EQUI-ENERGY REPLACEMENT OF NATIVE MAIZE WITH EXTRUDED MAIZE IN BROILER CHICKEN DIETS: EFFECT ON GROWTH PERFORMANCE, ENERGY UTILIZATION AND POST-PRANDIAL GLUCOSE RESPONSE

The effect of equi-energy replacement of native maize with extruded maize on the growth performance, energy utilization indices and post-prandial glucose response of broiler chicken was investigated in a 42-day trial. A commercial flock of broiler chickens (n = 20,000) were offered either a "native" maize or extruded maize-soybean diet and monitored for growth performance: daily liveweight gain (DLWG), feed conversion ratio (FCR), flock uniformity and mortality during the pre-starter, starter, grower and finisher phases of production. One-day old chicks (n = 16) were slaughtered to obtain baseline data for the energy utilization study and another 32 chickens (16 chickens per treatment, 4 chickens per replicate) were slaughtered at 35-days post-hatch, and whole carcasses were processed. Another 80 chickens (40 chickens per treatment, 8 replicates per treatment and 5 chickens per replicate) were used for total tract excreta collection from 32 − 35 days post-hatch. At 42 days post-hatch, 32 fasted chickens (16 chickens per treatment) were sampled for blood 30 mins pre-prandial and 15, 30, 45, 60, 120, 180, 240 and 360 minutes postprandial, and plasma glucose was measured. Chickens fed extruded maize diets showed significantly improved FCR and flock uniformity across phases, while DLWG improvements were seen only in the pre-starter, grower and finisher phases. Metabolizable energy (ME) was significantly higher in the control group (p = 0.03), but energy retention as fat and protein, net energy of production, heat of production and efficiencies of ME used for energy retention and protein retention were unaffected. The extruded maize diet improved the efficiency of ME used for fat retention (p = 0.03). Postprandial plasma glucose concentrations were higher after 15 mins (p = 0.00) and 360 mins (p = 0.00), indicating enhanced starch digestibility.