Rapid infection in market-weight swine following exposure to a Salmonella typhimurium-contaminated environment

OBJECTIVE: To evaluate the possibility of swine becoming infected with Salmonella Typhimurium when housed for 2 to 6 hours in an environment contaminated with Salmonella, similar to a lairage situation prior to slaughter. ANIMALS: 40 crossbred market pigs with an approximate body weight of 92 kg. PROCEDURE: Five trials were conducted (8 pigs/trial) in simulated lairage conditions. Superficial inguinal, ileocecal, and mandibular lymph nodes, cecal contents, distal portion of the ileum, and fecal samples were obtained from each pig after 2 (n = 10), 3 (10), and 6 (5) hours of exposure to an environment contaminated with feces defecated by 10 pigs intranasally inoculated with nalidixic acid-resistant Salmonella Typhimurium (chi4232). In addition, 5 control pigs that were not exposed were also evaluated in the same manner. RESULTS: Feces deposited on the floor by intranasally inoculated swine were mixed with water to form slurry with a resulting load of approximately 10(3) colony-forming units of Salmonella Typhimurium/g of material. Eight of 10, 6 of 10, and 6 of 6 pigs exposed to the slurry for 2, 3, or 6 hours, respectively, had positive results for at least 1 sample when tested for the specific strain of Salmonella Typhimurium. CONCLUSIONS AND CLINICAL RELEVANCE: Pigs can become infected during routine resting or holding periods during marketing when exposed to relatively low amounts of Salmonella organisms in the preslaughter environment. Intervention at this step of the production process may have a major impact on the safety of pork products.     

Interacting effects of soil degradation and precipitation on plant productivity in NE Patagonia,Argentina

Our objective was to examine the effects of inter-annual variation of precipitation on productivity of two dominant species (Chuquiraga avellanedae, an evergreen shrub, and Nassella tenuis, a perennial grass) in two communities of contrasting soil degradation: a herbaceous steppe with shrubs (HSS) and a degraded shrub steppe (SS). Data were collected during two consecutive years with different annual precipitation. Aboveground productivity was determined nondestructively using a double sampling approach. The number of inflorescences per plant was recorded too. Perennial grass productivity was lower in SS than in HSS in both years, while shrub productivity was lower in SS only during the year of below average precipitation. With rising precipitation the perennial grass increased the number of inflorescences while the evergreen shrub augmented vegetative biomass. In summary, the effects of precipitation on plant productivity are community dependent; abiotic factors, such as superficial and sub-superficial soil characteristics, and biotic factors, such as leaf area index (LAI) or tussock sizes, may interact to influence the responses of species to precipitation. Our results suggest that if precipitation increased, this would favor the dominance of shrubs over grasses.     

Effects of a "step-up" ractopamine feeding program, sex, and social rank on growth performance, hoof lesions, and Enterobacteriaceae shedding in finishing pigs

Increasing concern for animal well-being and food safety has stimulated the investigation of feed additives such as ractopamine (RAC), a beta-agonist widely used to improve production performance of finishing pigs. The objective of this study was to determine effects of RAC feeding, delivered as a "step-up" program (5 mg/kg for 2 wk followed by 10 mg/kg for 2 wk), on growth performance, Enterobacteriaceae shedding, including Salmonella, and hoof lesions, also taking into account sex and social rank of pigs. A total of 64 barrows and gilts (balanced by treatment and sex) were assigned to pens of 4 (by sex) as either control (CTL) or RAC treatment. Social ranks (dominant, intermediate, and subordinate) of pigs in each pen were determined by behavioral observation during 48 h post-mixing. Fecal samples were collected once per week for 5 wk. At slaughter, the 32 dominant and subordinate barrows and gilts (16/sex) were examined for hoof lesions, and luminal contents from ileum, cecum, and rectum were collected. Pigs fed RAC had increased growth performance (P < 0.05) with social rank of animals affecting overall ADG (P < 0.05). Gilts gained more backfat than barrows when comparing to baseline values at both 10th and last ribs (P < 0.05), whereas loin eye area increased at a similar rate for both barrows and gilts (P > 0.10). No significant effect of RAC feeding was found on backfat or loin eye area (P > 0.10). At slaughter, RAC-fed pigs had greater BW (P < 0.05). Despite the positive effects of RAC feeding on growth performance, pigs fed the compound had a greater frequency of front and rear hoof lesions as did barrows and dominant individuals (P < 0.05). Detectable concentrations of Salmonella shedding were not identified at any time during the experiment. Enterobacteriaceae shedding concentrations from RAC-fed pigs peaked at the first week of feeding and progressively decreased until slaughter. At slaughter, rectal and cecal Enterobacteriaceae concentrations were less in RAC-fed pigs than in CTL pigs (P < 0.05). Social rank tended to affect gut Enterobacteriaceae populations of barrows more than in gilts (P < 0.10). The effects of RAC feeding on hoof soundness and Enterobacteriaceae populations in the gastrointestinal tract of finishing pigs warrant further investigation. It is also proposed that the integration of the social rank status of the individual into future studies should be considered, because it may affect treatment responses.     

