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?

We will examine the published science with regard to timing and technique of castration of calves.

Weight gain

When bulls that are castrated at 6-7 months of age and then weaned 30 days later are compared to bulls castrated at 2-3 months of age, the late castrates weigh significantly less than the early castrates at weaning. Daily gain for the 30 days from castration to weaning was also significantly less for late castrates (Lents, 2006).

Bulls that are castrated early (at or before 3 months of age) gain more weight after weaning compared to bulls that were castrated late (after 6 months of age) so the negative effects of late castration never goes away (Worrell et al., 1987). Because we know that bulls castrated late have reduced feed intake (Fischer et al., 1996) this could be a large factor in their decreased gain.

When castration-associated weight loss was evaluated within the first 30 days post-castration, the weight loss increased quadratically as the age of castration increased indicating that castration by any of the methods, at birth or close to birth, drastically reduces the weight loss. Surgical castration performed after puberty has a detrimental effect on performance which extends for a period beyond the first 30 days post-castration. When castration is performed at birth, weight loss is scarce or zero. (Bretschneider, 2005)

Health/stress

In a study by Pinchak, et al. in 2004, bulls castrated after weaning and then transported had a 32% increase in morbidity when compared to bulls castrated early. In this same study the late castrates had a 25% decrease in overall gain.

In the England, regulations require that animals older than two months be castrated by a veterinarian, using local anesthesia. Anesthesia and analgesia are mandated for castration in Northern Europe. Castration of any age bull is not allowed in Switzerland without anesthesia, and use of rubber bands is prohibited. In Australia, surgical castration is only permitted for animals up to 6 months old.

Stress response of cattle castrated at an age < 6 months tended to be lower than that of cattle castrated at an age > 6 months, indicating that when calves are castrated younger they suffer less stress. (Bretschneider, 2005). Age at castration is not only an issue of profitability for the producer, but an issue of animal welfare for everyone. You can read "Welfare implications of castration of cattle" on the AVMA web site: http://www.avma.org/issues/animal_welfare/castration_cattle_bgnd.asp for more details.

Carcass characteristics

Marbling scores tend to decrease the older and heavier a bull is at time of castration. In a study by Worrell et al in 1987, they found that if bulls were castrated at weights over 700# the marbling scores at slaughter were not different from intact bulls. This same study showed a reduction in tenderness as bulls were castrated at heavier weights. When bulls were castrated over 900# the tenderness scores were significantly different than when castrated at 150#. Other studies showed no difference in tenderness with regard to weight at castration, but none have shown an increase in tenderness with increasing weight at time of castration.

In addition to a reduction in marbling scores dressing percent was also reduced in one study. (Lents, 2006).