Castration of beef calves: What does the science say about timing and technique? (Proceedings)
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.
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 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)
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).
Bull calves have a very low level of testosterone from birth to 4 weeks of age. This level increases slowly until 28-40 weeks of age so to get any growth effect due to testosterone, you must wait until after 40 weeks of age to castrate and previous studies have shown that the negative of this timing far outweighs the increase in testosterone. (Rawlings et al, 1972; Secchiari, et al 1976; Lacroix et al, 1977).
If calves are castrated at or soon after birth, the method of castration (surgical vs. rubber band) has no bearing on stress or weight gain. The studies are more inconsistent when castration at > 5 months is evaluated. While one study (Fisher, et al, 2001) found that surgical castration of 5.5 month old bulls was superior to banding, two other studies (Chase et al, 1995) found that in 20.3 month old bulls banding was superior to surgical castration and ZoBell and colleagues (1993) found banding superior to surgical on 8-9 month old bulls. The Fisher and Chase studies showed a significantly different time from banding to necrosis of the scrotum and one author thought this could be due to a difference in tension of the rubber band. When many studies are combined, there is generally no difference in average daily gain when surgical and banding are compared for the duration of the study.
There are negative health associated factors when comparing and contrasting surgical vs. rubber band ligation castration methods. The surgical method can result in a loss of blood that can cause morbidity and mortality or wound associated infections. For banding the risk of not getting the band tight enough and causing a massive swelling of the scrotum is not uncommon for those with little to no experience with the devices. Tetanus is also a real threat in these larger bulls and appropriate immunization must be given to prevent this disease. For optimum results the tetanus toxoid must be given 7-10 days before banding takes place. An often overlooked additional cost to the use of large rubber bands on bulls is their added cost of production If tetanus vaccine with or without an antibiotic are used, this becomes another cost that must be recouped.
While all the studies point to the advantages of early castration, is there a time that is too early? I was unable to find any studies that measured colostrum intake and time at castration (birth vs. 12 hrs. vs 24 hrs.) but we know that anything that limits colostrum intake in newborns is a negative. Therefore the conservative advice is to castrate at approximately 24 hours of age or after a vigorous suckling of colostrum.
Lidocaine is the most commonly used anesthetic agent and its use for mitigating pain during castration has been studied. Fischer et al in 1996 found that during the first two hours after castration the cortisol response was lower if lidocaine was used and castration was done 15 minutes after anesthesia. This of course is quite impractical. Faulkner et al (1992) used IV xylazine and butorphanol before castration and found no difference in acute stress response between control and treatment calves. The IV treatment was given 90 seconds before castration which would seem to limit its usefulness as an analgesic.
Caulkett and colleagues (1993) used a diluted xylazine epidural at a dose of 0.07mg/kg where the xylazine was mixed with saline to give a final volume of 7.5 ml. This was given 20-30 minutes prior to castration and was done by loading about six bulls tightly into the chute and alleyway so that the veterinarian could give the epidurals in an efficient manner. After the final epidural of the group, the first bull was ready for surgery. They noted that some bulls did lie down in the chute, but all got up when prompted.
Another advantage to early castration was the fact that there were no differences in cortisol response of calves castrated at 7 days of age as compared to uncastrated controls in work by Mellor et al (1991).
Two recent studies on pain relief show some promise for the future. Earley and Crowe showed that IV Ketoprofen lowered cortisol levels to that of controls while local administration of lidocaine did not. Both products were given 20 minutes before surgery which surely limits their usefulness in field situations.
Cortese and colleagues at Kansas State have been working on various methods of mitigation of pain in cattle and found that IV sodium salicylate attenuates cortisol response following castration. The product was given less than 30 seconds before castration as an IV bolus and kept cortisol levels below control (uncastrated) cattle for 240 minutes. In the same study oral acetylsalicylic acid (aspirin) failed to provide any attenuation of cortisol.
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 can be a reasonable alternative to castration soon after birth.