[Urea utilization in growing lambs. 4. N balances with unprocessed rations].

Area of Science:

• Animal Nutrition
• Ruminant Physiology
• Agricultural Science

Background:

• Optimizing nitrogen utilization is crucial for livestock growth and feed efficiency.
• Wheat-based diets may require supplementation to meet the nitrogen requirements of growing lambs.
• Urea and soybean meal are common protein supplements in animal feed.

Purpose of the Study:

• To evaluate the effect of urea and soybean meal supplementation on nitrogen balance and nutrient digestibility in lambs.
• To compare the efficacy of different urea inclusion levels and combinations with straw against soybean meal.
• To determine the optimal nitrogen supplementation strategy for wheat-based lamb rations.

Main Methods:

• Nitrogen balance experiments were conducted with lambs aged 8, 12, and 15 weeks.
• Lambs were fed wheat-based rations with varying supplements: urea (2%, 3%), straw (20%), and soybean meal.
• Digestibility of crude nutrients and nitrogen retention were measured across different treatment groups.

Main Results:

• No significant differences in nutrient digestibility or nitrogen retention were observed across different lamb ages.
• Supplementation with straw decreased the digestibility of organic matter, crude protein, crude fiber, and nitrogen-free extract.
• Urea and soybean meal supplements increased crude protein content and nitrogen intake, leading to higher nitrogen retention compared to unsupplemented wheat.
• Nitrogen retention was not significantly different between lambs fed urea (N2), urea with straw (N3), or soybean meal (N4).

Conclusions:

• Urea supplementation effectively increases nitrogen retention in lambs fed wheat-based diets.
• Urea can be a viable alternative to soybean meal as a nitrogen supplement, even when combined with straw.
• The results suggest that urea supplementation, at the tested levels, is comparable to soybean meal in improving nitrogen utilization in growing lambs.