Milk fever -The Masked Risk behind The High Yielding Animals
Kumar Shubham¹*, Vidhu Kumar¹, Aditya Singh¹
¹Animal Nutrition Division, ICAR-National Dairy Research Institute, Karnal, India
ABSTRACT: Milk fever is one of the most important metabolic diseases observed especially in high yielding dairy cattle. In addition to treatment based on the analysis of the stage in which the animal is, there is need to understand why the dietary management like feeding less calcium, more phosphorus is required to decrease the chance of milk fever. Optimal dietary cation anion balance is highly recommended nowadays which has seen to produce profound effect in decreasing the chance of milk fever. Factors like age, breed, parity should be considered and according to that prevention and managemental methods like more anionic diet, feeding of unfertilised forage containing less potassium, less stressful condition must be advised to the person associated with livestock farming.
Key words: Periparturient period, serum calcium level, dietary cation anion difference, body condition score, calcium borogluconate, anionic salts.
Introduction:
Milk fever or Hypocalcemia is referred to a metabolic disease when there is a drop in serum calcium level between 2 and 1.38mmol/L (8 and 5.5mg/dl) during periparturient period. Animals specially the high yielders are commonly affected, though the impact and degree may be different based on the value of serum calcium level, age, breed, parity, stage of lactation, diet and managemental factors. Animals lose their ability to rise and this led to the death of many animals due to negligence, late treatment or because of improper managemental and feeding practices adopted during pregnancy especially during periparturient period.
Predisposing factors which may lead to milk fever
- Age: Mature cows are more susceptible to milk fever especially during 3rdto 5th lactation as there is elevated level of milk production. After parturition the demand of calcium compared to dry period will be increased suddenly and body may not be able to provide that much of calcium. With increase in age, there is also the decrease ability in amount of calcium absorption, active transport of Ca from intestine, production of 1,25(OH)₂ D₃ and internal receptors for 1,25(OH)₂ D₃ and increased level of C24-hydroxylase in older cows causes inactivation of 1,25(OH)₂ D₃. Any of the reason or altogether they may lead to decrease in calcium level and make animal prone to milk fever.
- Breed:Common misconception is that Holstein Friesian being high yielders are more susceptible to milk fever. But studies showed that Jersey are more susceptible than Holstein Friesian as they have lesser numbers of receptors for 1,25(OH)₂ D₃ at intestine. With reduced receptors for 1,25(OH)₂ D₃ the activation of genomic events by the Jersey is less efficient. Apart from Jersey, Holstein Friesian in India crossbreds, and Indian cattle breeds like Gir and Sahiwal and buffalo breed like Murrah are also vulnerable to milk fever.
- Parity:Cows from 3rd to 5th lactation or further are more susceptible to milk fever.
- Diet: Cows fed with more protein diet before or after pregnancy especially those rich in sodium and potassium can raise the DCAD (Dietary Cation Anion Difference), makes the blood more alkalinewhich reduces tissue responsiveness to parathyroid hormone (PTH), which is essential for mobilizing calcium from bones, increase absorption of calcium from gastrointestinal tract along with Vitamin D and increase renal Phosphorus excretion. There has been a common practice among the farmers to feed more Calcium (Ca) and Phosphorus(P) during last trimester of pregnancy, while it is observed that feeding more Ca will increase serum calcium level and make parathyroid hormone irresponsive and after parturition due to high milk yield there is increase demand of Calcium compared to dry period which the body is unable to tackle, leading to condition called Milk fever. Optimum Ca: P ration is 2:1. Abrupt dietary changes can disrupt mineral balance and hormone regulation leading to milk fever.
- Managemental factor: Complete milking during 1st48h post-calving as opposed to suckling by calf may act as a predisposing factor. More than 90% of cases occur within 48-72 hours postpartum. High Body Condition Score (BCS) can lead to milk fever so exercise and exposure to Vitamin D is recommended. Vitamin D plays a major role in calcium absorption from Gastrointestinal Tract and urine and its insufficiency may cause loss due to improper absorption and cause its excretion.
Effects due to low Calcium level
Hypocalcemia reduces rumen and abomasal motility further increasing the risk of abomasal displacement. Hypocalcemia reduces feed intake so that greater body fat mobilization occurs in early lactation. Hypocalcemia reduces all muscle contraction including the teat sphincter muscle responsible for closure of the teat orifice after milking, thus increasing the risk of mastitis. Hypocalcemia can lead to improper clotting of blood and below a certain level of calcium animal is unable to rise.
Stages and symptoms associated with Milk Fever
Stage I: Standing: In this stage the total Serum Ca level ranges 8.0–6.5 mg/dl, Temperature slightly above normal and occurs within 48h of calving. Cow becomes lethargic and show muscular weakness. Ruminal stasis, circulatory failure and muscular twitching are observed. Anorexia is one of the common findings.
