Antibiotic Growth Promotors (AGPs) are a group of feed additives widely used to improve animal health and performance. Mode of action is actually still an area of debate, but it is clear we have moved away from a simple model of reduction of pathogens / reduction of microbiota competition with the host animal to one where reduction of inflammation and modulation of immune response is a more likely explanation.
AGPs are effective in enhancing performance. However, in the last 20 years a continued focus on resistance to antibiotic therapies for humans has led to a global campaign to remove them from the animal production cycle. This policy is now fully enacted in many parts of the world, and even in countries where legal bans are not enacted, “commercial” pressure leads production to be increasingly AGP-free.
Moving Away from AGPs
Whilst mode of action is debatable, what is not is that removing them can result in adverse results. Growth rate and feed usage efficiency can decline; enteric disease and damage to gastrointestinal tract increases; and there is often an environmental / animal welfare impact in wet litter / higher levels of detrimental compounds such as ammonia. So, can we remove AGPs and NOT experience these problems?
The answer is yes, but not by a simple replacement approach. The details below suggest a strategy to reduce the risk of adverse impacts of AGP removal, in order of importance to ensure your enterprise maintains performance and profitability.
The avoidance of challenges is obviously a priority; prevention is always better than cure!! Effective biosecurity of open sided houses is more difficult than environmentally controlled houses. However, even here use of nets and well-maintained infrastructure is a must. Control of visitors – including staff – is also a must. Anything that can reduce the transfer of pathogens into your stock should be considered; for example, staff members keeping their own livestock should be actively discouraged. Pest control, prevention of wild animal ingress is essential.
Generally, management of livestock will need to be fine-tuned. Ventilation will assume an even more important role, in conjunction with managing moisture levels in the house atmosphere. Drinkers must be set to avoid spillage and adding to potential wet litter problems.
Talking of litter, observing and checking litter is a mundane but essential task, in particular watching how litter quality changes over time.
Feed intake and water intake also help in indicating potential issues developing, especially the ratio between the two.
Monitoring and response generally have a key role. With an increased possibility of enteric diseases becoming a real problem rather than just an inconvenience, the ability to rapidly respond to a developing issue is crucial. Collection – and analysis – of good quality data will allow better strategic decisions and planning to be made, based on experience.
3. Move to Digestible Nutrients
Our understanding of animal requirements has steadily improved, and now we can define these requirements as nutrients that the animal absorbs and utilizes. An example is Standardized Ileal Digestibility (SID) for amino acids. Using this measure gives better guarantees of performance as well as placing higher values on more digestible sources. Another example is the use of Available, not total, Phosphorus (P).
Of course, these approaches also require an awareness of the inter-relationship of nutrient requirements, so a correct balance using up to date recommendations is essential. All of these measures reduce oversupply of nutrients; and such oversupply is linked to reduced gut health and higher excretion.
4. Reduce Crude Protein
Hand in hand with the use of SID amino acids to define animal requirements is the move to lower crude protein levels. An important point to make here is that animals DO NOT have a crude protein requirement; they have a requirement for amino acids and, to a limited extent, nitrogen. So the practice of formulating to a minimum crude protein is counter-productive and should be discontinued. By reducing crude protein levels we immediately reduce nitrogen excretion; reduce water consumption; and reduce the potential for bacterial overgrowth in the hind gut.
5. Use Enzymes-where appropriate
Use of Phytase is a must. This immediately reduces intake of mineral based P; and the excretion of indigestible vegetable-based P. It also improves digestibility of other nutrients, including amino acids. Use of appropriate non-starch polysaccharide (NSP) enzymes is also recommended, in diets containing wheat, barley, oats, triticale and rye. High NSP – especially soluble NSP – can increase digesta viscosity which in turn leads to reduced nutrient absorbance and increased risk of dysbacteriosis. However, a note of caution. We observe some excessively high values for both energy and other nutrients ascribed to enzymes. Our experience suggests a more conservative approach should be applied.
6. AGP Alternatives
As mentioned above, a simple replacement of an AGP with a single product is not likely to avoid problems. However, in conjunction with points above, use of alternative products can improve both animal performance and overall well-being. There are an incredible number of different types of products being touted; here we list some of the more well researched types, that might be active in maintaining gut structure and microbiota composition.
Most widely used are probiotics, live cultures that can influence the microbiota and the gut environment.
Prebiotics also have the potential to amend bacterial populations, encouraging “beneficial” strains.
Phytochemicals might well have similar effects to AGPs themselves but require more research to demonstrate modes of action.
The use of organic acids is already established, but again their application should be reviewed. In-feed reduction of potential pathogens is one application; influence on microbiota is a completely separate topic; and both should be considered separately.
7. Stocking Density
Cost effective production usually means maximizing profit in a given space; hence higher stocking density. Therefore having to use this approach is literally the last one that should be considered. It is really only relevant where above applications are not possible.
The actual solution for YOUR enterprise will certainly require several of the above suggestions. Your local Evonik colleague will be able to help you with guidance and advice to help reduce any adverse impact of removing AGPs from the feed of your stock.