Showing papers by "Steven D. Shackelford published in 2020"

Seasonal Prevalence of Shiga Toxin-Producing Escherichia coli on Pork Carcasses for Three Steps of the Harvest Process at Two Commercial Processing Plants in the United States.

Abstract: Shiga toxin (stx) –producing Escherichia coli (STEC) are foodborne pathogens that have a significant impact on public health, with those possessing the attachment factor intimin (eae) referred to as enterohemorrhagic E. coli (EHEC) and associated with life threatening illnesses. Cattle and beef are considered typical sources of STEC, but their presence in pork products is a growing concern. Therefore, carcasses (n=1536) at two U.S. pork processors were sampled once per season at three stages of harvest (post-stunning skins; post-scald carcasses; chilled carcasses) then examined using PCR for stx and eae, aerobic plate count (APC) and Enterobacteriaceae counts (EBC). The prevalence of stx on skins, post-scald, and chilled carcasses was 85.3, 17.5, and 5.4%, respectively, with 82.3, 7.8, and 1.7% swabs, respectively, having stx and eae present. All stx positive samples were subjected to culture isolation that resulted in 368 STEC and 46 EHEC isolates. The most frequently identified STEC were serogroups O121, O8, and O91 (63, 6.7, and 6.0% of total STEC, respectively). The most frequently isolated EHEC was serotype O157:H7 (63% of total EHEC). Results showed that scalding significantly reduced (P IMPORTANCE Seven serogroups of Shiga toxin-producing Escherichia coli(STEC) are responsible for most (>75%) cases of severe illnesses caused by STEC and are considered adulterants of beef. However, some STEC outbreaks have been attributed to pork products although the same E. coli are not considered adulterants in pork because little is known of their prevalence along the pork chain. The significance of the work presented here is that it identifies disease causing STEC, enterohemorrhagic E. coli (EHEC), demonstrating that these same organisms are a food safety hazard in pork as well as beef. The results show that most STEC isolated from pork are not likely to cause severe disease in humans and that processes used in pork harvest, such as scalding, offer a significant control point to reduce contamination. The results will assist the pork processing industry and regulatory agencies to optimize interventions to improve the safety of pork products.

Effects of space allowance and marketing strategy on growth performance of pigs raised to 165 kg.

Abstract: A total of 976 pigs (PIC 327 × Camborough; PIC, Hendersonville, TN; initially 22.0 ± 1.53 kg body weight [BW]) were used in a 160-d growth study to evaluate the effects of increasing space allowance and varying marketing strategies on growth performance of pigs raised to market weights of ~165 kg. Pens of pigs were blocked by location within the barn and allotted to one of six treatments. Pen served as the experimental unit, and there were eight replicate pens per treatment. The first four treatments consisted of increased initial stocking density and did not utilize topping strategies: (1) 14 pigs/pen (1.17 m2/pig), (2) 17 pigs/pen (0.97 m2/pig), (3) 20 pigs/pen (0.82 m2/pig), and (4) 23 pigs/pen (0.71 m2/pig). The fifth treatment began with 25 pigs/pen (0.66 m2/pig) and had four marketing events with the heaviest 3 pigs/pen removed on day 93, and additional pigs removed to a common inventory of 20 pigs/pen on day 122 and 17 pigs/pen on day 147 with final marketing on day 160. The final treatment began the experiment with 23 pigs/pen (0.71 m2/pig) with three marketing events to achieve a common inventory of 20 pigs/pen on day 108 and 17 pigs/pen on day 147. Pens of pigs were weighed and feed disappearance measured on days 0, 55, 93, 108, 122, 135, 147, and 160. As space allowance decreased from 1.17 to 0.71 m2/pig via increased initial pen inventory (treatments 1 to 4), overall average daily gain (ADG) and average daily feed intake (ADFI) decreased (linear, P 0.05). The treatments with multiple marketing events were compared with each other and with the treatment that began with 0.71 m2/pig and only marketed once at the end of the study. Overall ADG and ADFI were not different (P > 0.05) among these three treatments. Marketing pigs three or four times improved (P < 0.05) G:F compared with the treatment that began the study with 0.71 m2/pig and marketed only once. Reducing floor space allowance for heavy weight pigs decreased intake, which resulted in lower growth rate and final BW, with these reductions occurring before the critical k-value was reached. Total weight gain per pen was maximized with the lowest space allowance and the multiple marketing treatments. Thus, strategic use of pig removals prior to final marketing may allow producers to maximize both number of pigs and total weight marketed through a barn when feeding to heavy weights.

