Introduction Vitamins are indispensable organic compounds in metabolic activities. They are not structural substances of the body. With the exception of a few vitamins, they cannot be synthesized in the body but must be supplemented by dietary supplements. The vitamin content of the diet must be sufficient to ensure that the animal can effectively use carbohydrates, proteins, fats, minerals, and water to meet health and maintain physiological activities such as growth, development, and reproduction. If one or more vitamins are not available or are insufficiently consumed, the metabolic process is affected, resulting in disrupted production, inhibited growth, and disease. Excessive addition of certain vitamins can have special effects, such as enhancing immunity and improving meat or egg quality. Finding a cost-effective vitamin supplement level that does not affect the animal's optimal production performance is a difficult job for feed formulators and/or nutritionists, and the addition of vitamin supplements is A dynamic process should be conducted under the guidance of the preferred vitamin nutrition concept. 1. Why do vitamins need to be added to animal diets? The vitamin content of common feed ingredients can be obtained from many sources. However, these data are only given as an average, or based on a limited number of samples, and they do not correct for vitamin bioavailability and variations in vitamin levels between the same raw materials and different raw materials. If vitamins are only supplied from feed ingredients in the diet, the vitamin content is likely to be lower than the usual recommended amount. In short, feed ingredients are not a reliable source of vitamins and therefore need to be supplemented with vitamins in the diet. Second, how does the vitamin supplementation guideline develop? The National Research Council (NRC) and the British Agricultural Research Council (ARC) have done a great deal of work to develop guidelines for vitamin supplementation. The NRC and ARC recommendations are mostly based on controlled research results under laboratory conditions, so these add-on guidelines provide the minimum dietary vitamins needed to prevent clinical vitamin deficiencies and maintain acceptable health and productivity performance. Content, and they did not consider the negative factors that affect the actual requirements of livestock vitamins under commercial production conditions. Third, the lack of vitamins and adequate vitamins Traditionally judged vitamin deficiency or adequate amount can be based on the existence of a diagnosis of specific diseases or other clinical symptoms. If it is considered that the vitamin requirement is only equal to the amount of avoiding vitamin deficiency, the production performance and commercial efficiency of the animal will be affected. Vitamin content does not affect the benefit of the producer only when it reaches a clinically deficient state. Subclinical deficiency may exist even without typical deficiencies. This critical deficiency can both increase costs and make it difficult for producers to perform feeding management. They are often not valued or adjusted, resulting in poor returns and high costs, reduced fertility, and reduced production performance. Under feeding conditions, single vitamin deficiency is not common, but is a combination of multiple factors that are usually not as pronounced. The minimum requirement for vitamins in the publications is only to prevent the clinical lack of symptoms, which is not enough to obtain the best production performance, and this level varies with the level required for optimal production performance. This shows that if the amount of added vitamins needed to achieve optimal production performance is increased (due to influencing factors), then the need for vitamin deficiency prevention also increases. Similarly, if the vitamin requirement to achieve optimal performance is reduced, then the need to prevent deficiency is also reduced. IV. Adjusting vitamin levels In the past 40 years, the vitamin requirements of the NRC have remained almost unchanged, but the average amount of vitamins in the feed industry has increased significantly (30% to 500%) to meet the following needs: greater genetic potential, and more Fast growth rates, better feed efficiency, poorer quality feed ingredients, larger stables, and more disease all lead to increased stress. Therefore, the metabolic rate must meet immediate needs, so that the vitamin requirement must also change within a certain range. According to logical inferences, the amount of vitamins determined decades ago may no longer be suitable for animal needs that now have improved genetic performance. Table 1 Effect of vitamin levels and high-density