Texas FFA Livestock Judging Practice Test

Urea is specifically used as a non-protein nitrogen (NPN) source that can be effectively utilized by ruminants, such as cattle and sheep. Ruminants possess a unique digestive system that allows them to convert NPN into microbial protein through the action of the microbes in their rumen. This is a crucial aspect because ruminants can synthesize protein from ammonia, which is derived from urea.

Using urea in the diets of non-ruminants (such as pigs and poultry) is not advisable, as they lack the rumen and the ability to convert it to protein, making urea ineffective and potentially harmful for their nutrition. In contrast, soybean meal, fish meal, and corn gluten meal are protein sources that can be fed to both ruminants and non-ruminants, as they are protein-rich feeds that provide amino acids directly without the need for microbial conversion. Thus, the limitation of urea to ruminants makes it the correct answer in this context.