(Source: http://www.eyefetch.com/image.aspx?ID=405372)
HYPOCALCAEMIA
in dairy cattle
Sophie Rosevear, Jessie Neal, Tara Hall and Alex Doddridge
Introduction
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Calcium is essential, it is involved in many physiological processes
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Dairy cows have been heavily selected for the ability to produce high milk
yields
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There is a fine calcium balance in the dairy cow
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When demand for energy and calcium suddenly increases this balance
can be disrupted
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Calcium homeostasis fails = milk fever (also called periparturient paresis)
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Affects productivity and longevity of high producing dairy cows
The calcium balance
(Source: Horst 1986)
Calcium homeostasis
Failure of homeostasis and
development of hypocalcaemia
• Lactation generates a sudden, very high demand on calcium homeostasis
• Can result in an imbalance between calcium output and influx of calcium to
maintain the extracellular pool (plasma) from bone, kidney and intestine
• Failure of calcium homeostasis
• Between 5 and 20% of cows will develop milk fever
• Occurs within 12 to 24 hours of parturition
• Milk fever is hypocalcaemia severe enough to present clinical signs, when
plasma calcium levels are between 8 mg/dL and 6 mg/dL
Clinical Signs
(Source: http://informedfarmers.com/dairy-cattle-industry/downer-cow/)
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Hyper excitability with anorexia, listlessness and muscle weakness
Body temperature declines as condition worsens
Sternal recumbency with lateral neck kink (as shown above)
Ruminal atony and constipation due to a loss of smooth muscle contractile function causing bloat
‘Crush syndrome’ followed by 'downer cow’ syndrome
If parturient birthing process is suspended
Weak heart sounds and tachycardia
Later stages cow is laterally recumbent with a temperature as low as 32°C (normal temp 38-38.5°C)
Death can occur in a few to several hours, and is likely at a rate of 60-70% without treatment
Predisposing factors
Age
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Most common in cows in 3rd lactation and older
Studies showing that the intestinal receptors for 1,25-dihydroxyvitamin D decline in quantity with age
Older animals are also less able to mobilise calcium from bone
Older animals have a greater milk production = greater demand for calcium
Breed
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Breeds such as Channel Island, Swedish Red and White, and Jerseys are all more susceptible to milk fever than Holsteins
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One study showed that intestinal receptors for 1,25-dihydroxyvitamin D are around 15% less in Jerseys than Holsteins
Metabolic alkalosis (MA)
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Mostly caused by a diet that supplies more cations (K, Na, Ca and Mg) than anions (Cl, SO₄ and PO₄) causing a difference in
electrical charge in body fluids
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MA has been shown to blunt the homeostatic response of dairy cows to parathyroid hormone because it is believed that it
causes a change in conformation of the parathyroid hormone receptor in all target tissues
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Thus the cow cannot benefit from these homeostatic mechanisms and restore plasma calcium
Hypomagnesaemia
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Low levels of magnesium also interferes with the ability of parathyroid hormone to act on its target tissues
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Particularly in relation to magnesium’s action as a co-factor allowing parathyroid hormone to stimulate cyclic AMP production
(necessary for operation of calcium channels)
Prevention of hypocalcaemia
Prevention of hypocalcaemia, not just milk fever, should be a major goal of dairy farms
The DCAD method
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Induce a compensated metabolic acidosis in the cow restoring the ability of parathyroid
hormone to regulate blood calcium levels.
Reduce dietary cations and to increase dietary anions.
Causing a reduction in what is known as the Dietary Cation-Anion Difference (DCAD),
subsequently lowering the pH of the blood.
(Source: Horst et al. 2005)
Prevention of hypocalcaemia continued …
Feeding a calcium-deficient diet
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Reducing calcium in diet prior to calving
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Diets less than the required concentration of calcium can cause a slight decline in plasma calcium
stimulating increased release of parathyroid hormone
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Implemented days prior to parturition the homeostatic response, including osteoclastic bone resorption,
is already active and the cow is able to utilise calcium with maximum efficiency
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Demand for calcium is more easily overcome and hypocalcaemia can be avoided
Higher dietary Magnesium
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A higher dietary magnesium concentration prior to calving ensures that passive diffusion of magnesium
in the rumen can occur and levels of magnesium in the blood will be adequate
Treatment
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Should be implemented as early as possible
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Restores plasma calcium level
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Fastest: IV injection of calcium salts, usually calcium borogluconate
(recommended 2g Ca/100 kg bodyweight)
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Administer the Ca at a rate of 1 g/ min
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While listening to the heart to avoid fatal arrhythmia
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Oral gels containing calcium salts are given before, during and around 12-24
hours after parturition as a preventative treatment measure
CONCLUSION
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Economically important
Affects productivity
Reduces a dairy cow's productive life.
It costs the dairy industry not only through loss
of production but also in the cost of control and
treatment measures.
• Prevention is key
• Future research focus on regulatory mechanisms
of calcium metabolism.