stress conditions on performance and meat quality of broilers aged 0 to 40 days Vitamin premix type (content in the diet) Standard (control group) Best (test group) VA (IU) /kg)VD3(IU/kg) 2600 4000VE(mg/kg) 18.90 225.00VK3(mg/kg) 2.20 4.00VB1(mg/kg) 1.40 3.00VB2(mg/kg) 6.20 9.00VB6(mg/kg) 3.00 6.00VB12 (μg/kg) 21.20 40.00 Niacin (mg/kg) 33.00 60.00 Pantothenic acid (mg/kg) 10.40 15.00 Folate (mg/kg) 0.68 2.00 Biotin (mg/kg) 0.07 0.25VC (mg/kg) 0 100 Sheer Density (feather/shed) 70 90 70 90 Weight (g) 2122 Weight gain (g/d) 55.71 50.47 57.54 52.04 Feed intake (g/d) 96.63 91.66 100.71 92.73 Feed ratio 1.746 1.818 1.746 1.801 Breast meat (% of live weight) 16.33 15.61 16.59 15.84 Thoracic lipid peroxidation (nmol TBARS/g) 0.51 0.34 0.28 0.25 Breast meat VE level (mg/kg) 1.78 2.48 11.15 14.25 Breast meat VB level (mg/kg) 0.67 0.56 0.69 0.72 Breast meat pantothenic acid level (mg/kg) 13.85 11.56 13.22 16.28 Source: Perez-Vendrell et al., 2002 Addition of dietary vitamins to meet the minimum requirement in modern commercial production conditions does not reach the desired level. Expect the best production performance. Considering the factors that can increase the demand for certain vitamins in the diet, as well as the variation in the vitamin efficacy in the feed and the utilization in different feed ingredients, the amount of vitamins added to the diet must have a certain safety margin. Adjustments must reflect the differences between commercial production conditions and production goals. Vitamin deficiency is rare today, but conditions below optimal performance are common under commercial production conditions. Experienced dietitians will take note of this and evaluate and adjust vitamin levels based on industry experience and extensive research. When assessing and raising the level of vitamin supplements in animal diets, consider the “risk and economics of benefitâ€, that is, considering the cost of vitamin supplementation should weigh the risks of deficiency and non-optimal performance and health conditions that may cause economic loss. Table 2 Effect of Vitamin Level and Ventilation Stress Level on the Vitamin Content of Whole Eggs in Layers of 22-38 Weeks of Age Vitamin Premix Type (Content in the Diet) Standard (Control) Best (test) VA (IU) /kg) 8100 12000VD3(IU/kg) 2160 3500VE(mg/kg) 6.90 50VK3(mg/kg) 1.43 3.00VB1(mg/kg) 0.91 3.00VB2(mg/kg) 3.94 7.00VB6(mg/kg) 1.63 5.00 VB12 (μg/kg) 21.30 25.00 Niacin (mg/kg) 21.40 50.00 Pantothenic acid (mg/kg) 7.45 10.00 Folic acid (mg/kg) 0.31 1.00 Biotin (mg/kg) 0.02 0.15 VC (mg/kg) 0 100 Good ventilation and poor good whole egg VA level (μg/kg) 1771.5 1698.0 1844.1 1866.6 Whole egg VE level (mg/kg) 13.38 12.50 40.00 46.12 Whole egg VB1 level (mg/kg) 0.52 0.52 0.58 0.72 Whole egg VB2 level (mg /kg) 4.05 3.85 4.08 4.15 Whole Egg VB12 Level (mg/kg) 14.38 14.08 20.30 24.35 Pantothenic Acid Level (mg/kg) 15.60 14.30 18.38 18.62 Whole Egg Folic Acid Level (mg/kg) 0.51 0.41 0.71 0.64 Whole Egg Biotin Level (mg/kg) 229.50 210.00 323.50 326.25 Source: Perez-Vendrell et al., 2002b V. Different Ways of Vitamin Addition Vitamin supplements are no doubt necessary in animal diets, but in commercial production Under the most economically optimal amount is added to achieve health and optimum performance needed but controversial. One of the solutions is to find out the optimal amount of vitamins that can obtain the best health and optimal production performance and cost, while avoiding excessive vitamin addition, find the balance between the cost of adding and the economic benefits. In addition, it is also necessary to establish a cost-effective way to add optimal levels of vitamins. Table 3 Effect of vitamin levels and feeding conditions on the growth performance of 10 to 26 kg pigs The optimal lower limit of the vitamin premix type standard (control group) (control group) (control group) VA (IU/kg)VD3 (IU/kg)VE (mg/kg) 20 60 100VK3 (mg/kg) 0.5 2.5 4.0VB1 (mg/kg) 1 2 3VB2 (mg/kg) 4 5.5 8VB6 (mg/kg) 1 3 5VB12 (μg/kg) 20 30 40 Niacin (mg/kg) 15 30 45 Pantothenic acid (mg/kg) 10 15 25 Folic acid (mg/kg) 0.2 1 2 Biotin (mg/kg) 0.04 0.13 0.30 VC (mg/kg Kg) 0 50 100 Unfavorable feeding environment weight gain (g/d) Food intake (g/d) Meat-to-meat ratio 1.66 1.65 1.62 Best feeding environment weight gain (g/d) mining Food intake (g/d) Meat ratio 1.59 1.59 1.56 VI. Preferred vitamin nutrition 1. The concept of OVN OVN refers to the fact that all known vitamin levels provided in the diet can enable the animal to achieve optimal health and Better production performance enables producers to increase economic returns. This concept promotes the constant updating of vitamin supplementation levels in order to correctly reflect the development of genetic, environmental and production factors. It proposes a dynamic concept of vitamin nutrition taking into account changes in vitamin requirements under commercial production conditions. 