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

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, 0 min), moved to an exercise lot for 15 min, returned to stanchions, and sampled immediately and at 5, 15, 30, 60, and 120 min following return to their stalls. Following 15 min of exercise, plasma NEFA concentration increased, peaking at 5 min (225 microEq/L) and returning to basal (84 microEq/L) by 30 min (110 microEq/L). Cows were then moved to box stalls overnight, and 24 h 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 (184 microEq/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 (0 min), 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 120 min after initial sampling and at 135, 150, and 180 min. Plasma NEFA concentration was highest at initial lockup (0 min; 284 microEq/L), lowest at 180 min (178 microEq/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 60 min. Plasma NEFA concentration was highest 15 min after being placed in headlocks and lowest 60 min after lockup (221 and 113 microEq/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.