Effects of steam conditioning at low and high temperature, expander conditioning and extruder processing prior to pelleting on growth performance and nutrient digestibility in nursery pigs and broiler chickens

Abstract

The aim of the present study was to investigate effects of feed conditioning prior to pelleting and extrusion processing on average daily gain (ADG), average daily feed intake (ADFI), gain to feed (G:F) and coefficient of total tract apparent digestibility (CTTAD) in nursery pigs and broiler chickens. The mash, based on wheat, fishmeal and soybean meal, was subjected to 4 heat treatments (hydro-thermal processing) giving Diet 1: unconditioned mash as control (mash); Diet 2: low-temperature steam conditioning before pelleting (STP47); Diet 3: high-temperature steam conditioning before pelleting (STP90); Diet 4: expander conditioning before pelleting (EXP); and Diet 5: extruder processing (EXT).Nursery pigs (average body weight of 5.6kg) were used in a 36-d experiment. The results showed that hydro-thermal processing improved G:F in nursery pigs (P=0.006) compared to the mash. The G:F was also improved for pigs fed the EXT diet compared to the EXP diet (P=0.030). The CTTAD of dry matter was greater in pigs fed the hydro-thermal processed diets compared to the mash (P=0.018), and in pigs fed the STP47 compared to the STP90 (P=0.001). The CTTAD of organic matter was improved for pigs fed STP47 and STP90 diets compared to the EXP and EXT diets (P=0.010), and for the STP47 compared to the STP90 diets (P=0.001). The CTTAD of protein (P=0.004) and energy (P=0.001) was greatest in pigs fed the STP47 compared to the STP90. Starch digestibility was improved in pigs fed the EXT compared to the EXP diet (P=0.041).Broiler chickens (1-d old, average body weight of 41g) were used in a 21-d experiment. The ADFI and ADG were greater (P<0.05) for broiler chickens fed the STP47 and the STP90 diets compared to those fed the EXP and the EXT diets. The EXP diet improved ADG (P=0.015) and ADFI (P=0.003) compared to the EXT diet. Starch digestibility was greater in broiler chickens fed the hydro-thermal processed diets compared to the mash (P=0.023).In conclusion, hydro-thermal processing, in particular extruder processing, improved G:F for nursery pigs due to improved digestibility. For broiler chickens, all hydro-thermal processing increased starch digestibility, but due to reduced feed intake of the expanded and in particular the extruded diets, only steam conditioning before pelleting improved growth rate and feed utilisation.