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Reprinted from Avian Diseases, Vol. 24, No. 3, July-September, 1980

Variations in the Incidence of Tibial DyschondroplasiaAssociated with Different Environmental Conditions*

J. R. Veltmann, Jr., and L. S. Jensen

Department of Poultry ScienceUniversity of GeorgiaAthens, Georgia 30602

Received 21 January 1980

SUMMARY

Experiments were designed to study environmental factors thataffect incidence of tibial dyschondroplasia (TD) in broiler chickens.A significantly higher frequency of TD was observed in birds rearedin floor pens vs. those maintained in a battery brooder with wirefloors and fed the same diet. Incorporating either 5% raw or auto-claved broiler litter in the diet produced no significant effect on theincidence of the disease in chicks reared in floor pens covered withwood shavings or wire frames. During the first six months of 1979,the incidence of TD declined markedly in market-age broilers ofthe same strain fed similar diets and maintained on litter in thesame broiler house.

INTRODUCTION

Tibial dyschondroplasia (TD), a leg abnormality that afflictsbroiler chickens worldwide (2,3,5,7,10,13,15,17), is characterizedby an abnormal mass of unvascularized cartilage in the metaphysisof the proximal end of the tibia. Although histological and pathological states of the disease have been studied extensively (discussed most recently by Riddell [11]), the etiology of TD remainsobscure. Research data from several laboratories suggest that theincidence of TD is influenced by genetic (7,12,15), environmental(15), and nutritional factors (7,8,14). Preliminary investigationsfrom this laboratory revealed that the frequency of TD in broilerchicks reared in floor pens with litter (22.4%) was almost tentimes that of chicks reared in batteries (2.4%). Generally, legdisorders in poultry are exacerbated by wire flooring.

Experiments were conducted to study the apparent environmental effect on the incidence of TD in chicks, examining in par-

••Support by State and Hatch funds granted to the Georgia AgriculturalExperiment Station.

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Tibial dyschondroplasia and environment 627

ticular the effects of brooding site and type of flooring. Results ofthese experiments implied that litter increases the incidence of thedisease. Subsequently, experiments were conducted in which broilerlitter was incorporated into the diet. The effect of seasonal changeson the incidence of the disease was also investigated.

MATERIALS AND METHODS

Chicks and management. Day-old Hubbard male broiler chickswere fed a practical starter diet and water ad lib for four weeks inExperiments 1-6. In Experiment 7, Hubbard male chicks werefed various practical diets, typical of those used in commercialbroiler operations, for seven weeks. Group body weights and feedconsumption were recorded initially and at the termination of eachexperiment. Mortality was recorded daily.

Type of flooring, a) Floor pen. Each floor pen, measuring 6 sqM, was covered with either litter (new pine shavings) or galvanizedmesh wire (127 cm2), and elevated about 15 cm off the floor.Brooding heat was provided by infrared lamps; one automaticwaterer (Plasson) was allotted to each pen. Generally, 50 to 60chicks were randomly distributed to each pen.

b) Battery brooder. Thermostatically controlled battery brooders containing 30 X 91-cm pens were used. A water trough locatedat the end of each pen was cleaned and refilled daily with freshwater.

c) Lesion scoring. Birds were killed by exposure to an overdose of diethyl ether and were examined for TD by cutting longitudinally across the tibia. Birds having cartilage plugs greaterthan 2 mm in diameter were scored positive for TD.

Statistical Analysis System (SAS) (1) was used to analyzethe data; growth data were analyzed by analysis of variance andDuncan's Multiple Range Test, while significant differences amonglesion scores were determined by the Chi square test.

Expt. 1. In preliminary experiments, marked differences wererevealed in a comparison, between TD incidence in chicks rearedin batteries at the office-laboratory building and chicks maintained in floor pens at the University poultry farm. Therefore,Expt. 1 was conducted to validate the apparent differences in theincidence of TD associated with two sites of brooding. Two-hundred chicks and an equal number of hatchmates were maintained either in a battery brooder (laboratory) or in floor penscovered with wood shavings (poultry farm).

628 J. R. Veltmann and L. S. Jensen

Expt. 2. One-hundred chicks maintained in the same broilerhouse were placed in floor pens covered with either wood shavingsor a wire frame. The purpose of the experiment was to study theeffect of flooring on the incidence of the disease under similarenvironmental conditions.

Expts. 3, 4, and 5. To investigate the possibility that litter mayinfluence the incidence of TD, 50 birds were reared in a batteryand fed either 0 or 5% broiler litter (raw or autoclaved [Expt.3]). At the same time, another group of 50 chicks were reared in afloor pen for one week and then transferred to a battery for theremaining three weeks of the experiment; another group of chicksremained in a floor pen for four weeks.

In Expt. 4, in order to eliminate the possibility of either airborne or feed-spillage contamination when birds, housed in thesame battery, were fed the starter diet with and without 5% dietary broiler litter (raw or autoclaved), only one dietary treatmentwas randomly assigned to a battery brooder located in separatebuildings.

In both Expts. 3 and 4, randomly collected broiler litter wasincorporated into the practical starter diet. However, in Expt. 5,fresh broiler litter, obtained from experimental pens in whichchicks experienced a high incidence of TD, was added at 0 or 5% ofthe diet. Each diet was fed to 50 chicks maintained in floor penscovered with either litter or raised wire in two different broiler

houses.

Expt. 6. Since incorporation of ammonium chloride (NH4C1)in the diet was found to induce TD (8), TD incidence in chicks fedthe practical starter diet supplemented with 0 or 3% NH4C1 andmaintained in a battery was compared with incidence in chicks onthe same diet maintained in floor pens covered with litter or raisedwire.

