Practical Views on Global Meat Chicken Nutrition

I. INTRODUCTION

The global supply of poultry products will need to double by 2050 if we are to meet the aspiration of all people to be food secure. We will need to produce more poultry meat in the face of changing consumer perceptions and constrained resources. Consumers expect this to be achieved in a sustainable manner. The industry has the skills to achieve this. Genotypes continue to improve; production methods and business models are evolving; and we have enhanced our knowledge of poultry health and nutrition. However, our industry will need to develop by offering alternative products and by changing or improving production methods. These changes will occur in the foreseeable future.

The overarching consideration will be sustainability. The definition of sustainability is straightforward – sustainable systems should meet the needs of the current generation without compromising the ability of future generations to meet their own needs. In practice, sustainability is a concept with multiple facets, namely environmental, social and economic. Measuring sustainability is difficult because it depends on which metric is chosen for use, and often it can only be accurately determined in hindsight. Achieving alignment in one area often leads to failure in another, which is a challenge faced by broiler producers and legislators. For example, alternative production systems such as free-range and organic result in an apparent improvement in welfare, but at considerable cost to the environment (Williams et al., 2009).

There is a divide between global citizens. In developed countries, wealthy citizens consume poultry meat produced by ‘integrators’, delivered via well-developed supply chains, and sold through supermarkets and fast service restaurants. However, it is estimated that there are 2.5 billion people who depend on small farms for their livelihood and food security (FAO, 2013). These farmers have no access to supply chains, either for inputs or for the sale of product. Yet meat consumption is aspirational and poultry forms an important component of dietary protein supply. Most consumers desire access to cheap, safe animal protein, yet our industry is obliged to meet the changing consumer demands of more developed markets. Both market channels will need to be supplied in a sustainable way. Against this background, the primary focus of this paper is the nutritional interventions that can be applied to enable our industry to fulfil its mandate to ensure food security, sustainably.

II. SUSTAINABILITY AND DEMAND

Sustainability is neither a single entity, nor can we choose those aspects that suit our own particular beliefs. From an environmental viewpoint, sustainability impacts the entire poultry supply chain, causing pollution and ecological degradation. Social aspects of sustainability encompass both human and animal well-being. The compact of the five freedoms of welfare should be applied to all animals, while human health – including exposure to antibiotic-resistant bacteria and the well-being of poultry producers – needs to be considered (FAO, 2012). Paradoxically, most consumers are more concerned about their own well-being through the consumption of ‘natural’ products than about animal welfare (Magkos et al., 2006; Bray and Ankeny, 2018). The final and seminal aspect of sustainability is financial viability, which is the key enabler of all production systems.

From a nutritional perspective, all the objectives of sustainability should be aligned. The more efficiently chickens utilise feed, the more viable the feeding operation becomes, with a reduced carbon footprint through a lower demand for resources. Appropriate nutrition will also impact on bird welfare. The poultry industry believes that bird welfare and food safety are better when conventional systems are used, but this is not a view shared by wealthy consumers in the developed world. Public opinion is that ‘organic’ is natural, healthy and sustainable, and that use of medication and intensive farming is bad. Many of these beliefs are based on perception and misinformation, often created by the poultry industry itself, which has used ‘Hormone free’, ‘Drug free’ and ‘Free range’ as marketing slogans for decades. The danger of consumers imbibing harmful drug residues from eating poultry products, and the possible contribution of these drugs leading to an increase in drug-resistant bacteria, are more a perception than a reality (Cervantes, 2015). Regardless of the truth, failure to meet consumer demands will result in their rejection of our products. This happened in Norway, for example, where it was perceived that the use of ionophores was undesirable. The reduced demand for poultry meat ultimately led to the voluntary withdrawal of ionophores from all broiler diets (Kaldhusdal, 2018).

