Prepare a strategy to tackle milk fever in the weeks prior to the cows calving
One of my favourite books is Modern Dairy Farming that originally belonged to my great, great grandfather and was printed in 1911. It highlights milk fever as the most formidable of all conditions that attack dairy stock.
It also suggests methods of prevention which include a pound of Epsom salts given once a week, two weeks before calving, and keeping a cow with a tendency to the disease in lower condition prior to calving.
Treatment involved atmospheric air being injected into the udder -- I have visions of a farmer using some form of bicycle pump! Thankfully, things have moved on over the past century and milk fever as a metabolic disorder is now understood. With many dry cows now coming into their final month of pregnancy, it may be timely to prepare ourselves for the management of milk fever but, more importantly, its prevention.
Milk fever occurs when blood calcium (Ca) concentration becomes too low to support the functions of the nerve cells and the contractions of muscle tissue. Adequate status of calcium in the blood is in the range of 2-3mmol/l. This is maintained by contributions from the intestines (dietary calcium absorbed) and bones (where 99pc body calcium is stored) against the losses of calcium in urine, faeces and milk. These losses significantly increase after calving. For example, a 500kg cow can put 30g calcium into 25kg of milk every day.
Most cows manage the transition into lactation by mobilising sufficient skeletal calcium to meet the increase in demand, as a newly calved cow cannot absorb enough dietary calcium to compensate for high milk production.
However, cows with an inappropriate diet, hormonal imbalance or poor condition may lose more calcium than they can replace. Subclinical hypocalcaemia increases the risk of mastitis, ketosis, retained placenta and uterine prolapses. All these conditions are seen at calcium blood concentrations of 1.4-2mmol/l.
Clinical signs of milk fever are usually observed 48 hours after calving, with cows exhibiting hypersensitivity, excitability, muscular twitching, weakness and rumen stagnation. These signs are associated with blood concentration of less than 1mmol/l. A cow with milk fever should be propped up, kept warm and injected subcutaneously or intravenously with 8-14g of calcium as calcium borogluconate. Call a vet if you are unsure of this procedure or if the cow fails to improve within a few hours.