Role of feed additives in poultry nutrition: Historical, current and future perspectives

The feed industry has been aggressively searching for innovative solutions to augment the nutrition and feeding of contemporary poultry strains, one of them being feed additives that improve the productivity, intestinal microbiome, environmental impact, welfare and bird health. The past, present and future perspectives in feed additives, and key additives that present opportunities to sustain the productivity and health of poultry are highlighted in this review. Surprisingly, a clear definition of feed additives remains problematic because they are extremely heterogeneous. Historically, only the non-nutritive components were considered as additives. However, changes in the legal frameworks in the European Union to include nutrients as feed additives have added further confusion. The parallels between historical developments amongst nutrition, commercial poultry production and feed additives are explored. For the purpose of clarity, additives are examined under two major groups in this overview. First, the first-generation additives used since the advent of commercial poultry industry in the 1950s are discussed; these include antibiotic growth promoters, coccidiostats, antioxidants, anticaking agents, pellet binders, mould inhibitors, mycotoxin binders and deactivators, pigmenting agents, palatability enhancers, trace mineral-vitamin premixes and choline chloride. Second, the second-generation additives entering the feed sector in recent decades are considered, including emulsifiers, betaine, guanidinoacetic acid dietary fibre, L-carnitine and myo-inositol. The focus, however, will be on those dealing with current industry issues of sustainability, environment and consumer concerns. In particular, alternatives to antibiotic growth promoters, exogenous enzymes and feed-grade amino acids will be examined in detail. The available literature and the mechanisms underpinning the actions of each additive are briefly reviewed and critically evaluated.