Alternative production systems place a higher burden on the environment than conventional systems (Williams et al., 2009). Petersen (2017) estimates that, if only one-third of the US broiler industry were to switch to the use of slower-growing breeds, an additional three million hectares/year of land would be required to grow the necessary feed ingredients, while, “large scale antibiotic-free production will increase the industry’s carbon footprint” (Smith, 2016). More affluent people tend to eat fewer grains and more meat and high-value foods (FAO, 2013; Hofstrand, 2014). The price of poultry substitutes, for example fish and beef, are likely to increase disproportionately, further fuelling demand for poultry. The poultry industry’s innovative approach to product development has also led to increased demand. A rising demand for poultry products with specific quality and food safety attributes is likely, probably linked to increased levels of affluence (Narrod et al., 2012). In essence, the poultry industry will be expected to produce increased quantities of different product types, sustainably, without access to some technologies it has used for decades, and still make profits. Improved growth performance and feed efficiency will have a greater impact on sustainability than any other factor. Avendaño et al. (2017) state that the feed conversion ratio of broilers is improving by two to three points per annum. By simple calculation, a two-kilogram broiler, grown a decade from now, will require about 500 g less feed than it does today. This will reduce the environmental impact and make broiler production more financially robust. In short, chicken is the most sustainable meat option available (Henriksen, 2018).

III. IMPROVED FEED UTILISATION

The utilisation of feed chemicals by the broiler relies on a complex web of ‘cross-feeding’. This involves the substrates contained in the diet, the birds’ endogenous enzymes, enzymes produced by the gut microflora, and the few exogenous enzymes added to the feed. The use of antibiotic growth promoters (AGPs) masks imbalances in the gut microflora to a certain extent, although we still do not fully understand their mode of action (Broom, 2018). In future, we will need to unravel the complexity of the relationship between the broiler, its GIT microflora, the diet being consumed and the additives used.

Improving nutrient utilisation involves far more than simply enhancing dietary digestibility and some 400 kcal/kg of energy, 70% of phosphorus and between 10 and 20% of the essential amino acids in a typical broiler diet are not utilised. Indigestible substrates offer a resource to the nutritionist. Exogenous enzymes enhance digestion of substrates but also break down some of the anti-nutritional factors that occur in typical diets, rendering them harmless. This leads to reduced inflammation and enhanced nutrient uptake (Niewold, 2007). In addition, enzymes prevent the nutrients that escape digestion from becoming a source of nutriment for the GIT microflora. A broiler with a healthy, well-functioning GIT and a stable gut microflora will utilise its diet more effectively, resulting in enhanced digestibility. A well-developed gizzard leads to improved energy utilisation (Truong et al., 2017). Undigested nutrients represent a food source for the GIT microflora and may induce a shift to more proteolytic bacteria, which can lead to enteritis.

IV. PROTEIN

Modern genotypes require more protein and less energy per unit of growth than their predecessors. The efficiency of utilisation of protein is unlikely to change, but proportionally less protein will be used for maintenance purposes and more for protein-rich tissue production, such as breast meat. Future protein supplies will be more constrained than energy (Leeson, 2018), which is likely to increase the cost of protein. However, the efficiency of broiler production will enable our industry to afford more expensive protein when compared to less efficient competitors.

High dietary crude protein (CP) levels in broiler diets place a burden on the environment. Broilers that consume high protein diets emit more nitrogen (N) and ammonia. Ammonia is emitted from the manure through the breakdown of undigested protein and uric acid. It is responsible for water pollution (eutrophication) and soil acidification (Belloir et al., 2017). Legislators in Europe have placed limits on the levels of nitrogen allowed in poultry manure. Precise protein nutrition is beneficial to the sustainability of broiler meat production (Lambert and Corrent, 2018). For example, avoid feeding ingredients that are refractory to digestion (heat damage) or retard gut health and increase disease challenge (inflation and immunity demand protein). Simply reducing dietary CP is a strategy that will have both economic and environmental outcomes. It involves the use of enzymes and crystalline amino acid, or perhaps a simple reduction in feed specifications. Alhotan and Pesti (2016) emphasise that it is important to meet the non-essential amino acid requirements. They demonstrate that requirements for growth and feed conversion differ, but that an ideal ratio between the amino acid level of the diet and its true protein content (TP) exists. Practically, dietary protein may be reduced to a point that impairs performance and loses opportunity.

