United Poultry Concerns Fact Sheet
"Broiler" Chicken Skeletal Problems in the U.S.
(A summary of information sources from 1990-2001)

"Future research needs focus on new, old problems." A poll recently conducted by telephone to ask college professors which were the most important production problems facing the broiler industry: sudden death syndrome, ascites, scabby hip syndrome, and one very old problem-leg abnormalities-were the most frequently mentioned. . . .

Broilers fed diets seemingly adequate in all nutrients continue to display various types of leg problems. Apparently, the leg, and particularly the hock joint of the chicken, is a weak point. Perosis, twisted leg, and other types of leg problems can be observed to some degree in almost all commercial flocks. Some researchers have concluded that skeletal deformities and ensuing leg weakness is the price that must be paid for rapid growth of broilers. There is some disagreement as to whether or not rapid growth increases the incidence of leg problems, but most of the reported data indicate a positive relationship. The incidence of leg problems is generally higher in males than females. . . .

Leg abnormalities probably cause more economic losses than any other single abnormality in the chicken house. It has been estimated that 2-6% of all broilers display some observable signs of skeletal problems, while many more will be affected in a less visible way. Leg abnormalities result in mortality, reduced feed utilization and growth rate, and down-grading in the processing plant. [M]ost leg problems appear to result from a combination of several factors. It is not uncommon to find more than one type of leg disorder in a flock of broilers. . . . Leg problems that are known to be caused by disease organisms such as femoral head necrosis, osteomyelitis, synovitis and viral arthritis are often confused with nutritional problems. Attempts to correct these leg problems by dietary modification have failed and, in many instances, have aggravated the problem.

. . . . Twisted leg is probably the most predominant type of leg abnormality occurring in commercial broiler flocks and it is probably the least understood.

Source, Elbert J. Day, "Future research needs focus on new, old problems. Feedstuffs, July 23, 1990. Pp. 12, 15.

"AAAP [American Association of Avian Pathologists] 32nd annual meeting features skeletal problems talks." More than 300 veterinarians and avian pathologists from the United States and several foreign countries met in July in San Antonio, TX for the 32nd annual meeting of the American Association of Avian Pathologists. During a day-long symposium on skeletal problems in poultry, several new disease syndromes in chickens and turkeys were reported. . . .

During the skeletal disease symposium the leg problem issue in poultry was thoroughly discussed. Dr. Richard Julian, Ontario Veterinary College, noted, e.g., Angular bone deformities occur when the legs become bowed in or out, and may even be twisted. According to Dr. Julian, this problem is the most frequent cause of lameness in broiler chickens and possibly accounts for 60 per cent of the skeletal disease in chickens and 30 to 40 percent of the skeletal disease in turkeys. It was stated that 30 to 50 per cent of the male meat-type chickens and turkeys have tibial dyschondroplasia, but it only contributes to 5 to 25 per cent of the total lameness cases. Lameness doesn't exhibit itself in birds that have TD until the bones start to develop fractures or fissures. . . .

Source: "Dr. John Schleifer (Agri-Bio Corporation, PO Box 897, Gainesville, GA 30503), "AAAP 32nd annual meeting features skeletal problem talks." Poultry Digest, October 1990, pp. 10-12, 14, 16.

Leg and Bone Problems in Broilers. Broilers are subject to a variety of leg problems and abnormalities. Following is a list, along with probable causes, pp. 490-492, in Chapter 20, "Broiler, Roaster, and Capon Management,"

Source:Commercial Chicken Production Manual, 4th Ed. (1990) by Mack O. North and Donald D. Bell.

Dyschondroplasia is a very common defect associated with the growth plates of meat-type chickens, ducks, and turkeys. . . . In many broiler chicken and turkey flocks up to 30% of birds may have lesions of dyschondroplasia characterized by abnormal masses of cartilage below the growth plate, primarily in the proximal tibiotarsus but also at many other sites. Most birds show no clinical signs. If masses of cartilage are very large, signs will include a reluctance to move, a stilted gait, and bilateral swelling of the femoral-tibial joint often associated with bowing of the legs. In a recent survey [in western Canada] of leg weakness in broiler chicken flocks processed at 7 wk of age or earlier, few birds were culled because of dyschondroplasia. Downgrading of carcasses and trimming of deformed legs at processing have been attributed to dyschondroplasia. If broiler chickens are kept to roaster weights, lesions due to dyschondroplasia may be much more severe. A high association between leg deformities and tibial dyschondroplasia has been described in turkeys.

Source: C. Riddell, Chapter 34, "Developmental, Metabolic, and Miscellaneous Disorders," Diseases of Poultry, 9th Edition, 1991, pp. 831-832.

"Broiler industry reviews benefits, hazards of faster bird growth." Raising a broiler to 4 lb. in six weeks puts a great deal of pressure on the bird's structure and is a major source of stress, said Nick Dale, a poultry specialist at the University of Georgia. "The results of this stress are manifested in a number of ways, such as increased incidence of leg problems, ascites and sudden death syndrome," Dale said.

