Chapter 5
Drying Off and Milk Fever Prevention Diet
The end of lactation calls for a succession of dietary changes intended, first, to discourage milk production, then to build up the cow’s nutritional reserves and support the unborn calf, and finally to protect her against the metabolic imbalance that can lead to the condition known as milk fever.
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Drying Off
Before your cow has a new calf, she should be dried off, which means helping her to stop producing milk. Once you are absolutely certain she has been bred (it’s best to get a vet check), mark her due date on your calendar. She should have a dry period of fifty to sixty-nine days. Count back from her due date and mark the date to begin drying off. If when this date arrives she is giving twenty pounds or less (two and a half gallons) of milk each day, simply stop milking. Cut out her grain (this does not affect rumination) and feed her your second-rate hay. Don’t bring her into her milking area or do any of the things that encourage letdown. Check her udder twice a day. Allow it to get full but not hot. If she seems uncomfortable, bring her in and milk her out completely; give the milk to animals, as it won’t taste right. Continue low feeding and checking her udder. When her udder fills again it will likely not get hard. Unless it worries you (because it has a hard spot, for example), leave it alone. Within a week to ten days it should stay flabby. Don’t test it by taking a few squirts, as the teats will have formed an antibacterial plug that should be left in place.
If she is giving more than twenty pounds of milk a day when you are ready to dry her off, put her on low feed and milk her once a day for three days, then skip a day, milk once more, and start the above schedule. Use your own best judgment and adjust these suggestions to circumstances. When you milk her out it is best done completely; leaving her milked halfway is an invitation to mastitis.
Following the last milking, most authorities recommend a dry cow treatment, which involves an antibiotic inserted into the teat canal and an antiseptic teat dip, which leaves a protective coating. These are preventive measures against mastitis. Mastitis can sneak up on a cow during the dry period or prior to calving when the udder gets full and drips. These measures are routine in dairies. I am unable to judge their importance for a family cow. I have never done it. The one time I encountered fresh cow mastitis, a lapse in management (mine) was the cause; I had delayed milking her out. But if mastitis has been a persistent problem or if your cow’s surroundings are very muddy, a dry cow treatment may be advisable.
Instruct everyone not to attempt random squirts of milk at any time up to actual calving. You absolutely do not want the teat end opened and the waxy plug lost.
Warning repeated: Before drying off your cow, be sure to establish with absolute certainly that she is in calf. You may need a vet check or wish to do BioTracking, a pregnancy blood test for ruminants (see the resources). If you dry off an open cow—and it does happen—it may then be well over a year until you have milk again. A long vacation from milking while not in calf doesn’t do a cow any favors health-wise. She is almost certain to get too fat, and hormonal disturbances may also occur.
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Evaluate Her Condition
It is especially important to evaluate your cow’s condition at the beginning of drying off. Weight can be estimated by measuring with an inexpensive dairy weight tape available from feed and agricultural supply stores. To use the tape, measure her girth just behind her front legs. The tape will be marked with weights matched to girth for the three major dairy breeds, Holstein, Guernsey, and Jersey.
A more accurate estimate takes account of body length. Take the heart girth measurement (in inches) and the body length measurement (point of shoulder to pin), then perform this calculation: heart girth × heart girth × body length, then divide by three hundred. The result is a good estimate of your cow’s weight.
Expect to be able to discern the first three ribs of a dairy cow. A fatter cow is storing extra abdominal fat, which may interfere with calving. A thinner cow will struggle to support herself, her calf, and her milk production, and something will be compromised.
As soon as you are satisfied that your cow is dried off, put her back on good hay. If you decide to use anionic salts (see here), continue regular grain feeding. Or if she has been on pasture only, merge in any high-calorie grain or premixed ration you wish. If at any time she is too fat, slow down on everything but hay or grazing. She will still need the volume and quality of hay or grazing, but the extra carbohydrates of grain can be limited. You can stop grain altogether, but you will then have to find some other way to feed the anionic salts. As we’ll shortly discuss, milk fever prevention diets call for a tricky balance, which explains why much continues to be written on the subject. And as an aside, note that milk fever is seen less often in the grass-fed herd.
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Importance of the Dry Period
Except for the week or so when you are drying off your cow, her feed may need to be changed but not reduced. During her dry period a cow is making a new calf and storing nutrients for her next lactation. If her previous lactation diet included a significant amount of grain, she will profit from a chance to rest and restore her rumen. A cow’s stomach ferments feeds other than hay at a lower pH. This more acidic environment induced by grain can erode her rumen. A rest on a diet of mostly hay and grazing will give her rumen a chance to rebuild its surface and its muscle tone, which inevitably declines when long fiber has been restricted. However, avoid abrupt changes of diet. (For a discussion of rumen function, see chapter 9, “Feeding Your Cow.”)
