Vitamins are required for normal metabolic function; development of normal tissues; and health, growth, and maintenance. Some vitamins can be produced within the pig's body in sufficient quantities to meet its needs. Others are present in adequate amounts in feed ingredients commonly used in swine diets. However, several vitamins need to be added to swine diets to obtain optimal performance. Vitamin needs are more critical today than in previous years because of the use of simple diets containing fewer ingredients and confinement facilities.
Vitamins that should be added to swine diets can be divided into two groups--fat-soluble and water-soluble. The fat-soluble vitamins that are generally added are A, D, E, and K. The water-soluble or B-complex vitamins, which may be deficient in a corn- or milo-based diet, are pantothenic acid, riboflavin, niacin, choline, and vitamin B12. The recommended levels of addition are shown in Table 24. In addition, recent research shows that additions of folic acid and biotin may improve sow and litter performance when added to gestation and lactation diets. There is no need to supplement diets for growing-finishing swine with biotin or folic acid.
Green leafy plants, grasses, and alfalfa are excellent sources of vitamins for swine. However, with increased confinement rearing and continual usage of pastures and outside lots, very often little plant material is available. In addition, with fewer ingredients used in diet formulation, there is no longer the variety of feed ingredients to supply added vitamins. Finally, vitamin content of grains and protein sources may be unavailable or lost during storage. Therefore, when formulating swine diets, it is recommended to specify all vitamin and trace mineral levels as "added" levels. This helps to eliminate some of the confusion and difficulty in determining availability and concentrations in feed ingredients.
Because the natural sources of the vitamins may not be present in swine diets, it is recommended that a vitamin supplement be added. Synthetic vitamins are produced by many companies and are sold individually or in various combinations. Synthetic vitamins may be more accessible than some of the natural sources of vitamins.
A suggested vitamin premix is listed in Table 11. This premix is designed to be fed to all ages of pigs by adjusting its inclusion rate. Therefore, it is necessary to use a sow add pack (Table 12) for gestation and lactation diets. Although this single premix is over-fortified on certain vitamins for pigs depending on age, there is less potential for vitamin potency losses during long storage.
Even though the vitamin premix is correctly formulated before leaving the manufacturer, it does not necessarily mean that it will have adequate levels of vitamins to meet the pig's daily dietary requirements. Premix abuse can contribute to borderline vitamin deficiencies. Table 13 show factors that affect vitamin stability. Some vitamins are much less stable than others; therefore, care of the vitamin premix is extremely critical for optimum performance. To maintain vitamin potency, it is recommended that vitamins be stored in a dry, cool, dark place. Because vitamins are hygroscopic (absorb moisture) vapor barriers such as plastic-lined sacks will aid in reducing moisture levels, especially when the humidity is high. If trace minerals are present in combination with the vitamins in the premix or base mix, storage time should not exceed 60 days. However, if vitamins or minerals are kept separate, they may be stored up to six months.
Choline is important in nerve function, protein synthesis, and structural development. Choline in the strict sense is not a vitamin because pigs can synthesize sufficient choline for their needs, provided that specific chemical substances are available. However, as a safety factor, supplemental choline is recommended. Choline is one of the most expensive vitamins added to premixes. It may represent 10-25 percent of the cost of vitamin supplementation. The cost of choline in gestation diets can be justified by the increase in the number of live pigs born and weaned when it is added at the rate of 500 grams per ton of complete feed.
In the past, the cause of spraddle legs in baby pigs has been attributed to a deficiency of choline. Recent research indicates that choline deficiency is not a major factor in this condition. The cause(s) of spraddle legs is not fully understood, but it may involve several factors including: Genetics, management, slick flooring, mycotoxins, and a virus or combination of viruses.
Although the requirement for choline has not been defined, 100 grams per tone of complete feed is recommended to prevent a possible choline deficiency in growing-finishing pigs.
There is much debate as to how much vitamin E should be added to swine diets. This is a result of the many factors that influence vitamin E concentrations and requirements. Some of these include: artificial drying of grains, storage time and conditions, unsaturated fatty acids, and selenium concentrations. Because of the high incidence of Mulberry Heart Syndrome in North Carolina swine herds, at least 40,000 IU/ton of vitamin E should be added to sow and nursery pig diets.
Although vitamin K occurs in many natural feedstuffs and is also synthesized by intestinal microflora of the pig, a deficiency can be caused by low stability and moldy feeds. Deficiency characteristics are hemorrhaging and prolonged blood clotting time, but can also include blood-tinged urine, lameness, and listlessness. When specifying vitamin K requirements, it is important to indicate menadione, which is the active form of the vitamin.
Several experiments have been conducted to determine the value of supplemental vitamin C or ascorbic acid in swine diets. The majority of the research indicates that vitamin C supplementation will not improve pig performance.
Biotin and folic acid are two water-soluble vitamins that have been studied to evaluate their influence on overall reproductive performance. Biotin deficiency has been associated with foot lesions and toe cracks in sows. However, research is contradictory, with some experiments finding benefit from biotin additions and others not. The availability of biotin in grain may be a possible factor for these discrepancies. Therefore, 200 mg/ton biotin is recommended to be added to sow gestation and lactation diets as an insurance factor.
Folic acid participates in many enzymatic reactions that appear to be essential in assuring embryo survival. Research indicates that the addition of 1500 mg/ton of complete feed will increase the number of pigs born alive by approximately one pig per litter.
In the last 10 to 15 years, vitamin and trace mineral additions have become increasingly important because of changes in feeding, housing and management systems. Some of the more important changes include:
Increased confinement production has denied swine access to soils and grazing crops, which provided vitamins and minerals.
Increased use of slotted floors has prevented recycling of feces, which may be high in B-vitamins and vitamin K that are synthesized by microorganisms in the large intestine.
Reduced use of multiple protein sources in diets. If multiple protein sources are used, they often complement each other in providing the vitamin and mineral needs of swine.
Reduced daily feed intake during gestation. Dietary vitamin and mineral concentrations must be increased as daily feed intake is decreased. With the trend towards moving sows from outside gestation lots into environmentally controlled buildings, maintenance requirements and feeding levels will be lowered. Therefore, to prevent shortages with decreased feed intake, vitamin and mineral requirements should be expressed on an amount/day basis rather than percentages.
Earlier weaning of pigs. There is increasing pressure to wean pigs at an earlier age. Three to 4-weak weaning is commonplace. As weaning age decreases, the quality of the diet with respect to all nutrients becomes more critical.
Bioavailability of nutrients in heat-dried grains and feed ingredients appears to vary widely. Inhibitors and molds in feed may result in reduced absorption, increasing requirements for certain vitamins.
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