Technical note: Effect of sampling protocol on plasma nonesterified fatty acid concentration in dairy cows.

Abstract The objective of these experiments was to determine effects of sampling protocol on plasma nonesterified fatty acid (NEFA) concentration. In experiment 1, 8 nonlactating, nongestating dairy cows were blood sampled from a jugular vein catheter (basal, 0min), moved to an exercise lot for 15min, returned to stanchions, and sampled immediately and at 5, 15, 30, 60, and 120min following return to their stalls. Following 15min of exercise, plasma NEFA concentration increased, peaking at 5min (225μEq/L) and returning to basal (84μEq/L) by 30min (110μEq/L). Cows were then moved to box stalls overnight, and 24h after the basal sample, they were locked up and sampled again. Housing cows in a box stall overnight and locking them in headlocks increased plasma NEFA concentration (184μEq/L). In a second experiment at a large free-stall commercial dairy, 11 late-gestation nonlactating dairy cows were locked in headlocks at feeding, blood was sampled from the coccygeal artery or vein (0min), and cows were then released and allowed to finish eating and return to their stalls. Cows were then herded to headlocks and sampled immediately at 120min after initial sampling and at 135, 150, and 180min. Plasma NEFA concentration was highest at initial lockup (0min; 284μEq/L), lowest at 180min (178μEq/L), and intermediate at time points in between. A second group of 10 late-gestation nonlactating dairy cows were locked in headlocks at feeding, and blood was sampled immediately and at 5, 15, 30, and 60min. Plasma NEFA concentration was highest 15min after being placed in headlocks and lowest 60min after lockup (221 and 113μEq/L, respectively). At each time point in experiments 1 and 2, a behavior score was given (1 to 10; 1=calm; 10=extremely excited). In both experiments, there was a significant correlation between the plasma NEFA concentration and behavior score. In conclusion, plasma NEFA concentration was affected by sampling protocol.