Roles of Vitamins and Minerals Explored at World Congress31 October 2012
The World Poultry Congress 2012 brought together researchers from all branches of science to hear the latest findings and discuss the hot topics in the city of Salvador in Brazil in August, reports senior editor, Jackie Linden. Here is a selection of the papers presented at the meeting, which examined the vital roles of vitamins and minerals on poultry growth and health - from embryo to mature bird.
Feed Additives Contribute to Improving the Sustainability of Poultry Production
The globalisation of the food value chain is increasing day by day and we need to address the challenges associated with it in a sustainable way, said Dr F.J. Schöner of BASF in the introduction to his plenary presentation to the Congress. Globalisation will be driven by the following trends, he said: growth of the human population, continuing urbanisation, income growth, increase in meat production and consumption, further industrialisation and consolidation of farming, more stringent control of animal welfare, and higher food safety requirements.
To meet these challenges, poultry production will have to increase the efficacy of the resources deployed, improve food safety and put more emphasis on sustainability. Each improvement in the efficiency of animal production can be part of lowering the output into the environment. Calculations of the carbon dioxide footprints and greenhouse gases emitted by poultry and livestock have already been published.
Furthermore, he said, consumers have become more aware of the environmental impact of poultry production and therefore, sustainability has become a key issue that needs to be addressed.
There is no single definition of sustainability. Dr Schöner said that for the chairman of the BASF SE board of executive directors, K. Bock, sustainable development means the "combination of long-term oriented economic success with environmental protection and social responsibility". BASF Nutrition & Health's global SET-initiative (Sustainability, Eco-Efficiency, Traceability) combines applied science and value chain management to meet the challenges, he said.
The SET approach is holistic by looking at the entire value chain and at the same time incorporating as many relevant parameters as possible, as Dr Schöner went on to explain in more detail in his paper, including the contribution of mycotoxin binders and non-starch polysaccharide-degrading enzymes to improving the sustainability of poultry production.
Turning his attention to phosphorus, he explained that microbial phytase was one of the first feed enzymes to gain entry into animal nutrition around 1990. Phytase hydrolyses plant-borne phytate phosphorus, which cannot be utilised by monogastric animals, to yield available phosphorus. Because phytate can form complexes with minerals, starch, proteins and digestive enzymes, it is generally be seen as an anti-nutritive factor.
Over the last 20 years, phytase has become a success story in the nutrition of monogastrics and is applied in the majority of poultry feeds. In fact, the sweeping success of phytase led the way for research into other feed enzymes.
BASF was amongst the first researchers in the early 1990s to carry out balance trials with phytase in poultry, according to Dr Schöner, and the company was thrilled by the size of effects they found. From the beginning, phytase showed huge and reliable effects on the utilisation of phosphorus and also improved the digestibility of calcium, zinc, manganese, copper and iron.
Right from the beginning, the high potential of phytase for lowering phosphorus emission into the environment was recognised, he said. One example of the environmental benefit is derived from a feeding experiment with laying hens (Table 1).
|Table 1. Ecological effect of phytase in layers|
|Total phosphorus in feed||g/kg||5||3-5|
|Phosphorus excretion (egg)||g/d||0.11||0.11|
|Phosphorus in faeces||g/d||0.46||0.28|
|Source: Jeroch, 1995
Egg mass 55g; feed intake 115g/day
As a rule of thumb, average phosphorus excretion in poultry fed diets with added phytase is reduced by about one-third, Dr Schöner said. The global benefit from the use of phytase for the broiler production may be calculated from total worldwide broiler feed production of roughly 230 million tonnes per year. A standard dose of phytase equivalent to 1g of phosphorus from monocalcium phosphate (MCP), can therefore replace 230,000 tonnes of phosphorus from MCP. However, as complete diets contain on average 2.5g phytate-phosphorus per kg, of which about 1g per kg is made available by phytase, there is still ample room for improvement.
Further phosphorus release from dietary phytate-phosphorus by improvements in phytase application or source has a potential to decrease phosphorus emission into the environment by more than 500,000 tonnes, said Dr Schöner (calculated as MCP) - only from broiler production.
There is evidence that the use of phytase can also improve utilization of other nutrients, he added.
Feeding Breeders to Avoid Oxidative Stress in Embryos
Evidence is accumulating that the maternal diet can have profound effects on the hatching egg quality and health status, growth and development of newly hatched chick.
