Vitamin Requirements

The vitamin A requirements, expressed in terms of carotene, for swine, beef cattle, and sheep as given in the statements of recommended nutrient allowances by the National Research Council reflect the newer findings. Selected values for milligrams of carotene per animal per day follow: ( Carotene )

Swine: (milligrams) Beef cattle:Sheep:

50-pound pig -2.0 400-pound calf--- 2550-pound lamb-2. 7 200-pound pig-8.0 800-pound yea r-ling - 45 100-pound yearling 5.5 300-pound pregnant gilt-201,000-pound pregnant cow- 55 125-lb. pregnant ewe 6.75 400-pound lactating sow-40 1,000-pound lactating cow- 300125-lb. lactating ewe-8.10 It will be noted that for the growing and fattening animal, the allowances per unit of body weight are highest for beef cattle and lowest for swine, although the differences are small. In terms of practical feeding, when corn is the basic concentrated feed some interesting comparisons can be made between swine and beef cattle. When yellow corn is the only source of carotene (the forerunner of vitamin A), the average pig's requirements are met when the corn constitutes about one-fourth of the ration. In tests at Beltsville, we got full protection against blindness, nervous disorders, retarded growth, and other symptoms of vitamin A deficiency with such a level of yellow corn, which contributed approximately 4 milligrams of carotene per 100 pounds live weight a day, or the amount given in the National Research Council's table for Recommended Nutrient Allowances for Swine. On the other hand, steers on a fattening ration may not get enough carotene from a full feed of yellow corn of average grade to meet their needs. Fattening steer calves given a full ration containing 11 to 14 pounds of yellow corn, along with oat straw, developed symptoms characteristic of vitamin A deficiency, including stiffness, convulsions, blindness, and edematous swellings.

New information on the factors of the vitamin B complex is confined for the most part to the needs of pigs, ruminants having been shown to support synthesis of thiamine, riboflavin, nicotinic acid, and pantothenic acid. At Beltsville, we found that a pig's requirement for thiamine is related to its intake of carbohydrate and protein. In other words, the greater the proportion of fat in the diet the less the need for thiamine. We suggest a minimum of 0.61 to 0.64 milligrams per pound of carbohydrates and proteins consumed as necessary for normal growth, without much margin for building up the thiamine content of the body tissues. The figure, when translated to the average swine ration, is approximately 2.1 milligrams of thiamine per 100 pounds of live weight. Riboflavin is another of the vitamin B group essential for pigs. Without it, a pig cannot grow normally, and changes occur in its skin, hair, hoofs, and eyes.

We are not sure about the need for nicotinic acid. E. H. Hughes, of California, observed symptoms of poor appetite, vomiting, lessened growth, and unsteadiness in walking among pigs fed a purified diet composed of 81 percent sugar, 15 percent casein, and 4 percent of a salt mixture, supplemented with cod-liver oil, thiamine, riboflavin, pantothenic acid, and pyridoxine, but not with nicotinic acid. The addition of 10 milligrams of the vitamin, however, prevented the symptoms just described. Other investigators compared the growth of pigs fed a diet containing 10 percent of casein with one containing 26.1 percent. In the absence of nicotinic acid supplementation, the pigs on the low protein diet generally showed impaired nutrition, while those on high protein had better appetites and healthier appearance, and gained more nearly like the check group that received nicotinic acid. In work at Beltsville, however, we found that deficiency symptoms, such as impaired appetite, diarrhea, retarded growth, and necrotic lesions of the large intestine, occurred in most young pigs fed a purified diet lacking nicotinic acid and containing 25 percent of protein. Not all these symptoms developed in affected pigs, and the variability in growth was especially striking. Some pigs showed no effects of nicotinic acid deficiency.

The possible relationship of nutritional factors to necrotic enteritis in pigs has been studied for a number of years at the Michigan Agricultural Experiment Station. R. A. Rasmussen and associates have discussed results obtained by feeding cultures of S. choleraesuis to pigs and the subsequent development of necrotic enteritis in relations to dietary treatment. A combination of vitamins, including nicotinic acid, thiamine, riboflavin, pyridoxine, pantothenic acid, para-amino benzoic acid, and choline appeared to give more benefit than nicotinic acid alone. There was evidence, however, that when large doses of the organism culture were fed, complete protection could not be obtained either with vitamin mixtures or fresh liver to prevent death in the initial attack, but in the recovery period these substances were of distinct benefit.

The problem of nicotinic acid has been further complicated by observations of W. A. Krehl and other workers at the Wisconsin Experiment Station that corn in the diet tends to increase the apparent nicotinic acid requirements of the dog. Furthermore, growth retardation in the rat which was induced by a ration low in protein and containing 40 percent of corn grits could be counteracted by the addition of either nicotinic acid or tryptophane. More recently, G. M. Briggs reported that including gelatin in a chick ration also produced a depressing effect but was still capable of correction by the use of tryptophane. Our present evidence suggests that these relations hold true for swine, also.