The 23rd European Symposium on Poultry Nutrition (ESPN) took place in Rimini, Italy in June this year. If you missed it, or want to remind yourself of the key take home messages, this summary article will be of interest.
Kicking off ESPN 2023, Professor Emily Burton discussed the poultry sector's need to implement the three sustainability pillars (economic, environmental, and social sustainability) in everyday practice and that a close relationship between researchers and practitioners within the sector ensures innovation is at the forefront of decisions surrounding poultry nutrition. Economic sustainability is probably the most evaluated pillar within the poultry industry, particularly currently where raw material and ingredient prices are so volatile. In terms of environmental sustainability, the poultry industry is also making progress using multiple life cycle assessment (LCA) models and evaluating global warming potential in CO2 equivalency, though there are still a lack of models and metrics necessary for accurate quantification. Often overshadowed by economic and environmental sustainability, social sustainability is coming to light, regarding animal welfare among the meat and egg sectors with such policies like the ‘European Green Deal’. Prof. Burton concluded that it is now more important than ever that nutrition continues to facilitate production of high-quality protein from the lowest possible natural resource, but the three pillars must be ingrained into any future plans.
Wolfgang Siegert then spoke about optimal nitrogen nutrition with regard to sustainability. He explained that the over or under supply of requirement for digestible amino acids could reduce nitrogen utilisation efficiency (NUE). He further went onto explain that NUE could be influenced/improved in a plethora of ways, from phase feeding, increasing the knowledge of amino acid requirements, increasing the knowledge of amino acid digestibility and the potential for increasing nitrogen utilisation in current practical diets. Siegart concluded that NUE is a key figure for assessing optimal nitrogen usage, as improved NUE leads to less nitrogen wastage. The desire to improve NUE could be reduced if required, when food security or emission targets need to be prioritised.
Similar to nitrogen optimisation, Fifi Zaefarian discussed ways to improve energy utilisation in poultry. The energy commonly used in poultry is apparent metabolizable energy (AME), often corrected for nitrogen (AMEN). Sometimes correcting for nitrogen can penalise energy values of all feed ingredients and the magnitude of nitrogen correct can sometimes worsen the effect of protein sources with a higher protein quality. In the lecture, Zaefarian explained that net energy (NE) or ileal digestible energy (IDE) could be used as alternatives when formulating poultry diets. NE can be defined as metabolisable energy (ME) minus the heat losses; however, NE is sometimes not used as it requires a precise measure of AME and any error here would translate into NE. Another potential system was IDE, which was described to overcome the limitations of AME and align with using the digestible content of nutrients in feed formulations. Further research would be needed into IDE values if this was to be used as an alternative energy system.
Roselina Angel of the University of Maryland extended the sustainability of poultry production discussion, choosing to focus on optimal mineral nutrition, more specifically digestible calcium requirements. It is known that calcium has an impact on phosphorus availability among other nutrients. Using the total calcium values to formulate poultry diets can further impact the effect on other nutrients and implies the need to look into digestible calcium as a nutrient instead. Angel explained that the reasons why digestible calcium still isn’t used is due to a number of challenges including lack of robust dataset, the need to evaluate a large number of digestibility data on limestone sources and the vast variability between different sources region to region and globally. Requirements based on digestible calcium and digestible phosphorus may be present in mineral nutrition, though they are perhaps not as robust as they need to be.
Knud Eric Bach Knudsen of Aarhus University started plenary session 4 speaking about the effects of fibres in feedstuffs. A broad variety of analytical methods have been used to determine fibre levels in feedstuffs, the most common and oldest method is the crude fibre method which is still used in proximate analysis of feeds today. Detergent methods were used to measure fibre in roughages, then later applied to concentrate feeds. More recently the enzymatic-gravimetric methods have been developed which can give separate monomeric estimations of the fibre components such as, cellulose, soluble non cellulosic polysaccharides (NCP), insoluble NCP and lignin.
Interestingly, the difference in analytical method showed varying results. From own data, Knudsen showed that crude fibre values were much lower than values obtained from more modern methods; this may put into question the use of crude fibre in diet formulation as increased accuracy is always strived for.
Recently, more alternative cereals are being used in the UK feed industry due to volatile raw material prices. These feedstuffs often have a higher NSP content and can be more viscous, often meaning they have lower nutrient digestibility. High levels of NSP fractions can satiate a bird’s hunger without providing much nutritional benefit, viscosity of NSPs could interfere with endogenous enzyme activity and cell walls could have encapsulated potentially available nutrients. Despite low NSP degradation, Knudsen stated that the microbiota that ferment NSPs contributed to 3-4% metabolizable energy (ME) and the excretion of organic acids gave 2% of ME. In conclusion, the determination of fibre has advanced since the crude fibre methods so that information on solubility, fibre composition and nutrient contributions can be better understood to get the best out of feedstuffs for the birds.
