Extrusion and animal performance effects of extruded maize quality on digestibility and growth performance in rats and nursery pigs

A series of experiments in rats and nursery pigs were conducted to determine the effects of extruded maize quality on digestibility and animal performance. In experiment 1, a total of 50 male Sprague Dawley rats (mean body weight 296 g, 3 months) were used to determine effects of different extruded maize bulk densities on physicochemical properties, digesta viscosity, mean transit time on nutrient digestibility. There were 10 rats per diet. Rats were randomly allotted to five different meal diets containing extruded maize with 937, 18 10 and 2874 g/L bulk density. With conventional maize and broken rice were used as controls. Enzyme susceptibility, water absorption index (WAI) and water solubility index (WSI) were greater (P<0.001) in extruded maize diets compared to non-extruded maize diet. These values decreased (P<0.001) as the bulk densities were increased. Rats fed extruded maize diet with lower bulk density had less intestinal viscosity (P<0.01) and shorter digesta mean transit time (P<0.05). These resulted in decreasing of dry matter (DM), nitrogen (N), and gross energy (GE) digestibilities (P<0.001). In experiment 2, a total of 40 pigs (initially BW of 12.2 kg) were used to determine the effect of different extruded maize bulk densities on. DM, N and GE digestibility. There were eight pigs per treatment. Pigs were randomly allotted to five different pelleted diets containing extruded maize with 937, 18 10 and 2874 g/L bulk densities. Conventional maize and broken rice were used as controls. Pigs fed broken rice diet had greater N (P<0.01), DM (P<0.001), and GE (P<0.001) digestibility than those fed maize diets. DM, N and GE digestibilities increased in extruded maize diets with increasing bulk density to 1810 g/L. In experiment 3, a total of 240 pigs (initially BW of 7.5 kg) were used to determine the effect of different extruded maize bulk densities on growth performance in nursery pigs. There were four bar-rows and four gilts per pen and five pens per treatment. Pigs were randomly allotted to five dietary treatments as in experiment 2. Pigs offered the rice diet grew faster (P<0.05), ate less (P<0.01) and had a better gain/feed (P<0.01) than those offered the diets based on maize. For pigs offered the extruded maize diets both feed intake (P<0.01) and growth rate (P<0.05) increased linearly with increasing bulk density of the extruded maize. Results indicated higher bulk density of extruded maize is associated with improved growth performance in pigs and this appears to be associated with increased viscosity and transit time. (C) 2007 Elsevier B.V. All rights reserved.