Transition to diets without zinc oxide

As it is well known, the Committee for Medicinal Products for Veterinary Use (CVMP), in their opinion dated 9/12/2016, recommended to deny any marketing authorization application and withdraw the existing marketing authorizations of veterinary medicines that contained zinc oxide (ZnO), due to environmental issues and the creation of antimicrobial resistance. Regardless of whether the use of zinc oxide really causes environmental problems and resistance to antibiotics, the truth is that the sector has to plan its withdrawal from feeds, because this opinion was ratified by the CVMP in its meeting of 14-16 March 2017. The situation with colistin, a widely used antibiotic to control post weaning diarrhoeas, is very similar: Following the discovery of a resistance mechanism to this antibiotic through the MCR-1 plasmid (Liu et al. , 2016), and given its  use as a last line of defence antibiotic in human medicine, its use in animal production is not advisable.

The current pressure to reduce the use of antibiotics in animal production is so strong that a substitution strategy of one antibiotic by another one is not being contemplated. Instead, a completely new scenario is developing, where antibiotics are not given as a prophylactic measure, but only in occasional and particular instances when it is really needed, after careful evaluation of  which antibiotic would be more effective for the pathology encountered. 

Therefore, the restrictions in the prophylactic use of antibiotics open up a new period in the design of weaner and grower diets. The clear tendency to use hyperprolific sows emphasizes the problem, since it results in more piglets weaned per sow per year, though these pigs are smaller and weaker, and therefore more sensitive to diseases

A holistic approach is needed to carry out the transition to this new scenario, which means it must include changes in different aspects and must be addressed in a comprehensive way. A very brief summary including some, but not all, of the aspects to be developed is shown below:

• Apply more and better vaccination protocols (sows and piglets).
• Better farm biosecurity. Improve the cleaning, disinfection and drying protocols, and follow a strictly All In-All Out policy in the weaner and finishing rooms.
• Restrict the mixing of animals from different origins. Improve the planning and sizing of the nursery and finishing units, so as to avoid mixing the animals.
• Increase the wean-to-finish systems, to avoid problems related to entrance to the finishing units. 
• Improve management; give more attention to temperature and ventilation requirements. We must realize that we do not have any “insurance” that protects us, and that we must meet the heat requirements after weaning.
• Increase the weaning age from 21-23 days to 28 days whenever possible. This will also require a change in the farm planning and management, to avoid excessive loss of body condition in the sows between 21-28 days, especially in hyperprolific sows.
• Water quality. Water is the eternally forgotten nutrient, despite being a key factor, and will become more important from now on for two reasons: i) its microbiological and chemical quality, which needs to be guaranteed in order to prevent it from becoming a source of pathogens, and ii) it is a means to giving animals certain products to improve digestibility and prevent infections. The better efficiency of treatments administered in the drinking water (once the problem is already present), relies in the fact that a sick animal does not eat, but drinks, and also, the product reaches the animal’s digestive system in a faster, more efficient and more direct way.
• Encourage feed consumption during lactation and during the first days post-weaning, avoiding excessive intakes. To achieve this, the design and management of the feed will be essential, giving fresh feed several times per day.  
• Development of artificial lactation systems, to compensate the inability of the sow to maintain the potential growth of the piglets in big litters.   
• Safer diets: a new and vast field of work is opening up, because the design of diets to date very often incorporated antibiotics so, in order to remove them now, many different aspects will have to be redesigned, amongst them:     
  • Lower protein levels as much as possible, using the available synthetic amino acids.  
  • Formulate feeds based on net energy, possibly with levels slightly lower than the current ones. 
  • Improve digestibility of the protein ingredients, limiting soya meal until the piglets reach 11Kg LW.   
  • Guarantee a minimum quantity of milk components in the diet, providing lactose and milk protein.
  • Limit the buffer power when withdrawing the ZnO, and restrict CaCO3. 
  • In certain circumstances, use functional raw materials, such as porcine plasma, to ensure a correct post weaning feed intake.   
  • Increase the particle size, using meal diets or combining meal and pellet diets. 
  • Increase insoluble fibre, possibly with raw materials such as oats, which stimulate the movement of the food through the digestive system.
  • Combine functional additives, such as short chain organic acids, medium chain fatty acids or its monoglycerides, plant extracts to control the pathogenic flora or prebiotics/probiotics to stabilize the microbial flora. Besides, these additives can be combined with each other or with products that improve the digestive physiology, such as butyric acid in its different presentations (salts, protected salts, monobutytin, tributyrin)     

In relation to the functional additives, it is very difficult that one additive alone can mimic the effect of adding antibiotics or ZnO. Therefore, in order to obtain a prophylactic or treatment effect, a combination of different groups of additives in the water and the feed will be required, so they act in a synergic way. In the next few years new information about the ability of these combinations of additives to replace the current medications in weaner and grower diets should certainly be generated.    

Finally, regardless of what is true in the field of antimicrobial resistance in relation to the use of antibiotics in animal production, I firmly believe it is possible to produce in a competitive way with less use of antibiotics, and that in the long term, it will be positive for the industry as a whole.