Diet nutrient digestibility and growth performance in weaned pigs fed barley differing in fermentable starch and fibre profile

Abstract

Barley grain containing both fermentable starch and fibre might be attractive as energy source in weaned pig diets because of benefits on gut health. Rapidly fermentable carbohydrates and slowly fermentable fibre may decrease diarrhoea in weaned pigs serving as prebiotics. Steam explosion processing may disrupt the fibre matrix of cereal hulls, increasing slowly fermentable fibre of barley grain. Five diets were formulated to provide 10.0 and 9.6 MJ net energy (NE)/kg, 1.32 and 1.22 g standardised ileal digestible (SID) lysine/MJ NE for phase 1 (day 0–14) and phase 2 (day 14–28), respectively. Diets contained 593–644 g cereal grain/kg: 1) low-fermentable hulled barley (LFB); 2) LFB steam-exploded (LFB-SE; 1.2 MPa, 120 s); 3) high-β-glucan (70 g/kg) hull-less barley (HFBB); 4) high amylose (168 g/kg) hull-less barley (HFAB); or 5) low-fermentable wheat (LFW). A total of 220 pigs in 11 blocks of 5 pens each were fed 1 of 5 diets starting 1-week post-weaning for 28 days. For phase 1, the coefficient of apparent total tract digestibility (CATTD) of gross energy (GE) and crude protein (CP) of diets was greatest (P < 0.05) for LFW, intermediate for HFBB, followed by LFB-SE, LFB and lowest for HFAB. The calculated NE value was greatest (P < 0.05) for LFW, intermediate for LFB-SE, and lowest for HFBB, LFB and HFAB. For phase 2, the CATTD of GE was greater (P < 0.05) for LFW and HFBB than LFB, LFB-SE and HFAB; the CATTD of CP was greatest (P < 0.05) for LFW, intermediate for HFBB, followed by LFB, HFAB, and lowest for LFB-SE; calculated NE value was greatest (P < 0.05) for HFBB and LFW, intermediate for LFB and HFAB, and lowest for LFB-SE. For the entire trial (day 0–28), average daily feed intake (ADFI) and average daily gain (ADG) of pigs did not differ among diets, but gain-to-feed (ADG/ADFI) was lowest (P < 0.05) for the LFB-SE diet. For day 21–28, pigs fed LFB-SE diet had greater (P < 0.01) ADFI than pigs fed HFAB diet, whereas pigs fed LFW, LFB and HFBB were intermediate. Faeces consistency of pigs did not differ between LFB and LFW diets, but pigs fed LFB diet had firmer (P < 0.05) faeces than pigs fed HFBB, HFAB and LFB-SE diets. To conclude, the wheat diet had greater GE and CP digestibility than barley diets. Among barley diets, the HFBB had greater GE and CP digestibility than both LFB and LFB-SE; the HFAB diet ranked lowest. However, feeding barley to replace wheat grain in nursery diets formulated to equal NE value and SID amino acid content did not affect growth performance. Finally, dietary fermentable carbohydrates in barley made faeces less firm. Steam explosion of hulled barley grain did not increase GE or CP digestibility.