Expt. 7. Jensen et al. (4) conducted three experiments fromNovember 1978 to June 1979 concerning the Oily Bird Syndrome.In these experiments, between 100 and 200 7-week-old broilerswere killed and scored for TD. Each experiment used similar corn-soy diets, strain of bird (Hubbard males), floor pens with pineshavings, and the same broiler house.

RESULTS AND DISCUSSION

Birds reared in floor pens with litter in Expt. 1 had a significantly higher (P < .05) incidence of TD than did birds rearedin a battery brooder with wire floors (Table 1). In subsequentexperiments, the frequency of TD between chicks reared on litter

Tibial dyschondroplasia and environment

Table 2. Incidence of TD in broilers from floor-pen experiments terminatedduring the first six months of 1979 (Expt. 7).A

Expt.Month

ended

Body wt.

(9) No. birds

Incidence

of TD (%)

I Jan. 1990 200 33.0

II Apr. 1951 100 15.0

III June 1901 100 7.5

"Scored at 7 weeks of age.

vs. wire were not statistically significant, yet litter-reared chickstended to have a higher incidence of the disease (Expts. 2 and 3).No significant increase in the incidence of TD was observed inbroilers fed either raw or autoclaved broiler litter (Expts. 3 and4). In Expt. 5, irrespective of the building, type of flooring, or inclusion of dietary litter, the incidence of TD was considerably lowerthan in the previous floor-pen experiments. Even though a significantly higher (P < .05) incidence of the disease was found inbirds fed 3% dietary NH4C1, regardless of the type of floor penused, no significant difference was observed between the chicksfed the practical starter diet and maintained on wire and thosemaintained on litter-covered floor pens (Expt. 6). Mortality wasnot significantly affected in any of the experiments.

Body weight and feed consumption of birds fed either 5%autoclaved or raw broiler litter (Expts. 3, 4, and 5) and chicks fed3% NH4C1 (Expt. 6) were significantly lower (P < .05) than incontrol birds of the respective experiment (Table 1). Merkley (9)found no relationship between growth rate of individual birds andincidence of TD.

Of interest was the observation that the frequency of TDdeclined during the first six months of 1979 in broilers of thesame strain reared in the same house and fed similar diets (Expt.7, Table 2). These data demonstrate that the environment has apronounced effect on the incidence of TD in broiler chicks. Sheridan et al. (15) observed an environmental trend toward higherTD incidence in genetic-selection experiments, since heritabilityestimates exceeded 1.0 consistently. They suggested that geneticselection for TD resulted in a line of chickens highly susceptibleto an unknown or unsuspected pathogen.

Since the incidence of TD varied between environments and

630 J. R. Veltmann and L. S. Jensen

with time, it can be speculated that a pathological agent (or toxin)produced under certain environmental conditions may be involvedin the etiology of TD in commercial broilers.

REFERENCES

1. Helwig, J. T., and K. A. Council, eds. SAS User's Guide, 1979 Edition,SAS Institute, Inc. Raleigh, North Carolina. 1979.

2. Hemsley, L. A. A cartilage abnormality of broiler chickens. Vet. Rec.86:385. 1970.

3. Itakura, C, M. Goto, and Y. Fukiwara. Tibial dyschondroplasia inbroiler chickens in Japan. Jap. J. Vet. Sci. 35:239-297. 1973.

4. Jensen, L. S., I. Bartov, M. J. Beirne, J. R. Veltmann, Jr., and D. L.Fletcher. Reproduction of the Oily Bird Syndrome in broilers. Poultry Sci.In Press. 1980.

5. Laursen-Jones, A. P. A cartilage abnormality of broiler chickens. Vet.Rec. 86:445. 1970.

6. Leach, R. M., Jr. Problem: leg weakness. Arbor Acres Review. 22:1-2.1979.

7. Leach, R. M., Jr., and M. C. Nesheim. Nutritional and genetic andmorphological studies of an abnormal cartilage formation of young chicks. J.Nutr. 86:236-244. 1965.

8. Leach, R. M., Jr., and M. C. Nesheim. Further studies on tibialdyschondroplasia (cartilage abnormality) in young chicks. J. Nutr. 102:1673-1680. 1972.

9. Merkley, J. W. Tibial dyschondroplasia in broilers. Poultry Sci. 58:1021. 1979.

10. Prasad, S., W. T. Hairr, and J. T. Dallas. Observations of abnormalcartilage formation associated with leg weakness in commercial broilers. AvianDis. 16:457-461. 1972.

11. Riddell, C. The development of tibial dyschondroplasia in broilerchickens. Avian Dis. 19:433-462. 1975.

12. Riddell, C. Selection of broiler chickens for a high and low incidenceof tibial dyschondroplasia with observations on spondylolisthesis and twistedlegs (perosis). Poultry Sci. 55:145-151. 1976.

13. Riddell, C, J. Howell, and M. M. Kaye. Tibial dyschondroplasia inbroiler chickens in western Canada. Avian Dis. 15:557-565. 1971.

14. Sauveur, B., and P. Mongin. Tibial dyschondroplasia, a cartilage abnormality in poultry. Ann. Biol. Anim. Bioch. Biophys. 18:87-98. 1978.

15. Sheridan, A. K., C. R. Howlett, and R. W. Burton. The inheritanceof tibial dyschondroplasia in broilers. Brit. Poultry Sci. 19:491-499. 1978.

16. Siller, W. G. Tibial dyschondroplasia in the fowl. J. Pathol. 101-39-46. 1970.

17. Siller, W. G., and R. M. Duff. Cartilage abnormality in broiler flocks.Vet. Rec. 86:757. 1970.