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.
Studies show that intact bull calves will weigh 3-5% more (Bratzler, 1954, Bagley, 1989) than a non-implanted steer calf at
weaning while there is no difference in weight between intact bulls and implanted steers.
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
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.
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.
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).