If your cow is very thin, this advice does not apply. The need to gain weight during the dry period overrides other considerations, at least temporarily.
Inattention to diet during the dry period not only prejudices a cow’s ability to milk well next time and have a strong calf but will set her up for milk fever and ketosis. These are metabolic disorders, or hormonal derangements if you will.
Milk Fever and Ketosis
Milk fever has plagued dairy cattle from antiquity. It also strikes goats and is not unknown in dogs, cats, and other species. It is a form of paralysis resulting from failure to mobilize minerals, especially calcium, fast enough to meet the sudden demands of milk production. Calcium levels in blood are critical and must be maintained within a small margin of error, much as is the case with oxygen. Calcium is essential to muscle function. If calcium levels suddenly drop due to the imperious demands of the udder at parturition, muscles cease to function and paralysis results. In general our bodies, and those of cows, are so good at maintaining correct blood calcium levels that we don’t have to worry about it. But at calving time the metabolic balance may be overwhelmed, especially for heavy-producing cows.
Milk fever affects about 8 percent of cows at calving, with Jerseys being more susceptible due to their greater ratio of milk production to body weight. Before studies clarified the cause during the 1950s, some bizarre folk remedies were applied. These included cutting off the cow’s tail, insufflating the udder with air or water, and worse. It is now understood that dietary management during the dry period is the key to preventing milk fever. Symptoms and emergency treatment are discussed in chapter 15, “Treating Milk Fever.” Be sure to read this section, and be prepared to call the vet or treat the problem yourself should milk fever occur. It is an emergency and without treatment is fatal more often than not.
Ketosis is a metabolic disorder that may affect a cow after she recovers from milk fever, though it may also come on without this preamble. It results from rapid mobilization of fat stores in the cow’s attempt to meet the energy demands of lactation, which causes an abnormal buildup of ketones in the bloodstream. Ketosis can become chronic or even fatal. Loss of appetite, especially for grain, is the chief symptom, along with a sharp reduction in milk production. The other name for ketosis is acetonemia. The cow’s breath smells of acetone, like what is found in nail polish remover. Some people describe the smell as more like overripe pears. It isn’t an emergency like milk fever but requires treatment.
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The Dry Cow Diet
For many years a low-calcium diet was standard practice for a dry cow. The intent is to keep the hormones that mobilize calcium on standby alert and ready for their huge job when the cow freshens. A more recent type of dietary management requires restricting potassium so that the blood remains slightly acidic. Phosphorus intake must also be controlled because it not only favors alkaline conditions but above a certain level will suppress the parathyroid hormone, which must be active in order to synthesize vitamin D, which is key to calcium utilization. Nowadays one common approach to feeding the dry cow calls for using anionic salts to support calcium mobilization by maintaining an acidic balance in the blood.
The Low-Calcium Diet
Low-calcium feeds include corn in the ear, corn grain, corn silage, barley, and barley straw. Locating these feeds and restocking your cow’s pantry with a special diet can be a deterrent to their use. And changing feeds is a challenge for dairies of any size. A simpler and arguably more effective approach employing anionic salts is now generally favored. It does not require restriction of calcium.
All soluble minerals have an electrical charge, either positive (cation) or negative (anion). Potassium, sodium, calcium, and magnesium hold a positive charge and are cations. Chloride, sulfur, and phosphorus hold a negative charge and are anions.
The balance of minerals in a feed determines its dietary cation/anion difference (DCAD). Those feeds with a higher ratio of cations result in alkaline conditions in the bloodstream (higher pH). Those with a higher ratio of anions result in acidic blood (lower pH). Alkaline rations have been found to predispose to milk fever, whereas acidic rations help prevent it, in part by aiding the release of calcium from bones and the gut. The problem here becomes one of increasing acidic feeds to aid mobilization of calcium while limiting high-potassium feeds because potassium is a cation. Since this is just as difficult as putting together a low-calcium diet, formulations of anionic salts are available to add to feed to boost acidity.
Some feed stores sell anionic salt mixtures with suggested rates of feeding. These can be mixed with anything palatable. If you use them, experiment and find out what works. Start adding the salts ten days to two weeks before calving, not sooner.
The addition of anionic salts permits more latitude in feed selection because the salts promote acidic conditions in the bloodstream irrespective of diet. The point is not so much to enable calcium uptake, which it is now believed will take care of itself in even mildly anionic conditions, as to overcome the cation influence of potassium. If it is possible to feed your cow corn silage, a low-potassium feed, a lesser amount of anionic salts will be necessary in order to reach the desired pH levels in the bloodstream.
