Recent Advances in the Role of Feed Restriction in Poultry Productivity: Part I- Performance, Gut Development, Microbiota and Immune Response

Feed restriction (FR) strategies are classified into quantitative FR (quantity-limited of feed or time-limited access to the feeder) and qualitative FR (reduction of nutrients density particularly protein, amino acids and energy or diet dilution using fibres' sources). Application of early FR (during the 2(nd) wk of age) might be involved in stimulating the compensatory growth, enhancing feed efficiency and reducing mortality rate. The FR may induce the digestive-physiological adaptations in the form of increasing the weight of crop, proventriculus, gizzard, duodenum and caecum and length of duodenum and pancreas. Also, FR had no negative impacts on intestinal histomorphological characteristics (e.g. villus height, crypt depth and villus: crypt ratio). Furthermore, FR strategies are involved in establishing the intestinal microbial balance and supporting the host immune response. Additionally, FRs have several impacts on physiological status and blood biochemical constituents. The purpose of this review is to shed light on the recent results regarding the benefits of FR on growth performance, gut development, intestinal histomorphology, gut microbiome and immune responses in poultry.