Meat & Poultry -- January 2014 - 72

From the Corral
BY DR. TEMPLE GRANDIN
meatpoultry@sosland.com

Applying proper restraint
R

ecently I have run into several

direct response to being pinched or

pusher gate will move more slowly. If

places with problems caused by

when excessive pressure is applied.

the pressure control is set too high,

a head-holder or other devices apply-

the device will slowly apply too much

Pressure controls

pressure depending on the setting of

If cattle vocal-

Both hydraulic and pneumatic equip-

the speed control. As a comparison,

ize (moo, bel-

ment have pressure-regulation devic-

think of the pressure controls like a

low) in direct

es that can control the force exert-

water faucet. Speed controls control

response to re-

ed against an animal's body. These

the volume of flow through either a

straining their

should be adjusted so the device auto-

hydraulic or an air line. Turning the

heads in a head-

matically stops applying pressure be-

screw on a speed control is analogous

holder, there is

fore the animal starts to show signs of

to turning the knob on a faucet to re-

a problem that

agitation or excitement, such as vocal-

duce flow. The pressure regulator in a

needs to be cor-

ization, or struggling. Excessive pres-

pneumatic air system or the pressure

rected. In both

sure may also cause injuries, such as

relief valve in a hydraulic system lim-

cattle and pigs,

broken bones or bruises on the car-

its the maximum amount of pressure

vocalization

cass. Often, a restraint device will need

the system can apply. Speed controls

during handling

more than one pressure control. Less

have no effect on pressure.

and restraint is

hydraulic or air pressure is required

associated with

to operate a head-holder compared

Types of controls

physiological

to operation of a heavy door. If both

On devices designed to hold animals,

measu res of

the door and the head-holder are con-

the best type of valves for controlling

stress, such as

trolled from the same air regulator or

equipment, such as the head-holder

cortisol, glucose and lactate. Blood lev-

pressure-relief valve, excessive pres-

and a rear-pusher gate, are hand-op-

els of these substances increase when

sure may be applied to the animal's

erated control levers. The advantage

animals are poked with electric prods

head. A device that is capable of doing

of this type of valve is that it has throt-

or stressed by a restraint device. They

this requires a very skilled operator to

tling ability, similar to the accelera-

are also an indicator that the animal

prevent possible broken bones. When

tor of a car. The speed that the head-

has become agitated and excited. US

a head-holder is equipped with its own

holder moves depends on how far the

Dept. of Agriculture regulations state

pressure-limiting device, it should be

lever is pushed. It is easy for the oper-

that agitation and excitement must be

adjusted so it will automatically stop

ator to move the head-holder at vari-

minimized. Vocalization in a head-

before the animal shows indications

able speeds. When valves controlled

holder can be caused by one of four

of agitation and excitement. If a care-

by solenoids (electric switches) are

factors: Excessive pressure applied by

less operator keeps pushing on the

used, the system only has one speed.

equipment; sharp edges; animal is held

controls, the system will stop before

It is also essential to have mid-stroke

too long; and over-use of electric prods.

enough force is applied to the animal.

position control of cylinders on sys-

ing excessive pressure to an animal.

tems powered by air. This enables the

To prevent vocalization caused by
being held too long, either stunning

operator to stop the movement of the

A common mistake that is made by

head-holder when a pneumatic cylin-

within 15 seconds after the head is

some maintenance people is mixing up

der is only partly extended. ■

fully restrained. It is best if the animal

pressure control with speed control.

is either cut or stunned immediately.

If a speed control is placed in either

It is also essential to check for sharp

an air or a hydraulic line, the cylinder

edges. Cattle will often vocalize in

72

Speed vs. pressure

or religious slaughter should occur

that activates the head-holder or rear-

* Meat&Poultry * January 2014 * www.MeatPoultry.com

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.
http://www.MeatPoultry.com
Meat & Poultry -- January 2014

Table of Contents for the Digital Edition of Meat & Poultry -- January 2014
