Chair of Animal Nutrition and Dietetics, Ludwig-Maximilians-University of Munich, Oberschleißheim, Germany.
J Anim Physiol Anim Nutr (Berl). 2014 Apr;98(2):239-45. doi: 10.1111/jpn.12071. Epub 2013 Mar 30.
Hay stabilises urine pH in horses. It is unknown whether this is an effect of structure or of chemical composition. In this study, four ponies (230-384 kg body weight [BW]) were fed six different diets with either a structure or a composition similar to hay with and without acidifiers in a cross-over experimental design in amounts to maintain body weight with the following main compounds: Fresh grass (GRASS), alfalfa hay (ALF), grass cobs (COBS), grass silage (SIL), straw (STR) or extruded straw (STRe) for 2 to 10 days. Urine pH was measured in all trials, blood pH, blood base excess and bicarbonate as well as mineral balance were determined in GRASS, ALF, STR and STRe. In the trials with straw and extruded straw, urine pH decreased significantly (STR control: 7.8 ± 0.23, acidifier: 5.2 ± 0.38) when acidifiers were added, whereas in all other diets that were based on fresh or preserved green fodder, pH did not decrease below 7. Blood pH was similarly affected by diet and acidifiers. Acidifiers had little effect on the pre-prandial blood pH, only in diet STR there was a significant reduction in relation to control. Post-prandial blood pH was significantly reduced by acidifiers in all diets. Blood bicarbonate and base excess showed corresponding effects. Faecal and renal mineral excretion and apparent mineral digestibility were not systematically affected by diet or acidifiers except for chloride. Chloride added as inorganic chloride salt had an even better apparent digestibility than chloride originating from feed. Because only green plant material stabilised acid base balance, chlorophyll and its metabolites are discussed as potential mediators of the effect of green fodder on acid base balance.
干草可稳定马匹尿液的 pH 值。目前尚不清楚这种作用是源于结构还是化学成分。在这项研究中，4 匹体重为 230-384kg 的小马以交叉实验设计的方式喂食了 6 种不同的日粮，这些日粮在结构或组成上类似于干草，并添加或不添加酸化剂，喂食量以维持体重为准，日粮的主要化合物如下：新鲜牧草（GRASS）、苜蓿干草（ALF）、草捆（COBS）、草青贮（SIL）、稻草（STR）或膨化稻草（STRe），喂食 2-10 天。所有试验均测量了尿液 pH 值，GRASS、ALF、STR 和 STRe 中还测定了血液 pH 值、血液碱剩余和碳酸氢盐以及矿物质平衡。在稻草和膨化稻草的试验中，添加酸化剂后尿液 pH 值显著降低（STR 对照组：7.8 ± 0.23，酸化剂组：5.2 ± 0.38），而在所有其他基于新鲜或青贮绿色饲料的日粮中，pH 值均未降至 7 以下。日粮和酸化剂也同样影响血液 pH 值。酸化剂对餐前的血液 pH 值影响较小，仅在 STR 日粮中与对照组相比有显著降低。酸化剂使所有日粮的餐后血液 pH 值显著降低。血液碳酸氢盐和碱剩余也有相应的影响。粪便和肾脏矿物质排泄以及表观矿物质消化率除了氯之外不受日粮或酸化剂的系统影响。添加的无机氯盐形式的氯比来自饲料的氯具有更好的表观消化率。由于只有绿色植物材料可稳定酸碱平衡，因此叶绿素及其代谢物被认为是绿色饲料对酸碱平衡影响的潜在介质。
