ABSTRACT

The response of broiler chickens fed methanol extracts of selected medicinal plants as a replacement for antibiotics was investigated. The plant extracts encompass four available leaves; Gereinia kola (Bitter kola), Alcornea cordifolia (Christmas bush), Pterocarpus santalinus (Red scandal wood) and Chromolera odorata (Hagony or Siam weed). Antimicrobial activities, growth performance, carcass characteristics, internal organ proportions, hematological indices, serum biochemical indices and caecal microbial loads were considered. The experimental diet was same for all the treatment groups since the methanol extract of the leaves were administered in their drinking water against synthetic antibiotics. 180 unsexed Ross strain broiler chickens were randomly assigned to these dietary treatments which had 30 birds each. The treatments were replicated thrice with 10 birds per replicate in a Completely Randomized Design (CRD). Birds were fed these diets from day one; feed and water were provided ad libitum throughout the experimental period which lasted for 56 days. For growth performance at the starter phase, Treatment 2 (negative control) had the highest final body weight (920.67 g/b), average daily weight gain (31.60 g/b) and best feed conversion ratio (1.82), followed by treatment 5 (Alcornea cordifolia) which also had the highest value for feed intake (1690.33 g/b). At finisher phase, Treatment 5 (Alcornea cordifolia) had the highest final body weight (2886.66 g/b), average daily weight gain (69.52 g/b/d) and best feed conversion ratio (2.39), followed by Treatment 6 (Gereinia kola). Significant (p<0.05) differences were observed in the mean values of all the haematological parameters measured across the treatment groups except Eosinophil and Basophil at starter phase while significant (p<0.05) differences were observed only in PCV, WBC and Monocyte at the finisher phase. In serum chemistry, significant (p<0.05) differences were observed in the mean values of all the parameters measured with exception of total protein and globulin. However, the values obtained did not reveal any health problem. Carcass yield, cut parts and organ proportion of broiler chickens differed significantly (p<0.05). Treatment 5 (Alcornea Cordifolia) had a significant (P>0.05) reduction in abdominal fat when compared to the positive control group. There was no significant (P>0.05) difference in the antimicrobial activities of the methanol extracts of the selected medicinal plants. However, Treatment 5 (Alcornea cordifolia) extract had the highest and best values for the microbial activities tested for. Histomorphology indices revealed significant (p>0.05) difference for villus height and weight, crypt depth and width. Treatment 5 (Alcornea cordifolia) gave the highest nutrient absorption of the birds.  It can be concluded from this study that the methanol extracts of the selected medicinal plants has considerable constituents as component of broiler chickens diet. Alcornea cordifolia methanol plant extract can successfully be used to replace antibiotics both for starter and finisher phases of broiler production. Further research should be carried out on Alcornea Cordifolia and other medicinal plants to mitigate potential adverse effects on growth performance