ABSTRACT
The immediate refrigeration of meat after slaughter is a key issue for the proper storage and aging of meat. The industry standard cold chain relies on low temperatures and ventilation to lower the internal carcass temperature to 0-4 °C within the first 48 h, i.e., within four times the so-called semi-cooling time. On the other hand, for games, once bled and eviscerated, the carcass must be sent to a point where it can be sectioned or kept on air for maturation at refrigeration temperature. The precautions to observe are few and simple but essential: protect the meat and start the cooling process quickly. After preparing the animal (bleeding and evisceration), it may be necessary to face a period of transport that is sometimes long and not very easy; while small animals can be easily transported in a backpack, larger ones must necessarily be carried by several people or sometimes dragged to the vehicle capable of transporting them. It is obvious that a wild boar opened from the jaws to the pelvis and dragged for hundreds of meters will tend to be contaminated, although these contaminations are to be considered secondary for the preservation of the meat, compared to contamination by the intestinal contents. In an attempt to investigate the effect of delayed refrigeration on wild boar carcass contamination, the aim of this work was to determine a correlation between several hunting and logistic parameters (age, sex, animal weight, shooting distance, number of shots, weather and temperature and time from shot to refrigeration and to analysis) and bacterial contamination of the carcass. The correlation coefficient, r, was found to be 0.038 for the eviscerated body weight (p < 0.05), 0.091 for the external temperature on the day of hunting (p < 0.05), 0.027 for the time from shot to refrigeration (p = 0.081), 0.038 for the time from refrigeration to analysis (p < 0.05) and 0.043 for the time from shot to analysis (p < 0.05). These results stand for a negative correlation between the bacterial population and eviscerated carcass weight and between the bacterial population and external temperature and for a positive correlation between the time from shot to analysis and from refrigeration to analysis. No association was demonstrated between the bacterial population and the time from shot to refrigeration.
ABSTRACT
Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of paratuberculosis, a chronic granulomatous enteric disease of ruminants. MAP detection by faecal culture provides the definitive diagnosis of the infection. Automated liquid systems for MAP culture are more sensitive and rapid than culture on solid media, but they are expensive and require specialised equipment. In this study, a non-automated culture method using a modified Middlebrook 7H9 liquid medium (7H9+) was compared with Herrold's solid medium (HEYM) and direct real-time PCR on dairy cattle faeces. MAP growth in 7H9+ was monitored weekly by real-time PCR until the 12th week post-inoculation. The analytical sensitivity of the three methods was evaluated using faecal samples from a healthy cow spiked with ten-fold dilutions of MAP organisms (10(4)-10(-1)) and naturally MAP-infected faeces serially diluted 1 to 10 in negative faecal samples. The limits of detection of the solid culture and direct real-time PCR were 10(2) and 10(3)MAP/g, respectively. In comparison, the 7H9+ culture revealed as few as 1MAP/g. A marked reduction in time to detection of the pathogen, compared with HEYM culture, was obtained. In addition, the three methods were applied to environmental faecal samples collected from a high- and a low-prevalence herd. The culture in 7H9+ showed to be the most sensitive test in the low-prevalence herd and provided faster results than HEYM. In the high-prevalence herd the three methods showed the same sensitivity and the real-time PCR had the shortest turnaround time. In conclusion, the use of 7H9+ for MAP-detection from cattle faeces maximizes diagnostic sensitivity and reduces turnaround time and, therefore, could replace culture in solid medium. Hence, we propose a two-step protocol for the assessment of MAP faecal excretion based on: 1) direct real-time PCR on all samples; and 2) inoculation of negative samples into 7H9+ and analysis after 3 and, if necessary, 6weeks by real-time PCR.