Michael Bedford of AB Vista discussed nutritional values of ingredients with the use of enzymes to help improve these values; he, like Knudsen, also covered fibre along with phytate. Bedford started by stating that the broiler industry is not what it was 100 years ago and the infrastructure of the industry, including the ingredients we use to make modern poultry rations, are significantly different. Previously multiple ingredients would be mixed, few going above 20% inclusion. Currently, two to three ingredients will make up much of the total ration. Therefore, it was stated that these main ingredients increase the anti-nutritional effect through increased levels of anti-nutritional factors (ANFs) like fibre and phytic acid, for which the inclusion of enzymes are used to try and provide some relief. Adding an enzyme can depolymerise fibre and perform a similar process in phytic acid to increase the digestibility or availability of the nutrients in the feedstuffs. It was highlighted that the solubility of fibre fractions through the use of NSP enzymes (NSPase) should be considered. Insoluble fractions can influence nutrient density but also bind to available nutrients, act as a diluent, speed up passage rate (decreasing viscosity) and act as a stimulus to gizzard development. The soluble fractions on the other hand can increase viscosity, over supply can stimulate bacterial growth, fuel bacteria and have a prebiotic effect, cause a stimbiotic effect by making bacteria to produce their own fibre degrading enzymes or influence the immune system by changing bacterial populations. Irrespective of the ingredient, the benefit of an NSPase is far greater than just the energy released from the fibre digested Bedford stated. Further evolution of fibre related enzymes is necessary to gain the full value from these cereals, though oilseed ingredients should also be further focused on.
In terms of phytic acid, it is a significant anti-nutrient that binds to mineral and proteins reducing their digestibility. The use of phytase can release phosphate from phytic acid increasing the availability of phosphorus while also reducing the molecules' anti-nutritional capabilities. Phytate, unlike fibre, can be found in different areas of the feedstuff ie., the germ, aleurone layer or in cotyledons,potentially limiting the effectiveness of phytase enzymes. Phytate levels differ between different raw materials and these levels should be considered for phytase inclusion.
To close plenary session 4, Sonia Liu of the University of Sydney discussed the importance of digestive dynamics, specifically in broilers. As commonly known, proteins and amino acids are the building blocks of larger proteins and starch and glucose are the fundamental sources of energy. Both these groups are required for optimal growth in broilers. Liu explained that body proteins require a specific profile of amino acids depending on the proteins' function and each gram of protein requires 5.35KJ of energy in broilers. Digestive dynamics consider the rate and place of the nutrient digestion of amino acids and glucose to help underpin growth performance. Furthermore, balanced quantities of amino acids and glucose should be available at the sites of protein synthesis to drive efficient protein deposition.
Not all proteinogenic amino acids have the same rate of digestion either. It was described that amino acids with larger non-polar side chains (methionine, isoleucine, leucine and tryptophan) can be absorbed more rapidly than those with polar side chains (glutamic acid, aspartic acid, arginine and glycine). Liu stated in previous work that digestion rates of starch and protein showed a correlation with feed conversion efficiency, and that rapid digestible protein and slowly digestible starch benefits feed efficiency due to protein deposition. It was also shown that changing the balance of protein bound amino acids and non-bound amino acids was shown to be more useful when formulating lower protein diets. Furthermore, the rate of amino acid digestibility was shown to be influenced by the levels of any particular amino acid already within the body. A higher level in the body, the less digestible an amino acid. To summarise, matrix values for amino acid digestion rates, rather than linked to protein, may prove more useful when formulating diets.
Talking about oxidative stress (OS) in poultry, Mario Estévez explained the importance of the decision making on-farm and the crucial impact these decisions have on meat quality. Globally, malnutrition and hunger are still big issues, although meat remains an essential component of a balanced diet. Chicken in particular is the most popular and most consumed meat worldwide. As broiler genetic selection has improved over decades of changes and a 2kg broiler can be produced in less than 42 days, the quality of meat produced comes under scrutiny. Breast meat myopathies, such as white striping, wooden breast and spaghetti meat, can be seen in broiler production and are all related to oxidative stress which effects tissue generation causing these myopathies. Estévez describes that domestic birds are susceptible to suffer from OS as high energy demands to synthesis increased meat proteins over a short time period can cause an imbalance in oxidative homeostasis.
Although the susceptibility to OS is often most influenced genetically, nutritional changes to the diet can be made to help reduce the impact of OS. Avoiding high levels of polyunsaturated fatty acids and lipids, which can easily oxidise, is one change that can be made. Fortifying diets with antioxidative products can also help to reduce OS; these include tocopherol, ascorbic acid, carotenoids, selenium and some forms of methionine to name a few. Other more novel methods can include the use of phytogenic and probiotic products, as well as phytochemicals such as quinone/phenolic compounds. Overall, innovative ways to protect against OS can help when trying to fulfil global meat demands whilst assuring good nutritional quality, in addition to producing healthy high welfare chicken and offering the consumer nutritious and safe poultry products.
