Effects of Supplemental Feeding Using Different Nitrogen Sources on Body Weight Gain and Physiological Conditions on Grazing Castrated Lambs in the Steppe Zone of Mongolia

The pastoral livestock production system in Mongolia has traditionally been operated in natural open pastures, which occupies approximately 80% area of the country. The productivity of the system is extremely seasonal, and the nutritional values of pasture plants such as crude protein (CP) and total digestible nutrients (TDN) decrease until spring (Yamasaki et al., 2013), resulting in animals losing their live weight by spring. In recent years, the damage caused by disastrously snowy and cold conditions, termed dzud in Mongolian, has evidently worsened, thereby affecting farm management in the region. To overcome the dzud and establish a sustainable livestock production system, supplemental feeding during the cold seasons is required. Wheat bran is the most prevalent feed among the country’s herders. Brewers’ grain (BG) is one of the most important livestock feed resources because it is rich in energy, protein, fiber, and fat content (MAFF, 1995). The production of BG has been steadily increasing year by year (National Statistical Office of Mongolia, 2014), but the usage of BG in the country is restricted, particularly during summer. Then, ensilaging would be one of the key techniques to store and conserve the nutritional value of BG, as it is possible for even small-to-medium sized farmers and/or herders. In addition, the importation of urea into the country is beginning to accelerate and is expected to be a source of nitrogen (N) for ruminants. We then determined and compared the effects of the different N sources and the amounts on body weight gain and physiological conditions for animals, so as to contribute to the establishment of supplemental feeding technologies during the cold seasons in this region