Technical note: a technique for multiple liver biopsies in neonatal calves.

Our objective was to develop a rapid and safe liver biopsy technique that could be repeated on multiple occasions in individual neonatal calves. A pilot study was performed to verify the efficacy of sedation and restraint procedures and to evaluate different biopsy instruments. Following the pilot experiment, a biopsy trocar was fabricated and an experiment was conducted using this procedure. Liver biopsies were performed in neonatal calves on d 4, 9, 15, 21, and 28 of life to evaluate the effect of vitamin A intake on liver vitamin A concentrations. On these days, a single injection of ceftiofur sodium was administered i.m. 1 to 2 h prior to the procedure. Calves were lightly sedated with xylazine and placed on a surgical table in left-lateral recumbency. The right caudo-thoracic area was clipped and scrubbed with an iodophor agent. Following administration of a local anesthetic (lidocaine), a small incision was made in the skin between the 12th and 13th ribs approximately 15 cm from the dorsal midline. The biopsy trocar was inserted through the body wall and peritoneum and introduced into the liver parenchyma, and a liver sample was collected. Following the biopsy, the cutaneous incision was sutured and an antiseptic agent was applied to prevent infection. An i.m. injection of an analgesic was administered 1 h following the procedure to alleviate postsurgical discomfort. Most calves were able to stand within 2 h after the biopsy. The entire procedure, which could be performed by a single individual, usually required about 20 min from initial sedation until skin closure. Although liver samples of up to 500 mg were obtained, most samples weighed 75 to 150 mg (wet weight). A total of 156 liver biopsies were performed on 33 calves. Complications due to the biopsy procedure were observed in only two calves. Therefore, this procedure can be useful for studies designed to monitor changes in liver composition or enzyme activities over time.