I cannot emphasize enough the importance of nonslip floors. Animals panic when they start to slip in chutes or stun boxes. One of the most common problems in beef stun boxes is a series of rapidly repeating small slips. When this occurs, the animal will not settle down and stand still.
This problem can be easily fixed by welding a grid of steel rods and securing it in the floor of the box. Heavy, one-inch diameter rods should be used and it must be constructed so the mat lays flat. Do not criss-cross the rods on top of each other. Overlapping the rods can cause catching of the hooves.
Lay them out in a 12-inch x 12-inch square pattern. Sometimes a single small piece of rod welded in the correct location to prevent a foot from slipping sideways will cause the animal to settle down and stand still.
If a head holder is used, the animal will remain calmer if it moves with a steady, smooth motion. A sudden, jerky motion of equipment scares animals. Head holders with pneumatic or hydraulic systems should be equipped with flow controls to prevent jerky motion. The hydraulic or pneumatic system should also be designed so it will automatically stop before the pressure exerted by the head holder becomes excessive. One sign of excessive pressure or a sharp edge sticking into an animal is vocalization (bellow, moo or squeal) that occurs when the device is applied. An animal should not vocalize in direct response to application of a restraint device. Either stunning or religious slaughter should occur promptly after an animal is restrained in a head holder. If an animal is held in a head holder for more than 15 or 20 seconds, it is more likely to vocalize. This may cause the plant to fail the vocalization portion of an animal welfare audit. On pneumatic systems, mufflers should be installed to stop hissing sounds. Sudden hissing sounds will scare animals and they may refuse to enter the restrainer. Elimination of loud equipment noise will usually improve animal handling.
There are some common mistakes I have observed in the mechanical design of hydraulic and pneumatic systems on animal restraint devices. On pneumatic-(air) powered systems, the most common mistake is using the wrong type of valves. Valves with a return to center spool should be used so that the operator can control the amount of pressure applied to the animal. When the wrong valves are used, the system will either apply no pressure or the maximum pressure that is set at the regulator. This makes it impossible for the operator to use a lighter, intermediate amount of pressure.
Another common mistake is when the maintenance staff mixes up pressure control with flow or speed control. This mistake can occur on both hydraulic and pneumatic systems. If a speed control or flow control valve is put in the system, it can be used to slow down the speed of the cylinder, which operates the head holder. It has no effect on the maximum pressure that the head holder will exert on the animal. The system will squeeze the animal too hard. I have explained to many people that when you attempt to control pressure with a speed control, the system will still squeeze the animal too hard, but now it will squeeze it too hard, slowly.
Another common mistake is applying more and more pressure on an animal when it struggles. This will usually just cause more struggling and vocalization. There is an optimal pressure for holding an animal. It has to be tight enough so that it feels held but not so tight that it hurts. This is a hard concept for some people to understand because it uses principles of behavior instead of force.
Separate pressure control
Head holders require much less air or hydraulic pressure to operate compared to other parts of a restraint device, such as drive units or cylinders that operate heavy gates. To prevent excessive pressure from being applied, a head holder should have its own separate pressure control, which will automatically limit pressure. This prevents a careless operator from breaking an animal’s jaw with an overpowered hydraulic system. On hydraulic systems, the head holder must have its own separate pressure relief valve, which is set at a much lighter pressure than the main hydraulic system that operates heavy gates.
Dr. Temple Grandin operates Grandin Livestock Systems Inc., Fort Collins, Colo., and is a faculty member in the animal science department at Colorado State Univ.