An Investigation Of Broiler Leg Disorders In Large-Scale Farms And The Study Of The Role Of BFGF On The Occurrence Of Femoral Head Necrosis In Broiler Chickens

With the increase of large scale and intensive meat-type chicken farms,chicken production has been improved significantly,while the incidence of leg disorders in broilers becomes more and more serious in China,which results in economic losses and compromises animal welfare greatly.There are a variety of chicken leg diseases,including tibial dysplasia(TD),f’emoral head necrosis(FHN),rickets,and so on.FHN in leg problems is particularly important becase it can cause serious limp and lead to a failure for the chickens to get close to food and water.The study of FHN in broilers has been carried out for many years;however,the etiology of the disease is not understood clearly.Metaphyseal chondrocyte apoptosis may affect the blood perfusion of the femoral head,which may result in FHN after long-term of a lack of nutrition supply.So this study was designed to try to explore the possible mechanisms of the FHN by investigating chondrocyte apoptosis.Basic fibroblast growth factor(bFGF)is synthesized and stored in osteoblasts.It plays an important role in stimulating the proliferation of the osteocytes in the early stages while inhibiting the apoptosis of chondrocytes.At present,there are a few reports about the roles of bFGF in regulating the apoptosis of chicken chondrocytes during the course of FHN.Therefore,the objective of the present work was to investigate the current situation of leg disorders in large scale chicken farms in China.In addition,we tried to evaluate the roles of bFGF in regulating the apoptosis of chicken chondrocytes in FHN birds.1.An investigation of leg disorders in large-scale chicken farmsEpidemiological investigation of leg disease was conducted in nine broiler farms of a group company in Anhui province.And the gait scores of the birds were assessed according to the scoring method.Then 10 randomly selected broilers with leg diseases were culled,and another 10 normal birds were chose as the control at the same farm.After necropsy examination,bone tissues were collected for microbiological detection and pathological examination.Finally,leg disorders were diagnosed,classified,calculated and analyzed by combining the various diagnostic results.The results showed the incidence of leg disorders in broilers was 2.07%,in which birds with minor lesions accounted for the largest propotion(50.92%),and chickens with clear limp or which lost ability to walk accounted for 20.66%and 28.42%,respectively.Laboratory diagnosis indicated that the main factor resulting in leg disorders was bacterial infection,which accounted for 36.67%.Besides,TD and FHN were the most important in non-bacterial infection leg problems,which accounted for 34.44%and 13.33%,respectively.Futhermore,trauma fracture or other unknown factors accounted for 6.67%and 8.89%,respectively.2.The role of bFGF on the occurrence of femoral head necrosis in broiler chickensOne hundred 1 day old Ross 308 broilers were chose as the experimental animals.A standard diet and water were given ad libitum.Birds were killed at 42-days-old,and femoral integrity was examined.Then the liver index,number of apoptotic cells,mRNA expression of bFGF and apoptotic genes,bone length,bone index,bone strength,bone mineral density and bone ash were detected.The results showed that the incidence of FHN was 20.9%,there were no apparent differences among normal chickens and FHN chickens in body weight,liver index,bone length,bone weight,bone strength and bone mineral density,while there were marked differences in tibia ash proportion between normal birds and FHN chickens.Besides,there was a significant difference in the number of empty lacuna and apoptptic chondrocytes between normal birds and FHN birds,however,the number of chondrocytes in the resting zone had no marked difference.What’s more,FHN birds had an apparent decrease in the expression of bFGF protein,bFGF and Bcl-2 mRNA expression compared with normal chickens,while there was a significant promotion in the mRNA expression of Bax and caspase-3.In conclusion,our results provided evidence that chondrocyte apoptosis in the growth plate greatly promotes the process of femoral head necrosis in broilers.The mechanisms are possibly associated with bFGF expression inhibition and the activation/inactivation of related apoptotic effectors.