The impact of in ovo injection with L- arginine on carcass traits, blood metabolites, and small intestine histology of broiler chickens

Introduction: During the last stages of incubation, avian mortality commonly happens due to the lack of enough nutrients and amino acids (Fardoost et al. 2019). However, in ovo injection or in ovo feeding is considered a new technique for improving growth of chickens (Ebrahimi et al. 2017). Most studies indicated improving effect of in ovo feeding of nutrients (especially amino acids) on small intestine growth and histology as well as higher absorptive capacity of digestive system (Ebrahimi et al. 2017, 2018a,b; Elwan et al. 2019; Fardoost et al. 2019). Previous studies indicated an improving effect of excess feeding of arginine on growth performance, carcass traits, blood metabolites, and intestinal histology of broilers (Ebrahimi et al. 2013, 2014, 2016b). However, there are few records regarding the impact of in ovo injection of arginine on intestine histology of chickens. Accordingly, the present study was designed to evaluate the effect of in ovo injection of different levels of arginine on carcass traits, blood metabolites, and small intestine histology of broiler chickens.
Materials and methods: For this reason, 300 fertile broiler breeder eggs were divided into three treatment groups: 1- 0.5% L-arginine in ovo injection group (100 eggs), 2- 1% L-arginine in ovo injection group (100 eggs), 3- control group included distilled water injected (sham-control subgroup, 50 eggs) and non-injected (control subgroup, 50 eggs). Eggs were then set into the incubator for the first 18 days with the temperature of 37.8°C and six rotations per day. At d 14 of incubation, eggs were injected into the amniotic fluid (Ebrahimi et al. 2017) as follows: 1- in ovo injection of 5 mg L-arginine/ ml distilled water, 2- in ovo injection of 10 mg of L-arginine/ml distilled water, 3- control group included sham-control (in ovo injection of 1 ml distilled water) and control (received no injection). For in ovo injection, solution pH was set at 7.0. At d 18 of incubation, eggs were moved into hatchery boxes. After hatching, chicks were reared for 24 days. During the experiment, chicks received standard commercial diets based on Ross recommendations as starter (0-10 days) and grower (11-24 days), (Table 1). At d 24, blood samples of three chickens per each replicate were collected, centrifuged (3000 rpm for 20 minutes), and serum was separated to evaluate cholesterol, glucose, triglyceride, uric acid, and total protein by the Enzymatic Colorimetric method (Ebrahimi et al. 2017). Then, all birds were weighed, slaughtered, some carcass traits (scalped carcass, eviscerated carcass, breast, thigh, gizzard, proventriculus, pancreas liver without gall bladder, heart, duodenum , jejunum, and ileum were weighed, and their relative weight to chicken body weight were calculated.
Also, length of duodenum , jejunum, and ileum was evaluated and their samples were stored in 10% formalin for fixation to evaluate histological parameters (crypt depth, villus height, villus thickness, mucosal thickness, and crypt diameter) using Hematoxylin - Eosin staining method (Ebrahimi et al. 2017). Then, villus height to crypt depth ratios were calculated. Afterwards, data were analyzed based on a completely randomized design by the Proc GLM of SAS software (Ver 9.2). Also, Tukey-Kramer test was used for comparing treatments and results presented as least square means ± standard error.
Results and discussion: Based on the results, in ovo injection of different levels of L-arginine did not affect hatchability, day-old chick weight, chick weight to egg weight ratio, 24-day-old chicken weight, feed conversion ratio, relative weight of all carcass traits, cholesterol, glucose, total protein and blood urea nitrogen (P> 0.05), (Table 2). However, serum triglyceride was significantly affected by experimental treatments (P <0.01) and the highest amount was observed in 0.5% L-arginine in ovo injection group (Table 2). In a similar study, Gao et al. (2017) indicated that L- arginine in ovo injection increased weight gain of broiler chickens. Furthermore, Abdolalizadeh Alvanegh et al. (2017) reported the improving effect of in ovo injection of different ratios of L- arginine to L- lysine on chick weight and their carcass traits. Also, they reported higher serum total protein level, while lower blood urea nitrogen of broiler chicks with in ovo injection of different ratios of L- arginine to L- lysine (Abdolalizadeh Alvanegh et al., 2017).
Present results indicated no significant effect of in ovo injection of L-arginine on most weight and length parameters of small intestine length (P>0.05); however, relative weight of jejunum was significantly affected by in ovo injection of L-arginine (P<0.05) and the highest amount was observed in 0.5% L-arginine in ovo injection group (Table 3). Present results indicated no significant effect of in ovo injection of L-arginine on duodenal crypt diameter; jejunal villus height, crypt depth and diameter, and mucosal thickness; and ileum villus height, crypt depth, villus height/crypt depth ratio, and mucosal thickness (P>0.05), (Table 3). However, significant effect of in ovo injection of L-arginine was observed on duodenal villus height, villus thickness, crypt depth, villus height/crypt depth ratio, and mucosal thickness; jejunal villus thickness and villus height/crypt depth ratio; and ilium villus thickness and crypt diameter (P<0.05), (Table 3). Also, the highest amount in most histological parameters was observed in 1% arginine treatment (Table 3). In a similar study, it was reported that in ovo injection of L- methionine had a positive impact on small intestine length and weight with improvement in villus height, crypt diameter, crypt depth, and villus height/crypt depth ratio of duodenum and jejunum (Fardoost et al. 2019). Also, in ovo injections of L- lysine improved histological parameters of duodenum, jejunum, and ileum (Ebrahimi et al. 2017). Ebrahimi et al. (2018b) with in ovo injection of different DL- methionine to L- lysine ratios reported higher small intestinal weight and length along with higher Villus height and Villus height to crypt depth ratio.
Conclusion:
Based on the overall results of the study, injection of 0.5% arginine showed a positive effect on the growth and small intestine morphology of broiler chickens.