Belloir et al. (2017) evaluated the impact of a reduction in dietary CP in broilers (Table 1). The feed conversion ratio (FCR) and the breast meat yield were depressed in low CP diets, while abdominal fat increased. The N utilisation data was also of interest. N retention efficiency increased with a reduction in CP, and N excretion reduced. Each 1% reduction in dietary CP between 19–16% CP decreased N excretion by 13%. Litter moisture also decreased with reduced protein.

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Evonik (2017) has illustrated how opportunity may be lost by feeding low protein diets (Table 2). Modern broilers are highly responsive to an increased level of dietary protein in terms of body weight, FCR and breast meat yield. This effect appears to be independent of dietary energy content. Different levels of energy and balanced protein (measured as dietary SID Lys) were fed to male Ross PM3 broilers from 21 to 35 days of age. These data demonstrate that higher protein levels lead to improved yields of high value products, with improved feed efficiency. Clearly a compromise is required. We know that the birds respond to higher dietary protein, yet – from an environmental perspective – this is precisely what we need to avoid.

V. ENERGY

It is unlikely that the efficiency of energy utilisation for absolute growth will change (Lopez and Leeson, 2005; Tallentire et al., 2016), but the sooner a bird reaches target weight, the smaller the proportion of energy used for maintenance purposes will be. Our role as nutritionists is to meet the bird’s demand for sufficient calories on each day of the production cycle. As can be seen from Table 2, the broiler has the ability to maintain its energy intake regardless of the energy level of the diet. In commercial situations, however, it is not this simple since the pressure created by high stocking densities and limited feeding space prevents broilers from consuming enough feed to meet their energy demands. As a rule, energy intake increases as dietary energy levels rise, with a concomitant increase in field performance. It may not be possible to reduce the energy requirement of the bird, but it is possible to feed diets of different nutrient density in order to utilise cheap ingredients and maximise financial returns. Care should be taken not to focus on producing meat at least cost; rather, we should concentrate on maximising returns (profit).

The real challenge is to calculate energy balance in the broiler. To achieve this, an energy system is required, both to equitably quantify one ingredient relative to another and to enumerate the bird’s requirements. In theory, the values determined should be linear and additive. Any system should be straightforward, cost-effective and repeatable across laboratories. Parsons (2011) believes that the metabolisable energy (ME) system will be the primary and preferred measurement of energy in the foreseeable future; indeed, most commercial feed is formulated on this basis. Mateos et al., (2018) lament that despite abundant research, no simple procedure exists to evaluate the energy content of ingredients and diets.

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Choct (2017) argues strongly that the use of ME is limiting and that any efforts spent on a workable net energy (NE) system are justified. NE gives a closer representation of ‘true’ or usable energy, but it does have various shortcomings. It is complicated, time-consuming, expensive to analyse and, as yet, it has no standardised method. In addition, NE systems apply equations that utilise ME as a starting point. Thus, any errors in the ‘base’ ME values are automatically carried over. NE systems mostly use CP as a measure to calculate the expected heat increment (HI) of a diet. Not all N in the diets is amino nitrogen so perhaps this is an oversimplification. In addition, crystalline amino acids are high in nitrogen and therefore high in crude protein, but they have a close to zero HI in digestion since they are already in their basic form. This is relevant in modern poultry diets where the use of synthetic, crystalline amino acids is increasing. The NE system, as with all systems, fails to account for the non-linearity of fat and fibre addition to broiler diets (Leeson and Summers, 2005; Mateos et al., 2012).

Of interest, is the use of near-infrared spectroscopy (NIRS) technology to predict the chemical composition of an ingredient and hence to predict ME indirectly or, more interestingly, to directly predict AMEn (Hughes et al., 2016). The advantages of NIRS are that it is fast, cheap to run and gives repeatable results. Its limitation is that it is only as good as the calibration used in its set up. In addition, if a flawed energy system is used to calibrate the machine, this will be carried across to all results. The nutritionist is required to decide which energy values to use when formulating, and slavish adherence to a single source of information can be problematic.

