Leg problems of various types in turkeys have cropped up several times in the news over the last few weeks. Clearly, leg and foot conditions have implications in terms of both reduced welfare and production (poor growth and condemnations at the slaughterhouse).

Nutrition and feeding play an important role in a whole range of skeletal problems, and interact with genetic and environmental factors as previous research has revealed that nearly all leg conditions in poultry have multiple causes.

Breeding companies have focused a lot of attention on the role of genetics in the occurrence of lameness. Speaking at the International Poultry Day in November, Dr Jim McKay, Group Director Science & Technology EW-Group identified several important aspects for the poultry breeding sector in the future.

On animal health, robustness and welfare, Dr McKay said that the industry can only be sustainable if the highest possible standards of health and welfare are applied, in combination with improved economic performance.

Genetic approaches to leg health

The breeding programme of British United Turkeys (BUT) has a long history of phenotypic selection for leg health, with walking assessment of individual turkeys and culling for leg defects and poor walking ability since the 1970s.

In 2006, Aviagen Turkeys (part of the EW Group) implemented a multi-trait family genetic selection for a wider range of leg health traits, which included individual gait scoring and leg strength assessment. This has resulted in a marked reductions in the incidence of leg defects at the pedigree level.

A new technique - the Lixiscope - allows the assessment of the more dense bone structure, and it is used on all pedigree selection candidates for the incidence of tibial dyschondroplasia (TD). Both individual and family information are taken into account: any individual showing TD lesions or with a high incidence of TD recorded in the family are rejected for breeding. This approach has reduced the incidence of TD to between five and 10 per cent, the company says.

Highlighting the multifactorial nature of leg problems, research has consistently identified wet litter is a primary cause of another lameness problem in turkeys, foot pad dermatitis (FPD). Aviagen Turkeys has been recording FPD on every pedigree individual four years ago and includes the trait in selection to reduce its incidence.

Individual foot pad scoring, in combination with targeted exclusion of individuals creating wet litter is likely to be the most effective genetic means of improving the birds' foot pad health for the future, according to Aviagen Turkeys. The company has installed feed and water stations at its facilities which, combined with transponder technology, allow feeding and drinking behaviour of individual birds to be monitored on a large scale.

Their studies show a link between higher water to feed ratio and the incidence of wet litter. The company identifies individuals generating wet litter and exclude them from the breeding populations. This methodology has been implemented in selections since last year.

Genetic link to FPD confirmed

A newly published study in International Journal of Poultry Science has revealed that older (heritage) lines have a much lower tendency towards FPD lesions - both incidence and severity - than conventional broad-breasted white turkeys.

As expected, there were also large differences between the two lines with terms of live performance and carcass data.

The research was carried out by scientists at Delaware State University and Auburn University in the US and Masterfeeds in Canada.

Growth rate associated with bone fractures

According to a recent study in Poultry Science, femur (leg bone) fractures in turkeys bred for faster growth to market weight and significantly enhanced breast muscle yield are an ongoing concern for turkey growers, because affected birds must be culled, negatively impacting profit margins.

Researchers at Case Western Reserve University, Michigan State University, Ohio State University and Purdue University in the US say that while the average percentage of turkeys lost each year due to the problem is unknown, estimates range from two to 10 per cent – rates which, even on the lower end, are significant.

The group observed that, across the various lines of turkeys examined, the femur's morphological properties are largely governed by the turkey's body weight rather than age, while the femur's mechanical properties and ash content are determined, at least in part, by time.

"Unfortunately, at the present time, there is no means of addressing the femur fracture problem other than slowing the growth rate and reducing the final weight of the bird, neither of which is practical. But we are hopeful that further research will lead to concrete steps that growers can take that address this issue while still recognising the realities of the marketplace," commented the leader of the research group, Dr Darrin Karcher of Michigan State University.