ILEAL CRUDE PROTEIN DIGESTIBILITY OF FEATHER MEAL SUPPLEMENTED WITH PROTEASE IN BROILER CHICKS

Abstract

Conventional protein ingredients are expensive, thus necessitating the use of alternative sources of the nutrient. Feather Meal (FM) is high in Crude Protein (CP) but poorly digested by monogastric animals due to the presence of keratin. Poultry requires exogenous enzymes to break it down to its constituent amino acids. Information on digestibility of CP of FM in broilers is scanty. Therefore, ileal CP digestibility of FM supplemented with protease in broiler chickens was investigated.Broiler feathers were hydrolysed to obtain FM using standard procedures. The feathers and FM were analysed for their respective chemical compositions. One hundred and forty-four 2-week old broilers weighing 223.0±11.1g were randomly allotted to four diets containing 0, 2, 4 and 6% FM and TiO2 at 5 g/kg diet as marker for two weeks. Body Weight Gain (BWG, g/bird), Feed Intake (FI, g/bird) and Feed Conversion Ratio (FCR) were assessed. Digesta was collected from all birds to determine Apparent CP Digestibility (ACPD). Another 336 twenty-one-day old broilers were randomly assigned to eight diets containing 0, 2, 4 and 6% FM with 0 or 5 g protease/kg diet and TiO2 in a 2x4 factorial arrangement. At day 28, digesta was collected from all birds for Digestible CP (DCP) determination in FM using standard procedures. In a growth study, 360 1-day old broilers were randomly allotted to twelve diets containing 0 or 2% FM at three CP levels (15.5, 17.5 and 23%) based on recommended matrix value of protease and two protease levels (0 and 5 g/kg). They were fed for 42 days in a 2x2x3 factorial arrangement. The BWG, FI, FCR, carcass measures and organ weights were determined. Data were analysed using descriptive statistics and ANOVA at α0.05.Percentage chemical composition were 88.6 CP, 5.0 ether extract, 0.3 ash, 0.03 calcium, 0.04 phosphorus and 4.4 Kcal/g Gross Energy (GE) for the broiler feathers and 83.8 CP, 10.3 ether extract, 0.6 ash, 0.02 calcium, 0.03 phosphorus and 4.3 Kcal/g GE for FM. The ACPD (%) were 42.0±2.1, 52.0±1.9, 58.0±2.4 and 63.0±2.8; FI obtained were 358.3±9.8, 323.6±15.6, 283.9±13.1 and 307.8±1.2; BWG were 218.9±24.9, 194.6±19.0, 145.7±15.6 and 152.8±16.8 and FCR were 1.6±0.3, 1.7±0.2, 2.0±0.3 and 2.0±0.2. With protease supplementation, ACPD (%) were 58.8±2.0, 64.1±2.0, 75.8±1.5 and 85.3±2.3 for birds on diets 0, 2, 4 and 6% FM respectively. The DCP in FM was 65.9%±1.4 and 76.1%±2.3 without and with protease respectively. The functional relationship between DCP and CP intake from FM without protease supplementation was highly significant (R2=0.98). The FM inclusion significantly decreased FI from 63.4±2.1 to 55.2±0.7 and BWG from 243.7±7.5 to 197.3±6.6 but increased FCR from 2.7±0.1 to 2.9±0.1 at 0-21days. At 22-42 days FI decreased from 1647.5±25.3 to 1302.9±23.2, BWG from 605.4±15.0 to 579.1±18.7 and FCR from 2.8±0.0 to 2.3±1.0. Protease supplementation improved live weight, percent dressed weight and significantly increased the breast meat by 2.1, 1.9 and 4.1% at 42 days.Feather meal inclusion levels above 2% and its ileal digestibility required protease supplementation for improved broiler performance