A commonly discussed topic amongst the global egg industry world is the desire to extend the laying cycle of laying hens. This has multiple benefits, including less replacement birds needing to be used, less financial costs, environmental benefits, and the potential to lower the breeder flock size yet maintain the same egg numbers. Evelyne Delezie presented her work on how we could get the most from extending the laying cycle with some suggestions on how to do so. Delezie explained that although there is a push to extend the laying cycle to around 80-90 weeks, even to 100 with a push for 500 eggs laid per bird – the nutritional requirements for hens 70+ weeks of age is scarce. There is also evidence that extending production causes a decline in laying persistency and egg and bone quality. One suggestion was to use split feeding strategies; these strategies aren’t new but can target timely nutrition throughout the day to achieve best performance. Other feeding systems include free choice feeding, loose-mix feeding and sequential feeding, all with advantages and disadvantages of their own. Through trial work investigating split feeding, Delezie summarised that white and brown hens showed different responses to the same diet and that different nutritional strategies may need to provided depending on breed.
Another aspect of extending the laying cycle covered in this lecture was the calcium and phosphorus requirements for senior laying hens. It was highlighted that the nutritional requirements past 70+ weeks were still yet unknown, but through a trial using Lohmann Brown hens, no effect on bone quality, egg quality or performance was seen with available phosphorus as low as 0.11. It was clear that more work is needed in this area, but the outcomes greatly depend on the breed and feed ingredients used. Similarly to calcium and phosphorus requirements, energy and protein levels were investigated in senior hens. It is generally assumed that energy and protein demands reduce as the laying hens age. Results from another small trial showed that a 1% energy reduction and a 10% crude protein reduction can be used in 70+ week old hens with no compromise on performance or production as expected at that age.
Pre-lay period was also something that discussed during this lecture. A standout point that could sometimes be overlooked is that the contribution of the rearing period becomes greatly important when extended periods of lay are trying to be achieved. Often, a good pullet development is a prerequisite for a successful extended production cycle. As such, the nutrition of rearing birds comes to focus. Evelyne discussed an innovative wet ‘porridge-like’ diet being used in a recent broiler trial where birds consistently chose the wet diet compared to the dry diet and achieved 10% higher body weight in comparison. Although unlikely to be commercially viable, this could have a similar effect in rearing pullets – the whole aim of a wet diet would be to reduce dehydration from travel and vaccine stress when being moved to laying facilities. Overall, it is obvious that to extend the laying cycle a multifactorial approach needs to be carried out to build on the information already attained when trying to increase the laying cycle.
To finish off a brilliant ESPN 2023, Marcus Kenny of Aviagen Turkeys delved into the economical efficiencies of turkey nutrition. Kenny stated that current volatility and lack of consistent supply has meant the raw material market is somewhat unpredictable and feed as a proportion of the total cost to the enterprise is increasing. Kenny explained that for the best performance in turbulent times, nutritionists need to be able to make the most well-informed decision possible with the information provided. While it might be tempting to reduce energy density to save on feed costs, FCR, or some other performance parameter could be negatively affected. Therefore, understanding nutrient response can assist in ensuring the most efficient feed programme.
Aviagen ran a series of trials looking into various diets with differing energy and amino acid levels in heavy lines of male turkeys. They found that energy density positively impacted the response to increased amino acid (AA) concentrations when assessing liveweight and FCR. This suggests that as higher amino acid levels are fed, energy density should also be considered as a mutually inclusive combination.
Breast meat only accounts for 26-28% of the weight of the bird, but in most European countries where turkeys are typically processed into portions, it is the most valuable, representing 60-70% of the income. Therefore, as part of the series of trials, processing traits were also monitored with results showing that nutrient density had a positive impact on breast meat yield (BMY), with BMY continuing to respond to higher amino acid levels at higher energy densities. This again highlighted the importance of monitoring both nutrients when optimising diets for yield.
As well as performance responses, economic responses were also considered in this work. It was concluded from the results that optimal farm margins were achieved at 105% AA levels and 95% energy density (of standard), whereas optimal processing margins were achieved at the highest AA levels and energy density. It is crucial to note that these results will fluctuate and are scenario dependent as when feed prices and processing revenues were adjusted to reflect previous years, margin outcomes were different.
This work into feeding strategies highlights the breadth of nutritional performance, above or at the commercial standard depending on best economic performance or objective of individual businesses. It further highlights that feed prices have a significant impact on optimal diets and how important it is for reviews during volatile times of raw material prices.
If you need any assistance in applying any of this science to your unit and formulation/feeding programme, please contact your poultry account manager who will be happy to help.