An experimental study was conducted to examine the effects of adding serine-protease from Bacillus licheniformis on performance and physiological parameters of broiler chickens under Egyptian condition. A total of 600 one-day-old chicks were randomly divided into four experimental treatments. The treatments consisted of the control diet with 0, 100, 200 and 300 mg/kg serine-protease. Protease supplementation increased (P < 0.05) body weights (BW). Feed conversion ratio (FCR) was improved (P < 0.05) due to 200 and 300 mg/kg protease supplementation. The dry matter and crude protein digestibilities were enhanced (P < 0.05) by both 200 and 300 mg/kg protease supplementation. Plasma albumin and high-density lipoprotein (HDL) concentrations were increased (P < 0.05), while plasma total cholesterol (CHO) and low-density lipoprotein (LDL) concentrations were decreased (P < 0.05) at 100, 200, and 300 mg/kg of protease. Liver malondialdehyde (MDA) levels were declined (P < 0.05) due to 200 and 300 mg /kg protease supplementation. Supplementing 100, 200, and 300 mg/kg of protease increased (P < 0.05) lysine, methionine, and threonine levels in breast muscle. In conclusion, exogenous serine-protease could be used as a feed additive in broiler nutrition and supplementing 200∼300 mg/kg was sufficient to improve growth performance, probably because of its mechanism to enhance protein digestibility.

As the world population increases, there will be an increase in demand for poultry meat. To satisfy this requirement, sustainably will be a significant challenge as different countries in the world face different health problems. Additionally, for decades, poultry nutritionists have worked on sustainability in broiler manufacturing plants. The usage of short- and medium-chain fatty acids (MCFAs), which have positive effects as growth promoters and immunostimulants, is a pioneering way to decrease the cost of diets and improve environmentally friendly and sustainable production in this critical era. This study aimed at evaluating the influences of alpha-monoglyceride (alpha-monolaurin) on the growth performance, biochemical parameters, lipid profiles, liver oxidative stress, and immune response in broilers. Alpha-monolaurin was included at the levels of 0 (control), 0.25, 0.5, and 1 g/kg in broiler diets. After 33 days, dietary supplementation of alpha-monolaurin showed no impact on the feed intake; however, broilers fed 0.5 g/kg feed displayed a significantly reduced food conversion ratio, as compared to the control (p ≤ 0.05). However, body weight and body weight gain tended to increase after 0.25 g/kg alpha-monolaurin supplementation, as compared to other groups. The highest European production efficiency factor (EPEF) was obtained with 0.25 g/kg alpha-monolaurin supplementation. The ether extract utilization and spleen weight were improved substantially (p ≤ 0.05) by alpha-monolaurin supplementation, but muscle and other organ weights were not affected. Plasma alanine transaminase (ALT) was decreased significantly by alpha-monolaurin supplementation, while plasma total protein and albumin were enhanced (p ≤ 0.05). Interestingly, broilers fed alpha-monolaurin displayed an increased antibody titer of the Newcastle disease (ND) virus and muscle unsaturated fatty acid content, and a decreased liver content of malondialdehyde (MDA). It could be assumed that dietary supplementation of alpha-monolaurin positively impacts birds’ feed efficiency and immune response and can be applied as a natural immune enhancer in the broiler industry.