366 The Ham Halo condition: Characterization and a possible approach for mitigation

Abstract: The Halo condition is a meat quality defect characterized by very pale lean tissue on the superficial portion of fresh ham muscles. This tissue does not allow proper cured color development and has been the subject of customer complaints for ham processors. Surveys of raw materials revealed an issue affecting many suppliers and genetic lines. Further investigation indicated that the condition was most prominent in the distal portion of the biceps femoris muscle and was present in pigs of all ages and stages of production. Halo-affected tissue had much higher proportion of white muscle fibers. Consequently, Halo-affected tissue exhibited much lower myoglobin concentration, as well as much greater lightness, and much lower redness values, compared to normal tissue in the deeper portion of the muscle. These differences are consistent with increased expression of genes coding for white muscle fiber specific proteins in the Halo-affected tissue relative to tissue from the Inside portion of the biceps femoris muscle. Virtually all muscles evaluated have exhibited some degree of the Halo condition, but significant variation exists in the size of the affected portion of the muscle as well as the severity of the condition. Sire has a substantial impact on variation in Halo condition severity. Thus, genetic selection should help mitigate the condition. We will provide an overview of efforts to characterize the Halo condition and discuss genetic selection as a means to mitigate the condition.

Sire Variation in the Severity of the Ham Halo Condition

Abstract: A study was conducted to examine genetic variation in the ham halo condition. The distal portion of the biceps femoris was sampled by taking cores (2.54-cm diameter) from progeny (n = 1,016) from a Duroc meat quality–focused line. Commission Internationale de l Eclairage (CIE; “International Commission on Illumination”) color-space values (L*, a*, and b*) and myoglobin concentration were measured on the halo (“Halo”) and inside (“Inside”) portion of each core. The Halo portion of the biceps femoris had greater L* and b* and lesser a* and myoglobin content (all P < 0.001) than the Inside portion. Sires with 11 or more progeny were compared. The sire × muscle-location interaction affected (P < 0.001), L*, a*, and myoglobin concentration. Sire progeny groups differed for each trait in both portions of the muscle, but differences in the Halo portion of the muscle were not mirrored in the Inside portion of the muscle. Similarly, sire group affected the magnitude of the difference in L* (P = 1.4 × 10−4) and a* (P = 9.0 × 10−6) between the Halo and Inside portions of the muscle and tended (P = 0.08) to affect myoglobin content. However, the largest sire-group differences were not necessarily seen in the sires with the highest means for these attributes. Thus, selecting for myoglobin concentration, L*, or a* content in the Halo portion of the biceps femoris muscle would be an effective strategy for reducing the severity of the ham halo condition.

Seasonal prevalence and characterization of Shiga toxin-producing Escherichia coli on pork carcasses at three steps of the harvest process at two commercial processing plants in the US

Abstract: Shiga toxin (stx) -producing Escherichia coli (STEC) are foodborne pathogens that have a significant impact on public health, with those possessing the attachment factor intimin (eae) referred to as enterohemorrhagic E. coli (EHEC) associated with life threatening illnesses. Cattle and beef are considered typical sources of STEC, but their presence in pork products is a growing concern. Therefore, carcasses (n=1536) at two U.S. pork processors were sampled once per season at three stages of harvest (post-stunning skins; post-scald carcasses; chilled carcasses) then examined using PCR for stx and eae, aerobic plate count (APC) and Enterobacteriaceae counts (EBC). Skins, post-scald, and chilled carcasses had prevalence of stx (85.3, 17.5, and 5.4%, respectively), with 82.3, 7.8, and 1.7% respectively, having stx and eae present. All stx positive samples were subjected to culture isolation that resulted in 368 STEC and 46 EHEC isolates. The most frequently identified STEC were serogroup O121, O8, and O91(63, 6.7, and 6.0% of total STEC, respectively). The most frequently isolated EHEC was serotype O157:H7 (63% of total EHEC). Results showed that scalding significantly reduced (P IMPORTANCE Seven serogroups of Shiga toxin-producing Escherichia coli (STEC) are responsible for most (>75%) cases of severe illnesses caused by STEC and are considered adulterants of beef. However, some STEC outbreaks have been attributed to pork products although the same E. coli are not considered adulterants in pork because little is known of their prevalence along the pork chain. The significance of the work presented here is that it identifies disease causing STEC, enterohemorrhagic E. coli (EHEC), demonstrating that these same organisms are a food safety hazard in pork as well as beef. The results show that most STEC isolated from pork are not likely to cause severe disease in humans and that processes used in pork harvest, such as scalding, offer a significant control point to reduce contamination. The results will assist the pork processing industry and regulatory agencies to optimize interventions to improve the safety of pork products.