Acidosis in preruminant lambs: effect of sodium bicarbonate on nitrogen utilization and voluntary feed intake

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Abstract
Thirty-three male crossbred lambs, aged 2–5 days at the start of the experiment, were used in four experiments. Experiment 1. Low protein milk replacers (0.10 of total energy as protein) that differed in acid-base balance and contained casein (diet A), cows' milk proteins (diet B) or isolated soybean proteins (ISP; diet C) were each fed to three lambs. Lambs given diet C excreted more urinary ammonia, chloride and phosphorus, but less magnesium and sodium than lambs given diets A and B. Experiment 2. Three lambs were given diet C (49 mg sodium per MJ) in three successive 9–11 day periods. When sodium bicarbonate (114 mg sodium per MJ) was added in period 2, there was a reduction in urinary ammonia nitrogen excretion (from 0.23 to 0.10 of total urinary nitrogen), but no net change in nitrogen balance. Experiment 3. The supplement of sodium bicarbonate to diet C was increased to 228 mg sodium per MJ for three lambs. Urinary ammonia nitrogen excretion decreased to 0.03 of total urinary nitrogen, but nitrogen balance was again unchanged. Experiment 4. Nine lambs were given diet C with a supplement of sodium bicarbonate to provide an additional 282 mg sodium per MJ. Nine lambs were given the unsupplemented diet (49 mg sodium per MJ). The quantity of milk replacer offered was slowly increased on alternate days. Voluntary intake fell below the amount offered after 7 days in both groups. The voluntary intake of lambs given sodium bicarbonate was significantly higher than that of the unsupplemented lambs after 9 days.