SOILS, CROPS, MINERALS, ANIMALS

C. F. Huffman, N. R. Ellis, L. A. Moore

OF ALL the nutrients that livestock get from forages, the mineral elements depend most directly on the soil and climate.

The energy-yielding nutrients are built up by the aid of carbon dioxide breathed in by the plant leaf structure. Even some of the protein originates from synthesis by bacteria growing in nodules on the roots of legumes, which gather nitrogen (a constituent of protein and of living matter) from the air.

Thus we see why animal life is so dependent on soil and climate when it comes to the mineral elements. The constant leaching by rains and the removal of the elements by plants, by grazing animals, and by harvesting impoverish the soil of these needed minerals. Another aspect and example of this close relationship of soils, crops, minerals, and animals is that certain toxic minerals present in the soil in excessive amounts are taken up by plants and in turn exert poisoning effects on the animals that eat the plants. This point was mentioned in the preceding discussion and is amplified here; also mentioned earlier were the mineral elements of greatest importance in livestock feeding, among them phosphorus.

Cows particularly need phosphorus, which is a part of the protoplasm of all living cells and occurs in rather large amounts in nervous tissue, bones, and milk. When they do not get the needed element, their appetite lags and milk production drops sharply. In many sections of the United States, pastures, ranges, and hay crops are low in phosphorus because the soil has a low phosphorus content, or it lacks available phosphorus, or climate (like too little rainfall) is unfavorable. It is an example of regional deficiency of certain minerals too acute to support efficient production in farm animals that consume much roughage.

Phosphorus deficiency in cattle may be associated with a depraved appetite (pica), a craving for things not ordinarily classed as food, such as bones, wood, hair, and putrid flesh. Depraved appetite is of little diagnostic value because it is also manifested in cobalt deficiency and many known and unknown conditions. The outstanding symptom of too little phosphorus is a lack of appetite for food: The animal starves amid plenty. Milk production, in the case of milking cows, and body weight drop markedly. Eventually animals become emaciated.

A long-continued phosphorus deficiency may result in erosion of the cartilage at the ends of the bones and the animals may walk with difficulty. When the intake of calcium and phosphorus is low, their continued withdrawal weakens bones and makes them easily fractured. When the calcium intake is more than adequate and the phosphorus content of the ration is low, the breaking strength of the long bones remains normal.

Since depraved appetite is not a reliable index of phosphorus deficiency and a lack of appetite may be due to many other conditions, the positive diagnosis of phosphorus deficiency is difficult. Chemical analysis of the blood and the feed may give the answer, but such a service is not often available.

The best way to determine phosphorus deficiency on the farm is to feed a phosphorus supplement. If the animals improve in appetite then lack of phosphorus can be considered the cause of the trouble. Calves under a year of age seldom show phosphorus deficiency. If the cows in a herd show a lack of appetite while the heifers under 1 year of age have normal appetites, then a phosphorus deficiency among the cows is indicated.

The lack has not been observed among dairy cattle that get liberal amounts of roughage when the herbage contains 0.18 percent or more of phosphorus on the air-dry basis even when corn was the only supplement. Growing beef cattle appear to grow normally when the phosphorus content of the roughage tops 0.13 percent.

For the forage crops, enough phosphate fertilizer should be used to give maximum crop yields and to increase the phosphorus content if it is low. Under some conditions plants take up too little phosphorus to supply the needs of the animals. The positive method of assuring plenty of phosphorus for livestock is to allow them free access to a mixture of one-third special steamed bonemeal and two-thirds salt. Defluorinated phosphate may be used in place of bonemeal. Phosphorus can also be supplied by reasonable amounts of wheat bran, wheat middlings, or cottonseed meal.

Cobalt

Another example of regionalized deficiency is cobalt, a silvery metal of the iron-cobalt-nickel triad. Ruminants, especially cattle, have failed to thrive in some districts and often have died although they were fed seemingly good rations. This "wasting disease" has occurred in the United States for more than a century; in 1935 investigations of the condition among sheep and cattle in New Zealand and Australia resulted in the discovery of the role of cobalt in nutrition. Since then the use of a tiny amount of cobalt as a supplement to the ration of affected cows and sheep has produced dramatic recoveries. It is hard to understand how so little can do so much and so quickly. Many farms where cattle and sheep farming had never been productive are profitable livestock farms today.

As with phosphorus, the commonest symptom of too little cobalt is a lack of appetite but many other abnormalities put livestock off their feed and the diagnosis of the disorder often involves chemical and biological tests plus feeding trials to establish fully the part that a specific element plays.