REFERENCES
Bigras-Poulin, M. & Tremblay, A. 1998, ‘An epidemiological study of calcium metabolism in non-paretic postparturient Holstein cows’,
Preventive Veterinary Medicine vol. 35, pp. 195-207
DeGaris, P. J. and Lean, I. J. 2007, 'Milk Fever in dairy cows: A review of pathophysiology and control principles', The Veterinary Journal vol.
176, no. 1, pp. 58-69
El-Samad, H., Goff, J.P. and Khammash, M. 2002, ‘Calcium homeostasis and parturient hypocalcaemia: An integral feedback perspective’,
Journal of Theoretical Biology vol. 214, pp. 17-29
Goff, J.P. 2008, ‘The monitoring, prevention, and treatment of milk fever and subclinical hypocalcaemia in dairy cows’, The Veterinary
Journal vol. 176, pp. 50-57
Goff, J.P., Reinhardt, T.A. and Horst, R.L. 1991, ‘Enzymes and factors controlling vitamin D metabolism and action in normal and milk fever
cows’, Journal of Dairy Science vol. 74, no. 11, pp. 4022-4032
Goff, J.P., Ruiz, R. and Horst, R.L. 2004, ‘Relative acidifying activity of anionic salts commonly used to prevent milk fever’, Journal of Dairy
Science vol. 87, pp. 1245-1255
Hamali, H. 2008, 'Post estrus hypocalcemia in a repeat breeder half-breed holstein cow', Journal of Animal and Veterinary Advances vol.
10, pp. 1301-1304
Hangping, C., ZhongHua, W. and Fuchang, Li 2010, 'Effects of dietary calcium levels on calcium homoeostasis in lactating dairy cows',
Chinese Journal of Animal Nutrition vol. 22, no. 5, pp 1286-1292
Horst, R.L. 1986, ‘Regulation of calcium and phosphorus homeostasis in the dairy cow’, Journal of Dairy Science vol. 69, pp. 604-616
Horst, R.L., Goff, J.P. and Reinhardt, T.A. 1994, ‘Calcium and vitamin D metabolism in the dairy cow’, Journal of Dairy Science vol. 77, pp.
1936-1951
Horst, R.L., Goff, J.P. and Reinhardt, T.A. 2005, ‘Adapting to the transition between gestation and lactation: Differences between rat,
human and dairy cow’, Journal of Mammary Gland Biology and Neoplasia vol. 10, no. 2, pp. 141-156
REFERENCES continued
Kimura, K., Reinhardt, T.A. and Goff, J.P. 2006, ‘Parturition and hypocalcaemia blunts calcium signals in immune cells of dairy cattle’,
Journal of Dairy Science vol. 89, pp. 2588-2595
Kronqvist, C., Emanuelson, U., Sporndly, R. and Holtenius, K. 2011, 'Effects of prepartum dietry calcium level on calcium and magnesium
metabolism periparturient in dairy cows', Journal of Dairy Science vol. 94, no. 3, pp. 1365-1373
Lean, I. J., DeGaris, P. J., McNeil, D. M. and Block, E. 2006, 'Hypocalcemia in dairy cows: meta-analysis and dietary cation anion
difference theory revised', Journal of Dairy Science vol. 89, pp. 669-684
McNeill, D. M., Roche, J. R., McLachlan, B. P. and Stockdale, C. R. 2002,'Nutritional strategies for the prevention of hypocalcaemia at
calving for dairy cows in pasture-based systems, Australian Journal of Agricultural Research, vol. 53, no. 7, pp. 755-770
Oba, M., Oakley, A.E. and Tremblay, G.F. 2011, ‘Dietary Ca concentration to minimise the risk of hypocalcaemia in dairy cows is affected
by the dietary cation-anion difference’, Animal Feed Science and Technology vol. 164, pp. 147-153
Peacock, M. 2010, ‘Calcium Metabolism in Health and Disease’, Clinical Journal of the American Society of Nephrology vol.5, pp. s23-s30
Radositis, O.M., Gay, C.C., Hinchcliff, K.W. and Constable, P.D. (2007), 'Veterinary Medicine - A textbook of the diseases of cattle, horses,
sheep, pigs and goats,' Saunders Elsevier, worldwide (Sydney)
Reinhardt, T. A., Lippolis, J. D., McCluskey, B. J., Goff, J. P. and Horst, R. L. 2011, 'Prevalence of subclinical hypocalcemia in dairy herds',
The Veterinary Journal vol. 188, pp. 122-124
Ramberg, C.F., Johnson, E.K., Fargo, R.D. and Kronfeld, D.S. 1984, ‘Calcium homeostasis in cows, with special reference to parturient
hypocalcaemia’, America Journal of Physiology vol. 246, no. 15, pp. R698-R704
Schenck, P. A. and Chew, D. J. 2008, 'Hypocalcemia: A Quick Reference', Veterinary Clinic Small Animal vol. 38, pp. 455-458
Shahzad, M. A. and Mahr-un-Nisa, M. S. 2008, 'Influence of varying dietary cation anion difference on serum minerals, mineral balance
and hypocalcemia in Nili Ravi buffaloes', Livestock Science vol. 113, pp. 52-61
Questions?