Effects of dietary supplementation with herbal extract as methionine replacer on growth performance, meat composition, oxidative stability and liver gene expression in broiler chickens

In the present study, an herbal feed additive was tested for partial-to-complete replacement of synthetic methionine in poultry diets, along with its effects on performance, breast and thigh meat chemical composition, oxidative stability during refrigerated storage and the expression of five target genes in liver. In a 35 days trial, 600 one-day-old male chicks were randomly allocated to 4 groups with 10 replicates. Birds in the control group were fed a regular maize–soybean-based diet that covered DL-methionine needs while the second group (Meth40) was similar to control but contained only DL – Methionine at 40% of control diet. Diet in third group contained DLMethionine at 40% of control and the herbal feed additive Methiorep ^TMMeth40+Mrep) with extracts of Boerhavia diffusa, Azadirachta indica, Vigna mungo and Trigonella foenum-graecum. Diet of fourth group was formulated to totally replace DL Methionine by Methiorep ^TM (Mrep). Body weight gain and feed consumption were weekly recorded. At the end of the trial, all birds were slaughtered and 2 chickens per pen were selected for meat and liver sampling. The liver was tested for the expression of five target genes, namely Methionine synthase (MTR), Tyrosine aminotransferase (TAT), Spermidine synthase (SMS), Methionine sulfoxide reductase (MSRB1) and Betaine homocysteine S-methyltransferase (BHMT). The results showed that the Meth40 group had reduced body weight compared to the Meth40+Mrep group while the Control and Mrep groups had comparable weights. Feed intake and feed conversion ratio did not differ among the experimental groups. Carcass, breast and thigh meat yield were higher in the Mrep and the Control compared to Meth40 and Meth40+Mrep groups. Also, meat oxidation was significantly lower in herbal groups compared to the control group. After normalization to β-actin expression, quantitative real-time PCR analysis revealed an induction in the expression of MTR and SMS genes in the liver of both herbal treated groups. No changes were observed for the TAT, MSRB1and BHMT genes in the herbal treated groups compared to the control or the Meth40 group. In conclusion, herbal feed additives with specific plant extracts may be able to improve both growth performance and antioxidant activity of broiler chickens, phenolic content; yet, they may also support in amino acid efficient use of broiler.