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Review Articles |
Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1
Correspondence: 1 Corresponding author: sleeson{at}uoguelph.ca
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SUMMARY |
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 TOP SUMMARY DESCRIPTION OF PROBLEMEFFECT OF CHANGES IN...BIRD HEALTH, ANTIBIOTICS, AND...ENVIRONMENTAL ISSUESNUTRITION AND FEED PROGRAMSHUMAN HEALTH, TRACEABILITY,...CONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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Key Words: diet formulation • feeding program • production goal • human health • environment • traceability
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DESCRIPTION OF PROBLEM |
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TOPSUMMARYDESCRIPTION OF PROBLEMEFFECT OF CHANGES IN...BIRD HEALTH, ANTIBIOTICS, AND...ENVIRONMENTAL ISSUESNUTRITION AND FEED PROGRAMSHUMAN HEALTH, TRACEABILITY,...CONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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There is a prediction for consumption of around 65 million tonnes of broiler meat in 2015, which equates to a yearly live production of 80 million tonnes or about 40 billion 2-kg birds. The industry will require some 160 million tonnes of feed. There will likely be a change in location of such production. Currently we have major production centers in the Americas, Europe, and Asia. The Americas and Asia will continue to meet world demand, whereas Europe seems destined to supply its own local market for niche products. Within the Americas, the United States and Brazil will continue to be the major producers and exporters, whereas in Asia, China will likely represent the major region for growth, both for domestic production and also for exports. It is obvious that although it is possible to produce broilers in almost any geographical region, it is the location of ever more sophisticated processing facilities that dictate major centers of meat production. Some countries will continue with marketing of live birds (e.g., Mexico and Peru), and although this effectively excludes imports, it does limit future expansion and profitability and now poses unique problems of biosecurity in movement of live birds. Processing and further processing are the keys to market penetration of poultry meat, and these facilities are becoming increasingly expensive to establish and maintain. The current trend to producing heavier birds is merely a response to reducing processing costs per unit of meat yield. The limiting factor to processing in the next 20 yr will be an adequate and economical supply of water that meets every increasing standard for pollutants and contaminants. We will meet these standards by utilizing water purification systems, which will necessarily add to our cost of production.
The only real challenge to the dominance of global poultry meat production will come from the swine industry. As they develop production strategies similar to those characteristic of broiler chicken production, such specialization and economy of scale will result in cheaper cost of production. However, their higher maintenance energy requirement will always mean a less efficient feed utilization, and so the broiler industry will continue to lead in least-cost production of lean meat. Also, as the pork industry delves into further processing, like the poultry industry, they will see advantages to marketing of heavier pigs, and this will help the broiler industry to maintain its competitive edge. It seems likely that the emerging modern swine industry will mirror developments in the poultry industry, and in most situations, our main competitor will be physically situated in very close proximity to poultry producers. The swine industry will also be our major competitor for sourcing of corn, soybean meal, and fats.
The egg layer industries are also undergoing change, in terms of potential for egg processing and more recently the start of major international trade in shell eggs. The major production areas will be the Americas and Asia, with some niche markets relating to housing systems remaining in Europe. Layers, like broilers, will be fed diets based on corn and soybean meal. By 2015, we will have 1.2-kg mature weight white egg strains eating about 95 g daily and producing 345 eggs by 72 wk of age. For brown egg birds, intake will be around 100 g daily, and production will be 335 eggs by 72 wk of age. Although cages will continue to be the main system for housing birds, there will be niche markets for noncage production systems [1]. However, cage systems will be the only competitive production alternative for global export markets, especially for processed egg products.
We have to resolve the ongoing problem of eggshell quality, which considering the number of eggs that will be produced by layers in the future, will invariably become a more serious problem. We need a better understanding of Ca flux of the hen throughout the entire 24-h cycle of egg formation [2] and how this is affected by nutrition, housing, environment, and health status of the bird. There will undoubtedly be new niche markets opening up for eggs and egg products. There is going to be greater emphasis on value-added production of egg products, and for this reason, we need to know a great deal more about factors that influence the solids content of an egg and not merely factors that influence egg weight. We can also have the bird include novel fats and proteins into the egg, which make them even more attractive for human consumption, as novel designer foods for other animals such as baby pigs and other industrial uses.
