Research evaluating the effects of housing systems and genetic strains on broiler mobility demonstrated that slow-growing strains exhibited fewer footpad health problems than fast-growing strains in both indoor and outdoor environments.
“Based on previous research, we hypothesized that both slow- and fast-growing strains would have improved mobility and footpad conditions in the silvopasture environment compared to the indoor environment,” reported Athena He-DeMontaron, graduate student, North Carolina State University (NCSU), who is advised by Allison Pullin, PhD.
However, the results showed that, compared with the fast-growing strain, the slow-growing strain produced lower footpad scores, translating to healthier footpads in the indoor environment. Additionally, the slow-growing strain had better mobility than the fast-growing strain in both environments.
He-DeMontaron discussed the research and mixed results at the 2025 Poultry Science Association annual meeting.
Monitoring gait, footpad health
Researchers used 500 SASSO broilers for the slow-growing strain and 500 Ross 708 broilers for the fast-growing strain. SASSO birds were raised to 56 days of age and the Ross 708 birds to 42 days of age.
The NCSU chicken education unit was used for the indoor conventional environment. A local farm provided a silvopasture environment with daytime access to trees and grass.
Both locations housed 50 birds per pen and five pens per breed. All pens had two drinkers, two feeders and the same amount of indoor space, 188 square inches per bird. The silvopasture pens had an additional 288 square inches of space outdoors per bird.
The research team conducted gait scoring at 41 and 42 days of age using a 3-point scale from the National Chicken Council Welfare Guidelines. Birds were walked for 5 feet and mobility scored: 0 (normal), 1 and 2.
Footpad scoring was performed during processing after feather plucking and also used a 3-point scale from the welfare council. Normal footpads scored 0. Footpads with less than 50% lesions were 1, and footpads with more than 50% lesions were 2.
SASSO gait, footpad scores best
“We were examining genetic strain, rearing location and the interaction between the two,” He-DeMontaron reported. “For gait, rearing location did not affect the percentage of broilers within any gait-score category, so I will discuss how each score differed by strain.
“Regardless of location, the SASSOs demonstrated overall better mobility than the Rosses,” she continued. “More SASSOs were able to walk balanced for 5 feet, while more Rosses had abnormal gait scores of 1.” An abnormal gait must be uneven, awkward steps for 5 feet.
Footpad scores revealed more differences between strains. The SASSOs exhibited three times as many normal footpads as Ross 708 birds.
“There was an interaction between strain and rearing location for the footpad score of 1,” He-DeMontaron said. “SASSOs reared indoors had the lowest prevalence of score 1, while SASSOs reared outdoors had similarly high prevalences as the fast-growing Rosses in both environments.”
She noted that the outdoor unit was hit by a tropical storm that produced 12 to 14 inches of rain.
“Footpad dermatitis was exacerbated by the weather and negatively impacted our birds,” she explained. “Mitigating ground moisture in outdoor environments definitely warrants further investigation.”
Genetic strain effects
The results of this research show that genetic strain was the main predictor of walking ability. The fast-growing Rosses were more susceptible to lameness and gait issues than the slow-growing SASSOs, which showed improved gait in both outdoor and indoor environments.
“Contrary to our original hypothesis, rearing location did not affect mobility,” He-DeMontaron said. “Although previous literature has reported that improvements in walking ability were associated with silvopasture, that was not the case in this study.”
