SUMMARY Dietary fibre has traditionally been considered an energy-diluting component of laying hen diets. With low energetic values, and sometimes negative impacts on digesta viscosity and gut function, formulations have often aimed to minimise crude fibre contents. Increasing fibre contents can mean that the level of fat required to meet nutritional standards must be increased to account for the decrease in energy, with consequential impacts on feed handling. By contrast, recent research has shown that some dietary fibres can have beneficial effects on laying performance, driven by changes in digestibility, gut structure and function, as well as shifts in the gut microbiota. However, there is often a lack of clarity as to the quantity and type of fibre required to yield production benefits. Broadly, soluble fibres – while largely detrimental to nutrient digestibility – can act as prebiotics, favouring beneficial intestinal microbiomes, while insoluble fibres stimulate intestinal development and may have some preventative effects on feather pecking and cannibalism.

Oxidative reactions in premixes or final-compound feed pose considerable challenges to the poultry industry, both in terms of rancidity reducing palatability and shelf life and in vivo oxidative stress negatively impacting animal performance. Whilst there has been broad awareness of feed oxidation for many years, recognition of the impact of oxidative stress on the poultry industry has grown in the past twenty years. The appearance of woody breast and associated muscle meat myopathies has led to a rapid increase in research output and awareness of in vivo oxidative reactions. Oxidative stress has been widely demonstrated to damage tissue, lipids, and DNA, and is thought to be linked to conditions such as leaky gut, coccidiosis, and ascites, amongst others. The use of dietary antioxidants has been found to both protect feed from oxidation and ameliorate some of the detrimental effects associated with oxidative stress, including improving performance, increasing antioxidant capacity, and mitigating the effects of heat and transport stress. Therefore, the aim of this review is to provide insight into the process of in-feed oxidation and in vivo oxidation including a summary of the benefits of different kinds of antioxidants in feed as well as their potential in vivo added value, based on findings reported within all scientific literature.

Supplementation of a combination of lysolecithin, a synthetic emulsifier, and monoglycerides (LEX) in liquid and dry form to broiler diets with different energy levels was investigated to determine their effect on performance, litter quality and subsequent occurrence of footpad lesions. One thousand two hundred and forty-eight-day-old Ross 308 broilers were assigned to 1 of 6 treatments for a 42-day study: a basal diet with a normal energy content (NE); NE + 300 g/t LEX in liquid form (LEL); NE + 500 g/t LEX in dry form (LED); a basal diet with low energy (LE, -90 kcal/kg starter, -100 kcal/kg grower, finisher), LE + 300 g/t LEL and a LE + 500 g/t LED. Each treatment consisted of 13 pens of 16 birds each. Diets were fed in 3 phases (starter d 0-10, grower d 11-21, finisher d 22-42). Feed intake and weight were measured on d 0, 10, 21, and 42. On d 42 a litter sample was collected from each pen and 2 birds per pen were assessed for footpad lesions and breast scald. Data were analyzed using JMP 16, with means separation achieved using Tukey's HSD; significance was assumed at P < 0.05. Results showed a higher (P < 0.05) cumulative bodyweight gain with LEX supplementation (NE CON = 2,718 g, NE+LED = 2,829, NE+LEL = 2,895, LE CON = 2,722, LE+LED = 2,787, LE+LEL = 2,893; P = 0.0027). An increased feed intake was observed for the LE diets, however cumulative FCR of LE+LED and LE+LEL remained equal to the NE control (1.657 NE CON, 1.657 LE+LED, 1.623 LE+LEL; P > 0.05), suggesting LEX enabled the birds to compensate for the energy gap. Litter dry matter was significantly improved with both LED and LEL supplementation compared to the control groups, and resulted in lower (P < 0.05) occurrence and severity of footpad lesions and breast scalds. Considering the income over feed cost (IOFC) of the NE treatment as the reference point for comparison, all other treatments improved profitability, with NE+LEL and LE+LEL achieving the greatest IOFC with 154.58 and 175.96 €/1,000 birds respectively. In conclusion, feeding broilers a combination of lysophospholipids, a synthetic emulsifier and monoglycerides resulted in improved bird performance. The use of the LEX also improved litter quality and footpad health, therefore improving animal welfare indicators such as breast scald and footpad measurements.