Table 4 Summary of published studies evaluating the effect of N-carbamoylglutamate supplementation to ruminants on the potential to mitigate environmental nitrogen pollution

60 Chinese Holstein multiparous dairy cows; 78 ± 17 DMI, 635 ± 60 kg BW and 42 ± 8 kg/d milk yield

0, 10, 20, 30 g/NCG/d; 50:50 mix with corn starch

Top dressed on TMR twice daily

10 d adaptation and 7 weeks treatment

(3 times daily milking)

↓ Plasma ammonia N (1200 vs. 595 μmol/L)

↓ MUN (12.4 vs. 11.5 mg/dL)

↓ BUN (7.06 vs. 6.24 mg/dL)

↓ UN (1071 vs. 794 mg/dL

Greatest ↓ in 20 g/d group vs. control

[39]

Cattle (Holstein bulls; 408 kg 450 d old); n = 24 (6/group)

0, 20, 40, 80 mg NCG/kg BW

Mixed in feed

Best in 40 g/d group:

↓ BUN (2.54 vs. 1.99 mmol/L)

↓ Plasma ammonia (64.8 vs. 34.4 μmol/L)

↓ (trend) faecal N (70.5 vs. 62 g/d)

↓ (trend) urinary N (80.2 vs. 68.3)

↑ N retention (46.6 vs. 61.5 g/d)

↑ N utilization % (23.6 vs. 32.1)

[75]

Holstein bulls (490 kg BW; n = 24 (6/group in individual pens)

Control diet (0) vs. Control diet + NCG (40 mg/kg BW) vs. urea diet vs. urea diet + NCG (40 mg/kg BW)

Mixed in feed

2-week diet adaptation

7-week treatment (2 times daily feeding)

Control vs. Control + NCG:

↓ Faecal N (8.2 vs. 69.9 g/d)

↓ Urinary N (105 vs. 95.2 g/d)

↑ N retention (62.2 vs. 73.3 g/d)

↑ N utilization (0.24 vs. 0.31 g/d)

↓ BUN (3.52 vs. 3.14 mmol/L)

↓ Plasma ammonia (55.1 vs. 45.5 μmol/L)

[76]