Broiler diets demand balanced vitamin supplementation

Broiler performance has improved enormously in recent decades. As a result, nutrition patterns have also changed. Based on the genetic progress of the birds, proper vitamin supplementation levels are needed. The Optimum Vitamin Nutrition (OVN) concept is a useful tool for supplying the correct amount of vitamins to broiler diets.

By Alex Maiorka and Ananda Portella Félix, Federal University of Paraná, Brazil, and José Otávio Berti Sorbara and Jeffersson Lecznieski, DSM Nutritional Products, Brazil

Vitamins are micronutrients that participate in numerous organic metabolic processes and are therefore indispensable for excellent animal health and productive performance. When compared to other nutrients, there have been very few studies carried out in recent years to estimate the optimum levels of vitamins for broilers, and there is a huge variation in the levels used commercially. Most levels recommended by the NRC (1994) have been based on old studies, performed under controlled conditions, and using the minimum levels to avoid signs of deficiency, not evaluating the best performance under the challenge conditions found in the field. Moreover, modern breeds have a higher growth and production rate, and have higher nutritional requirements to express their genetic potential.

Besides production rates, other parameters are also presently evaluated to determine vitamin requirements, such as immunity, animal welfare, carcass characteristics, microbiological analysis, etc. Supplementation with higher levels than the minimum recommendations will result in higher production performance and carcass quality, and better health and welfare of the birds.

Multiple disorders

Vitamins are micronutrients that take part in almost all organic metabolic processes, and are vitally important for achieving good performance and health. Deficiency of one or more vitamins can lead to multiple metabolic disorders, resulting in decreased productivity, delayed growth, reproductive problems and/or decreased immunity.

Vitamins can be divided into two groups based on their solubility in lipids (liposoluble) or water (hydrosoluble). The liposoluble vitamins include vitamins A, D, E and K, whereas the complex B vitamins (B1, B2, B6, B12, folic acid, nicotinic acid, pantothenic acid) and vitamin C are classified as hydrosoluble. In general, liposoluble vitamins have specific functions in the development and maintenance of tissue structures, while the hydrosoluble vitamins participate in catalytic functions or act as control mechanisms of the metabolism, as coenzymes.

Literature shows a large variation in vitamin levels used in commercial supplements for broilers. It is for this reason that there is great interest in new studies to determine the levels that provide the best economic return, without interfering with the production performance of birds.

Vitamin recommendations

When nutritionists consider the need for vitamin supplementation, several factors have to be taken into consideration as each can demand changes in the birds’ requirements. These factors include breed, sex, management practices, development status of the bird, stress, and diseases. There are also factors related to the feed as ingredients, energy level, processing, storage, and vitamin sources. Studies are being performed on the use of higher levels of certain vitamins to improve the nutritional value and meat quality for the consumer. Vitamin recommendations suggested by international research bodies as the National Research Council (NRC), Agriculture and Food Research Council (AFRC) and Institut National de Recherche Agronomique (INRA), and the Brazilian recommendations, as the Brazilian Tables for Poultry and Swine, are important foundations to estimate the levels that should be used in different production stages.

However, they only present the minimum requirements, which are usually not sufficient under field conditions, and have low correlation with the levels that are presently used by the industry. Most studies to determine the vitamin requirement of broilers were performed under controlled experimental conditions using purified or semi-purified diets. These diets are highly digestible, their nutrients have high bioavailability, and include ingredients that are not usually fed to broilers, as isolated soy protein or casein (protein sources), and dextrose, starch or sucrose (energy sources), which also demonstrates the low correlation with the field situation. Moreover, few trials have been performed in the past 30 years to estimate the vitamin requirement of broilers with higher genetic potential for growth, with more than 20% improvement in feed conversion (higher weight gain in a short period) and a 87% increase in daily weight gain (from 26.8 g/day in 1970 to 50 g/day in 2000).

New parameters evaluated

Besides deficiency signs and/or weight gain and feed conversion, new parameters are being evaluated to determine the vitamin requirements of broilers. These include immune response, animal welfare, and quality of the final product (meat and eggs). The goal is to improve the aspect and nutritional value of the product, and lengthen its shelf-life. Higher vitamin levels have been used in the diet of broilers to compensate for variations in intake, bioavailability of the vitamins in the diet, anti-nutritional factors of the feedstuffs, stress (e.g. temperature, stocking density, management practices, diseases), etc. These are some of the other factors that can prevent the minimum requirements of the birds from being met.

