Suitability of Sainfoin (Onobrychis Viciifolia) Hay As a Supplement to Fresh Grass in Dairy Cows (Report‪)‬

INTRODUCTION Pasture grass from intensive grazing systems is characterized by high concentrations of rapidly degradable protein (van Vuuren et al., 1991) and carbohydrates (O'Grady et al., 2008) as well as low concentrations of physical effective fiber (O'Grady et al., 2008). Due to the fast ruminal degradation of protein, ammonia is available after feeding at an excessive level and can not be utilized to a sufficient amount by the ruminal microbes. Therefore, ammonia has to be metabolized by the liver to urea, causing liver stress. This metabolic pathway is also energy consuming, and nitrogen (N) is lost through urine. Also, high concentrations of ammonia in the blood may impair fertility (Visek, 1984). The high content of rapidly degradable carbohydrates, in turn, increases the yield of VFA, which may reduce ruminal pH in grazing cows to an acidotic level (O'Grady et al., 2008), particularly when combined with a reduced ruminal buffering capacity. The latter depends on saliva flow and, consequently, chewing activity, which may be impaired when cows are consuming feed with a low physical fibrousness (Balch, 1971). Furthermore, ingestion of feed with a high moisture content, which is characteristic for fresh grass (van Vuuren et al., 1991), was described to be associated with less saliva production (Meyer et al., 1964).