Dietary supplementation of rumen-protected methionine decreases the nitrous oxide emissions of urine of beef cattle through decreasing urinary excretions of nitrogen and urea.

BACKGROUND

Two consecutive trials were carried out to study the effects of dietary supplementation of rumen-protected methionine (RPM) on nutrient digestibility, nitrogen (N) metabolism (Trial 1), and consequently the nitrous oxide (N O) emissions from urine in beef cattle (Trial 2). Eight 24-month-old castrated Simmental bulls with liveweights of 494 ± 28 kg, and four levels of dietary supplementation of RPM at 0, 10, 20, and 30 g head d , were allocated in a replicated 4 × 4 Latin square for Trial 1 and the N O emissions from the urine samples collected in Trial 1 were measured using a static incubation technique in Trial 2.

RESULTS

Supplementation of RPM at 0, 10, 20, and 30 g head d to a basal ration deficient in methionine (Met) did not affect the apparent digestibility of dry matter, organic matter, neutral detergent fiber, or acid detergent fiber (P > 0.05), but decreased the urinary excretions of total N (P < 0.05) and urea (P < 0.001), increased the ratio of N retention / digested N (P < 0.05) in beef cattle, and decreased the estimated cattle urine N O-N emissions by 19.5%, 23.4%, and 32.6%, respectively (P < 0.001).

CONCLUSION

Supplementation of RPM to Met-deficient rations was effective in improving the utilization rate of dietary N and decreasing the N O emissions from urine in beef cattle. © 2019 Society of Chemical Industry.