium when treating hypocalcaemia in ewes?
It may be beneficial to administer magnesium as these ewes often also have hypomagnesaemia and it can be beneficial to administer phosphate as this will trigger parathyroid hormone release to increase blood calcium levels
How do you prevent hypocalcaemia in ewes?
Prevent stressors in late gestation
Ensure adequate dietary calcium intake
Supplement calcium if feeding cereals and/or root crops
When does hypomagnesaemia typically occur in ewes?
Hypomagnesaemia typically occurs in the periparturient period and peak lactation in sheep
What causes hypomagnesaemia in ewes?
Hypomagnesaemia in ewes is caused by insufficient dietary magnesium. Sheep need a continuous supply of magnesium as they cannot store it and thus have limited reserves to manage changes in dietary magnesium intake
What are the risk factors for hypomagnesaemia in ewes?
Grazing pasture rich in potassium
Rapidly growing grass
Cold/wet weather
i.e. lush, rapidly growing grass in spring/summer has low levels of magnesium
How does grazing potassium rich pasture increase the risk of hypomagnesaemia in ewes?
High potassium levels in the pasture can inhibit magnesium absorption from the gastrointestinal tract as potassium competes with magnesium for absorption in the rumen and thus when there is an excess of potassium, magnesium is not absorbed as efficiently
How does rapidly growing grass increase the risk of hypomagnesaemia?
Rapidly growing grass can reduce gut transit time in ewes primarily due to its high water content and high digestibility. Increased gut transit time decreases the time available for magnesium to be absorbed into the gastrointestinal tract
How does cold/wet weather increase the risk of hypomagnesaemia in ewes?
When the weather is cold/wet, ewes don’t eat as much grass, and the grass preferentially absorbs potassium over magnesium to fuel its growth
What are the clinical signs of hypomagnesaemia in ewes?
Sudden death (most common)
Staggering gait
Apparent blindness
Restlessness
Collapse/recumbent
Nystagmus
Hypersalivation
How can you diagnose hypomagnesaemia?
History and clinical signs
Blood sample
Post-mortem sampling from anterior or posterior chamber of the eye
How do you treat hypomagnesaemia?
Subcutaneous 50ml 25% MgSO4
Why should you inject 25% MgSO4 at multiple sites?
You should inject 25% MgSO4 as there is a risk of skin necrosis
What is the prognosis for hypomagnesaemia?
Often hypomagnesaemia has a poor response to treatment as the response to treatment is very slow as the intracellular cerebrospinal fluid levels of magnesium have to return to normal for clinical signs to resolve, and it can take a long time for subcutaneous MgSO4 to reach that site
How do you prevent hypomagnesaemia?
Provide magnesium licks