Source: Robert H. Brown, "Broiler industry reviews benefits, hazards of faster bird growth." Feedstuffs, January 28, 1991, p. 38.

"Skeletal problems cause losses." Annual losses in the United States from skeletal problems are estimated at $80 million to $120 million in broilers, and $32 million to $40 million in turkeys, according to a review by Tom W. Sullivan, Dept. of Animal Science, University of Nebraska, Lincoln, NW 98583-0908 (Poultry Science 73:879-882, 1994).

Increases in mortality and cull birds, condemnations from septicemia-toxemia, downgrading from trimming of breasts and legs, and reduced feed conversion and rate of gain are losses attributed to skeletal problems.

Abnormalities include long bone distortion (bowed leg), tibial dyschondroplasia, rickets, kinky back, brittle bone disease, spraddled legs, chondrodystrophy, staphylococcosis, infectious synovitis, viral arthritis and foot pad dermatitis.

Source of Abstract: Poultry Digest December 1994, p. 72.

"Poultry industry should reconsider if bigger is better." Re: The conference sponsored by the agricultural directorate of the European Commission. The intent of this conference is to review the use of growth-promoting substances in animal husbandry. The above conference will deal very little with poultry since steroids and hormones are not used to enhance the performance of poultry. That's the good news. The bad news is that we don't need growth-enhancing substances due to the success of our genetic selection programs. The point is apparent in a recent report from North Carolina State University. . . . [T]he downside of the progress attained by genetic selection has been the increase in the incidence of metabolic disorders associated with rapid growth rate. For example, in the North Carolina study the "old fashioned" chicken had an incidence of tibial dyschondroplasia of 1.2%. This is in contrast to 49% incidence of the "modern" chicken fed modern diets. Half of this increase in tibial dyschondroplasia could be attributed to the "improved" nutrition associated with modern broiler feed.

. . . . Although the poultry industry does not rely on drugs and hormones to enhance performance, it is beginning to be attacked for the success of its genetic selection program. Animal welfare activists would like to see restrictions on selection for growth rate coupled with increased emphasis on selection for the absence of metabolic diseases such as tibial dyschondroplasia and ascites. In fact, slow growing broilers are now being marketed in France and the U.K. for consumers with welfare and culinary concerns. It will be interesting to see whether this trend will be adopted by the poultry industry in the U.S. where it has been a tradition that "bigger is better."

Source: Roland M. Leach Jr. "Poultry industry should reconsider if bigger is better." Feedstuffs, August 26, 1996, p. 10.

"So It's True What Growers Have Been Saying - 'Bird quality gets worse and worse!'" In the February 22, 1998 Sunday Arkansas Democrat-Gazette. Michael Whiteley reports that the major poultry breeders are now admitting that they have been "pushing the birds" beyond what their bodies can endure. The Gazette reports that Dr. John Tierce, Vice President of Research and Development at Peterson Farms says, "We have metabolic disorders. We've got heart failure. We've got leg disorders." Peterson Farms supplies one-third of the world's breeder males, according to the article.

Source: Poultry Grower News, August 1998, p. 9.

"Bone Research Gives Poultry Stronger Lets To Stand On." A model developed to measure bone strength in poultry may help farmers choose breeds that meet market demand for meaty birds, while eradicating bone deformities associated with rapid weight gain. Alfred Soboyejo, an Ohio State University agricultural engineering researcher, studied physical and biochemical factors associated with poultry breeding to determine what combinations increase tibia and femur bone strength in turkeys and broiler chickens. Genetic selection of poultry breeds to improve body weight increases weight gain without compensating for increased bone strength to support the weight. The result is leg bone deformities, such as "bowing" and "buckling" that cause lameness, broken bones and inflammations, and costs the poultry industry $32 million a year in production losses. . . .

Source: AgAnswers, June 22, 2001. www.aganswers.net

From Joy Mench, UC-Davis, Fri. July 13, 2001. JAMench@UCDavis.Edu

Dear Karen,

There are no figures for the percentage of broilers in the US with leg deformities because no one has done a large-scale study. The only (recent) large scale study with which I am familiar was done in Denmark by Gurbakhsh Singh Sanotra (who will be here at our meeting in August, by the way), but it has only been published in Danish. I can get you that reference. . . . It is only an approximation to the US situation, though, since different genetic strains of broilers are used here, and the US industry also houses them at a lower stocking density than in Europe-high European stocking densities seem to be a contributor to the incidence of leg problems there, although the primary contributor is certainly selection for fast growth.

--Joy Mench, email to Karen Davis, July 13, 2001.

United Poultry Concerns, Inc.
PO Box 150
Machipongo, VA 23405-0150
FAX: 757-678-5070

(UPC Fact Sheet - "Broiler" Chicken Skeletal Problems in the U.S.)

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