Alex+and+Tara+8D


 * ====Hypocalcemia= blood concentration <2.0mmol/L Ca. ====
 * ====Large Calcium demand --> Slow response of intestinal absorption or bone resorption of calcium. ====
 * ====Calium too low --> receptors in the parathyroid gland activated --> PTH released --> increase blood calcium (eg. from bones). Also stimulates Ca resorption from urine and GI tract. ====
 * ====Milk fever associated with other metabolic disorders; retained fetal membranes, abomasal displacement, metritis. ====
 * ====Dietry Cation-anion Difference (DCAD) --> low in the diet= blood more acidic=release of more carbonate from bones to maintain normal blood pH --> cow is able to cope with mass demand for calcium after calving. DCAD between -100 and 0 mEq/kg ideal. Feed Ionic salts. ====
 * ====Feed low Ca diets- when abundant Ca is fed, the efficiency of the system to transfer Ca from the skeleton become sluggish --> increased chance of milk fever. Control Ca concentrations to around 0.4%-0.6% before calving. ====
 * ====Failure of one of the metabolic process will inevitably impact on the efficiency of others. ====
 * ====Most at risk four weeks before and after calving. This is known as the Transition Period. ====
 * ======Loss of blood calcium to milk may exceed 50g per day during lactaction (lactaion can increase the Ca requirement 2-4 fold). Pre-calving the daily requirements are approx 30g (15g in faecal and urinary loss and 15g to foetal growth). ======
 * ======Blood calcium is maintained within a narrow range of 2.0-2.5mmol/L. Only 50% of blood Ca reserves can be lost before hypocalcemia onset. ======
 * ======Most cows have some degree of Hypocalcemia at calving. ======


 * Hypocalcaemia is one of the more prominent diseases found in dairy cows. The frequency of milk fever can reach up to 25% but is usually around 0-10% in a heard. There have been cases where the occurrence has reached 80% in some research trials.


 * Hypocalcaemia has many side-effects and contributes to many infections/diseases, such as mastitis. It reduces how effectively immune cells respond to stimuli, contributing to disease, and also leads to displaced abomasum due to its affect on smooth muscle contraction. This same muscle contraction is lessened in the cows teats and this leads to mastitis.


 * It has been shown that for a Holstein dairy cow the optimum level for dietary calcium at early lactation is 0.68%.


 * Potassium also plays an important role in hypocalcaemia/milk fever, there are studies showing that on a few occasions it can be brought on by excess Potassium. These same studies also demonstrated that excess dietary chlorine, and on the odd occasion sulfur, can help the cow’s ability to maintain calcium homeostasis.


 * Feeding a forage based diet with low levels of calcium, potassium and sodium are at the focus of many preventative strategies along with the use of chloride and sulfate in the form of an ‘anionic feed’.


 * Most studies are showing that prevention is better than treatment and there are a few prevention strategies being examined at the moment. One such strategy is to induce mild metabolic acidosis about 3 weeks prior to calving by feeding anionic salts to reduce the DCAD of the prepartum diet. This decreases the incidence of hypocalcaemia by increasing the tissues response to the parathyroid hormone.


 * The incidence of milk fever increase by 9% per lactation. This increase can be explained by a decrease in the ability to mobilize Ca from the bone and also a reduced number of 1,25 dihydroxy-cholecalciferol (1,25(OH)2D3) receptors in the small intestine.


 * Calcitonin, Parathyroid hormone and 1,25(OH)2 vitamin D3 are all involved in the regulation of calcium homeostasis.


 * Reports show that the heritability of hypocalcaemia is low.


 * It is well established that the Channel Islands breeds of cattle (Jersey, Guernsey etc) have a higher susceptibility to hypocalcaemia than Holsteins.


 * The risk of hypocalcaemia also increases with over-conditioned cows (i.e. >3.5 on a body condition score of 1-5).


 * Calcitonin is involved in the physiological control over Ca Homeostasis, it is released in response to high concentrations of Ca in the blood. On the other hand, the parathyroid glands release parathyroid hormone(PTH) in response to low concentrations of blood Ca. Mobilisation of Ca from the bone is increased by the PTH.


 * Resorption of Ca from the bone and increased intestinal absorption of Ca are activated by the active metabolite of vitamin D. Vitamin D is provided by the ingestion of Vitamin D2 which arises from the photochemical conversion of 7-dehydrocholesterol to cholecalciferol (vitamin D3).

__** Reference List**__

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 * Reinhardt, T. A., Lippolis, J. D., McCluskey, B. J., Goff, J. P. and Horst, R. L. 2010 "Prevalence of subclinical hypocalceamia in Dairy Herds" Veterinary Journal Vol: 188 Issue: 1 Pgs: 122-124
 * 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 Issue: 5 Pgs: 1286-1292
 * 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 Issue: 3 Pgs: 1365-1373
 * 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 Issue: 7 Pgs: 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 Issue: 3-4 pgs: 147-153
 * DeGaris, P. J. and Lean, I. J. 2007 "Milk Fever in dairy cows: A review of pathophysiology and control principles" Veterinary Journal Vol: 176 Issue: 1 Pgs: 58-69
 * ====Shannon//<span style="font-family: Calibri,sans-serif;">, //N//<span style="font-family: Calibri,sans-serif;">. // 2010, Dairy Extension, Department of Primary Industries, Wodonga ====
 * ====<span style="color: black; font-family: Calibri,sans-serif;">Champness,//<span style="font-family: Calibri,sans-serif;">D. //2007, Department of Primary Industries, Hamilton ====
 * ====<span style="color: black; font-family: Calibri,sans-serif;">El-Samad, H., Khammash, M., Gof, J. 2000, //<span style="color: black; font-family: Calibri,sans-serif;">Calcium Homeostasis: a Feedback Control Point of View //<span style="color: black; font-family: Calibri,sans-serif;">, Proceedings of the American Control Conference, Chicago, Illinoi. ====
 * ==== <span style="color: black; font-family: Calibri,sans-serif;">Lean, I., DeGaris, P. 2010, //<span style="color: black; font-family: Calibri,sans-serif;">Transition Cow Management //<span style="color: black; font-family: Calibri,sans-serif;">, Dairy Australia. ====