Advantages of replacing slow-release urea instead of common urea or plant protein sources in ruminant diets (Review)

Dietary protein plays an important role in ruminant nutrition, because in addition to providing amino acids, it’s a nitrogen source for microbial protein synthesis. Providing protein, especially for high-producing livestock, is one of the most important concerns of livestock farmers. Soybean meal has been used for a long time as an excellent source of CP for ruminants, but with the increase in its price, has challenge due to the limitation of production and direct consumption by humans. Due to the ability of ruminants to use NPN (urea), nitrogen unit density and its low price, it has been used as an alternative in ruminant diets. Urea is converted into ammonia in the rumen, on the other hand, fiber-digesting bacteria in the rumen need ammonia to growth. Hydrolysis of common urea is faster than the growth of microbes and the digestion of structural carbohydrates in the rumen, so it will reduce the efficiency of nitrogen use and even nitrogen poisoning in livestock. Slow-release urea (SRU) is a type of urea that slows release of nitrogen in the rumen. Substitution of SRU instead of common urea in the diet of ruminants that have a limit with protein sources can reduce the competition between humans and animals. Also, it will not have the dangers of common urea for livestock. This article review the effects of using SRU instead of common urea and plant protein sources in ruminants diet on feed intake, digestibility, fermentation parameters, growth and production, blood parameters and carcass characteristics.