Experimental rapid infection in market swine following exposure to a Salmonella contaminated environment

The objective of these experiments was to evaluate the possibility of swine becoming infected with Salmonella Typhimurium after a short time interval in a contaminated environment. Two experiments were conducted. Experiment 1 consisted of five trials with eight market weight swine. Pigs were necropsied at 2 (n = 10), 3 (n = 10) and 6 (n = 5) hours after continuous exposure to an environment contaminated with feces shed by swine intranasally inoculated with nalidixic acid-resistant Salmonella Typhimurium (chi 4232). In Experiment 2, pigs were necropsied after 30 minutes (n = 6), 60 minutes (n = 6), 2 hours (n = 6), and 6 hours (n = 3). In addition, control animals with no exposure were also necropsied in both experiments. At necropsy, the superficial inguinal, ileocecal, and mandibular lymph nodes, as well as cecal contents, distal ileum portion, and feces were evaluated. All samples were cultured for the presence of the nalidixic acid-resistant Salmonella. Feces deposited on the floor by intranasally inoculated swine were mixed with water to form slurry with a resulting load of 10(3)-10(5) Salmonella Typhimurium CFU per gram. In Experiment 1, 80% percent of animals with a 2-hour, 60% of animals with a 3-hour, and 100% of animals with a 6-hour exposure to this slurry had at least one sample test positive for the marked Salmonella Typhimurium strain. In Experiment 2, 50% of the 30 minute, 50% of the 60 minute, and 33% of the 2-hour exposed pigs had at least one sample test positive. These experiments show that market swine can become infected during routine resting or holding periods when exposed to relatively low levels (10(3) CFU) of Salmonella in the simulated pre-slaughter environment, and that exposure times as short as 30 minutes are sufficient to produce contaminated gastrointestinal tracts. They also demonstrate the high risk of holding pigs longer than six hours. Intervention at this step in the swine production process may have a significant impact on the safety of pork products.     

β-Glucan plus ascorbic acid in neonatal calves modulates immune functions with and without Salmonella enterica serovar Dublin

To determine if β-glucan plus ascorbic acid affects adherence and pathogenicity of Salmonella Dublin and innate immune response in neonatal calves, 20 calves were fed control or supplemented diets (β-glucan, 0.9 g/d, plus ascorbic acid, 500 mg/d) until d 23. On d 21, 5 calves per treatment received 2.4 × 10(8)CFU of S. Dublin orally. S. Dublin spread through intestinal tissues into mesenteric lymph nodes (MLN), spleen, and lung tissues within 48 h. All supplemented calves had less mRNA expression of IL-1 receptor antagonist in liver. Leukocyte cell surface markers changed in lung cells, but not in blood, MLN, or spleen. CD14 in lungs was greatest for calves receiving supplement and challenge, but CD18 in lungs was greater for challenged than control calves. Lung DEC205 was greatest for challenged calves with and without supplement compared to controls, but more lung cells expressed CD14 for all treated groups compared to controls. These data show that S. Dublin briefly inhabited the intestinal tract, moving quickly to spleen, MLN, and lung tissues. Lung tissue was modulated by S. Dublin, but supplement alone increased CD14 expressing cells. The supplement appears not to attenuate invasiness but modified some lung cell populations by 48h.     

