Effect of morphological changes in feather follicles of chicken carcasses after defeathering and chilling on the degree of skin contamination by Campylobacter species

Abstract

Campylobacter jejuni and C. coli are the leading causes of enteric infections in many developed countries. Healthy chickens are considered to act as reservoirs of campylobacters, as the organisms colonize the intestinal tract. Once infected birds enter a processing plant, contamination of chicken carcasses with campylobacters occurs over the entire skin during defeathering and evisceration due to leakage of crop and/or intestinal contents. Although the role of feather follicles in the contamination of chicken carcasses by campylobacters during processing is still debatable, it has been considered that the microorganisms would be entrapped and retained in the follicles due to the morphological changes resulting from defeathering and chilling. In the present study, we observed the morphology of feather follicles in chicken carcasses after defeathering and chilling. A total of 3,133 feather follicles were examined for morphological changes before and after chilling. Shortly after defeathering, most (91.5%) of the follicles were closed, whereas after chilling they were either closed (85.5%) or open (6%), although a small proportion of enlarged follicles became smaller or closed (2.6%). Moreover, 5.9% of the follicles that were slightly open became further enlarged after chilling. Furthermore, the proportion of enlarged feather follicles that became closed after chilling showed no discernible relationship with the degree of campylobacter contamination in different areas of the carcass skin, suggesting that campylobacters may not be confined to feather follicles as a result of the morphological changes attributable to defeathering and chilling.

Keywords: Campylobacter; chicken carcass; contamination; feather follicle.

Fig. 1.

Temperature kinetics (mean value ± SD) in the subcutaneous region of 3 carcasses after chilling.

Fig. 2.

Morphological changes in feather follicles examined after defeathering and chilling. Based on the mean area of feather follicles after defeathering and chilling, representative 4 types of morphological changes are photographed: (A) closed→open, (B) slightly open→enlarged, (C) open→smaller or closed, and (D) closed→closed. The area of all closed follicles is considered to be zero. The “slightly open→enlarged” type is defined as a feather follicle with an area of more than zero after defeathering, and becoming larger after chilling. The “open→smaller” type is defined as a feather follicle with an area of more than zero after defeathering, and becoming smaller or closed after chilling.

Fig. 3.

Area of feather follicles after defeathering and after chilling. A total of 3,133 feather follicles of carcasses after defeathering and after chilling were photographed, and areas of the follicles were compared. The bar represents the average area of follicles examined. *P<0.01.

Fig. 4.

Proportions of enlarged follicles that became closed and contamination by campylobacters in different skin areas of chicken carcasses after chilling. The number of contaminating campylobacter cells was determined by the MPN method. The number of Campylobacter represents the average from 3 chicken carcasses.