Method for Preventing Parturient Paresis in Dairy Cattle

The invention described herein was made in the course of work under a grant or award from the Department of Health and Human Services.

This invention relates to a method for prophylactically treating dairy cattle for parturient paresis using a mixture of 25-hydroxycholecalciferol and 1.alpha.-hydroxycholecalciferol.

Parturient paresis (milk fever) is a metabolic disease of dairy cows wherein severe hypocalcemia, resulting from parturition and the initial formation of milk, leads to a disorder characterized by the cow's inability to command use of their muscles and a placid, immobile appearance.

The disease is manifested by a decrease in plasma calcium, usually between six to thirty hours after parturition, to a value so low as to induce tetany with resultant immobilization of the cow. There is also generally an accompanying decrease in the blood phosphate level. As an example, the plasma calcium level in a cow prior to calving is about 10 mg./100 ml. (or 10 mg. percent). Following parturition this level will normally dip to about 7-8 mg. percent but will then rise in a reasonable time to the more normal 10 mg. percent range. In a cow afflicted with milk fever, however, after parturition the plasma calcium may dip more drastically, such as into the 5 mg. percent range, and it is recognized that at such plasma calcium levels the cow can go into tetany and a condition known as Downer's Syndrome.

Such low plasma calcium levels are not necessary in all cases to induce milk fever disease and the disease is experienced at substantially higher calcium levels depending upon the individual animal involved. If treatment for such condition is not however, immediate and successful there is a real danger that the cow may die or be afflicted with a lasting paralysis, or at the very least that its milk production will be substantially decreased. (See "Milk Fever Causes, Methods of Treatment and Prevention," S. H. Morrison, Vol. 1, No. 2, a publication of Borden Chemical Company and J. M. Payne, Brit. Vet. Assn. "Recent Advances in Our Knowledge of Milk Fever," presented at 87th Annual Congress of the Association, Sept. 6, 1964).

The incidence of milk fever disease has been estimated to be in the range from about 3.5-5% of the world's dairy cows. In individual herds, however, the incidence may be as high as 60-70%. It appears that the incidence of the disease is highest among high milk producing cows during the third and later lactation periods although at times it has been observed in the second lactation period. In any event, once a cow has had milk fever there is an 80-90% probability that she will again be so afflicted after her next parturition. As a consequence, there has been much interest in developing procedures for preventing this disorder.

For example, feeding of a low calcium diet or feeding a high phosphate in a grain ration, which is tantamount to a low calcium diet, has been suggested as a preventative for the disease. Since, however, it is necessary to feed cattle a high calcium diet during their non-lactating periods to replenish the calcium stores depleted by previous milking such treatment is not a very practical solution for milk fever problem. Other methods of treatment suggested include air inflation of the udder--a treatment not used because of the danger of mastitis and other infection--and acidification of silage which alleviated the disease. This latter method is impractical because of problems engendered by the acid intake. Hibbs and co-workers (Hibbs, J. W. and Conrad, H. R., J. Dairy Science 49, 243, 1966) were the first to use very large doses of vitamin D to reduce the incidence of parturient paresis and currently the most widely used treatment for milk fever is the administration of vitamin D in massive dosage. For example, in one method the cow is fed 20 million units per day of vitamin D for three to seven days before calving while in another method 10 million units of vitamin D is injected intramuscularly before calving. Although these methods are of value they are associated with potentially high risk and other disadvantages. With administration of such large dosages of vitamin D there is a real danger of vitamin D toxicity and, as a consequence, death of the cow or damage through abnormal calcification of the soft tissues such as the kidney, aorta, etc. Even if the animal survives without damage the milk produced may not be fit for human or calf consumption for some time because of the high content of vitamin D in the milk. Furthermore, the unpredictability of the calving date places an added difficulty on the farmer as to when the vitamin D dosage should be given. If the vitamin D dosage is given too far in advance the incidence of milk fever disease is actually increased by the treatment.

