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.