216 Effect of conditioning time on standardized ileal digestibility of amino acids and total tract digestibility of energy in diets fed to growing pigs

Two experiments were conducted to determine the effect of conditioning time prior to pelleting on digestibility of energy and AA in diets fed to growing pigs. For both experiments, the dietary treatments consisted of a mash diet and 3 separate pelleted diets that were conditioned for 30, 60, or 180s prior to pelleting. For Exp 1, Twelve barrows (DNA 200 x 400, DNA; BW: 34.1±1.03 kg) were allotted to a 4 x 3 balanced incomplete Latin square design with 4 treatments and 3 periods, for a total of 9 replicates per treatment. Pigs were housed individually in metabolic crates equipped with a feeder, a drinker, and partial diamond-slatted floor. For each experimental period, the first 5d were considered adaptation and the next 5d were collection. During collection, a screen and urine pan were installed underneath the floor of the crate to allow for the total collection of feces and urine samples. For Exp. 2, twelve barrows (DNA 200 x 400, DNA; BW: 44.9±2.70 kg) were allotted to a replicated 4 x 4 balanced Latin square design with 4 treatments and 4 periods, for a total of 12 replicates per treatment. Pigs were housed individually in the same metabolic crates as Exp. 1. Each experimental period consisted of 5d of adaptation and 2d of ileal collection. For Exp.1, conditioning diets for 60s increased (P < 0.05) DE and ME compared to the mash control and diets conditioned for 30s; however, conditioning diets for 180s decreased (P < 0.05) DE and ME compared to all other treatments. For Exp. 2, a treatment effect (P < 0.001) was observed for SID of CP, all indispensable AA, all dispensable AA, and total AA. There was no evidence of difference for Lys, Met and Trp. The SID of CP, Arg, Leu, Thr, Ala, Ser, and Tyr was greater (P < 0.05) in the pelleted diets compared to the mash diet. For His, Ile, Phe, Val, Asp, and Glu, mash diets had decreased (P < 0.05) SID compared to the pelleted diets conditioned for 60s and 180s. However, there was no evidence of difference in SID of Val for any of the conditioning lengths. For SID of Cys, mash diets had decreased (P < 0.05) SID compared to the pelleted diets conditioned for180s and there was no evidence of difference between the mash diets and pelleted diets conditioned for 30s or 60s. These results indicated that increasing conditioning time up to 180s did not negatively impact AA digestibility, but improved AA digestibility for certain AA. It was also demonstrated that conditioning the diets for 60s optimized the DE and ME of the diet, while conditioning up to 180s decreased the DE and ME of the diet.