The perfect energy system does not exist. This may be because the energy content of a diet is not a property of the diet itself, but rather a property of the bird consuming that diet. However, even if a system is not perfect, it only has to be better than the approach it supersedes. We should accept the flaws of the ME system while we strive for something better, a standardised NE system.

VI. MINERALS

Minerals comprise a small proportion of the diet, but their importance to the birds cannot be overlooked. Dietary supplementation with high levels of inorganic trace minerals is expensive and may be harmful to the environment. Organic minerals are compounds in which minerals are covalently complexed with organic ligands. They are less reactive than mineral salts, but can be supplemented at lower concentrations than sulphates and oxides without impacting on bird performance (M’Sadeq et al., 2018). Currently, organic minerals are an expensive option but, in future, their use will increase.

Phosphorus (P) and calcium (Ca), deserve special attention. Not only are the global supplies of P constrained, but the way in which P is managed in poultry diets is a key component of sustainability from an environmental perspective. Nutritional strategies can improve the effective use of P, to avoid overfeeding and minimize P excretion (Rousseau et al., 2016). Current research would indicate that the P requirements broilers are lower than mostly used in practice, and the use of phytase allows levels to be reduced still further (Faridi et al., 2015; Kim et al., 2017 and Cheng et al., 2018). These findings are in stark contrast to the recommendations of the primary breeding company and to general commercial practice. New recommendations have been published by INRA (Khaksar et al., 2017) and (Angel, 2018). Although these recommendations differ from each other, they are consistent in that they recommend low levels of both minerals in grower and finisher diets. Phytase doses will likely increase, resulting in more complete degradation of the phytate plant material. Implementation of these strategies will lead to reduction in demand for P and will also decrease the polluting levels of P in broilers manure. Our current approach when formulating diets is to use some measure of available P and the total Ca. Clearly, we would do a better job of formulation if we were to use a measure of available Ca, and then formulate accordingly (Angel, 2017; Ravindran, 2018).

VII. DISCUSSION

As clichéd as the term ‘precision nutrition’ is, it is the goal that nutritionists strive for. If we are able to meet the nutrient requirement of each individual in a flock, on each day of the production cycle, we will enhance our ability to produce poultry meat in a sustainable manner. Bear in mind that well-performing flocks will have different requirements to poorer flocks. This is challenging when most operations use only three or four phases of feed throughout the broiler cycle. In order to achieve the lofty ambition of precision nutrition, ingredients will need to be quantified more accurately than they are at present. Formulating diets by using a single value for energy ignores the fact that we are unsure of how to measure energy or to cope with variability in the first place. The non-linear nature of fat and fibre addition to bird diets will need to be accommodated.

The efforts made by nutritionists will need to be matched by improvements in feed manufacture. Some form of real-time energy determination and formulation adjustment would be helpful. Disparate parcels of ingredients will need to be identified and preserved, before being precision weighed and mixed. These suggestions will bring about an unimaginable level of management complexity and cost in terms of ingredient purchasing, storage management and logistics. On farms, the bulk of management resources are likely to be utilised in deciding which diet to feed to which flock.

Clearly a more pragmatic approach will be required. Nutritionists will have to make considered decisions about ingredient energy and nutrient content. Decisions about feed specifications will also need to be made, bearing in mind sustainability, the cost and availability of ingredients, farm management, the end products and, importantly, net returns. Feeding programmes will have to be designed to ensure that bird requirements are met, while minimising harmful pollutants. These programmes will have to match the logistics of specific farms, as determined by feed bin size, delivery vehicle capacity and bird numbers. Feed millers will need to manage their ingredients more adroitly, for example by using multiple bins for key ingredients, but probably not by changing formulations on an hourly basis.

The feeding and nutrition of meat chickens have never been more complex and the advances are going to continue. Rather than expecting computer systems to make our lives easier, professionals in the broiler industry will be required to make more decisions than ever before. Although we are a long way from the goal of precision feeding, the use of the information already at our disposal will ensure that the broiler industry moves towards sustainability in every aspect.

Abstract presented at the Australian Poultry Science Symposium 2019. You can check the details of the 2021 edition of this event.