Milk fever in cows, also known as hypocalcaemia, is a disorder seen mainly in dairy cows just after calving (or more rarely, just before calving) and is a condition caused by a temporary deficiency of calcium in the bloodstream. It may lead to dystocia, stillborn calves and even the death of the cow. The condition must be considered one that needs immediate attention. Between 3 and 5% of dairy cows that are close to calving, or lactating cows shortly after calving, may suffer from the condition. However, it is preventable by adapting the diet to ensure optimal calcium levels in the bloodstream.
The majority of milk-fever cases in cows occur within 24 hours of calving because the high level of colostrum and milk production during this period requires that a lot of calcium is extracted from the blood. If the animal is unable to replace the calcium in the blood fast enough from calcium reserves in the bones, it suffers from calcium deficiency in the blood. Animals at risk of milk fever include: old cows unable to absorb calcium effectively, cows with a diet too high in calcium during pregnancy (causing the body to stop mobilising calcium from bones to correct calcium levels in bloodstream), animals on diets that are too low in calcium, animals suffering from vitamin D deficiency (although this is rare in SA due to a lot of sunshine), and animals with relatively alkaline digestive systems (diet-induced e.g. too much potassium) which creates a scenario not conducive to optimum calcium absorption.
Milk fever in cows can be detected by looking for the following signs, especially if these signs occur shortly after calving:
Administer an intravenous infusion of calcium and minerals as soon as possible. The solution must be at body temperature during the winter or adverse weather. It is advisable to have veterinarian perform the procedure, because administering calcium too fast or too much of it, may lead to heart arrhythmias which may be potentially lethal. If no veterinarian is available, administer the bottle of calcium at various sites under the skin - preferably not more than 50 ml in one spot. If the cow does not get up, turn the cow over onto her opposite side and keep turning the cow every two hours to prevent muscle damage from lying on one side too long. Leg massaging and removal of the calf may be necessary in acute cases.
Monitor the animals’ feed and test the mineral content of forage. Consult with an expert regarding the right mineral balance in the feed. Where needed, remove free-choice mineral feed and administer mineral supplements. Supplement with vitamin D for better calcium absorption. In high producing herds, some nutritionists will recommend the use of anionic salts in the period just before calving (steaming-up period) in order to acidify the rumen to ensure optimal calcium absorption. Avoid feeds high in calcium (such as lucerne) during the dry period. Administer calcium injections just before and after calving, especially in cows with a history of contracting milk fever.
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