In his oral presentation at the World Poultry Congress, Dr Peter Surai2 of Scottish Agricultural College in the UK and Feed-Food, highlighted that the maternal diet determines the development of the embryo and of the chick for the first few days post-hatch. He said that the accumulation of vitamin E and carotenoids in the liver during embryonic development is considered to be an adaptive mechanism to overcome the stress of the hatching process.
Increased vitamin E, carotenoid and selenium supplementation of the maternal diet have proven to be beneficial for embryonic and early postnatal development of the chick, he continued.
Post-hatch, the antioxidant defence changes from antioxidant accumulation to the synthesis of antioxidant enzymes with more sophisticated and effective regulation at the gene level. The immune and digestive systems of the chick develop during first two weeks after hatching; they are at risk of oxidative stress and need effective antioxidant protection over this period, said Dr Surai. An anti-stress formula provided in the drinking water has been developed and used successfully under commercial conditions in the Ukraine and Russia, he added.
Examining firstly vitamin E in egg yolk and embryo, he said that this nutrient is considered to be the main antioxidant in yolk; it is delivered from the feed and transferred to the developing embryo.
In the poultry industry, vitamin E concentration in feed ingredients is not counted and supplemental vitamin E is the main source of the vitamin for poultry. The recommended vitamin E supplementation for breeders (Cobb and Ross) is 100ppm, increased to up to 250ppm for laying hens under conditions of heat stress.
Vitamin E is effectively transferred to the egg yolk and further to the developing embryo. The highest vitamin E concentration is found at time of hatching and the nutrient accumulates in the embryonic liver. For the first two weeks post-hatch, there is a dramatic (10- or 20-fold) reduction in vitamin E concentration in the chicken liver. While vitamin E concentration in the egg determines vitamin E status of the chick for the first week post-hatch, newly hatched chicks are unable to assimilate vitamin E from the diet effectively and so vitamin E supplementation of the feed at this time has limited effects.
According to Dr Surai, increased vitamin E supplementation of breeders - more than 100ppm - under commercial conditions does not always improved performance or egg quality.
Turning his attention to selenium, he said that this element is an essential part of a range of selenoproteins. Feed ingredients contain variable concentrations of selenium but most are deficient in this element. Although the physiological requirement is low, the bird's antioxidant system may be compromised if the supply is inadequate. High doses are toxic. There are two main sources of selenium for poultry are a natural source in the form of various selenoamino acids including selenomethionine or inorganic selenium in the form of selenite or selenate.
As with vitamin E, the concentration of selenium in the egg depends on its concentration and form in the maternal diet, and increased concentrations in the egg yolk and albumen are related to increased levels in the embryonic liver and increased antioxidant defences of the developing chicks. Maternal selenium has a long-term consequences for the developing embryo and newly hatched chicks.
Dr Surai also mentioned ascorbic acid as a nutrient with antioxidant properties. However, as it is synthesised by the chicken and not found in the egg, its role in egg quality is questionable, he suggested. However, under stress conditions, ascorbic acid supplementation of the breeder diet may have some positive effects.
Selenium Yeast and Vitamin E for Broiler Breeder Pullets
Selenium yeast supplementation to broiler breeder pullets increased tissue selenium concentrations and helped maintain tissue selenium concentrations during egg production, according to Dr Pescatore3 of Alltech-University of Kentucky Nutrition Research Alliance in Lexington, Kentucky, USA.
The study evaluated the effects of selenium and vitamin E supplementation on tissue selenium status of developing broiler breeder pullets.
The experiment utilised 640 Cobb500 broiler breeder pullets that were allotted to four treatments with 32 birds per pen in a 2×2 factorial design. Treatments consisted of a corn-soybean meal-basal diet (with no added seleniun or vitamin E), supplemented with 0.3mg selenium per kg diet as selenium yeast (Sel-Plex®, Alltech, Inc., Nicholasville, KY), supplemented with 30IU vitamin E per kg as all-rac-α-tocopheryl acetate, or supplemented with both selenium and vitamin E.
Pullets received photo stimulation at 22 weeks of age. At 14, 18, 22 and 26 weeks of age, two pullets per pen were randomly selected and euthanised. Liver, pancreas and breast samples were collected and stored at -80°C until subsequent selenium analyses.
Until 26 weeks of age, tissue selenium concentrations for liver, pancreas and breast were significantly higher for the birds receiving selenium yeast than those not receiving selenium yeast (P<0.01).
