Melendez P, Chelikani P K, Patel D, Garbarino E
School of Veterinary Medicine, Texas Tech University, Amarillo 79106.
Health Science Center, Texas Tech University, Amarillo 79106.
JDS Commun. 2021 Oct 22;3(1):59-65. doi: 10.3168/jdsc.2021-0154. eCollection 2022 Jan.
The objectives of this cross-sectional, nonintervention, observational study were to compare urine and blood parameters between cows consuming a positive dietary cation-anion difference (DCAD) diet [early dry cows, DCAD + 250 mEq/kg of dry matter (DM), n = 15] with the same cows consuming a negative DCAD diet (-220 mEq/kg of DM) 10 d after moving them from the early dry to the prepartum group. The most remarkable finding was that cows consuming the anionic diet had very low urine pH and very low base excess in blood, suggestive of uncompensated metabolic acidosis. Importantly, the metabolomics data revealed that only urine concentrations of essential and aromatic amino acids were decreased, and that concentrations of total nonessential amino acids and glucogenic amino acids were increased in plasma and reciprocally decreased in urine, suggesting that the cows fed anionic salts were attempting to meet a high glucose demand by mobilizing gluconeogenic amino acid reserves. Notably, the dietary anionic salts exerted marked effects on glycerophospholipids, with a reduction in most phosphatidylcholine containing diacyl (PC aa) and acyl-alkyl (PC ae) moieties in plasma and urine. Further characterization of these metabolomic profiles may lead to the development of novel biomarkers to identify cows susceptible to metabolic acidosis and other metabolic diseases.
这项横断面、非干预性观察性研究的目的是比较奶牛在食用具有正的日粮阴阳离子差（DCAD）的日粮[干奶前期奶牛，DCAD + 250 mEq/kg干物质（DM），n = 15]时与将它们从干奶前期转移到围产期组10天后食用负DCAD日粮（-220 mEq/kg DM）时的尿液和血液参数。最显著的发现是，食用阴离子日粮的奶牛尿液pH值非常低，血液碱剩余非常低，提示存在未代偿的代谢性酸中毒。重要的是，代谢组学数据显示，只有必需氨基酸和芳香族氨基酸的尿液浓度降低，血浆中总非必需氨基酸和生糖氨基酸的浓度升高，而尿液中则相反降低，这表明饲喂阴离子盐的奶牛试图通过动员生糖氨基酸储备来满足高葡萄糖需求。值得注意的是，日粮阴离子盐对甘油磷脂有显著影响，血浆和尿液中大多数含二酰基（PC aa）和酰基烷基（PC ae）部分的磷脂酰胆碱减少。对这些代谢组学特征的进一步表征可能会导致开发新的生物标志物，以识别易患代谢性酸中毒和其他代谢疾病的奶牛。