Other methods which have been suggested for combatting milk fever disease utilize the administration of 25-hydroxycholecalciferol (U.S. Pat. No. 3,646,203, issued Feb. 29, 1972), 1.alpha.-hydroxycholecalciferol (U.S. Pat. No. 3,879,548), and 1,25-dihydroxycholecalciferol (U.S. Pat. No. 4,110,446).

That 25-hydroxyvitamin D.sub.3 (25-OH-D.sub.3) can markedly reduce the incidence of parturient paresis will be evident from the following table although it should also be observed that 25-OH-D.sub.3 does not eliminate or totally prevent the disorder.

It is evident from the above data that the preferred dose would be 4 mg. of 25-OH-D.sub.3 to achieve the lowest incidence of the disease.

In like fashion 1.alpha.-hydroxycholecalciferol (1.alpha.-OH-D.sub.3) is also capable of reducing the incidence of parturient paresis as will be evident from the following table.

It should be observed from the above data that, as with the use of 25-OH-D.sub.3, treatment with 1.alpha.-OH-D.sub.3, although substantially decreasing the incidence of the disease does not totally prevent it.

It has now been found, however, that if 25-OH-D.sub.3 and 1.alpha.-OH-D.sub.3 are used in combination in treating dairy cows with a view toward preventing parturient paresis, the combination of compounds appears to afford complete protection against the disease as will be apparent from the following Example which is intended to be illustrative only. Since it is the consensus in the industry that high-producing cows, generally beginning with the third lactation, are most susceptible to parturient paresis, only such animals were used for evaluation.

Third lactation or better Holstein cows (a high producing strain) were fed a diet in the dry period of high calcium and low phosphorus. This diet was also maintained throughout the parturition portion of the experiment. One-half of the cows randomly selected remained untreated whereas the remainder received 0.5 mg. of 1.alpha.-OH-D.sub.3 and 4 mg. of 25-OH-D.sub.3 dissolved in 5 ml of corn oil intramuscularly at least 7 days before the predicted calving date. The cows were reinjected with the same preparation every seventh day for a period of 3 weeks. Upon successful calving, treatment was discontinued. Results are shown in Table 3 below.

It is obvious from the foregoing data that dairy cows treated with the combination of 25-OH-D.sub.3 and 1.alpha.-OH-D.sub.3 were most unexpectedly, afforded complete protection from parturient paresis. This strongly suggests that the combination of any 25-hydroxylated form of vitamin D with any 1.alpha.-hydroxylated form of that vitamin would provide an unexpectedly effective means for preventing parturient paresis.

Effective and practical administration of the combination of 25-OH-D.sub.3 and 1.alpha.-OH-D.sub.3, or, more broadly, the combination of a 25-hydroxylated form of vitamin D with a 1.alpha.-hydroxylated form of vitamin D can be accomplished by injection of the material intravenously, intramuscularly or subcutaneously while dissolved in a suitable vehicle such as an innocuous oil or propylene glycol. Alternatively, the combination of 25-OH-D.sub.3 and 1.alpha.-OH-D.sub.3 can be compounded with other materials to form a bolus, or can be encapsulated, so that oral administration can be the preferred route of administration. Or, if desired the materials can be applied topically in a suitable vehicle and perhaps in the presence of an agent e.g. dimethyl-sulfoxide, which enhances penetration of the skin.

Although the dosages in the foregoing Example are effective in providing total protection against parturient paresis, the particular dosages, or ratios of 25-OH-D.sub.3 to 1.alpha.-OH-D.sub.3 specified are not necessarily critical, other dosages, as well as ratios, of the combination of these compounds being equally effective. Dosage can, of course, vary with the size of the cow to which it is being administered. In any event, sufficient of the combination in effective ratios of one to the other must be given to accomplish the desired end, namely, complete protection against the incidence of parturient paresis. The use of more than sufficient material to accomplish such end should be avoided as an economically unsound practice.