Stage II: Down: In this stage total Serum Ca level ranges 6.4 – 4.0 mg/dl. Temperature will be subnormal (36-38°C) marked by disappearance of tetany, Staring, Dry eye lids with dilated pupils which can be confirmed by a torch light, normally cattle don’t blink in this stage and most important sign is sternal recumbency.
Stage III: Dying: In this stage Total Serum Ca level is less than 4.0 mg/dl. Lateral recumbency, loss of consciousness and death could be there. The recovery from this stage is very difficult.
Diagnosis
Examine every animal carefully rather than having an overlook of whole herd. Proper examination of animal especially postpartum regarding its appetite, alertness, cold ear. Be alert if the animal is lethargic. For the diagnosis, no full proof test is there but serum Ca analysis and other blood parameters can give an idea of hypocalcemia, serum Ca level below 6.4mg/dl is matter of concern and need quick medical intervention. High level of Glutamate Oxaloacetate Transaminase (GOT) and Creatinine Phosphokinase (CPK) in blood are often observed. Serum Inorganic Phosphorus(iP) levels are usually low, less than 3mg/dL. This drop is often secondary to hypocalcemia and plays a critical role in the pathophysiology of the disease. Alkaline urine though it’s not always because of milk fever but can be considered as one of the parameters and can be easily observed with a pH paper. Alkaline urine reflects metabolic alkalosis while hampers calcium mobilisation from bone and also calcium absorption from intestine. Low serum magnesium level can also be indicative of factors leading to hypocalcemia.
Treatment
Ideally animals respond to the treatment when they are in first stage of milk fever. Parental administration of Calcium salts is recommended. Calcium borogluconate (400-800ml) can be administered based on requirement but a keen monitoring related to temperature and heart beat is required before, during and after the treatment followed by 1-1.5g Calcium salt (50-60mL) based on available commercial composition to be administered subcutaneously. Oral administration of CaCl₂ before parturition and 24 hrs after parturition is recommended. Calcium chloride can induce metabolic acidosis in cow and ulceration of mouth leading to inappetence so, Calcium propionate though it has lesser calcium level than calcium chloride but still considered a better alternative as it has no acidifying or caustic effect, have more sustained effect and has an added advantage of propionate which is a glucogenic precursor. Single dose of 1,25(OH)₂ D₃ or its analogue like 1-α-OH- D₃, 24-F-1,25(OH)₂ D₃ @10 million units through intramuscular route is advised but Regarding use of Vitamin D is still debatable as cows treated with vitamin D or its analogues are unable to produce endogenously 1,25(OH)₂ D₃. Therefore, they may be unable to cope up completely from episodic hypocalcemia.
DCAD (Dietary Cation Anion Difference)
Incidence of milk fever depends on the abundance of cations Sodium (Na⁺) and potassium (K⁺) relative to amounts of Cl⁻ and SO₄²⁻. Increased anionic salts to a ration result in reduction in pH of blood and urine and further reduction in incidence of milk fever. So, the strategy is to increase anionic salts in diets i.e. chlorides and sulphates (of Ca/NH₄/Mg) and decrease cationic salts of Na and K salts in diets. Palatability should not be compromised of diet and best indicator of how much anionic diet is to be fed comes from urinary pH which should range between 5.5-6.2. If pH declines below 5.5 reduce dietary anions. Optimum Cation anion balance is between -50 to -100meq/kg diet.
Management
Prevention is better than cure, so management is the best method. Avoid excess calcium during dry period as this will inactivate the activity of PTH. Feed adequate phosphorus. Avoid over-fattening, Body Condition Score (BCS) over 3 on a scale of 5 is not recommended. Appetite should be proper though due to stress during periparturient period it is decreased, so appetite should be stimulated. Avoid stressful condition to animal. Keep special watch for cows prone to milk fever especially during 48-72h before and after parturition. At calving give an oral dose of Ca salt as gel followed by a diet high in Calcium.
Conclusion
Prevention of milk fever should be one of the major issues which need to be focussed rather than treatment as in most of the cases due to ignorance or late treatment of milk fever, lead to death of animals. Special vigilance of animals till 72hrs post-partum should be there to notice any signs of milk fever. If found lethargic or have inappetence, examination should be done properly and if found to be affected, Calcium borogluconate (400-800ml) administration intravenously followed by 1-1.5g Calcium administration subcutaneously based on available commercial preparation and oral administration of Calcium are recommended. High level of Calcium administration especially through oral rate should be checked as toxic dose may lead to death of animal.
Competing interests
The authors declare that they don’t have any competing interests.
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