Response of broiler chickens fed low-energy diets to increase levels of lysolecithin: linking growth performance with lipid metabolism gene expression, gut microbial modulation, intestinal morphology, and economic efficiency.

Lowering dietary energy density cuts feed costs but impairs broiler growth due to the limited fat digestion capacity of young birds. Supplementing low energy diets with lysolecithin (a hydrolyzed soy lecithin product) has been reported to counteract this limitation, as its emulsifying action may enhance fat digestion and energy utilization and thereby help to restore performance. This study is designed to evaluate the effects of lysolecithin supplementation on growth performance, remodeling of lipid genes metabolism and intestinal microbiota, antioxidant status, immunological response, and intestinal morphology in broiler chickens fed low-energy diets. A total of three hundred twenty (320) broiler chicks (Ross 308 breed) were obtained from a commercial hatchery and randomly allocated to four nutrition regimens (8 replicates/group, 10 chicks/replicate): Group 1, control basal diet with standard energy and no emulsifier (CS); Group 2, control low-energy diet with 80 kcal/kg lower metabolizable energy and no emulsifier (CLow); and Groups 3 and 4, control low-energy diets supplemented with lysolecithin at 125 and 250 mg/kg diet, respectively (CLowE125 and CLowE250). Lysolecithin-supplemented groups significantly outperformed the unsupplemented low-energy group in terms of total body weight, final body weight gain, and feed conversion ratio (p < 0.01) without having an impact on feed intake. Serum triglycerides were decreased in the lysolecithin-treated groups compared with the standard-energy group, whereas serum cholesterol was reduced in the low-energy and 125 mg/kg lysolecithin groups. Dietary lysolecithin supplementation dose-dependently remodeled the expression of key intestinal and hepatic lipid transport and metabolism genes (SLC27A4, PPARα, PPARγ, ACSL1, CD36, NPC1L1, MGAT2, MTTP, APOB, and FABP), with the 250 mg/kg dose eliciting the most pronounced upregulation. Supplementing the low-energy diet with lysolecithin restored the depleted beneficial genera (Lactobacillus, Bifidobacterium, and Bacillus populations) as quantified by real-time quantitative PCR (qPCR). Adding lysolecithin at a level of 250 mg/kg to the low-energy diet improved (p < 0.001) oxidative and immune status by lowering malondialdehyde and increasing catalase, superoxide dismutase, lysozyme, total antioxidant capacity, and serum IgM. By increasing villus height and the villus height-to-crypt depth ratio (p < 0.001), duodenal morphology was positively impacted by lysolecithin supplementation. Overall, the lysolecithin emulsifier is a promising nutritional approach that enhances feed and economic efficiency while maintaining production standards under energy-restricted diets.