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This study was conducted to assess the effects of dietary Moringa oleifera leaf meal (MOLM) supplementation as a possible alternative to antibiotic growth promoters on bone breaking strength (BBS), tibia bone morphology and inorganic ash content in broiler chickens. A total of 2400 one-day-old Cobb-500 broiler chicks of mixed sex were randomly allocated to five dietary treatments in six replications of 80 birds per pen. Dietary treatments were as follows: T1, positive control, 668 g salinomycin and 500 g zinc bacitracin per kg of feed; T2, T3 and T4, graded levels of MOLM, that is (starter (1, 3 and 5 g), grower (3, 9 and 15 g) and finisher (5, 15 and 25 g)) per kg of feed; and T5, a negative control (without supplementation). Birds were provided with feed and water ad libitum. Bodyweights (BW) and feed intake (FI) of broilers were measured weekly, and feed conversion ratio (FCR) and average daily gains were calculated accordingly. At 35 days (d) of age, 12 birds per treatment, two from each replicate pen, were randomly selected, stunned electrically at 70 volts, and slaughtered by cervical dislocation. Six left and right tibiae were randomly chosen from each treatment, without being de-fleshed, and were sealed individually in plastic bags to minimize moisture loss. The tibiae were stored at −18 ºC for BBS and tibia ash determination, as well as analyses of their calcium (Ca) and phosphorus (P) composition. Of birds fed diets with higher MOLM levels, T4 had the highest BW, while T1 had the lowest. On days 7 and 21, birds on T4 had the highest average daily gain (ADG) and T1 the lowest, respectively. There were no significant dietary effects in FI on days 7, 21 and 35; while on days 21 and 35, FCR (feed : gain) was highest in MOLM-supplemented birds and lowest in T1 birds, respectively. There were no treatment effects on tibia length (TL), tibia weight (TW) and/or dried tibia weight (DW). A positive correlation (r = 0.667) was observed between TW and DW. There were no treatment effects on BBS and ash percentage, but tibia ash weight was highest in T4 and lowest in T2. Calcium percentage was highest in T1, and lowest in T2 and T5. Phosphorus percentage was lowest in T1 and highest in T5. The highest Ca : P ratio was obtained in T4. The positive correlation observed between BW, TW and TL, and the high P, Ca and ash levels in tibiae from MOLM-supplemented birds depicts the genetic relationship that exists among these parameters. Furthermore, it reveals the effectiveness of MOLM supplementation to enhance nutrient utilization efficiency, increase mineral bioavailability and support bone strength.
Keywords: Bone quality, calcium, Cobb-500 broilers, antibiotic growth promoters, phosphorus