Effects of Dietary Protein and Macleaya Cordata Alkaloid Extract Supplementation on Growth Performance, Apparent Ileal Digestibility of Protein and Plasma Amino Acid Concentration in Broiler Chickens

The current study evaluated the effects of feeding a phytogenic substance, Macleaya cordata alkaloid extract (MCAE), on the growth performance and protein digestibility of broiler chickens fed two dietary concentrations of protein. A total of 560, one-day-old male broiler chicks (initial body weight = 39.9 ± 0.1) were randomly assigned to eight dietary treatments with five replicates (14 broiler chickens per replicate) in a 2 × 4 factorial arrangement including two concentrations of dietary crude protein (100 and 95% of established requirements; control and low-protein diets, respectively) and four inclusion rates of MCAE (0, 180, 360, and 540 mg/kg diet). Crude protein (CP) and MCAE interactions occurred on the apparent ileal digestibility of CP (P = 0.05), organic matter (P = 0.01), and ash (P = 0.01) at d 35. However, no interaction between CP and MCAE occurred for body weight, average daily gain, and the feed conversion ratio. Dietary MCAE supplementation increased body weight (P = 0.01) at d 35, average daily feed intake (P = 0.04), and average daily gain (P = 0.02) from d 1 to 35 of the broiler chickens linearly. Greater carcass yield and reduced abdominal fat were observed with a higher level of dietary protein intake (P = 0.01). Dietary supplementation with MCAE also reduced the relative weight of the ceca linearly (P = 0.01) without affecting carcass yield at d 35. Dietary treatments had no effects on plasma free Met, Thr, and Gly concentrations at d 35 and serum uric acid and creatinine concentrations at d 15 and 35. In summary, these results indicated that dietary supplementation with MCAE may improve body weight and average daily gain of broiler chickens at both dietary protein levels, by enhancing apparent ileal digestibility of dietary CP and organic matter, as well as by increasing feed intake.