Background and Aim: With the increased concerns about global protein supply, chicken meat, especially from male layer chicken, constitutes an alternative in terms of quality and carcass traits. Probiotics have been proposed for replacing antibiotic growth promoters (AGPs), which have been prohibited as poultry supplement feeds. The present study aimed to determine the efficacy of dietary supplementary probiotics during the starter period on growth performances, carcass traits, and immune organs of male layer chicken.

Materials and Methods: In this study, one hundred and eighty 1-day-old male chicks from the strain ISA brown were used. They were divided into six groups according to the feed: 100% basal feed (T0), basal feed+2.5 g AGP/kg feed (T1), basal feed+probiotics 1 mL/kg feed (T2), basal feed+probiotics 3 mL/kg feed (T3), basal feed+probiotics 4 mL/kg feed (T4), and basal feed+probiotics 5 mL/kg feed (T5). Probiotics (Lactobacillus acidophilus, Lactobacillus plantarum, and Bifidobacterium spp.) were given at a concentration of 1.2×10⁹ colony-forming unit/mL. Virginiamycin was used as AGP. ISA brown layer chicken was treated for 21 days. Growth performances (body weight, feed consumption, and feed conversion ratio [FCR]), carcass traits (weight at slaughter, weight of the carcass, breast muscles, liver, lungs, kidneys, and heart), immune organs (spleen, thymus, and bursa of Fabricius), and non-edible organs (head, legs, and wings) were analyzed.

Results: Probiotic supplementation at 4 and 5 mL/kg feed (T4 and T5) during the starter phase improved the body weight, FCR, and feed consumption. The weight at slaughter, weight of the carcass, breast muscles, and liver from the T4 and T5 groups were significantly greater than those in the other treatment groups. In addition, the weight of the heart, lungs, and kidneys was increased in the T1, T2, T3, T4, and T5 groups compared with that measured in the T0 group. Furthermore, there were significant differences regarding the immune organs between the T0 and the other treatment groups. The weight of the head, legs, and wings was also greater in the probiotic and AGP supplementation groups (T1, T2, T3, T4, and T5) than that in the basal feed group (T0).

Conclusion: Probiotic (L. acidophilus, L. plantarum, and Bifidobacterium spp.) supplementation at 4 and 5 mL/kg feed during the starter period can be used to improve the growth, carcass traits, and weight of immune organs in male layer chicken.

Keywords: feed supplementation, growth performance, ISA brown layer chicken, probiotic, starter period.