Pantothenic Acid What it is At the beginning of the century, work began to identify the many, somewhat legendary, food factors. As early as 1901, Wildiers described an essential food factor for the growth of yeasts which he named bios. More than thirty years later, (1933), Williams isolated crystalline bios from yeast and renamed it pantothenic acid. Earlier, in 1931, Ringrose had demonstrated a pellagra-like dermatitis in chicks on a restricted diet but it was not until 1939 that Jukes showed that pantothenic acid was the chick anti-dermatitis factor. A year later the chemical configuration was determined and the first sample of pantothenic acid was prepared in the laboratory. Free pantothenic acid is an unstable hygroscopic oil. It rarely occurs in nature in the free state but is very widely distributed in plants and animals as a component of coenzyme A. It is formed by joining pantoic acid to beta-alanine so, chemically, it is an extended amino acid. It is optically active and only the dextrorotatory isomer has vitamin activity. Both the alcohol (panthenol) and the various salts of d-pantothenic acid are absorbed by animals and are converted to the acid with consequent vitamin activity. It is sometimes referred to as vitamin B5 and, to add to the confusion over identities, it is occasionally called vitamin B3 in American literature. (Vitamin B3 is normally understood to be niacin). What it does Pantothenic acid is an essential part of coenzyme A which is at the centre of energy metabolism. It is also involved with the synthesis and degradation of fatty acids, the citric acid cycle, the formation of antibodies and -- through acetylcholine -- neural function. The most important function of coenzyme A is to act as a carrier for carboxylic acids. Such acids, when bound to coenzyme A, have a high potential for transfer to other groups. The combination with acetate to form active acetate (acetyl CoA) with a higher energy bond is particularly important. This is a precursor of cholesterol and thus also of steroid hormones. If too much is given Although small amounts are stored in the heart, liver and kidneys, excess pantothenic acid is rapidly excreted. There has never been any case of toxicity from megadoses of pantothenic acid reported in animals or man, even from experimental intakes of 1 g per kg liveweight. Biosynthesis The microbial colonies in a horse’s caecum and colon synthesise relatively large amounts of d-pantothenic acid. It is not known how much benefit horses derive from this synthesis but it seems likely that about a quarter of the output is absorbed through the wall of the colon. Grazing horses and those on large amounts of hay or other fibrous food probably benefit to a greater extent from the pantothenic acid synthesis than those on a high proportion of concentrates because the fibre content slows the rate of passage and provides a substrate for microbial activity. It follows that performance horses require proportionally more pantothenic acid than ponies or hacks. Pantothenic acid supplies are highest in yeasts, plant products such as bran and maize gluten feed and animal protein materials containing liver, heart or kidney offals. How it is measured No International Units of the biological activity of pantothenic acid have been defined. Older units are the Yeast Growth Unit, which is equivalent to 0.8mg calcium d-pantothenate, and the Chick Unit which is 14mg calcium d-pantothenate. Assay results and requirements are generally expressed in mg d-pantothenic acid. Calcium d-pantothenate has about 92% and sodium d-pantothenate 93% the vitamin activity of d-pantothenic acid; panthenol is weight-for-weight similar to the acid. Assessment of status No satisfactory method of determining the pantothenic acid status of an animal has been defined. It is possible to measure the pantothenic acid circulating in the blood but the amounts fluctuate widely and rapidly because of the rapid excretion of any excess. Little is stored so liver and kidney contents are of minor significance. An assessment of coenzyme A content would vary between active tissues. Nitrogen retention is maximised in the presence of adequate coenzyme A and thus can be used to determine whether dietary pantothenic acid is sufficient. The estimation of d-pantothenic acid in feeds is undertaken microbiologically using Lactobacillus casei or Lactobacillus arabinosus. The accuracy of these assessments at the levels of pantothenic acid found in feeds is probably of the order of ’20%. Antagonists The only common feed micro-ingredient to antagonise the activities of pantothenic acid is cuprous copper which appears to affect the rate of production or function of coenzyme A. There has been a suggestion that the l-isomer interferes with the metabolic use of d-pantothenic acid but this has not been confirmed by recent studies. Relationships with other ingredients Both folic acid and biotin are required for the proper utilisation of pantothenic acid. Similarly pantothenic acid and biotin are together involved with the metabolism of niacin. It is also interesting to note that supplies of ascorbic acid partly compensate for a deficiency of pantothenic acid. Requirements and allowances Livestock requirements are usually determined in mg of d-pantothenic acid even though this is not the normal supplementation form. Experimental work over the past 40 years has produced a very wide range of requirements dependent on the method of assessment. Optimum nitrogen retention has been used as a criterion of adequacy and this tends to produce higher apparent requirements than the examination of experimental animals for symptoms of deficiency. In the absence of any contrary information, a minimum requirement of 5 mg per kg total dietary dry matter should avoid deficiency disorders. However allowances may need to be four times the minimum requirement to ensure maximum metabolic activities. In addition to a lack of precision in the assay method there is a wide variation in d-pantothenic acid contents of different samples even of the same feed. Average values from tables of reference may provide little accurate information regarding the pantothenic acid contents of a particular sample of feed. The following rates of supplementation assume normal feed specifications without excessive use of fats and fillers. mg / kg   mg / day Adult performance horses in training   4,5   45 Adult performance horses in light work   4,5   27 Ponies, hacks & hunters   4r   12 Mares & stallions   4   16 Young horses 1-2 years   5   15 Foals & young horses less than 1 year 5 5-15 Stability Pantothenic acid is an unstable oil. The usual forms for feed supplementation are calcium d-pantothenate (d-calpan, or cal-d-pan), sodium d-pantothenate and d-panthenol (liquid). Both salts are white hygroscopic powders which are readily soluble in water; panthenol is a colourless viscous oil which may crystallise during storage. In a cool dry place all three products are fairly stable but they are affected by heat, particularly if the atmosphere is humid. Under warm, moist condition they undergo hydrolytic cleavage which is accelerated by acid or alkaline conditions (pH less than 5 or greater than 9). Racemic calcium pantothenate Some of the products available for supplementing feeds consist of racemic calcium pantothenate. These contain approximately equal amounts of l- and d-pantothenate. They are generally sold with a guarantee of 45% d-pantothenate. Some products which are currently available are very hygroscopic. When used, the levels of supplementation should be adjusted to allow for the lower d-pantothenate contents. The recommendation is first multiplied by 1.07 (to equate the calcium d-pantothenate to pantothenic acid) and then by 2.22 to allow for the 45% content. Thus a supplementation requirement of 5mg d-pantothenic acid per kg requires 5 x 1.07 x 2.22g 45% calcium pantothenate per tonne, i.e. 11.9 g/tonne. Livestock conditions suggesting further needs If appetite and general vitality are below expectations dietary inputs of all the B-group vitamins can be increased since symptoms of marginal inadequacy are similar for all of them in the early stages. Dermatitis conditions may be caused by parasites, disease or nutrition and pantothenic acid deficiency is one of several nutritional problems that might be involved.