Cobalt deficiency, limited to ruminants, has been called a variety of names "salt sick" in Florida, "neck ail" in Massachusetts, "Grand Traverse" or "Lake Shore Disease" in Michigan, "Burton-ail" in New Hampshire, and many other names in different parts of the world.

Sheep are more susceptible to it than cattle; young animals suffer more than mature animals of the same species. Apparently cobalt works through the rumen, because only ruminants appear to need the element and the injection of cobalt into the blood stream does not give so good results as feeding by mouth.

The symptoms of cobalt deficiency in sheep and cattle are a loss of appetite and emaciation; finally death from starvation despite plenty of other good nutrients. In sheep the wool is weak and easily broken. Cattle, especially calves, frequently show depraved appetite and many chew wood, hair, bones, tin cans, and similar objects.

Anemia is usually present in sheep and cattle in cases of long standing, but is of little help in diagnosing the trouble. In cattle the symptoms are the same as those of phosphorus deficiency. The difference can be determined from blood-phosphorus analysis, but usually this is out of the question. Heifers from 6 months to 1 year old are more likely to suffer from a lack of cobalt than mature cows. Consequently, if some of the heifers show a lack of appetite for feed and the milking cows are eating satisfactorily, then cobalt deficiency is indicated. The best methods of determining cobalt deficiency is to feed cobalt. If the appetite of the animals returns in 3 to 7 days, the ration is deficient in cobalt. If appetite has not improved within 10 days, the trouble is not cobalt, but something else.

Extensive investigations in Australia showed that the cobalt content of pasture generally varies with the amount in the soil. The cobalt content of pastures apparently tends to increase in late fall and early winter when growth is retarded, and to go down in the spring and summer when growth is at its maximum. Several studies show the effect of adding cobalt compounds to the land on the cobalt content of the herbage. As little as 4 ounces of cobalt chloride to the acre resulted in healthy pastures for a period of 2 years. Usually, however, 2 pounds of cobalt sulfate are applied per acre. Apparently plants take up more cobalt when cobaltized superphosphate is used.

The most satisfactory method of administering cobalt to cattle and sheep is to mix 1/2 to 1 ounce of either cobalt chloride or cobalt sulfate with 100 pounds of salt. Cobalt carbonate is sometimes used, but the amounts added to salt should be 1/4 to 1/2 ounce per 100 pounds. When young milk-fed calves develop cobalt deficiency, an ounce of cobalt sulfate or cobalt chloride dissolved in a gallon of water and fed at the rate of a teaspoonful of the solution per calf per day is effective.

Calcium and Magnesium

Large roughage-consuming animals seldom suffer from a lack of calcium in the ration. The calcium content of forage plants depends largely on the species. Legumes are excellent sources of the element; nonlegumes, however, may not contain enough calcium for heavy-milking cows. Both calcium and phosphorus decline as the plant matures. During drought, the calcium increases and the phosphorus decreases. There are not very many areas in the United States where cattle, especially milking cows, and also sheep and horses may need a calcium supplement. Generally the lack of legumes and exclusive use of mature grasses, either as grazing or a hay crop, is an important factor. The lack of sufficient calcium results in withdrawal of calcium from the bones and its secretion in the milk of milking cows.

In areas where a calcium supplement may be needed, free access to a Mixture of one-third calcium carbonate and two-thirds salt is a good way to supplement the ration. The calcium carbonate may be ground limestone, high-grade marl, or ground oyster shell. Bonemeal or defluorinated phosphate, which are also excellent sources of phosphorus, may be used in place of calcium carbonate. The most practical answer in many sections is to introduce a legume into the pasture and hay-crop mixtures.

Too little magnesium is comparatively rare among farm animals on pasture or when liberal amounts of rough-ages are fed, even though variations in magnesium content (that are due to species of plant and soil characteristics) are found among forage crops. But there occurs a condition sometimes referred to as "grass tetany" that does not appear to be associated with low magnesium content of the ration, although the addition of magnesium supplements cures it. In this condition there is a disturbed magnesium metabolism in which the blood plasma magnesium drops, followed by various degrees of excitability. In mild cases, the eyelids, ears, or various muscles may twitch. In the extreme form the animal goes into a violent convulsion and dies. The blood magnesium shows a seasonal drop, which usually hits bottom during March, April, and May.

When the symptoms of low blood magnesium are first noticed, it is necessary to start feeding magnesium compounds immediately. In the case of sheep and calves, one ounce of magnesium sulfate (epsom salts) should be given each day. Heifers and cows should receive 2 and 4 ounces a day, respectively. Treatment with magnesium sulfate should be discontinued after a week. Magnesium carbonate in the form of a high-grade, finely ground dolomite may be used in place of magnesium sulfate in one-half the amounts.