AN IMPROVED METHOD FOR THE ROUTINE BIOPSY OF BOVINE MAMMARY TISSUE

Eight primiparous cows in midlactation were used to determine a method for the mammary biopsy of standing cows in full lactation. Cows were mildly sedated; therefore, preoperative feed withdrawal was not necess ary. A core of secretory tissue (0.75 to 1 g) was extracted using a ro tating stainless steel cannula with a retractable blade at the cutting edge. Postoperative recovery was rapid, taking only 15 min per cow, a nd the method was reliable and efficient. The presence of secretory ti ssue was verified by histology and in situ hybridization with alpha(s1 )-casein and alpha-lactalbumin probes. The capsular end of the core co ntained more connective tissue, and the parenchyma showed heterogeneou s expression of alpha(s1)-casein and alpha-lactalbumin. Despite some p ostoperative bleeding, milk yield and composition in the biopsied glan d were affected only transiently. Yield recovered by 3.5 d after biops y, and composition recovered by 6.5 d after biopsy. Yield and composit ion of milk from the control glands were not affected by the procedure . Biopsy sites healed rapidly and without infection. No clinical masti tis was observed in any of the biopsied cows throughout the remainder of the lactation.