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EFFECT OF CHANGES IN PRODUCTION SYSTEMS |
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TOPSUMMARYDESCRIPTION OF PROBLEMEFFECT OF CHANGES IN...BIRD HEALTH, ANTIBIOTICS, AND...ENVIRONMENTAL ISSUESNUTRITION AND FEED PROGRAMSHUMAN HEALTH, TRACEABILITY,...CONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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Worldwide, there has been general standardization in the type of housing and management systems of broiler farms, and to some extent, this leads to standardization of feeding programs. New farms today will likely involve a site for 8 to 10 houses, each holding around 50,000 to 60,000 birds. These houses will be fully controlled environments or open-sided with more elaborate insulated curtains, usually incorporating tunnel ventilation. Although simple pole and wire structures were commonly built in temperate regions in the 1970s, we now realize that the extra cost involved in having greater control over environmental conditions is more profitable in terms of broiler performance over the 20- to 25-yr life span of the building.
In the mid 1980s, broiler producers in tropical climates were encouraged to abandon their low-lying farms because of problems with heat stress and establish new facilities at higher altitudes, which were much cooler. Since then, ascites emerged as a major cause of mortality [3], and farming broilers of any age at <15°C caused high mortality. Unfortunately, there are always cool/cold nighttime conditions at high altitude, and so these new locations were unsatisfactory. Therefore, we are once again concentrating on lower altitude sites for broiler farms, because today, the effects of heat distress can be better managed with new environmental systems and a better understanding of the effect of nutrition on heat-stressed birds. Another future concern is an adequate supply of clean water for any broiler operation. In many regions, ground water levels are receding, which means more power is required to pump to surface levels. In arable regions, the levels of minerals and pesticides will become more critical as a consequence of their gradual (20- to 30-yr) movement through soil and our inevitable advances in being able to detect ever-decreasing quantities of any residue. Likewise, the trace mineral content of water is changing over time, and this can affect nutrition.
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BIRD HEALTH, ANTIBIOTICS, AND ALTERNATIVES |
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TOPSUMMARYDESCRIPTION OF PROBLEMEFFECT OF CHANGES IN...BIRD HEALTH, ANTIBIOTICS, AND...ENVIRONMENTAL ISSUESNUTRITION AND FEED PROGRAMSHUMAN HEALTH, TRACEABILITY,...CONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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The most striking feature of modern growth potential occurs in the first week, in which today we have a male broiler capable of increasing its BW by 300% [5]. Using specialized prestarter diets, we have actually achieved a 400% increase in the 0- to 7-d growth, yet the 300% achieved with commercial diets is extraordinary compared with other farm animals. Relative growth after this time is little different, yet the additional weight achieved by d 7 is compounded by subsequent weekly percentage increases, such that by 8 wk, we have a broiler that today is 1 kg heavier than its 1970 counterpart. However, tempering this early growth, for reasons not fully understood, does seem to reduce the incidence of metabolic disorders occurring after 28 d of age. Such growth reduction can be achieved by using mash diets, very low nutrient density diets, perhaps by physical feed restriction, or more commonly by extended periods of darkness. We can temper early growth rate without too much loss in feed utilization, because during the first 7 d of growth, some 80% of feed is used for growth and only 20% used for maintenance [6]. At 49 d of age, only 20% of feed is used for growth, whereas 80% is used for maintenance, and so trying to temper growth at this age is detrimental to feed efficiency. If mortality/morbidity can be reduced sufficiently by a system of early feed restriction, then the overall feed efficiency of the flock can actually be improved. There is some indication of compensatory growth in broilers [7]. It will be increasingly difficult to sustain such corrective management procedures to what is effectively a consequence of continued genetic selection for faster growth and increased potential for feed consumption. In the near term, current and emerging metabolic disorders will be of sufficient magnitude to necessitate a moderation in selection pressure for growth rate.
