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Vitamins are organic compounds that are essential in small amounts (micronutrients, µg to mg/d) to maintain metabolic balance and normal production in pigs. All vitamins are essential compounds that:
- Either the pig does not synthesize (in the case of vitamin C);
- it does synthesize, but not in sufficient quantities for the body to function properly (in the case of vitamin A);
- or its necessary synthesis is limited by the production system and facilities (in the case of vitamin D).
Vitamins are essential for proper growth and also for ensuring proper function of the nervous system, immune system, reproductive system, bone development, and cell repair. They do not provide energy, and each vitamin performs specific functions that none of the other vitamins can.
In swine nutrition, given that the vitamin content in raw materials is usually poor and highly variable, vitamins are incorporated into the diet through vitamin-micromineral premixes (concentrated premixes that provide vitamins and microminerals in small amounts) to ensure and meet the recommended levels.
Vitamin deficiencies are not usually observed in conventional pig production systems. Moreover, the cost of vitamin supplementation in feed is minimal compared to the many benefits it provides. However, there is considerable variability in the recommended inclusion levels recommended by different companies and nutritional tables. For example, Shastak and Pelletier (2023) published a table showing the variability in Vit A recommendations according to genetic origin and production phase (Table 1).
Table 1. Vitamin A recommendations (IU/kg of feed) for some genetic lines. Adapted from Shastak and Pelletier, 2023.
| Genetic line | Piglets | Finishing and replacement | Gestating sows | Lactating sows | Source |
|---|---|---|---|---|---|
| DanBred | 8,8001 | 4,0322 | 10,000 | 10,000 | DanBred, 2020, Nutrient Specifications |
| PIC | 11,000 | 5,510 - 6,600 | 9,920 | 9,920 | PIC, 2016, Nutrient Specification Manual |
| Genesus | 12,000 | 4,188 - 5,510 | 12,000 | 12,000 | Genesus, 2017, Genesus Nutrient Specifications |
| Topigs | Min. 16,000 | 7,000 - 10,000 | 10,000 | 12,000 | Topigs Norsvin, 2016, Manual Topigs 20 |
| Bundes Hybrid Zucht Programm | 16,000 | 5,200 - 6,500 | 12,000 | 12,000 | BHZP, 2016 |
| Hypor | 8,000 | 8,000 | 12,000 | 14,000 | Hypor, 2017a,b |
1 The amount of vitamin A added to feed must not exceed the local regulatory maximum.
2 Recalculated based on recommendations for retinol content per MJ of metabolizable energy.
Classification and naming
Vitamins are classified into two groups according to their solubility: water-soluble vitamins (B-complex vitamins: thiamine (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), folic acid (B9), cobalamin (B12), and vitamin C) and fat-soluble vitamins (vitamins A, D, E, and K).
The main difference between the two groups is their storage capacity in the body.
Fat-soluble vitamins are absorbed in the intestine, where they bind with dietary fats to form micelles. They are then incorporated into chylomicrons along with fatty acids and transported through the lymphatic system into the bloodstream, where they are stored in the liver and adipose tissue.
Fat-soluble vitamins have a high storage capacity in animals. In contrast, water-soluble vitamins are not associated with fats and are easily metabolized and eliminated via the urine when consumed in excess.
Therefore, water-soluble vitamins generally do not pose toxicity risks, while excessive intake of fat-soluble vitamins can cause adverse effects due to hypervitaminosis, damaging the liver, causing bone abnormalities, vomiting, and other adverse clinical signs.
In fact, vitamin A and D inclusion levels in pig nutrition are regulated with a maximum inclusion in the final feed at the European level. According to European regulations, currently in feeds with a moisture content of 12%, the maximum inclusion values are:
- Vitamin A (codes 3a672a, 3a672b, 3a672c): 16,000 IU/kg in piglets (suckling and nursery), 6,500 IU/kg in finishing pigs, and 12,000 IU/kg in sows.
- Vitamin D3 (code 3a671): 2,000 IU/kg in all phases of pig production.
Table 2 summarizes the different nomenclatures and chemical structures of the main water-soluble and fat-soluble vitamins used in swine nutrition.
Table 2. Nomenclature and chemical structure of the main vitamins used in swine nutrition.
| Group | Nomenclature | Chemical structure | ||
|---|---|---|---|---|
| Water soluble | Vitamin B1 | Thiamine |  |
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| Vitamin B2 | Riboflavin |  |
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| Vitamin B3 | Niacin |  |
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| Nicotinic acid (pyridine-3-carboxylic acid) |
Nicotinamide (pyridine-3-amide) |
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| Vitamin B5 | Pantothenic acid |  |
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| Vitamin B6 | Pyridoxine |  |
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| Vitamin B7 | Biotin |  |
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| Vitamin B9 | Folic acid |  |
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| Vitamin B12 | Cobalamin |  |
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| Vitamin C | Ascorbic acid |  |
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| Fat soluble | Vitamin A | Retinol |  |
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| Vitamin D | Vitamina D3, cholecalciferol |  |
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| Vitamin E | Tocopherol |  |
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| Vitamin K | Vitamin K |  |
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In the second part of this article on vitamins, we will discuss assessment, requirements, safety margins, and stability.
