Objective: To evaluate the effects of growth, maturity, and pregnancy on epidural pressure in cattle.
Animals: 50 healthy Holstein cattle (18 heifers, 23 lactating cows, and 9 pregnant nonlactating cows).
Procedure: Each of the cattle was restrained in a standing position. Height of the second lumbar vertebra's transverse process (2LTP) and humeral tuberosity (HT) on the right side as well as abdominal girth (AG) were measured in each animal, and body condition score (BCS) was ascertained. Skin caudal to the first lumbar spinous process was aseptically prepared, and anesthetic was injected. After inserting a 16-gauge 120-mm Tuohy needle in the ligamentum flavum, a calibrated pressure transducer was connected to the needle. Then, the needle was introduced into the epidural space, and epidural pressure was recorded.
Results: Mean +/- SD residual epidural pressure of heifers (-9.3+/-3.3 mm Hg) was significantly higher than that of lactating (-174+/-5.5 mm Hg) or nonlactating (-14.5+/-2.4 mm Hg) cows. Stepwise regression of 5 variables revealed that only the difference in height between 2LTP and HT (2LTP - HT) in heifers and only BCS in lactating cows were significantly correlated with residual epidural pressure. For all cattle, the optimal equation (R2 = 0.47) describing the relationship was y = -12.7 + 6.3x, - 0.4x2 - 0.1x3, where y is epidural pressure, x1 is BCS, x2 is 2LTP - HT, and x3 is age.
Conclusions and clinical relevance: Negative epidural pressure was detected in standing cattle. Growth, maturity, and pregnancy affect epidural pressure in cattle.