Differential effects of maternal dietary and in ovo L-arginine supplementation on late embryonic mortality in Alope Unhas 1 chickens

Abstract

Background and Aim: Improving embryonic survival and hatchability is essential for increasing the productivity of indigenous chicken breeds. L-arginine is a functional amino acid involved in nitric oxide synthesis, angiogenesis, protein metabolism, and immune regulation, and researchers have investigated it as a nutritional intervention to improve embryonic development and post-hatch performance. However, information regarding the combined effects of maternal dietary and in ovo L-arginine supplementation in indigenous chickens remains limited. This study evaluated the effects of dietary and in ovo L-arginine supplementation on embryonic development, hatchability, embryonic mortality, growth performance, intestinal morphology, and muscle histomorphology in Alope Unhas 1 chickens. Materials and Methods: A total of 108 Alope Unhas 1 breeder chickens (90 hens and 18 roosters) were allocated to four treatments in a completely randomized design with three replicate pens per treatment. A total of 120 fertile eggs (30 per treatment, with 10 eggs per replicate) were allocated for hatchability and embryonic mortality assessments. The treatments consisted of a basal diet without L-arginine supplementation or in ovo injection (T0); a basal diet with in ovo injection of 2% L-arginine (T1); a basal diet supplemented with 0.25% L-arginine (T2); and combined dietary supplementation and in ovo injection (T3). The in ovo injection was administered on day 18 of incubation using 0.5 mL of 2% L-arginine solution delivered into the amniotic cavity through the air cell. Embryonic development, hatchability, embryonic mortality, post-hatch growth performance, intestinal morphology, and muscle histomorphology were evaluated. The replicate pen was considered the experimental unit for statistical analysis. Data were analyzed using one-way analysis of variance followed by Duncan's multiple range test, with statistical significance set at p < 0.05. Results: Maternal dietary and in ovo L-arginine supplementation did not significantly affect embryonic development, hatchability, hatch weight, post-hatch growth performance, intestinal morphology, or muscle histomorphology (p > 0.05). However, late embryonic mortality differed significantly among treatments (p = 0.024). The dietary L-arginine supplementation group (T2) exhibited the lowest late embryonic mortality (0.00 ± 0.00%), compared with the untreated control group (T0; 7.49 ± 1.45%) and the combined dietary and in ovo supplementation group (T3; 15.61 ± 9.27%). Late embryonic mortality was significantly lower in T2 than in T3, whereas the difference between T2 and T0 was not statistically significant. Although hatchability was numerically highest in T2 (83.89 ± 21.10%), no significant differences were observed among treatments (p > 0.05). These findings suggest that maternal dietary L-arginine supplementation may influence late embryonic survival, whereas combining dietary and in ovo supplementation did not provide additional benefits under the experimental conditions. Conclusion: Maternal dietary L-arginine supplementation may improve late embryonic survival in Alope Unhas 1 chickens without significantly affecting post-hatch growth, intestinal morphology, or muscle histomorphology. In contrast, combining dietary and in ovo L-arginine supplementation did not confer additional biological advantages and may adversely affect late embryonic survival. These findings provide useful baseline evidence for optimizing L-arginine supplementation strategies in indigenous chicken breeding programs and warrant further dose-response, mechanistic, and long-term studies to establish effective supplementation protocols. Keywords: Alope Unhas 1 chickens, embryonic development, embryonic mortality, hatchability, in ovo feeding, intestinal morphology, L-arginine, muscle histomorphology.

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