One major welfare issue affecting broilers is lameness, which is related to the genetic selection and management for rapid growth. Lameness is also influenced by the fast breast muscle development of the bird. Seventy or eighty years ago, broilers took about 13 weeks to reach market weight- now they only take about 6 weeks! Gait disorders may be painful, can cause birds to have trouble reaching food and water, and may even cause downgrading or condemnation of the carcasses at the plant.
Producers can monitor the leg and foot health of their flocks easily by gait and foot pad scoring. These techniques can also be applied to turkeys and cage-free layers (with some modifications).
Gait scoring can be conducted by walking the length of the house and observing about 100 birds split between various locations. The birds should be able to walk at least 5 feet without sitting down or showing any visible signs of lameness. Ideally, two or fewer birds out of 100 would show signs of lameness or not be able to walk 5 feet (refer to the National Chicken Council guidelines for the full procedure).
Foot pad scoring can be done in the house as a lead indicator of welfare (within the growing cycle so corrective action can be implemented) or at the plant as a lag indicator of welfare (after the fact, but possibly useful information to apply to the next flock). If the scoring is done in the house, the producer should take care that the birds are handled properly and not unduly stressed by catching. A foot pad "pass" would be either normal colored skin or slight discoloration, hyperkeratosis (thickening of the skin), or a lesion covering less than half of the foot pad. A foot pad "fail" would be erosions, scabs, or ulcerations covering more than half of the foot pad. Out of 100 birds, at least 90 should pass.
Corrective action should be taken and documented if either the gait scores or the foot pad scores do not pass by the required percentage. One way to improve foot pad health is to maintain the litter. Litter should ideally be dry and friable, and only loosely compacted when squeezed in the hand. If it forms a clump, it is too wet. Litter quality is affected by the external and internal air humidity, type and maintenance of the drinker system, water consumption rate, stocking density, bird age, and weight, ventilation rates, temperature, and certain diseases. Managing the ventilation, drinkers, and bird health are all things that a producer can usually control in their houses (at least to some extent).
Source : psu.edu