Growth performance, nitrogen balance, and metabolism of calcium and phosphorus in growing pigs fed diets supplemented with alpha-ketoglutarate

We investigated the effects of dietary alpha-ketoglutarate (AKG) supplementation on growth performance, the nitrogen (N) balance, and metabolism of calcium (Ca) and phosphorus (P) in growing pigs. Sixteen healthy animals (Large × White × Landrace) of similar initial weight (40.08 ± 0.78 kg) were randomly assigned to two dietary groups. The pigs were fed a basic diet containing either 0 (control) or 10 g AKG kg−1 for 28 d. Their faeces and urine were collected continuously from Days 23–25. On Day 28, all of them were killed and their right rear femurs and tibias were removed. Pigs fed diets with AKG tended to have higher average daily gain (ADG; P = 0.088), but their urinary-N levels and excretion of total N were 24.50% (P = 0.012) and 23.67% (P = 0.011) lower, respectively, when compared with corresponding values measured from the control group. However, their apparent N-digestibility and net protein utilization were increased by 2.43% (P = 0.044) and 11.84% (P = 0.002), respectively, over the control. Furthermore, supplemental AKG decreased faecal- and urinary-Ca levels by 29.56% (P = 0.045) and 24.54% (P = 0.001), respectively, while enhancing P-retention, apparent Ca-digestibility, and apparent P-digestibility by 27.10% (P = 0.002), 14.51% (P = 0.041), and 16.62% (P = 0.010), respectively. The addition of AKG also elevated the concentrations of ash, P, and Ca (P = 0.012, P = 0.002, and P = 0.004, respectively) in the femur samples, and increased bone density (P = 0.003), but did not affect those parameters in the tibias. These results indicate that dietary supplementation with AKG can improve the utilization of N, Ca, and P; while effectively reducing N, Ca, and P emissions; and promoting N-, Ca-, and P-metabolism in growing pigs.