Control over coccidiosis and necrotic enteritis is likely to be our major future concern regarding infectious disease of broilers. With the introduction of ionophore anticoccidials, concerns over coccidial control diminished, because these products were universally efficacious. Resistance to older chemical coccidiostats occurred quickly, because their mode of action involved only a few enzyme systems within the oocyst controlled by a limited number of genes. The ionophores, on the other hand, caused massive disruption to cell membranes, affecting numerous enzyme systems and control mechanisms. As anticipated, it has taken oocysts much longer to mutate such that oocysts can withstand this more widespread biochemical disruption [8]. Unfortunately, ineffective control of coccidiosis often leads to necrotic enteritis caused by an opportunistic clostridial bacterium. Although coccidial vaccines have been used successfully for breeders, their use to date for broilers has met with variable success, again due to development of resistance. A novel approach in the future may well be the sequential use of a vaccine followed by an ionophore anticoccidial.
Current production systems rely on feedborne antibiotics and growth promoters. With current growth rates of broiler chickens, the classical effects of growth promoters are less easy to quantitate [5]. However, most of these compounds are efficacious against clostridial infection and without them, it is often difficult to control necrotic enteritis and associated outbreaks of coccidiosis. However, it seems as though we are destined to routinely use less of these pharmaceutical products, and although they may be available on prescription for treatment use, alternatives are a fruitful area of research and development. So-called probiotics and prebiotics seem logical alternatives to antibiotics and growth promoters [9], and the key to their use is very early dosing of the bird. Such treatment of chicks on arrival at the farm may prove to be too late to prevent colonization of pathogens. This leaves the hatchery as the most logical site for treatment.
Reuse of litter material is another contentious issue. In the United States, 6 to 8 flocks are commonly used on the same built-up litter, whereas in most other regions of the world, litter is removed and houses thoroughly cleaned after each crop of birds. Many producers argue that reusing litter simply does not fit into modern biosecurity and health management programs. However, if the previous crop of broilers was healthy, then their litter and the dirty facilities provide a useful resource for initiating a competitive exclusion program (i.e., the general microbial population from the previous flock is used to seed the next flock of birds). Rather than dismiss the idea of reusing litter, there are circumstances in which it can be used to advantage in a health management program.
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ENVIRONMENTAL ISSUES |
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TOPSUMMARYDESCRIPTION OF PROBLEMEFFECT OF CHANGES IN...BIRD HEALTH, ANTIBIOTICS, AND...ENVIRONMENTAL ISSUESNUTRITION AND FEED PROGRAMSHUMAN HEALTH, TRACEABILITY,...CONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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We can certainly reduce N and P output in manure, simply by limiting the dietary inputs [5, 6]. In many situations today, it is still most economical to overformulate for these 2 nutrients, and imposing maximum constraints during formulation often leads to increased cost. The impetus to reduce N and P loading of manure will necessarily come from legislation involving nutrient management of farmland. In these situations, P is likely to be the major problem, because in many areas today, we are at the saturation point in soil levels of P as dictated by current environmental guidelines. Corn and soybeans take minimal quantities of P from the soil, suggesting that conventional cropping is not a short-term solution to any future problems. The P levels in soil can most quickly be depleted by growing forages, and removing this as hay or silage, a situation that is not always convenient in areas of intensive poultry production. We can certainly reduce the P output of broilers through use of phytase enzyme added to feed [10], although it is unfortunate that conventional pelleting temperatures [11] and formaldehyde treatment of feed deactivates some phytase enzymes. Low-phytate content corn and soybean meal will certainly help to limit P excretion.
Incineration may be an answer in many locations. With efficient incineration, only inorganic elements remain, and these can be used as a fertilizer or as an animal feed ingredient. The ash remaining after incineration is much condensed in volume (95%) and can be more economically moved away from the immediate area of production, to locations where perhaps the corn and soybean used to feed the birds was grown. Intensive broiler production does not create P or N; it merely concentrates its presence, and redistribution back to its original source seems the ultimate example of recycling.
