WHITE STRIPING APPEARANCE ALONG GROWTH ON BROILER CHICKENS TREATED WITH DIFFERENT COCCIDIOSIS CONTROL PROGRAMS

White striping (WS) is an alteration of broiler muscle characterised by the presence of white striations parallel to the direction of muscle fibers. This condition is becoming increasingly important in broiler production because it affects the acceptance of raw meat by the consumer and its hysicochemical characteristics, thus decreasing the economic value (1). In this study the age of WS onset in broiler chickens and the effect of diet and of different coccidiosis control programs on WS prevalence at slaughter, were evaluated. Four groups of 180 chickens were randomly allotted to four experimental treatments: control (C), coccidiostat (Cox), vaccinated (V), and vaccinated fed with a low energy diet (VLE). The birds were weighed at 12, 25, 42, and 51 d of age. Twenty animals per treatment were sacrificed at 12 and 25 d of age, whereas the remaining chickens at 51 d. Breasts were categorized based on the degree of WS following the lesion score proposed by Kuttappan et al. (2): 0=absence (normal breast), 1=moderate (breast with white lines less than 1 mm thick), 2=severe (breast with white lines more than 1 mm thick). For histological evaluation, up to now 34/80 (d 12) and 46/80 (d 25) breast samples were examined. At 12 d of age all breasts were classified as normal (WS score 0), whereas at 25 d of age WS was macroscopically evident with score 1 in a limited number of birds (3/20 group C, 2/20 group Cox, 3/20 group V, 1/20 group VLE). Histologically, myopathic changes were found in 29/34 (85%) of samples at d 12, and 46/46 (100%) of samples at d 25. At d 12, breast muscles were affected by fiber size change, and multifocal mild degeneration/necrosis, while at d 25 these alterations were increasingly severe and associated with heterophilic and macrophagic infiltration, early interstitial fibrosis, and fat infiltration. The absence of macroscopic lesions at d 12 associated with the presence of early and mild histological lesions in some samples indicates the onset of WS around 12 d. At 51 d of age the prevalence of WS was above 90% in all groups, and the prevalence of WS score 2 was 77.6%, 64.4%, 62.6% and 61.6%, for Cox, VLE, V and C, respectively, being significant (P<0.001) the difference Cox vs V and C. The coccidiostat effect on the increase in WS severity seems attributed to the higher initial birds’ growth. This study provided a new perspective for the control of WS prevalence and a starting point for further studies. REFERENCES 1. Kuttappan, V. A., V. B. Brewer, P. W. Waldroup, and C. M. Owens. 2012. Influence of growth rate on the occurrence of white striping in broiler breast fillets. Poult. Sci. 91:2677–2685. 2. Kuttappan, V. A., H. L. Shivaprasad, D. P. Shaw, B. A. Valentine, B. M. Hargis, F. D. Clark, S. R. McKee and C. M. Owens. 2013. Pathological changes associated with white striping in broiler breast muscles. Poult. Sci. 92:331-338.