Effects of full fat soybean particle sizes on growth performance and nutrient digestibility in postweaning pigs

Abstract

Two experiments were studies to investigate the effects of particle sizes of full fat soybean on physical characteristic, production cost, anti-nutritional content, apparent fecal digestibility of nutrients and growth performance. Raw soybeans were ground with a hammer mill equipped with 3 sizes of splited screens (3.0 x 3.0, 3.0 x 2.5 and 2.5 x 2.5 mm opening area). Each ground soybean particle size was passed through the single-screw extruder to produce full fat soybean which was used as a feedstuff at the level of 25% in postweaning pig diet. In experiment 1, raw soybean, ground soybean, extruded soybean and diet were determined for physical characteristics (mean and standard deviation of particle size, surface area, angle of repose and bulk density) production cost (energy consumption and production rate) and anti-nutritional content (trypsin inhibitor, protein solubility, and urease index). In experiment 2, nutrient digestibility and growth performance were measured. Twelve barrows and twenty four female crossbred piglets (H L D) weaned at 21+- 3 days of age were blocked by replicate allocated into 3 treatments which composed of 4 replicates of 3 pigs each (1 barrow and 2 females). The pigs were fed on their diets for a period of 4 weeks. Body weight and feed intake were weekly recorded. Seven days before the end of the 2[superscript nd] and 4[superscript th] week of experimental periods, chromic oxide were mixed (4 g/kg diet) and fed. Fecal samples were collected by rectal massage and analyzed for nutrients digestibility. Experiment 1, reducing screens size of hammer mill from 3.0 x 3.0 to 3.0 x 2.5 and 2.5 x 2.5 mm. decreased mean of ground soybean particle size (P<0.001), full fat soybean particle size (P<0.05) and diet (P<0.05). The reducing of full fat soybean particle size increased uniformity (P<0.001) and surface area (P<0.05) but not differed for bulk density and angle of repose (P>0.05). Reducing particle size in grinding process decreased production rates (P<0.05) but increased energy consumption (P<0.001). However, no significant differences among particle size of total energy consumption and production cost (P>0.05) of both grinding and extrusion processes were found. All methods for analyzing anti-nutritional content, similarly decreased when heated in grinding and extrusion processes but particle size did not contribute to the decrease of anti-nutritional content. In experiment 2, reducing of full fat soybean particle size increased apparent DM and CP digestibility at 2[superscript nd] week (P<0.001) but not at 4[superscript th] week of experimental period and showed the positive impact on gain:feed ratio (P<0.05) at 2[superscript nd] week and ADG (P<0.01) at 2[superscript nd] week and the overall period (P<0.05) of the experiment.