The influence of ground barley straw on the net energy value of diets for growth in pigs

Abstract

An experiment with 36 Danish Landrace growing pigs has been performed to study the influence of barley straw or crude fibre from barley straw, added to balanced diets, on nutrient digestibility and the efficiency of utilization of metabolizable energy. The pigs (three litters of females and three litters of male castrates) were distributed over six treatment groups on a within-litter basis, taking into account the live weights of the pigs. The six different diets were formulated in principle by supplementing a balanced diet with up to 30% ground barley straw. To this was added 50 g digestible crude protein per kg straw dry matter. The daily intakes of the different diets were regulated in such a way that the daily gains in the different treatment groups were almost identical throughout the entire experimental period (from 20 to 90 kg). Three digestibility and nitrogen-balance experiments were performed on each pig, and at ∼90 kg live weight the pigs were killed, dissected, ground, mixed and analysed chemically. An increase in crude fibre from barley straw by 1% depressed the digestibility of gross energy by ∼2.9% (2.1 % units) and depressed the efficiency of utilization of metabolizable energy by 1.0% (0.7 % units). Energy concentration (ME/kg DM) accounted for 93% of the variation in the net energy value of the metabolizable energy. Digestibility experiments with ileo—caecal cannulated pigs indicated that the proportion of digested energy disappearing in the caecum—colon increases with increasing content of ground barley straw, which supports the negative influence of crude fibre from barley straw on the efficiency of utilization of metabolizable energy. The negative influence of the addition of barley straw to the diets corresponds to ∼110 g digestible crude protein and 2.3 MJ net energy per kg straw dry matter.