Edible mushrooms: Role in the prevention of cardiovascular diseases

Edible mushrooms are a valuable source of nutrients and bioactive compounds in addition to a growing appeal for humans by their flavors and culinary features. Recently, they have become increasingly attractive as functional foods for their potential beneficial effects on human health. Hence, food industry is especially interested in cultivated and wild edible mushrooms.     

Biological Evaluation of Seaweed Composting

Large quantities of green seaweed, linked probably to eutrophication, are cast ashore every summer on the Puerto Madryn beaches (Patagonia, Argentina, 42°S, 65°W). This algal biomass interferes with recreational uses of the beach, and therefore must be periodically collected and disposed. Part of this algal biomass was composted with the objective to produce an amendment to improve physical and nutritional characteristics of some local soils used in intensive horticulture, and at the same time to find a way to reduce environmental pollution. The compost was then biologically evaluated by determining the growth rate of tomato plants cultivated on various substrata (washed sand, sandy loam soil, and sandy loam soil plus inorganic fertilizers) to which different doses of compost were added. Results showed that in all cases the addition of compost increased water holding capacity and plant growth. The increase of tomato plants (Licopersicum esculentum var. platense) was proportional to the compost doses. Also, plants grown on sustrata containing at least ten percent compost had significant benefits compared to control plants, improving growth and water stress resistance. Although the quality of this seaweed compost was limited by excessive amounts of sand and low nitrogen content, it proved to be a good amendment that improved both physical and nutritional characteristics of local sandy loam soils used in intensive horticulture. According to these results, composting is a useful technology both to solve environmental pollution problems and to produce a valuable organic fertilizer for soils.     

Controlling Salmonella infection in weanling pigs through water delivery of direct-fed microbials or organic acids: Part II. Effects on intestinal histology and active nutrient transport

The objective of this study was to evaluate the effects of water-delivered, direct-fed microbials (DFM) or organic acids on intestinal morphology and active nutrient absorption in weanling pigs after deliberate Salmonella infection. Pigs (n = 88) were weaned at 19 ± 2 d of age and assigned to 1 of the following treatments, which were administered for 14 d: 1) control diet; 2) control diet + DFM (Enterococcus faecium, Bacillus subtilis, and Bacillus licheniformis) in drinking water at 10(9) cfu/L for each strain of bacteria; 3) control diet + organic acid-based blend (predominantly propionic, acetic, and benzoic acids) in drinking water at 2.58 mL/L; and 4) control diet + 55 mg/kg carbadox. Pigs were challenged with 10(10) cfu Salmonella enterica var Typhimurium 6 d after commencement of treatments. Pigs (n = 22/d) were harvested before Salmonella challenge and on d 2, 4, and 8 after challenge. Duodenal, jejunal, and ileal mucosal tissues were sampled for measurement of villus height and crypt depth. Jejunal tissue was sampled for determination of active nutrient absorption in modified Ussing chambers. Duodenal villus height was greater in pigs fed in-feed antibiotic before infection (P < 0.05). Jejunal crypts were deeper in DFM- and acid-treated pigs on d 4 after infection compared with all other treatments (P < 0.05). Salmonella infection resulted in a linear decrease in phosphorus (P < 0.001) and glucose (P < 0.05) active transport, and an increase (P < 0.001) in glutamine uptake immediately after challenge. Salmonella infection reduced basal short-circuit current (I(sc)); however, water-delivered DFM or organic acid treatments caused greater basal I(sc) on d 2 after challenge than did carbadox. Carbachol-induced chloride ion secretion was greatest in negative control pigs before infection (P < 0.01) and DFM-treated pigs (P < 0.05) after infection. In conclusion, both the DFM and acidification treatments induced increases in basal active ion movement and jejunal crypt depth, which could be interpreted as responses consistent with increased Salmonella pathology, but none of the additives markedly affected intestinal absorptive and secretory function in response to Salmonella challenge.