Zinc Injection As a Novel Castration Method in Beef Bulls: Effects on Carcass Traits and Consumer Acceptability

One hundred eighty bulls (BW = 337 ± 10.9 kg) were blocked by BW and assigned randomly to 1 of 3 treatments on d 0: 1) INJ; received 1 mL (100 mg Zn) of a Zn solution in each testis, 2) BAN; received blood-restrictive rubber band placed around the dorsal aspect of the scrotum, 3) BUL; bulls with testicles remaining. Cattle were harvested by block on three separate dates (d 155, 176, and 197) when blocks reached similar BW (656 ± 4.4 kg) and visual adipose accretion. Striploins were removed from the left side of the carcass, wet-aged 14 d, and frozen at -20°C. Frozen striploins were sliced into 2.54-cm-thick steaks and remained frozen until analyses. Data were analyzed as a randomized complete block design (3 treatment pens/block and 10 cattle/pen) using the MIXED and GLIMMIX procedures of SAS with pen as the experimental unit for all dependent variables. Hot carcass weights were greater (P < 0.01) in INJ and BUL treatments compared to BAN. Similarly, longissimus muscle area was greater (P < 0.01) in INJ and BUL compared to BAN. Numeric yield grade was not different between treatments (P = 0.12). Percentage of USDA Choice carcasses was greater (P < 0.01) in BAN compared to INJ and BUL. Consumer panelists (n = 152) perceived greater (P = 0.02) tenderness from BAN steaks as compared to BUL whereas INJ was intermediate. Panelists scored BAN steaks with greater (P < 0.01) juiciness ratings than either BUL or INJ. Beef flavor was rated by panelists as greater (P = 0.01) in BAN and BUL compared to INJ. Overall acceptability was greater (P < 0.01) in BAN compared to INJ whereas BUL was intermediate. Percentage cook loss of striploin steaks (P = 0.47) and Warner-Bratzler shear force values (P = 0.11) were not different between treatments. Cooked color lightness values (L*) and redness values (a*) were not affected (P ≥ 0.23) by treatment. Yellowness values (b*) of striploin steaks were greater (P = 0.02) in BAN and BUL compared to INJ. Cooked steaks from INJ cattle displayed a greater (P = 0.05) ratio of red-to-brown (630:580 nm) compared to either BAN or BUL. Compositionally, INJ steaks were more similar to BUL than BAN, suggesting limiting efficacy of INJ as a castration method in older beef bulls. Compared to BAN, INJ increased HCW and LM area, yet quality grade and consumer acceptability were reduced.