The 2008 National Animal Health Monitoring System (NAHMS) data indicates 77% of bull calves in the U.S. are castrated before marketing and 75% of those are castrated before three months of age. With regard to age at castration, does the science support this timing or should we delay castration of bulls to gain some additional weight?

Virtually every study indicates a bull calf will outweigh a non-implanted steer calf at weaning. But what happens if we castrate that bull at weaning or even months later?

There have been hundreds of studies looking at everything from stress to muscle tenderness; if you want to prove something you can find at least one study that will support your bias. But what happens when we combine the studies to make best management practice recommendations?

• In nearly every case, studies that compare implanted steers to intact bulls at weaning show no difference in weaning weight. Low-dose implants given at 2-4 months of age are one of the most underutilized technologies in the beef industry. This suckling implant will add about 20 lbs. to calf weaning weight.

• Calves castrated (surgically, banded or emasculatome) at or after weaning show increased stress, sickness and death loss. This becomes not only a financial issue — less profit for the feedlot — but an animal-welfare issue.

• Calves castrated after weaning have increased gain up until the time of castration. But when compared to calves castrated at less than three months of age, those castrated late in life weigh 20 lbs. less at slaughter and are marketed 12 days later than those castrated early in life. Although a bull weighs more than a steer (non-implanted) at weaning, the stress of castration at this later age sets the calf back and he never catches up.

• There seems to be no difference in using a rubber band or a knife to castrate calves less than three days of age. If you've never banded a baby calf, be sure you “count to two” before securing the band. Your veterinarian may say some unkind words if he has to peel a testicle away from the scar tissue that is around that retained testicle some months later.

• In an ideal world, a calf would be castrated after a full belly of colostrum is ingested, but I know how hard they can be to catch at 24 hours of age.

• Calves castrated before three months of age show no differences in performance, health and carcass traits to calves castrated soon after birth.

• A bull calf has a relatively modest increase in testosterone production up until about seven months of age, so the “testosterone advantage” is minimal up to that point. The negatives of castrating late nearly always outweigh this minor benefit.

• Bulls castrated over 500 lbs. tend to have less marbling than bulls cut earlier. Beef tenderness ratings also decrease the heavier bulls are at time of castration. This becomes quite pronounced for bulls weighing more than 900 lbs. at time of castration.

• Bull calves are and should be discounted at feeder auctions. A 500-lb. bull will sell at a $5-$7/cwt. discount to his 500-lb. steer mate. As bulls get heavier, the discount increases even more.

Castration of bull calves soon after birth is ideal in terms of physiology (lower stress). It also results in improved animal welfare, improved health and gain in the feedlot, and enhanced marbling and tenderness compared to castration at or after weaning. Castration at less than three months of age is a reasonable alternative to castration soon after birth. Let's all strive for a 100% rating in the 2018 NAHMS study.

View the NAHMS survey results at: nahms.aphis.usda.gov/beefcowcalf/.

W. Mark Hilton, DVM, is a clinical associate professor of beef production medicine at Purdue University in West Lafayette, IN.