THE IMPORTANCE FOR CALCIUM SUPPLEMENTATION Over the past 25 years, the demands which we have placed upon our national dairy herd have increased, with the expected average milk yield during this time having risen by almost 30%. As a consequence, the natural control of blood calcium levels in a cow are falling deficient and milk fever is becoming an important and common production disease. This is a disorder which we cannot afford to ignore. Milk fever occurs around calving due to the sudden increase in calcium demands at the onset of lactation. Jerseys are predisposed, as well as older cattle due to their higher productivity and reduced ability to mobilise bone stores of calcium. Clinical milk fever results in a ‘downer cow’: in the latter stages the animal is unable to stand, lethargic, cold and reduced gut turnover. However, it is often said that up to five cows in the herd could be suffering sub-clinical disease, where productivity is being affected even though the animal appears outwardly normal. This can have a huge economic impact on a herd, with sub-clinical milk fever potentially leading to increased calving problems, retained foetal membranes, metritis, mastitis and reduced milk yield and fertility. The mainstay of preventing milk fever is effective management and nutrition during the dry period. The dry cow must not be over-conditioned but dry matter intake must be maximised usually by providing a high-fibre and relatively low-protein diet. The dairy cow must not be fed high levels of calcium during the dry period. Instead, she needs high levels of magnesium and vitamin D to help in preparation for the absorption of more calcium from her diet and internal stores at the commencement of lactation. Unfortunately, a solely grass-based forage diet will not achieve this. The acidity of the diet may be manipulated to improve calcium utilisation by adding mineral salts and avoiding certain feeing stuffs. Another preventative measure is the utilisation of calcium supplementation throughout the 72-hour risk period after calving. The natural balance if calcium within a cow is determined by 4 different hormones, working in unison to store or release calcium from the bones, kidneys and gut. Once hypocalcaemia begins, it can take up to 72 hours for the body to respond and counteract the deficiency. A cow is, therefore, at risk of developing milk fever for up to three days following calving. During this time of hormonal change, the gut becomes the most important source from which the cow derives calcium supplies, making oral calcium supplementation during this period an important consideration alongside management changes. In summary, milk fever is a production disease that is a challenge for the dairy industry. While management and nutrition form the basis of prevention, oral calcium supplementation can form a suitable additional therapy. Remember that more is not always better as excessive calcium risk’s suppression of the body’s natural hormonal mechanisms. The inclusion of vitamin D and magnesium are just as important to aid the absorption of calcium.
Posted on: Tue, 13 Jan 2015 09:37:17 +0000
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