2. Definition of OVN OVN can be defined as such a level of supplementation, which generally exceeds the need for prevention of deficiency and satisfies (but does not exceed) the attainment of optimal health conditions and performance goals. This level offsets the factors that affect animal vitamin requirements under commercial production conditions, including production goals or levels, genetic, nutritional and health status, stress levels, vitamin stability and antagonistic factors, feed mycotoxin contamination and environmental conditions, etc. . This of course also includes a vitamin safety margin to ensure that the animal's intake actually meets the requirements. In order to apply OVN in actual production, several items must be clearly defined. See Figure 1 (abbreviated). 1 "Average animal response" refers to the animal's response to the average production performance and health of vitamin intake, such as growth rate, feed conversion efficiency, reproductive performance, animal welfare, health and immune status, etc.; 2 "Overall level of vitamin intake" Refers to the total amount of vitamins obtained from all dietary sources, that is, the sum of natural vitamins in feed ingredients plus the amount added; 3 "lack" or "critical" vitamin intake refers to the level of supplementation below the NRC requirement. Vitamin supplementation can cause animals to suffer from clinical deficiencies and disorders caused by insufficient vitamin intake. 4 “Better†intake means that intakes usually meet or slightly exceed NRC requirements, and this level can prevent clinical deficiencies under good production conditions (but sub-clinical under stress and disease conditions may occur. Lack of disease), but it does not maintain animal health and meet the requirements of optimal production performance; 5 "best" intake refers to compensating negative factors that affect animal health and production performance, thus helping modern animal breeds to fully realize their production potential; 6 "Excessive" intake is still safe but not economical. Under actual production conditions, only excess VA and VD will occur. 3. Recommended Vitamin Levels for OVN Because of changes in vitamin requirements under actual production conditions, the vitamin recommendation is best expressed as an addition range rather than as an absolute value. These additions range from extensive research in universities and industries, to the already developed requirements, and from production practices, and these additions are suitable for practical use by nutritionists and veterinarians. 4. Verification of the OVN concept Recent publications on animal testing carried out in the laboratory and under actual production conditions show that the OVN concept works well in commercial production systems (Table 1, Table 2 and Table 3). For example, adding at the OVN level under modern genetic conditions does not limit the production performance, in fact it maximizes the genetic potential. Because today's animal breeds have a higher ability to grow and protein synthesis and are more sensitive to stress, whether they are physiological, immune or environmental, they are involved in protein and energy metabolism, reduce stress and antioxidant defense mechanisms. Vitamins are particularly important. Under these conditions, the best levels of VC, VE, and B vitamins have been shown to effectively improve growth performance and carcass quality and reduce mortality. It is very important that all vitamins must be considered in the OVN. Attempts to determine the order of limiting vitamins have proved futile. Vitamins, especially B vitamins, are highly interacting with energy and protein metabolism. In principle, all vitamins need to be added at optimal levels to achieve the true potential of OVN in actual production. 7. Conclusions Directing vitamin supplementation based on the concept of optimal vitamin nutrition is the safest and most secure way to ensure that poultry production reaches optimal production performance. Adding the best levels of vitamins in poultry feed is the most economical way. The preferred vitamin nutrition concept takes into account the optimal level of all vitamins and considers the factors that affect the vitamin requirements, providing an actual recommended amount of vitamin supplements. As modern poultry production systems become more dynamic, it is recommended that vitamin supplement levels be reassessed and adjusted periodically to find the balance between vitamin deficiency and non-optimal production performance and the risk of loss due to health conditions and added costs.