The production of antibiotic-free (ABF) poultry is now a common trend worldwide, since growth promotant antibiotics (GPA) have been banned by some governments and because many consumers are increasingly avoiding food products that contain antibiotics. Despite GPA having been an excellent tool in controlling dysbacteriosis and enteropathogens in animal production for the past 50 years, the negative publicity of GPA in the media, as well as market trends and perceived marketing opportunities, indicate that the majority of the poultry industry will or should now implement some level of ABF production.
Many poultry companies have years of experience working with the ABF system. Some still have difficulties in controlling diverse health challenges, while others have had successful experiences, due to improvements in housing and changes in feeding, management, and health programs. These measures, implemented to control the multitude of factors that may affect intestinal health, incur additional costs. ABF systems can be profitable, as long as the prices of the final ABF products can cover the costs implicated in the investments necessary to develop these products.
There are numerous concepts around the ways that ABF systems in poultry meat production can be implemented or improved in order to reach flock health and welfare conditions, while improving productivity.
What is the level of ABF production that the poultry company wants to achieve?
There are many categories in ABF production, depending on the type of certification, market claims or products to be offered to consumers. Some of these main groups are:
Each system may raise certain difficulties for producers managing flock health. For example, they could implicate higher costs of production, lower levels of productivity and difficulties in achieving low mortality and good poultry welfare.
A common misconception surrounding ABF production is to focus only on intestinal disease control. Generally, the attention is placed on coccidia or specific enterobacteria like Clostridium or Salmonella. This misunderstanding comes from daily experiences that indicate these are the main health issues observed when any ABF program is implemented. However, the reality is these are the consequences and not the causes of the main issue. The excess of nutrients in the hindgut, from either high levels in the diet or suboptimal digestibility, cause microbial proliferation in the hindgut.
Nutrients in excess, especially protein and fat, are not well digested and absorbed at the end of each feeding phase. This increases the microbial proliferation in the ceca. Appropriate digestibility can be achieved and maintained once there aren’t too many nutrients in the diet. This can help control all microbes and the diseases that they generate. Therefore, phase feeding or increasing the dietary phases currently offered to improve feed formulation precision, according to animal needs, is necessary for ABF production.
The following steps are necessary to stimulate appropriate digestive function in all poultry species:
Exogenous enzymes are the second best tool to control bacteria proliferation in the intestines. They have been widely adopted due to the cost-saving impact in diet formulation and as productivity enhancers. A secondary effect of all enzymes is their positive impact on gut Microbial Communities (MC). Exogenous enzymes reduce microbial proliferation by reducing the indigestible components of feed, the digesta viscosity or the irritation to the gut mucosa. Enzymes also generate metabolites that promote microbial diversity which helps to maintain more stable gut ecosystems that are more likely to inhibit pathogen proliferation.
Good quality feedstuffs are essential for optimum digestibility. Therefore, every single feedstuff should be evaluated for its quality and for possible factors that may affect digestion.
Water quality and sufficient consumption of water is also important in aiding proper digestion. The physicochemical characteristics should be measured and controlled and the pH should be maintained slightly acidic, between 5 and 7, because basic water pH reduces the activitymof most enzymes.
In the same way that water deprivation can cause intestinal issues, feed withdrawal during grow-out should be avoided completely in ABF programs. After 5 or 6 hours of feed withdrawal, gut mucosa traits shift, making chickens more susceptible to mucoid enteritis. Feed withdrawal stimulates mucin production by goblet cells in the intestinal mucosa. This extra mucin is avidly used by bacteria, irritating the mucosa, generating more mucus and inflammatory reactions. The disruption in mucus properties facilitate adherence of enteropathogens and coccidia infection.
Some feed additives and mineral levels can help to maintain healthy MC in all gut regions. This can occur independently of feed withdrawal, intestinal infections with coccidia, or heat stress and even maintain the normal diversity of MC observed in control groups of chickens. Therefore, these products become an additional tool for ABF production.
A number of feed additives may be included in feed to improve gut health, such as probiotics, prebiotics, enzymes, organic acids and essential oils (plant extracts, herb extracts, phytobiotics):
The combination of probiotics and prebiotics can be referred to as synbiotics. Each type of product has demonstrated varied efficacy while administered independently or in combinations. It is important to point out that each product group discussed is a big category, as broad as antibiotics, and consequently almost each product has a unique characteristic and effect. Only appropriate testing, use, and rotation can guarantee its success in a sustainable ABF program.
