Evaluation of the nutritional value of glycerol for nursery pigs

In Exp. 1, a total of 144 pigs (BW, 6.68 ± 0.17 kg) were weaned at 21 d, blocked by BW, and allocated to 48 pens with 3 pigs per pen. Pens were randomly assigned to 1 of 6 dietary treatments (0, 2.5, 5, 7.5, and 10% glycerol supplemented to replace up to 10% lactose in a basal starter 1 diet containing 20% total lactose, which was fed for 2 wk), and a negative control diet with 10% lactose and 0% glycerol. A common starter diet was fed for the next 2 wk. In Exp. 2, a total of 126 pigs (BW, 6.91 ± 0.18 kg) were weaned at 21 d of age, blocked by BW, and allocated to 42 pens with 3 pigs per pen. Pigs were assigned to 1 of 6 treatments in a 2 × 3 factorial arrangement in a randomized complete block design with factors being 1) glycerol inclusion in replacement of lactose in starter 1 diets (0 or 5%) fed for 2 wk, and 2) glycerol inclusion in starter 2 diets (0, 5, or 10%) fed for 3 wk. In Exp. 1, glycerol supplementation at 10% improved (P=0.01) ADG (266 vs. 191 g/d) and G:F (871 vs. 679 g/kg) during the starter 1 period when compared with the negative control. Incremental amounts of glycerol linearly (P<0.05) increased ADG and ADFI, but did not affect G:F during starter 1. There was no effect of feeding glycerol during the starter 1 phase on subsequent performance during the starter 2 phase or overall. Serum glycerol concentrations increased linearly (P=0.003) with increasing dietary glycerol, and serum creatinine (P=0.004) and bilirubin (P=0.03) concentrations decreased with increasing glycerol. In Exp. 2, glycerol did not affect performance during starter 1, but it linearly increased (P≤0.01) ADG and ADFI during starter 2 (464, 509, and 542 and 726, 822, and 832 g/d, respectively) and overall (368, 396, and 411 and 546, 601, and 609 g/d, respectively). At the end of the study, pigs were 1.0 and 1.5 kg heavier when fed 5 and 10% glycerol, respectively (linear, P<0.01). Serum glycerol concentrations increased linearly during starter 2 (P<0.001), but were not affected during starter 1. Glycerol supplementation increased serum urea N quadratically (P<0.001) and decreased creatinine linearly (P<0.05) in the starter 2 phase. Overall, data indicate that glycerol can be added to nursery pig diets at 10%, while improving growth performance.