Timed ammonia release for steers

Area of Science:

• Animal Science
• Ruminant Nutrition
• Agricultural Chemistry

Background:

• Ruminal ammonia availability is crucial for microbial protein synthesis in cattle.
• Optimizing ammonia release rates from urea supplementation can potentially enhance nutrient utilization in steers fed forage diets.

Purpose of the Study:

• To investigate the impact of different urea administration rates on ruminal ammonia kinetics, nutrient digestibility, and nitrogen retention in steers.
• To determine if simulated slow ammonia release improves metabolic use of ammonia in the rumen.

Main Methods:

• Four ruminally-cannulated steers were fed prairie hay hourly.
• Dietary treatments included continuous, moderate, and rapid urea supplementation, plus a control (no urea).
• Ruminal ammonia, non-ammonia nitrogen, dry matter digestibility, and nitrogen retention were measured.

Main Results:

• Rapid urea supplementation (R) and moderate (M) treatments resulted in peak ruminal ammonia concentrations of 41.8 and 37.1 mg/dl, respectively.
• Urea supplementation increased non-ammonia nitrogen by 23% and dry matter digestibility by 5% across all rates.
• Nitrogen retention was positive for continuous (12.4 g), moderate (12.2 g), and rapid (11.4 g) urea, but negative for the control (-7.1 g).

Conclusions:

• Simulated slow ammonia release rates did not enhance dry matter digestibility or nitrogen retention in steers fed forage.
• Metabolic use of ammonia in the rumen was not improved by attenuated release rates.
• Urea supplementation generally increased nitrogen utilization, but the rate of release did not significantly alter key nutritional outcomes beyond providing ammonia.