Effect of sampling protocol on plasma NEFA concentration.

The objective was to determine effect of sampling protocol on plasma non-esterified fatty acid (NEFA) concentration. Plasma NEFA concentration is often used as a tool to assess metabolic status of dairy cows during the periparturient period. In experiment 1, 8 nonlactating, non-gestating dairy cows were blood sampled (basal), 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. Following 15 min of exercise, cows displayed an increase in plasma NEFA concentration, peaking at 5 min (225 µEq/L) and returning to basal (84 µEq/L) by 30 min (110 µEq/L; P < 0.001). Cows were moved to box stalls overnight and 24 h after 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 µEq/L; P < 0.01). In a second experiment at a large freestall commercial dairy, 11 late gestation dairy cows were locked in headlocks at feeding, blood was sampled (0 min), and cows were released and allowed to finish eating and return to stalls. Cows were then herded into headlocks and sampled immediately (120 min), and at 135, 150, and 180 min. Plasma NEFA concentration was highest at initial lockup (284 µEq/L), lowest at 180 min (178 µEq/L) and intermediate at time points in between (P < 0.05). A second group of 10 late gestation dairy cows were locked in headlocks at feeding and blood sampled immediately, and at 5, 15, 30 and 60 min. Plasma NEFA concentration was highest 15 min after being placed in headlocks and lowest at 60 min (221 and 113 µEq/L, respectively; P < 0.05). At each time point, a behavior score was given (1 to 10; 1=calm; 10=extremely excited). There was a significant correlation between plasma NEFA concentration and behavior score (r=0.55 for experiment 1, r=0.31 for experiment 2; P < 0.05). In conclusion, plasma NEFA concentration was altered with different sampling protocols. [ABSTRACT FROM AUTHOR]