Department of Veterinary Medicine and Animal Health, Università degli Studi di Milano, Lodi, Italy.
Vet Clin Pathol. 2022 Sep;51(3):408-413. doi: 10.1111/vcp.13115. Epub 2022 Apr 5.
Season is known to affect serum analyte concentrations in dairy cows, and the same can be hypothesized for urinary analytes, but information in this regard is lacking.
The aim of the study was to assess the effect of seasonality on urinary variables in healthy dairy cows.
Twelve Italian Holstein cows were randomly selected from a local herd, and urine specimens were collected once in each season of the year. For each cow, the lactation stage at each sampling time was also registered (lactation vs dry period), and physical examination and hematology and serum biochemistry measurements were used to assess health status. Three cows were voluntarily culled from the herd during the year; therefore, nine cows were included. Concentrations of urinary analytes recorded in each season for each cow were compared.
Seasonality affected urinary protein-to-creatinine ratios (P = 0.012) with lower median values in summer compared with spring (P = 0.020) and autumn (P = 0.004); differences were also found in urinary sodium-to-urinary creatinine ratio (P = 0.009), with lower medians in summer compared with spring (P = 0.003) and autumn (P = 0.020). The direct consequences of higher summer temperatures and the acclimation strategies needed to adapt to this environment could explain the changes in urinary analytes that were recorded in the current study; in fact, decreased food and water consumption tend to increase urinary creatinine concentrations and decrease renal excretion of proteins and electrolytes.
The present results suggest that seasonality can affect urinary variables of healthy dairy cows.
已知季节会影响奶牛的血清分析物浓度，同样可以假设尿液分析物也会受到影响，但这方面的信息还很缺乏。
本研究旨在评估季节性对健康奶牛尿液变量的影响。
从当地牛群中随机选择 12 头意大利荷斯坦奶牛，并在每年的每个季节采集一次尿液标本。对于每头奶牛，还记录了每次采样时的泌乳阶段（泌乳期与干乳期），并进行了体格检查和血液学及血清生化测量，以评估健康状况。在这一年中，有三头牛自愿被淘汰出牛群；因此，有九头牛被纳入研究。比较了每头奶牛在每个季节记录的尿液分析物浓度。
季节性影响了尿蛋白与肌酐的比值（P=0.012），夏季的中位数低于春季（P=0.020）和秋季（P=0.004）；尿钠与尿肌酐比值也存在差异（P=0.009），夏季的中位数低于春季（P=0.003）和秋季（P=0.020）。夏季较高的温度和适应这种环境所需的适应策略可能是导致本研究中记录的尿液分析物变化的直接原因；事实上，食物和水的摄入量减少会导致尿肌酐浓度升高，肾脏对蛋白质和电解质的排泄减少。
本研究结果表明，季节性会影响健康奶牛的尿液变量。