Anionic salt mixtures are not palatable but apparently taste even worse when premixed with grain and allowed to stand. The salts are better accepted when freshly mixed into feed. Those that I have purchased work out to ¼ cup of the actual salts on feed twice a day. Premixed and pelleted salts are available.
Do not overdo it with anionic salts and push the DCAD ratio too far or kidney damage can result. Graduated paper test strips are available to check the acidity of a cow’s urine. Test about four hours after she eats her dose. She will oblige with a urine sample if you stroke next to the vulva. Normal urine pH is about 8.0. With successful DCAD treatment, Jersey urine will be 5.5 to 6.0 and that of larger breeds 6.2 to 6.8.
A convenient treatment option that has received favorable mention from the scientists at Hoard’s Dairyman magazine is a pelleted anionic preparation called Animate (see the resources at the end of this book). It is palatable and calls for no accompanying feed changes. I have not yet tried it but plan to when next my cow calves.
Feeding Calcium
Dietary calcium must not be restricted too radically. Suitable feeds with moderate calcium content include rye, oat, and timothy hay or grass, which is convenient information for graziers. Alfalfa at all stages is one of the feeds highest in calcium and probably best not fed until after calving. Needless to say, protein cannot be ignored. For those who would like detailed analyses and formulae, a good source is Caring for Transition Cows by Mike Hutjens and Earl Aalseth, available from Hoard’s Dairyman (see the bibliography).
Calcium gel (150 grams) should be given on the day before and the day after calving and high-calcium feed provided from this day forward.
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The Vitamin D Option
Another measure now recognized as effective in preventing milk fever is the massive vitamin D shot. This is a stand-alone treatment not combined with diet changes or anionic salts. A single injection of ten million IU of crystalline vitamin D (IV or SC) given eight days before calving is likely to be effective. It can be repeated if a cow doesn’t calve on time.
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Other Considerations
If there were simple final answers, less discussion would be needed and research could cease. In general, if left to chance, a first-calf heifer is least likely to develop symptoms. Any cow that was previously stricken has a greatly elevated chance of a repeat of both milk fever and ketosis. (Of course, if your cow was previously owned the former owners will probably play down any such problems.)
A cow on good pasture that includes a variety of grass species and forbs (broad-leafed “weeds”) may balance her own nutrients in such a way as to preserve herself from milk fever. In these circumstances the rumen flora become more efficient at extracting nutrients. Evidence for enhanced efficiency is found in the decrease in methane production by cows on good mixed pasture. Methane (CH4 or natural gas) is essentially the same high-energy gas that we use in cooking. Methane that the cow burps up (eructation) is energy lost to the cow for her own purposes. Nonetheless, eructation is normal, and some will always occur in all ruminants.
An additional factor undoubtedly working to prevent milk fever in cows on pasture is vitamin D. Calcium is not absorbed or processed without vitamin D. A cow can make her own through her skin if she is outdoors in the sunshine. Vitamin D is also formed on sun-cured hay. Obviously these factors vary according to circumstances. Calcium uptake and mobilization are also dependent upon function of the thyroid and parathyroid glands, as noted, and these in turn must be supplied with adequate iodine. Kelp is a reliable source of iodine. I make a practice of adding a handful every day to my cow’s grain. It can also be offered free choice from a fixed box in your cow’s loafing area.
Milk fever is unpredictable. One year my cow Helen nearly died of it on Easter. She was saved only because my vet came straight to the farm despite the holiday and administered calcium IV. The following year I went out on a sunny early morning in early June and found a big healthy heifer standing at Helen’s side among the buttercups, and she wasn’t sick a day. Who knows why? Perhaps because it was two months later in the spring and the combination of sun and good grazing made the difference.
Some dairymen say they never see milk fever. They usually have totally grass-fed herds with lower production, with many years of fine-tuning the management. I applaud their success. For family cow owners, often with a new cow and unimproved pasture, perhaps having to settle for whatever hay is available, I suggest that it is best not to be overconfident where milk fever is concerned. Institute a feeding plan, make emergency preparations, and don’t feel like a failure if milk fever occurs despite your best efforts. Given treatment, most cows make the miracle recovery described in the section on treatment (see here).
My grandmother used to quote old-timers as saying milk fever hit “always my best cow.” We are fortunate now to have informed approaches to this formerly often fatal disorder, which does indeed disproportionately affect the best producer. The last word has not yet been written on milk fever, and research continues. I can think of few more useful applications of tax dollars than the research on milk fever, much of it done by our land-grant colleges.