Methods of reducing bird activity on a shackle line

Ideally there should be no flapping on a shackle line, or as little as possible; however, lack of flapping does not necessarily indicate a bird is unstressed.

Handling, inversion, the act of shackling and tight shackles may induce stress, pain and flapping, which may lead to dislocations (particularly of the wings), fractures and muscle haemorrhages. Struggling may adversely affect meat quality by producing a build-up of lactic acid in the muscle, resulting in a low muscle pH, which reduces the water-holding capacity of the meat. So, in addition to its welfare importance, there is a financial incentive in encouraging birds to limit their activity as much as possible.

Breast contact strips

Breast contact strips are commonly used to reduce the incidence of wing flapping. A breast contact strip should extend below each bird’s head (Figure 3) and the strip must be in constant and full contact with every bird’s breast along the entire length of the line, from the furthest point for shackling, until a bird enters the electrified water. This is easier to achieve if the shackle line is straight but if it is not, the strip must also extend around any bends. The contact strip should be made of one solid piece of non-conductive material, to avoid feathers becoming trapped in joins between sections of material (which may cause discomfort or hold back the body, relative to the legs and shackle, which may cause the bird to swing sideways when released). The material should be rigid to ensure heavier birds do not distort the strip which may prevent lighter-weight birds making effective contact. Contact strips should be sufficiently tall and adjustable so their height and angle can be suited to every type of bird slaughtered at the abattoir. Slightly angling a contact strip may create greater contact with birds’ chests, which may be particularly important for small birds or for flighty birds that tend to pull their chests away from the strip whilst flapping. If they are to work effectively, breast contact strips must be repaired or replaced if the surface of the material begins to wear or become uneven (eg buckle).

Figure 3. Broiler chickens on a shackle line with a breast contact strip.

Shackling techniques that may reduce wing flapping

Flapping may tend to occur when birds are loaded into the shackles and for a short time thereafter. To prevent this, immediately after the shackling action, a shackler should routinely either run their hands down a bird’s body or briefly hold onto the bird’s legs - care must be taken not to scratch or squeeze a bird, or its legs, during this process in case it exacerbates any disturbance. If a bird shows potential signs of distress, such as excessive wing flapping or excessive vocalising, it should be tended to immediately, eg an operator’s hand should be gently placed on the bird’s breast, or the bird should be gently held against the breast contact strip, whilst allowing it to move with the advancing shackle line (otherwise, when the handler lets go, the bird may swing sideways and cause it to resume flapping). If this does not stop the struggling, the bird should be stunned and killed immediately using a humane back-up method, preferably before it is removed from the shackle. The shackle and the shackle line should be examined for possible causes of the disturbance.

Bird types and varying activity levels

Different types of birds can differ in their activity levels whilst on a shackle line, eg slow-growing chickens may have a shorter latency to more intense struggling compared to fast-growing and heavy lines of chicken; and heavy-line chickens may be less active than fast-growing chickens. Anecdotally, broiler chickens are typically shackled close together to prevent wing flapping at the point of shackling. Geese may bite nearby personnel or neighbouring shackled birds.

Some bird types, and particularly those that tend to be active on a shackle line, may benefit from being adequately spaced out (eg if the shackle pitch cannot be spaced further then there should be an appropriate number of unoccupied shackles in between occupied shackles). This may limit opportunities for physical aggression as well as prevent struggling birds from beating their wings against other individuals, hopefully reducing transmission of disturbance. If certain types of birds cannot be shackled without causing distress and/or high levels of continuous activity, then alternative methods of restraint and stunning may be necessary.

Breast support conveyors

A breast support conveyor can be constructed underneath, and advance in time with, a standard shackle line (Figure 4). The conveyor supports some of the weight of the birds, thereby removing some of the pressure on their legs in the shackles. A conveyor may also keep the birds relatively upright. Compared with a conventional shackle line, this may result in reduced struggling at hang-on, more efficient entries to the electrified water and a lower incidence of wing damage. It is critical that the shackle line is straight because birds traversing corners on a conveyor may display increased disturbance and struggling, compared to birds on a conventional shackle line.

Whilst a breast support conveyor may be advantageous for all types of birds, it may be particularly useful for heavy birds. Even when using a breast support conveyor, shacklers are likely to be easily fatigued by shackling large birds so shacklers must be regularly rested to ensure they are physically and mentally able to afford the birds the necessary gentle care during handling.

Conveyors must be constructed of suitable plastic which will not trap birds’ feathers, skin or other body parts. When breast support conveyors are used, operators must monitor birds and, when necessary, adjust the system or reposition individual birds. For example, the speed of a conveyor must be adjustable so it can match the speed of the shackle line. The height of a conveyor must be adjustable so the distance between the conveyor and the shackles allows birds to lie in comfortable positions. Operators must immediately tend to any birds that adopt awkward postures that lead to struggling or discomfort. Any healthy birds which are gasping or gulping in an unusual, strained manner must be assessed to determine why – they may be lying too far forward on their chest and require repositioning. The use of breast support conveyors, and supporting research, are in their infancy. Therefore installation of such devices must be carefully considered and continuously monitored to ensure welfare is not impaired in any way and that birds cannot escape the shackles.

Figure 4. Broiler chickens and turkeys atop a breast support conveyor. Once each bird is shackled and sitting appropriately upon the conveyor, the shackler should fold the birds’ wings into the natural closed position, to reduce the risk of pre-stun shocks.

Next: Pre-stun electrical shocks