Dietary supplementation with red cabbage extract rich in anthocyanins increases urinary hippuric acid excretion and consequently decreases nitrous oxide emissions in beef bulls

Two consecutive experiments were conducted to investigate the effects of dietary supplementation with red cabbage extract (RCE) rich in anthocyanins on the nitrogen (N) metabolism in beef bulls and the nitrous oxide (N 2 O) emissions from the soil applied with the urine of beef bulls. In Experiment 1, 8 Simmental beef bulls (body weight 387.9 ± 40.7 kg) were used as experimental animals . Two levels of RCE, i.e. 0 and 114 g dry matter per day, were supplemented to a basal ration as experimental treatments. The animals and the treatments were allocated in a 2 × 2 crossover design. In Experiment 2, the static incubation technique was used to determine the N 2 O-N emissions from the soil applied with the urine samples collected from Experiment 1. The results of Experiment 1 indicated that RCE supplementation did not affect the N excretion, N retention, and N retention rate in beef bulls ( P  > 0.10). However, RCE supplementation increased the ratio of hippuric acid-N/urinary N ( P  < 0.05) and tended to increase the ratio of creatinine-N/urinary N ( P  = 0.081) without changing the excretion of other urinary nitrogenous components ( P  > 0.10). Plasma metabolome analysis indicated that RCE supplementation upregulated 12 metabolites while downregulated 18 metabolites ( P  < 0.05). The results of Experiment 2 indicated that RCE supplementation reduced the estimated urine N 2 O-N emissions by 33.1% through decreasing the ratio of N 2 O-N/urine-N ( P  < 0.05). In conclusion, RCE supplementation did not affect the N retention and N excretion of beef bulls, whereas it attenuated the urine N 2 O-N emissions of beef bulls through increasing urinary hippuric acid excretions.