Evaluation of the spot urine sampling technique to assess urinary pseudouridine excretion in lactating dairy cows

Authors

• Kevin J. Shingfield Grassland and Ruminant Science Department, SAC Auchincruive, Ayr, KA6 5HW, United Kingdom
• Nicholas W. Offer Grassland and Ruminant Science Department, SAC Auchincruive, Ayr, KA6 5HW, United Kingdom

DOI: https://doi.org/10.23986/afsci.72866

Abstract

The potential of the spot urine sampling technique to assess urinary pseudouridine excretion was evaluated. Twelve multiparous Holstein-Friesian cows were fed two experimental diets in a complete change-over design with two 14 day experimental periods. Diets were either silage fed ad libitum with a concentrate supplement offered as a single meal (SF), or a complete diet formulated from the same ingredients (CD). Total urine collections were performed for 24h at 2 h intervals on days 11 and 14. Pseudouridine and creatinine excretion during each 2h interval depended on time of collection (pseudouridine, P<0.01 and creatinine, P<0.05) and on cow (pseudouridine, P = 0.092 and creatinine, P<0.01), but were unaffected by differences due to sampling day or treatment. Variations in the molar ratio of pseudouridine to creatinine(Ps/c) followed similar diurnal patterns observed for pseudouridine excretion. Data was used to assess the accuracy of spot urine sampling to predict daily mean Ps/c ratios. Collection of multiple samples within a day was more reliable than collecting fewer samples over several days, while prediction errors were generally greater for CD compared to SF. Even the most intensive sampling regimen did not allow an acceptable prediction of the daily mean Ps/c ratio, minimum r values 0.528 and 0.080 for SF and CD treatments, respectively. Furthermore, mean Ps/c ratios accounted for only half of the variation observed in daily pseudouridine excretion, A total urine collection appears necessary to assess accurately daily pseudouridine excretion in dairy cows.