Upon the onset of egg production (26 weeks of age), the Lexington researchers found that liver selenium concentrations were reduced by 44.9 per cent and 60 per cent for the control and vitamin E treatment, respectively, compared with values for the previous weeks. Liver selenium concentrations of animals fed selenium yeast were only reduced by 33 per cent. A similar trend was observed for the pancreas selenium concentrations.
In-ovo Supplementation Protects Embryos from Oxidative Stress
The use of in-ovo technology is an innovative means of vaccination and embryonic nutrient supplementation, according to Dr Ramón Malheiros of North Carolina State University in his paper4 to the World Poultry Congress. Early work by Uni and Ferket developed in-ovo feeding as a technique for the administration of nutrients and other agents into the amnion of the late-term avian embryo to advance its development, both before and after hatch. The same technology can also benefit important physiological and biochemical processes, including enhancing oxidative protection.
In the paper, Dr Malheiros explored the potential applications of in-ovo supplementation for enhancing the antioxidant status of chicks during the critical last days of incubation, by explaining the concept of lipoperoxidation, free radical formation and the factors affecting oxidative stress during incubation.
Considering how early feeding of antioxidants can help, he addressed the role of vitamins. Vitamin E is the major fat-soluble antioxidant that quenches the chain reaction of lipid peroxidation. The antioxidant system of the brain is of great importance because of the development of nutritional encephalomalacia, which occurs in young chicks as a result of vitamin E deficiency. Vitamin E is distributed in all compartments in the egg, and the concentrations changes as the incubation period progresses, he said.
Antioxidants, like vitamin E, have been used to alleviate the adverse effects of the peroxidation of lipids and cholesterol in domestic animals. A highly positive correlation has been observed between dietary vitamin E levels in the maternal hen's diet and the levels of this vitamin in egg and subsequently, in chick tissues. Vitamin E levels have been correlated with the immune response of chicks and turkey poults. In-ovo vitamin E administration has been shown to change the total lipid content of tissues at hatch, enhancing the antioxidant status of hatched chick's tissues and protecting lipid membranes from radical oxygen species.
Vitamin C has been demonstrated to improve immunoresponsiveness and increase disease resistance in poultry by optimising the immune system, continued Dr Malheiros. Ascorbic acid has also been shown to have a sparing effect on vitamin E by acting as a redox system reducing tocopheroxyl radicals back to their reduced state, tocopherol. In-ovo injection of vitamin C has been shown to increase hatchability rate in chicks and ducklings when administered on days 15 and 20 of incubation, respectively.
Other elements that can be used in-ovo to have beneficial antioxidant effects include thiamin (vitamin B1), which is a co-factor for several enzymes catalysing descarboxylation and transkeletolation reactions, continued Dr Malheiros. Deficiency of thiamin in eggs causes high mortality of embryos just prior to hatching, and chicks that do hatch show signs of polyneuritis. Deficiency of vitamin B6 (pyridoxine) has been shown to lead to early embryonic death and a reduced immunoglobulin response to a challenge.
Oxidative stress is among the most limiting threatening conditions that the avian embryo must overcome as it develops towards hatch through to the initiation of feed consumption, concluded Dr Malheiros. Although the embryo benefits from various antioxidant compounds deposited by the hen to combat oxidative damage, incubation distress can place a significant drain on these limited amounts and critical functions may be affected.
The antioxidant status of the embryonated egg is determined by the hen's nutritional and physiological state. Because the antioxidant status of hatching eggs is variable and unpredictable, supplementation of antioxidants by in-ovo feeding technology may yield significant benefits. Preliminary studies have indicated the potential benefits of in-ovo feeding solutions containing various antioxidant compounds, including vitamin E, ascorbic acid, L-carnitine, organic trace minerals, carotenoids and antioxidant peptides. Further research is needed to assess better the practical application of antioxidants by this route, added Dr Malheiros.
All papers were presented at the World Poultry Congress 2012 in Salvador, Brazil. August 2012.
1. Schöner, F.J. Contribution of feed additives to a more sustainable poultry production.
2. Surai P. and V.I. Fisinin. Feeding breeders to avoid oxidative stress in embryos.
3. Quant A.D., A.J. Pescatore, A.H. Cantor, M.J. Ford, J.M. Unrine and J.L. Pierce. Effect of selenium yeast (Sel-Plex®) and vitamin E supplementation on tissue concentration of developing broiler breeder pullets.
4. Malheiros R.D., P.R. Ferket and F.M. Gonçalves. Oxidative stress protection of embryos by 'in ovo' supplementation.