Market reports of white striping in broiler breast fillets have been increasing, which has generated concerns in the broiler meat industry regarding negative effects on consumer acceptance.

Two papers - one from Brazil and one from Italy - published in the current issue of Journal of Applied Poultry Research report on the scale of the problem in these two countries.

The study¹ conducted in Brazil by Liris Kindlein and colleagues at the Federal University of Rio Grande do Sul aimed to characterise macro- and microscopically the condition of white striping at varying degrees of severity on Cobb 500 broiler breast fillets slaughtered at 42 days of age.

Carcasses of 2,512 broilers presenting white striping were slaughtered and macroscopically classified according to the degree of severity of the striations as moderate or sever. Further histological microscopic evaluation demonstrated degenerative myopathy in both moderate and severe cases but 75 per cent of those breast fillets were classified as moderate.

Typically, the samples classified macroscopically as moderate showed microscopic necrosis only (65.2 per cent) or moderate multifocal necrosis (9.8 per cent), whereas those classified as severe showed diffuse and strong necrosis (25.0 per cent).

The proliferation of connective tissue was not observed for either of the degrees of white striping investigated in this study, characterising this profile as an acute occurrence, added Kindlein and co-authors.

The incidence of white striping under commercial conditions in medium and heavy broiler chickens in Italy was investigated by M. Petracci and colleagues at the University of Bologna².

Several types of muscle abnormalities are present in the poultry industry as a result of genetic selection, leading to decreased quality of meat and consequent economic loss, they report.

The appearance of thin (moderate) to thick (severe) white striping striations parallel to muscle fibres on the surface of broiler breast fillets is one of the most troubling issues in the poultry industry.

They explain that white striping also has unfavourable implications on visual acceptance, nutritional value and processing traits of breast meat.

The aim of the Bologna survey was to assess the influence of market class (medium and heavy birds) and genotype (standard- and high-breast yield hybrids) on the incidence of white striping in broiler chickens raised under commercial conditions in Italy.

The incidence of white striping for both medium and heavy broilers was high (43.0 per cent), with 6.2 per cent of samples considered severe.

Heavy flocks had significantly higher percentages of both moderate (46.9 versus 25.8 per cent; P≤0.001) and severe (9.5 versus 2.7 per cent; P≤0.001) white striping than medium flocks.

Considering the effect of genotype, high-breast yield hybrids exhibited a higher incidence of both moderate (40.2 versus 33.2 per cent; P≤0.001) and severe white striping (7.2 versus 5.0 per cent; P≤0.001) than standard-breast yield birds.

In addition, within the medium class, the occurrence of white striping reached higher levels in flocks of males.

The heavy class consisted of male flocks separated into two slaughter weight categories. Birds that reached higher slaughtering weights (3.8 to 4.2kg) exhibited higher incidence of white striping than flocks slaughtered at lower weights (3.0 to 3.8kg) at a similar age.

The main broiler genotypes used for commercial production were affected by a high rate of white striping, concluded Petracci and colleagues, and the hybrids selected for higher breast yields were more prone to this abnormality.

Furthermore, they added, severe cases of white striping are even more prevalent at higher slaughter age and weight, while reduced growth rate is associated with a lower incidence and severity of white striping.

Reference

1. Ferreira T.Z., R.A. Casagrande, S.L. Vieira, D. Driemeier and L. Kindlein. 2014. An investigation of a reported case of white striping in broilers. J. Appl. Poult. Res. 23(4):748-753. doi: 10.3382/japr.2013-00847
2. Lorenzi M., S. Mudalal, C. Cavani and M. Petracci. 2014. Incidence of white striping under commercial conditions in medium and heavy broiler chickens in Italy. J. Appl. Poult. Res. 23 (4):754-758. doi: 10.3382/japr.2014-00968

To read the full report (fee payable), click on the title links in the references above.

December 2014