Particle size and heat treatment of barley in diets for early-weaned piglets

Abstract

One hundred and twenty male piglets weaned at 20 days and weighing 5.7±1.0 kg were used in a 28-day trial to evaluate the effect of dietary particle size and heat treatment of barley on performance and total tract apparent digestibility. There were four dietary treatments: coarsely ground barley (4.5 mm screen); finely ground barley (2.5 mm screen); micronized and then finely ground barley (2.5 mm screen); and finely ground (2.5 mm screen) and then expanded barley. All the diets contained 500 g of barley issued from the same batch/kg. There were six replicates of five piglets per treatment. Total tract apparent digestibility of organic matter (OMD), energy (ED) and crude protein (CPD) were assessed from samples taken at 14 and 28 days from each replicate using chromic oxide as indigestible marker. No differences were found between results associated with screen sizes in the raw barley-based diets. Processing of barley caused an increase in starch gelatinization, a decrease in the proportion of large particles (>1.25 mm) and an increase in the proportion of fine particles (<0.16 mm; p<0.05), as compared with unprocessed barley. Piglets fed processed barley-based diets grew faster than piglets fed raw barley-based diets only in the first 14 days of experiment (232 vs. 204 g per day; p=0.04). Feed conversion was not modified by barley processing. Processed barley-based diets showed higher values for OMD, ED and CPD than raw barley-based diets, but only the difference for OMD approached significance (0.817 vs. 0.784; p=0.07). It is concluded that processing of barley improved piglet performance in the first 14 days post-weaning, and that no differences exist between processing techniques or grinding size of barley for any of the traits studied.