An emerging area of concern in poultry nutrition is the accumulation of Zn and Cu in soil, and again, this may attract legislation regarding manure composition. Likewise, there is emphasis on quantitating NH3 release from many industries including agriculture [12].
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NUTRITION AND FEED PROGRAMS |
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TOPSUMMARYDESCRIPTION OF PROBLEMEFFECT OF CHANGES IN...BIRD HEALTH, ANTIBIOTICS, AND...ENVIRONMENTAL ISSUESNUTRITION AND FEED PROGRAMSHUMAN HEALTH, TRACEABILITY,...CONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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If we want meat birds to achieve ever-increasing weight for age, or more specifically, decreasing age for weight, then greater emphasis will have to be placed on both early- and late-phase nutrition. With females that are potentially marketed at 30 d of age (1.75 kg of live weight), the conventional starter period of 0 to 15 d represents 50% of growout time, and birds must be on a withdrawal diet by 24 to 25 d. The concept of specialized prestarter diets becomes more interesting [13], whereas the philosophy around producing inexpensive withdrawal diets will become a dated concept.
In using prestarters, one assumes that there will be faster early growth (or more uniform growth) and that this will translate into greater weight for age. Each gram of additional weight at 7 d of age translates to 5 g of extra weight at 49 d [5]. Therefore, a chick at 180 vs. 150 g at 7 d can be expected to be 150 g heavier at 49 d. Formulating prestarter diets revolves around the selection of digestible ingredients rather than there being a need for higher nutrient density. Prestarters either precondition the chick such that it can digest complex substrates or provide more digestible substrates until the enzyme production of the chick has matured. Although corn-soybean meal diets are regarded as ideal for poultry, there is evidence that digestibility is suboptimal for the young chick. The idea in formulating prestarter diets is to correct any such deficiency and so hopefully increase early growth rate, improve uniformity of such early growth, or both.
Two types of prestarter diets are used for broiler chickens [14]. The first option is to use greater than normal levels of nutrients, whereas the alternate approach is to use more highly digestible ingredients. If we increase nutrient supply by 10 to 15%, it should be possible to correct any deficiency in digestibility and so realize expected AMEn and amino acid utilization. A potential problem with this approach is the acceptance that nutrients will not be optimally digested. Unfortunately, such undigested nutrients will fuel microbial overgrowth. An alternate approach is to use more highly digestible ingredients, with little change in level of nutrients. Such prestarter diets are very expensive, because alternative ingredients are invariably more expensive than are corn and soybean meal per unit of available nutrients. Using these ingredients, it is possible to achieve 200 g of BW at 7 d, compared with 160 to 170 g with conventional corn-soybean diets. This improved early growth rate usually ensures a heavier bird at subsequent ages.
Toward the end of the feed program, we will have to pay greater attention to nutrient needs during the last 5 to 10 d of growout. There is currently considerable interest in defining amino acid needs of older broilers [15]. At some time, we will likely have to consider programs that temper the growth rate of broilers. This concept will initially be applied to the small weight category female, marketed at around 1.75 kg of live weight. Currently, 32 to 34 d is a common market age, although with continued genetic progress, market age could be 28 d in 5 to 10 yr time. At 28 d, the limit to successful production will be skeletal integrity of the broiler. The skeleton of such young birds will not likely be adequately calcified/mature to withstand the rigors of commercial processing. Either we have to rethink nutrition/feed management or we have to temper growth. It is very difficult to reduce growth rate simply by altering nutrient density. With high-energy or low-amino acid diets, the birds become obese, whereas with low-energy diets, the broiler still has an amazing ability to increase its feed intake to maintain energy intake. For broilers, the limit to growth will be the maturity of the skeleton, relative to bird welfare and the stresses of mechanical processing. For layers, the limit to production will be eggshell quality. Metabolic disorders related to skeletal integrity will be our major challenge over the next 10 to 15 yr and will ultimately pose the limit to increased productivity in all areas of poultry production.
