Influence of in ovo threonine on growth performance, immunocompetence and carcass characteristics in broiler chickens

The experiment was conducted to investigate the effect of in ovo threonine (Thr) injection on 18th embryonation day at the broad end of the egg using 24G needle on growth performance, organs development, immunocompetence and carcass yield in broiler chickens. Fertile eggs (n=500) were randomly distributed to 5 groups, viz. (i) uninjected control, sham control (0.5 mL sterile water), Thr @15 mg/egg, Thr @30 mg/egg, and Thr @45 mg/egg. Hatchability was better in chicks treated with 45 mg Thr/egg compared to other Thr-injected groups. In ovo Thr injection had quadratic effect on weight gain (WG) and production index at the 2nd and 3rd weeks. Chicks fed 45 mg Thr/egg had better feed conversion ratio (FCR) at 2nd week compared to other groups while feed intake (FI) was not affected. Thr injected chicks had higher thymus weight (d0), bursa weight (d3), spleen weight (d3 and d7) whereas quadratic effect were observed on weights of bursa, thymus and spleen at d21. In ovo Thr administration improved (group-wise, linear or quadratic) the relative weights of gizzard, intestine, and liver at hatch, proventriculus at d7, as well as intestine and liver at d21. No significant difference was recorded for humoral and cell mediated immune response following in ovo Thr injection. Carcass traits of broiler chickens were not influenced by in ovo Thr administration, except breast meat which slightly differs, among the treatment groups. The results of this study suggested that in ovo Thr can improve growth performance, digestive and immune organs development at the early age.