The effect of in ovo feeding of L- methionine on carcass traits, small intestine morphology, and blood metabolites of day-old broiler chicks

Methionine, as the first limiting amino acid in poultry, is necessary for protein synthesis and growth. Several studies evaluated the impact of in ovo injection of DL- methionine, but there is no report regarding the in ovo injection of L- methionine. Therefore, the purpose of this study was to investigate the effect of in ovo feeding of L- methionine on weight, carcass traits, small intestine morphology, and blood metabolites of day-old broiler chicks. To achieve the aim of the study, 240 broiler breeder eggs (Ross 308) were used based on a completely randomized design with eight experimental treatments and 30 eggs per each treatment. Experimental treatments included: six levels of L- methionine (0.19, 0.38, 0.57, 0.76, 0.95, and 1.14% L- methionine), a sham control (injection of distilled water), and a control (non- injected group), which were injected into the amniotic fluid at 14 days of incubation. After hatching, chicks were weighed, blood samples were collected, and they were humanly euthanized to evaluate carcass traits and small intestine morphology. After that, serum of blood samples was collected and used for measuring metabolite concentrations. The results of the study indicated that in ovo feeding of L- methionine increased carcass efficiency and thigh, breast, gizzard, and thymus weight (P<0.05), but did not influence hatchability (P>0.05). In addition, reducing effects of L- methionine treatments on serum glucose, triglyceride, and blood urea nitrogen were observed (P<0.05). Moreover, in ovo injection of L- methionine improved length and weight of small intestine, and duodenum and jejunum morphology parameters (villous height, villous height/crypt depth ratio, crypt diameter, and crypt depth), (P <0.05). According to the results of this study, in ovo feeding of 0.19% L- methionine had an improving effect on hatchability, carcass traits, blood metabolites, immune system organs, and morphology of small intestine; therefore, 0.19% L- methionine is an advisable level for in ovo feeding.