While evaluating two levels of vitamin supplementation for broilers, Castaing and co-workers concluded that the highest level (approx. two times the standard dose used by the industry) resulted in higher weight at 38 days (1,919 g) than with the lower level (1,878 g). Moreover, the deposition of vitamin E in the carcass was also higher (5.4 mg/kg in the group supplemented with 20-25 mg vitamin E and 12.5 mg/kg in the group supplemented with 240 mg).

Pérez-Vendrell and co-workers obtained similar results when they studied two supplementation levels under controlled conditions (12.7 birds/m²) or under stress (16.4 birds/m²). The best outcomes (weight gain, feed intake, breast yield, vitamin deposition in the meat) were obtained with the higher supplementation level in both stocking densities.

Four vitamin levels

In this context, supplementation can be based on the Optimum Vitamin Nutrition (OVN) concept, which is presented by DSM as the optimum level of both hydrosoluble and liposoluble vitamins. The objective is to optimise the health status, welfare and productivity of the animals, while assuring efficiency in the production of quality food. By using this concept it is possible to determine four vitamin supplementation levels related to the degree of animal response.

They are depicted in Figure 1 and described below.

Deficient: Vitamin supplementation below the required level. The animal is at risk of developing clinical signs of deficiency as a result.
Sub-optimum: Vitamin supplementation in amounts that are appropriate to prevent deficiencies as long as the animals are under adequate health, environmental and physiological conditions (low challenge). However, when the animals undergo any type of stress, the level of vitamin supplementation is not sufficient to prevent reduced performance or reproduction rates.
Optimum: Contributes for the maximum expression of the productive potential of modern breeds under field conditions. 4 – Special applications: Besides their contribution to the maximum performance of the animal, these vitamin supplementation levels improve certain attributes as the quality of the final product (meat and eggs) and immunity.

Representative in practice

As for most nutrients, the vitamin requirements for broilers have probably undergone very few modifications in the past 30-40 years, as the nutrient levels required for maintenance are practically fixed and the composition of muscles/tissues are resistant to changes. There has, however, been an increase in the vitamin requirements for specific metabolic processes, as the immune responses related to performance expectations of broilers under high stocking densities imposed by today’s commercial rearing conditions. As an example, there has been a linear decrease in vitamin E intake in the past 20 years, of 0.8%/year/kg weight gain, considering 20 IU vitamin E/kg feed and a feed conversion of 1.0 in 1987 and 1.7 today.

Much emphasis is currently given to nutrients with nutraceutical functions, mainly the vitamins, as they play an important role in promoting health, well-being and immunity. The classical dose-response curve evaluation, often used to estimate the requirements of other nutrients, does not seem to be the most adequate for vitamins. Older studies evaluated the minimum requirement of vitamins needed to prevent the animal from presenting deficiency signs, or they evaluated basic performance variables as weight gain, feed conversion and mortality. As most of these trials were performed under controlled environmental conditions (low challenge), the levels that were obtained are not really representative of actual practice. To find the optimum levels for broilers reared under industrial conditions, other factors beside performance should be evaluated, such as carcass characteristics, breast yield, microbiological quality, and immune response.

Levels used in Brazil

Table 1 shows the relationship between the average levels found in the vitamin supplements used by the major Brazilian broiler companies in 2008, the levels based on the Optimum Vitamin Nutrition (OVN) concept for broilers, and also the levels used in Brazil in 2005. It can be seen that there was an increase in the vitamin levels used by the Brazilian industry during the growth period when 2005 and 2008 figures are compared. It can be concluded that the companies are aware of the need for higher vitamin supplementation to follow the birds’ genetic development, although the levels used are still below those put forward by the broiler breeding companies and the OVN levels recommended by DSM.

Cost of vitamin supplementation

The physical and chemical characteristics of vitamins are important aspects that should be taken into consideration not only by the premix producer but also by the buyer of the vitamin premix. Both should demand that high quality raw materials are used in the production of the premix. The increase in the vitamin levels represents only a 0.5% increase in the total cost of the feed (Figure 2). However, if the quality of the vitamin premix is not assured, the supplementation of marginal vitamin levels can cause serious losses in the performance of the animals.

Changes in the research parameters and methods are necessary to obtain more accurate results, applicable to practical conditions. Vitamin requirements of today’s broiler breeds are related to optimum performance, final quality of the product, and financial return. Besides the production rates within this context, there are also important variables to be analysed as immunology, interaction between vitamins and other nutrients, composition, meat quality and food safety, performance under stress conditions, and the effect of supplementation of the breeder’s diet on chick quality. New trials involving vitamin requirements of modern broiler breeds reared under industrial conditions are needed. These trials should include some form of stress to the birds in order to better reflect the industry’s real situation. They should also take into account variables such as vitamin levels in the final product (meat and eggs), shelf-life and organoleptic characteristics.