[Nitrogen and mineral metabolism of growing lambs fed straw treated in different ways]

Lambs were fed diets containing 500 g straw, 50 g sucrose and 30 g minerals per day. The straw was untreated (A), wafered after addition of NaOH (B) or gassed with ammonia. Diets A and B, in addition contained urea, so that equal amounts of dietary N were offered. Digestibility of OM was increased by 12 units after addition of NaOH and by 8 units after gassing with NH3. As significantly more faecal N was excreted in animals fed diet C, it is concluded that N of NH3-treated straw is less available than of added urea. When NaOH-treated straw was fed, renal excretion of phosphorus was increased.