Richard Holliday DVM, Dr. Richard Holliday Holistic Veterinary Practice
One of your best cows calved a couple of days ago and now she's down, lying on her sternum, head lying along her side with a kink in her neck. Her eyes are glazed over, pupils dilated and she can't get up. If observed earlier, she may have been off feed and exhibiting muscle tremors and unsteady gait. This is an easy diagnosis for most dairy farmers to make… milk fever, parturient paresis (calving paralysis), or hypocalcemia (hypo- or low) calcemia (calcium). Whatever term you use, if untreated, this condition can result in death in a few hours.
I believe that almost all dairy cows suffer from some degree of low blood calcium at calving time. Most are subclinical (not showing symptoms) in nature and do not show the classical signs described above. Calcium is necessary for all muscle function. Even moderately low blood calcium can set cows up for calving problems, retained placentas, uterine prolapse (cast withers), and reduced reproductive performance, as well as digestive and metabolic disorders such as displaced abomasa and ketosis. Low blood calcium affects the immune response and may be a factor in mastitis, metritis, and other infections.
Incidence of this condition may vary from 3% to as high as 30% in some herds. Estimated profit loss from lost production, death loss, and veterinary costs associated with clinical cases of milk fever range as high as $225 for each episode. The losses from subclinical milk fever may be substantial but are more difficult to measure. Some old-timers say that if a cow "yawns" when you pinch her withers, it indicates low blood calcium. Hmmm…?
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The standard treatment for this emergency is calcium borogluconate. It may be administered intravenously (in the vein), subcutaneously (under the skin), or intraperitoneally. If the animal does not respond, a solution containing magnesium and phosphorus along with calcium may be necessary. In early cases, or as a preventative in high risk cows, liquid calcium or calcium chloride gels given orally may be beneficial. (Always check with your certifier.)
Different authorities cite different causes for milk fever. In the past, excess calcium was considered the culprit and limiting calcium levels in the dry cow ration was the standard recommendation. Some blame the high potassium in legumes and some grasses caused by inappropriate fertilizer practices. Low calcium, high calcium, high potassium, low phosphorus, low or high Vitamin D, low magnesium, reduced mineral adsorption if rumen pH is over 6.8–7.2 , water pH over 8.5—all have been implicated at one time or another. I guess you can just take your pick. In truth, all these factors play a part and the common denominator is a "mineral imbalance." While mineral balance is important to animal health at any time, it is especially critical for the dairy cow at calving time.
During the dry cow period, and especially in the last three weeks before calving, if the Ca/P ratio is 1:1 or even higher in Ca, there is a relative deficiency of phosphorus. To compensate for this, the body sets up to reject calcium and to absorb phosphorus. After calving, it takes 72 hours for the metabolism to readjust to absorb adequate amounts of calcium.
As the cow approaches calving, large amounts of calcium are drained from the blood reserve to form colostrum (high in calcium) and to begin milk production. At calving, the sudden increased demand for calcium by the mammary gland uses up blood calcium faster than it can be replenished from other body reserves; this sets the stage for hypocalcemia.
The key to prevention of milk fever is management of the close-up dry cow.
Milk fever is not a disease but only the clinical expression of a mineral imbalance at a period of physiological stress. While the final expression of milk fever is caused by low blood calcium, a predisposing cause can be either low phosphorus in the ration or sources of phosphorus that are relatively unavailable. What an animal actually absorbs into its system is the only thing that counts.
Remember: it's all about internal mineral balance!
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