Urea is broken down by microorganisms in the rumen of cattle into ammonia, which can then be used to synthesize bacterial protein. This process allows urea to serve as a protein supplement, reducing the need for traditional protein feeds. However, urea itself is not a true protein, and its effectiveness depends on various factors such as the type of feed, the microbial population in the rumen, and the overall nutritional balance of the diet.
It is generally recommended to add urea to cattle diets during winter and spring when the main feed sources are roughages like wheat straw, dried corn stalks, and hay—feeds that are typically low in crude protein. In contrast, feeding urea during summer and autumn, when green feeds such as grasses, weeds, and wild vegetation are abundant, is often less effective or even counterproductive. Green feeds tend to be rich in crude protein, with levels ranging from 12% to 20%, and they are highly digestible and nutritionally complete, providing essential amino acids that are vital for animal growth and health.
Studies have shown that when the crude protein content in the feed is below 11%, urea utilization in the rumen can reach up to 70%, leading to a significant increase in weight gain—up to 39% in some cases. However, as the crude protein level in the feed increases, the benefits of adding urea diminish. Once the crude protein content exceeds 12%, the positive impact on weight gain disappears, and in some cases, feeding urea may even lead to reduced performance or weight loss.
This is because high-protein green feeds already provide sufficient nitrogen for microbial protein synthesis, making additional urea unnecessary and potentially harmful. Overfeeding urea can lead to ammonia toxicity, which can negatively affect the cow’s health and productivity. Therefore, it's important to adjust feeding strategies based on seasonal changes in feed availability and nutrient composition to maximize both efficiency and animal well-being.
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