effect of in ovo injection of different nutrients and 36 h starvation after hatch on hatchability, blood metabolites, intestinal morphology and growth performance of broiler chicks

introduction: many birds do not have access to feed until 48 h after hatching (27). in ovo injection technology is a practical means for safe introduction of nutrients into developing embryos, including amino acids, carbohydrates, vitamins, l-carnitine, and hormones which may benefit post-hatch growth and bw gain (19, 36). the objective of this study was to evaluate the effects of in ovo injection of amino acids and dextrose, on hatchability, growth performance, blood metabolites, immune organs and intestinal morphology of the broiler chicks. materials and methods: the experiment was conducted in a completely randomized design with 5 treatments, 3 replicates of 16 fertile eggs from ross 308 breeders (28 week old). treatments consisted of control (no injection) and injection of 0.7 ml of different nutrients into the amniotic sac of fertile eggs on 17.5th day of incubation including: distilled water (sham), amino acids, dextrin 10% and dextrin 20%. the injection point from the broad end of the egg which was disinfected with alcohol and then 0.7 ml of each solution was injected into the amnion, using a 23- gauge needle with depth of 25 mm. the holes were then sealed using commercial glue. hatched chicks were fasted for 36 hours. body weight, feed intake and feed conversion ratio were recorded weekly. on days 1 and 3, blood samples were collected from one chick per replicate to determine serum metabolites (glucose, triglyceride, cholesterol,high density lipoprotein (hdl) and low density lipoprotein (ldl)). on days 1, 3, 7, 14 and 42, one bird per replicate was slaughtered and the relative weight of the immune organs (bursa of fabricius, spleen and thymus) was determined. on day 3, villus height, crypt depth and villus height to crypt depth ratio were also measured. results and discussion: the results showed that in ovo injection of amino acids can led to heavier birth weight compared to sham and control treatments (p=0.05) . chicks hatched from control eggs (no injection) showed the lowest significant weight gain and feed intake. different treatments had no significant effect on feed conversion ratio. improved growth performance could be attributed to increase in glycogen stores during the prenatal period (39). because the late-term embryo, orally consumes the amniotic fluid (comprised primarily of water and albumen protein) prior to piping, in ovo injection of dextrose, amino acids or albumin may help to overcome any nutrient deficiency that may limit embryonic growth. thus, it was hypothesized that administration of carbohydrates to the amnion may improve the energy level of the broiler embryo and reduce internal energy consumption (proteins and lipids) during piping, thereby increasing chick bw (45). glucose is the major energy source in living organisms. maintenance of glucose homeostasis during few days pre and post hatch is a great challenge in the chick’s life. the frequent activity of embryos implies a large amount of energy consumption, and higher glucose demand for fuel (45, 46). serum glucose level after hatch was significantly higher in treatment dextrin 20% compared to sham treatment (p<0.05). serum triglyceride level was also higher in control compared to amino acid, dextrose 10% and shame treatments (p<0.05). no significant differences were observed for serum metabolites after 36 h starvation. in ovo injection of amino acids and dextrin 10% and 20% led to a higher relative weight of thymus at 1 and 3 days of age (p<0.05). the relative weight of bursa in 1 day old birds was also significantly higher than control, sham and amino acid treatments (p<0.05). jejunal villus height was significantly higher in chicks injected by dextrose 20% at 3 d of age (p<0.01). the immune system of birds is partly developed at hatch and thereafter grows rapidly in the same way as the development of immune function in mammals (44). for a few days of post hatch, the bursa of fabricius increases in weight and during this time the chick does not have the capability to produce igg. as a result, after hatching, the chick is dependent upon maternal antibody for humeral immune protection. chicken embryos have limited ability to digest and absorb nutrients prior to hatch (39). this rapid intestinal growth is due to accelerated processes of enterocyte proliferation and differentiation (13). in addition, the intestinal crypts, which begin to form at hatch, are clearly defined several days post hatch, increasing in cell numbers and size (13). previous studies have shown that feeding immediately post hatch leads to an acceleration of small intestinal morphological development (40), whereas late access to external feed results in delayed development of the small intestine mucosal layer (13). conclusion: in conclusion, it seems that in ovo injection of nutrients especially 20% dextrin solution may be helpful for improvement of growth performance and immunity in hatched broiler chicks.