Nutrient digestibility of heat- or heat plus citric acid-pretreated dried distillers grains with solubles for pigs

Abstract

A study was conducted to determine the effects of pretreating whole stillage (WS) with heat or heat plus diluted citric acid on nutrient digestibility of the resulting dried distillers grains with solubles (DDGS) for growing pigs. The WS was untreated or pretreated with heat (160 °C at 70 psi for 20 min) alone (heat) or with the heat plus citric acid (12 g/L; heat+CA) at 70 psi for 20 min. Untreated and pretreated WS were paddle-dried before their inclusion in diets. Five diets were fed. The diets were cornstarch-based containing DDGS, untreated WS, heat-pretreated WS, or heat+CA -pretreated WS as the sole source of protein; and N-free diet, which was included for estimation of basal ileal endogenous losses of AA. The DDGS diet was included for comparison. The 5 diets were fed to 10 ileal-cannulated barrows (57 ± 1.53 kg body weight) in a replicated 5 × 5 Latin square to give 10 replicates/diet. On dry matter basis, DDGS contained 307 g/kg crude protein (CP), 37.1 g/kg starch, 31.1 g/kg ether extract (EE), and 342 g/kg neutral detergent fiber; whereas untreated WS contained 369.4 g/kg crude protein, 45.1 g/kg starch, 90.4 g/kg EE, and 364.6 g/kg neutral detergent fiber. Pretreatment of WS with heat or CA improved (P < 0.05) coefficient of apparent ileal digestibility (CAID) of gross energy (GE) in diet from 0.742 to 0.823 or to 0.797, respectively; and CAID of CP in diet from 0.782 to 0.847 or to 0.820, respectively, respectively. Pretreatment of WS with heat or heat+CA did not affect coefficient of apparent total tract digestibility (CATTD) of GE in diet. The untreated WS diet had lower (P < 0.05) CAID and CATTD of GE by 4% and 2% compared to DDGS, respectively. Pretreatment of WS with heat or heat+CA increased (P < 0.05) DE value of the WS. Pretreatment of WS with heat or heat+CA reduced (P < 0.05) CAID of all indispensable amino acids (except threonine) by at least 2.91%. In conclusion, pretreatment of WS with heat or heat+CA improved energy digestibility, but reduced amino acid digestibility. Thus, pretreatment and drying of WS at conditions employed in the current study can improve energy value, but reduce amino acid availability of the resulting DDGS for pigs.