Nelson E A, Sanchez L C, Mallicote M F, Warren L K, Robelen A M, Reuss S M
Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL, USA.
Current Address: San Luis Rey Equine Hospital, Bonsall, CA, USA.
N Z Vet J. 2020 Jan;68(1):60-64. doi: 10.1080/00480169.2019.1655498. Epub 2019 Sep 4.
To compare urine urinary pH, blood pH and concentration of electrolytes in blood of healthy horses fed an anionic salt supplement to achieve diets with a dietary cation-anion difference (DCAD) of -40 or 0 mEq/kg DM, with horses a fed a diet with a DCAD of 85 mEq/kg DM. Eight healthy horses received each of three diets in a randomised crossover design. Diets consisted of grass hay and concentrate feed, with a varying amount of an anionic supplement to achieve a DCAD of 85 (control), 0 or -40 mEq/kg DM. They were fed for 14 days each with a washout period of 7 days between. Urine pH was measured daily and blood samples were collected on Days 0, 7 and 14 of each study period for the measurement of pH and concentration of electrolytes. Four horses voluntarily consumed the anionic supplement with their feed, but four horses required oral supplement administration via dose syringe. During the study period mean urine pH was lower in horses fed diets with a DCAD of 0 (6.91; SD 0.04) and -40 (6.83; SD 0.04) mEq/kg DM compared to the control diet (7.30; SD 0.04). Compared with horses fed the control diet, mean urine pH was lower in horses fed the 0 and -40 mEq/kg DM diets on Days 1-12 and 14 (p < 0.05) of the study period. On Day 13 it was only lower in horses fed the -40 mEq/kg DM diet (p < 0.01). Urine pH was similar for horses fed the 0 and -40 mEq/kg DM diets (p = 0.151). The DCAD of the diet had no effect on blood pH, ionised Ca or anion gap. Mean concentrations of bicarbonate in blood were affected by diet (p = 0.049); they were lower when horses were fed the 0 mEq/kg diet relative to the control diet on Day 14. The anionic supplement reduced urine pH in horses fed diets with a DCAD of 0 or -40 mEq/kg DM compared with 85 mEq/kg DM. However as urinary pH did not fall below pH 6.5, the pH below which calcium carbonate uroliths do not form, this reduction in urine pH is unlikely to be clinically significant. The supplement was variably palatable and showed minimal promise as an effective urinary acidifier at the doses administered in this study.
为比较给健康马匹饲喂阴离子盐补充剂以实现日粮阴阳离子差（DCAD）为-40或0 mEq/kg干物质的日粮时，其尿液pH值、血液pH值及血液中电解质浓度，与饲喂DCAD为85 mEq/kg干物质日粮的马匹之间的差异。8匹健康马匹采用随机交叉设计接受三种日粮中的每一种。日粮由禾本科干草和精饲料组成，添加不同量的阴离子补充剂以实现DCAD为85（对照）、0或-40 mEq/kg干物质。每种日粮饲喂14天，期间间隔7天的洗脱期。每天测量尿液pH值，并在每个研究期的第0、7和14天采集血样以测量pH值和电解质浓度。4匹马自愿在采食时摄入阴离子补充剂，但有4匹马需要通过剂量注射器进行口服补充。在研究期间，与对照日粮（7.30；标准差0.04）相比，饲喂DCAD为0（6.91；标准差0.04）和-40（6.83；标准差0.04）mEq/kg干物质日粮的马匹平均尿液pH值较低。与饲喂对照日粮的马匹相比，在研究期的第1至12天和第14天，饲喂0和-40 mEq/kg干物质日粮的马匹平均尿液pH值较低（p<0.05）。在第13天，仅饲喂-40 mEq/kg干物质日粮的马匹尿液pH值较低（p<0.01）。饲喂0和-40 mEq/kg干物质日粮的马匹尿液pH值相似（p=0.151）。日粮的DCAD对血液pH值、离子钙或阴离子间隙无影响。血液中碳酸氢盐的平均浓度受日粮影响（p=0.049）；在第14天，与对照日粮相比，饲喂0 mEq/kg日粮的马匹血液中碳酸氢盐浓度较低。与DCAD为85 mEq/kg干物质的日粮相比，阴离子补充剂降低了饲喂DCAD为0或-40 mEq/kg干物质日粮马匹的尿液pH值。然而，由于尿液pH值未降至6.5以下（低于此pH值碳酸钙尿路结石不会形成），尿液pH值的这种降低在临床上可能无显著意义。该补充剂的适口性各不相同，在本研究施用剂量下作为有效的尿液酸化剂前景渺茫。
