Nitrogen retention by lambs fed oscillating dietary protein concentrations

Area of Science:

• Animal Nutrition
• Ruminant Physiology
• Environmental Science

Background:

• Nitrogen excretion by beef cattle contributes to environmental pollution through volatilization and runoff.
• Improving dietary nitrogen utilization in cattle can mitigate these environmental losses.

Purpose of the Study:

• To investigate the impact of oscillating dietary crude protein (CP) concentrations on nutrient retention in lambs fed high-concentrate diets.
• To determine if altering CP levels at different intervals (24-h vs. 48-h) affects nitrogen (N) and mineral retention.

Main Methods:

• Two 5x5 Latin square experiments were conducted using ten St. Croix lambs (27 kg BW).
• Lambs were fed diets with constant CP levels (10%, 12.5%, 15%) or oscillating CP levels (10% and 15% at 24-h or 48-h intervals).
• Nitrogen, phosphorus, potassium, and sodium retention and excretion were measured over 35-day periods.

Main Results:

• Nitrogen retention increased linearly with increasing dietary N intake across all constant CP levels.
• Oscillating CP at 24-hour intervals did not significantly affect N retention compared to a constant 12.5% CP diet.
• Oscillating CP at 48-hour intervals increased N retention by 38% in one trial and did not affect it in the other.
• Phosphorus retention increased with dietary CP and was higher in the 48-h oscillation group in one trial.

Conclusions:

• Oscillating dietary CP concentrations may enhance nitrogen utilization in ruminants consuming high-concentrate diets.
• A 48-hour oscillation interval shows potential for improving nitrogen retention, warranting further investigation.
• This feeding strategy could offer a method to reduce environmental nitrogen losses from beef cattle operations.