Effects of microencapsulated DL-methionine on meat quality, muscle fatty acids, and the expression of growth- and antioxidant-related genes in broiler chickens: A dose–response study

• The study evaluated the efficiency of microencapsulated DL-Met in broilers. • 90-100% DL-Met replacement increased n-3 fatty acids in thigh meat. • Microencapsulated DL-Met enhanced oxidative stability in tissues. • Meat quality remained stable, except for increased redness. • GHR and IGF1 expression were upregulated with higher DL-Met levels. Microencapsulation of DL-methionine (DL-Met) may enhance delivery and efficacy in broilers. A completely randomized, dose–response trial assigned 1,260 one-day-old Arian chicks to six diets for 35 d (seven replicates per treatment and 30 birds per replicate): a control corn–soybean diet meeting the breeder-recommended digestible Met (dMet) requirement with crystalline DL-Met, and five diets supplying 60%, 70%, 80%, 90%, or 100% of that requirement from microencapsulated DL-Met (CM60–CM100; dosed on 72% active content). Results showed that body-weight gain and feed efficiency (gain: feed) were greater in CM80–CM100 than CM60–CM70, with CM90 exceeding the control (P < 0.05; linear/quadratic trends P < 0.01); feed intake was unchanged. Carcass and leg yields were unaffected, whereas breast yield increased in CM90 vs. CM60 (P < 0.05). Breast fat decreased (except CM70) alongside a protein increase at CM90; thigh fat decreased in CM90–CM100 (P < 0.05). Meat-quality indices were largely unchanged apart from higher redness (a*) in breast (CM90) and thigh (CM80–CM100). Breast SFA decreased and PUFA/SFA increased in CM90–CM100; in thigh, n-6/n-3 fell while EPA, DHA, and total n-3 PUFA rose (predominantly linear; P < 0.05). Total antioxidant capacity and GPx increased and MDA decreased in liver/breast/thigh, with SOD/CAT largely stable; Nrf2 (maximal at CM90) and GPx1 were upregulated in CM90–CM100. GHR expression increased in CM80–CM100 vs. CM60 and in CM90–CM100 vs. control and CM70; IGF1 increased in CM90–CM100 vs. CM60; mTOR was unchanged (P > 0.05). In conclusion, formulating 90% of the dMet requirement from a 72%-active microencapsulated DL-Met can be adopted to improve growth efficiency, enrich n-3 fatty acids, and strengthen oxidative stability without compromising intake or meat quality.