Needle Size Matters
Dr. Ken McMillan
Concerning needle size, I recommend the smallest gauge needle possible. Large needles make bigger holes, are more painful and cause more damage, and product can leak back out. I use 20-gauge, 3/4-inch needles for SQ vaccinations on calves. With adult cattle, or when administering thick medications, I use a 16-gauge with a 3/4-inch needle. I only use needles once.