A category of phytobiotics, EO blends are mixtures of phytochemical compounds with selective antimicrobial properties, such as carvacrol, thymol, cinnamaldehyde, among others. Some specific EO blends have shown promising results towards the reduction of Clostridium perfringens colonization and proliferation and control of coccidia infection, consequently helping to reduce necrotic enteritis. Additionally, a combination of EOs with benzoic acid has shown a reduction in the mucin production in the small intestine for broilers.
Proper house environmental conditions should be observed for effective ABF production. Optimum temperature, air velocity, and relative humidity according to the age, phase of production and size of the birds should be considered. Any bird under environmental stress, due to heat, cold, very dry or very humid air could have their feed intake patterns and intestinal motility affected, causing reduced digestibility. Lighting programs may also impact feed intake behaviors, motility and digestion. Light intensities lower than 10 lux and 4 to 6 hours of total darkness per day improve feed conversion ratios, indicating slower feed intake and better digestibility. Good house ventilation is key for ABF programs to minimize condensation, litter moisture, and caking. Keeping litter moisture below 30% is the goal, but it is also important that litter does not become too dry.
Preventing coccidiosis and necrotic enteritis are normally the main concerns during ABF production. In cases where no anticoccidial medications are allowed, coccidiosis vaccines and litter management are the principal ways to control Eimeria spp. Cocci vaccination for broilers has been applied in traditional poultry production systems and new ABF programs for years, in many countries. However, control of other intestinal parasites, worms and poultry diseases which have an impact on intestines and immunity, is also necessary when working to improve health programs for the whole ABF production cycle. Proper vaccination of breeders, and at the hatchery, can aid to prevent Newcastle, infectious bursal disease, and infectious bronchitis. Specific vaccines for Salmonella or E. coli could be applied to breeders to minimize the impact of these common pathogens in the progeny.
Daily functional biosecurity practices are necessary to ensure breeder flocks and grow-out farms are free of Mycoplasma gallisepticum and Mycoplasma synoviae. Practices include:
Broiler breeder nutrition is fundamental for adequate development of their progeny. Embryo development is totally dependent upon egg nutrients deposited by hens. Specific nutrients such as vitamin D, trace minerals, carotenoids, and fatty acids play key roles in immunity and gut development. Hens affect embryo nutrition and development by eggshell properties, such as egg porosity and shell thickness, which determine conductance. Eggshell conductance dictates the capacity of eggs to exchange gases and water vapor, consequently affecting embryo yolk and general nutrient utilization.
These physical factors, especially the capacity to obtain sufficient oxygen, limit the type of metabolism, rates of tissue development, and embryo growth. This is more important during the last three or four days of incubation prior to hatch, in the plateau stage of oxygen consumption when development of many tissues, including GIT, bones and muscles, is at its fastest rate. As breeders can transfer intestinal microbes and immunity to their progeny, companies practicing ABF programs should make sure that intestinal health is adequate in breeders and that their vaccination programs are effective, to prevent issues in the progeny.
These effects have implications in the digestive capacity of the chicks and probably in the incidence of intestinal problems and resistance to parasites.
Suboptimal incubation generally tends to increase the hatch window causing some chicks to either hatch too early, 36 to 48 hours before pulling chicks out of hatchers, or too late. Both conditions cause issues with development of the lymphoid tissue associated to the gut and general immunity. Chicks without access to feed and water for 48 hours post-hatch showed a delay on all immunity responses in the ceca and colon and on colonization of lymphocytes in the bursa. This causes reduced immune activity during the first two weeks of life when the majority of primo vaccinations are applied and birds have their first contact with potential enteropathogens.
The ABF programs for poultry meat production are becoming more common. To make these programs successful, extra attention needs to be placed on the whole production system. Not only are feed, feed additives or enteric pathogen control important, but also housing management, water quality and biosecurity at breeder and grow-out levels. Even proper hatchery conditions should be improved to make ABF programs successful.
On the nutritional side, feed formulation precision and phase feeding should be used. Feed processing, using coarse grinding or whole grains, is necessary to stimulate gizzard function and peristalsis. Also, more stringent feed quality assurance programs should be implemented. The use of exogenous enzymes play a key role in aiding improved digestibility and mitigating the negative impact of some antinutritional components. Feed additives with eubiotic characteristics are important tools to modulate microflora whenever any of the other factors previously reviewed cause bacteria proliferation, and therefore help increase productivity in ABF programs.
References available on request.
29 November 2018
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