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HUMAN HEALTH, TRACEABILITY, ACCOUNTABILITY |
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TOPSUMMARYDESCRIPTION OF PROBLEMEFFECT OF CHANGES IN...BIRD HEALTH, ANTIBIOTICS, AND...ENVIRONMENTAL ISSUESNUTRITION AND FEED PROGRAMSHUMAN HEALTH, TRACEABILITY,...CONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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Value-added functional foods can be produced through the modification of the conventional production systems and usually by modifying the diet of the bird. For the most part, such approaches are straightforward, and the outcome in terms of product composition is fairly predictable [16, 17]. However, as society moves to accepting/demanding more processed food, the role of poultry nutrition in contributing to functional foods will become less clear. During the processing of food products, it is perhaps easier to add or enrich the nutraceuticals directly into a product rather than rely on the bird to bioconvert and deposit within the body or eggs. Currently, functional animal foods revolve around the manipulation of fats and fat-soluble nutrients [17, 18]. It is fairly easy to manipulate the total quantity of fat, and its fatty acid profile, in both eggs and meat. Protein, amino acids, and most minerals on the other hand are very resistant to manipulation through dietary modification.
An often-neglected component of functional foods is the emotional value of food. In many instances, the purchase and selection of foods is based on emotional issues, and in reality, these decisions relate to the emotional well being and health of the consumer. In this regard, animal welfare is often a key issue, and certainly, organic certification usually involves welfare standards [19]. In the future, we may well see environmentally friendly foods being marketed, especially in view of traceability, and this will again affect poultry nutrition, especially in terms of oversupply of certain nutrients.
Traceability of animal products is inevitable either through legislation or through marketing strategies. Such traceability will require accountability of the composition of poultry feeds. Our current quality control procedures are a major weakness in the food supply chain. Rapid analysis systems are being developed in many industries, but at best, most analytical systems at feed mills provide information that is incorporated into a historical database. The feed industry will be compelled to develop real-time feed analysis. Such analyses will be for components that affect poultry performance/economics, such as protein and energy, whereas other analyses will be required for bacteria, pharmaceutical products, and contaminants.
Various light and sound reflectance/absorbance techniques will be developed to achieve these goals. We currently have infrared analysis [20], and in the future, use of directed lasers and radar may be used in analysis. Although near-infrared analysis has been used for 30 yr in feed analysis, there are still many unknowns to using the technology, and unfortunately, little research is carried out in this area. Within 20 yr, it is conceivable that we will have infrared, laser, or sound-based detectors placed in the surge bins feeding the mixer. Using fiber optic probes attached to a central analyzer, it should be possible to provide immediate analysis of ingredients as they flow into the mixer, and this information will be integrated with the formulation program and the weigh scale. Directed fine-tuning of the formulation and weight of each ingredient should ensure more consistent composition of a diet. Such nutrient analysis would also be stored and used to update standard values and so provide a more precise estimate of current ingredient usage. Real-time analyses for pharmaceuticals/contaminants obviously imposes an even greater order of complexity in analyses, yet nutritionists and feed mill managers are encouraged to keep themselves appraised of the rapidly advancing disciplines of chemical, physical, and biological analyses.
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CONCLUSIONS AND APPLICATIONS |
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TOPSUMMARYDESCRIPTION OF PROBLEMEFFECT OF CHANGES IN...BIRD HEALTH, ANTIBIOTICS, AND...ENVIRONMENTAL ISSUESNUTRITION AND FEED PROGRAMSHUMAN HEALTH, TRACEABILITY,...CONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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REFERENCES AND NOTES |
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TOPSUMMARYDESCRIPTION OF PROBLEMEFFECT OF CHANGES IN...BIRD HEALTH, ANTIBIOTICS, AND...ENVIRONMENTAL ISSUESNUTRITION AND FEED PROGRAMSHUMAN HEALTH, TRACEABILITY,...CONCLUSIONS AND APPLICATIONSREFERENCES AND NOTES |
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