This study assessed the effectiveness of penetrating (PCB; 190 psi; N = 363) and non-penetrating captive bolt guns (NPCB; 210-220 psi; N = 92) to stun a total of 455 cattle (Zebu and Zebu Cross). Physical bolt parameters (momentum, kinetic energy and energy density) were evaluated. Clinical indicators of brain function were recorded after stunning (GR), after being hoisted (HO) and at the bleeding rail (BL). Physical bolt parameters (bolt velocity, momentum, kinetic energy, energy density and sectional density) were significantly higher (P < 0.001) for PCB. The need for two or more shots was more frequent for NPCB (210-220 psi; 29% vs. 12%, P < 0.001). Cattle were more likely to collapse at first shot with PCB (190 psi; 99%) compared to NPCB (91%; P < 0.002) which can be attributed to the higher values of bolt physical parameters. Incidence of eyeball rotation (5% vs. 1%) and righting behaviour (7% vs. 1%) were higher (P < 0.001) for NPCB (210-220 psi) at GR than PCB. The NPCB with 210-220 psi had a higher frequency of response to nostril stimulation (2% vs. 0%; P < 0.001) than PCB. Rhythmic respiration was more frequently found for NPCB with 210-220 psi at GR, HO and BL. Therefore, PCB with 190 psi was more effective in ensuring unconsciousness in cattle.

Brain damage resulting from penetrating and non-penetrating stunning of Nelore cattle using pneumatically powered captive bolt guns was evaluated. Heads were shot using penetrating captive bolt gun with 160 psi (P1; n = 10), 175 psi (P2; n = 10), 190 psi (P3; n = 12), and non-penetrating operating with 220 psi (NP; n = 10). Skin and bone thickness, bolt penetration angle, bolt penetration depth, haemorrhage over the cerebral hemispheres and laceration were assessed. Only P1 had shots that failed to perforate the skull (n = 2; 20%). Bolt penetration depth and haemorrhage over the right cerebral hemisphere was significantly (P ≤ 0.05) greater for P3. Subarachnoid haemorrhage over the frontal, parietal and occipital lobes was higher for NP. Lacerations were observed only for penetrating gun in the cortical region of frontal and parietal lobes. Subarachnoid haemorrhage surrounding the brainstem and laceration in the midbrain and pons was only found for P3. Thus, penetrating captive bolt gun operating with 190 psi is more effective to achieve unconsciousness.

The efficiency of stunning cattle was assessed in 443 animals (304 pure Zebu and 139 crossbred cattle), being mainly mature bulls and cows. Cattle were stunned using a Jarvis pneumatically powered penetrating captive bolt gun operating with low (160-175psi, N=82) and high (190psi, N=363) airline pressure, which was within the manufactures specifications. Signs of brain function and the position of the shots on the heads were recorded after stunning. Velocity of the captive bolt and its physical parameters were calculated. Cattle shot with low pressures showed more rhythmic respiration (27 vs. 8%, P<0.001), less tongue protrusion (4 vs. 12%, P=0.03) and less masseter relaxation (22 vs. 48%, P<0.001). There was an increased frequency of shots in the ideal position when cattle were shot with the low compared to high airline pressures (15.3 vs. 3.1%). Bolt velocity and its physical parameters were significantly (P<0.01) higher when using high pressure. Airline pressures below 190psi are inappropriate when shooting adult Zebu beef cattle with pneumatically powered penetrating captive bolt guns.