Changes in the hematological variables in pigs supplemented with yeast cell wall in response to a Salmonella challenge in weaned pigs

Authors: Sanchez, Nicole; Carroll, Jeffery - Jeff Carroll; CORLEY, JIMMIE - Phileo Lesaffre Animal Care; Broadway, Paul; CALLAWAY, TODD - University Of Georgia

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2019
Publication Date: 7/24/2019
Citation: Sanchez, N.C., Carroll, J.A., Corley, J.R., Broadway, P.R., Callaway, T.R. 2019. Changes in the hematological variables in pigs supplemented with yeast cell wall in response to a Salmonella challenge in weaned pigs. Frontiers in Veterinary Science. 6:246.

Interpretive Summary: In addition to being an animal health and productivity problem in the livestock industry, Salmonella infection is responsible for approximately 1 million foodborne illnesses each year. Livestock producers lose millions of dollars annually due to poor growth and increased medication costs in their animals associated with Salmonella infection. Additionally, the medical costs associated with human patients hospitalized for Salmonella infections exceed $9,000 per patient annually. Therefore, management practices that reduce the negative effects of Salmonella infection in pigs and reduce the number of foodborne illnesses is of significant importance. To address this issue, scientists from the USDA-ARS Livestock Issues Research Unit conducted a study with scientists from the Food and Feed Safety Research Unit and Phileo-Lesaffre Animal Care to determine if feeding weaned pigs a diet containing a yeast cell wall supplement would reduce the severity of a Salmonella infection. Data from this study found that adding a yeast cell wall product to the diet of weaned pigs reduced the severity of infection, thus resulting in less illness. This information will be of particular interest to swine producers and to individuals seeking non-antibiotic alternatives to prevent disease and improve productivity in livestock.

Technical Abstract: The objective of this experiment was to evaluate the performance and immune responses of weaned pigs supplemented with yeast cell wall (YCW) when challenged orally with Salmonella typhimurium. Weaned pigs (n = 39; 7.1 ± 0.1 kg BW) were housed in an environmentally-controlled facility equipped with individual pig pens (1.2 x 0.6 m). Pigs were weighed upon arrival, blocked by BW, and assigned to one of three treatments (n = 13/treatment): Control diet, which was a non-medicated starter diet (Control); control diet supplemented with YCW at 250 mg/kg BW (YCW250; Phileo Lesaffre Animal Care, Milwaukee, WI); and control diet supplemented with YCW at 500 mg/kg BW (YCW500). Pigs were fed for 18 d, and pigs and feeders were weighed weekly. Pigs were anesthetized on d 7 to insert intraperitoneal temperature recording devices and on d 14 to insert jugular cannulas. On d 15 blood samples were collected at 6 h intervals from -6 to 72 h relative to oral Salmonella typhimurium (target dose: 1 x 106 cfu/pig) challenge. Serum was analyzed for cortisol, glucose and NEFA concentrations, and whole blood was utilized to measure hematology. Data were analyzed using the Mixed procedure of SAS specific for repeated measures. There was a tendency (P = 0.07) for a treatment effect for ADG with YCW500 pigs having reduced ADG than YCW250 pigs, and there was a tendency (P = 0.08) for a treatment effect for feed intake, such that feed intake was reduced in YCW250 pigs compared to Control pigs. Additionally, gain:feed was greater in YCW250 compared to Control and YCW500 pigs (P = 0.001). Baseline intraperitoneal temperature, measured at 1-hr intervals, was greater (P < 0.001) in YCW250 pigs than Control and YCW500 pigs. There was a treatment x time interaction for the change in intraperitoneal temperature (P < 0.01) and post-challenge cortisol (P = 0.03), white blood cells (WBC; P = 0.03), neutrophils (P = 0.02), and neutrophil:lymphocyte ratio (P = 0.03). Control pigs had greater (P < 0.05) cortisol at 0 h than both YCW-supplemented groups, but Control pigs had reduced (P < 0.05) cortisol compared to YCW500 pigs at 24 and 30 h post-challenge. Control pigs had greater (P < 0.05) WBC counts than both YCW-supplemented groups 6 and 12 h post-challenge, and YCW250 pigs had reduced (P < 0.01) WBC counts than Control and YCW500 pigs 18 h post-challenge. Neutrophil counts were greater (P < 0.05) in Control pigs than both YCW-supplemented groups at 6 and 12 h post-challenge and were greater (P = 0.02) than YCW250 pigs at 18 h post-challenge. Lymphocytes were greater (P < 0.001) in Control and YCW500 pigs pre- and post-challenge compared to YCW250 pigs. Control pigs had the greatest (P < 0.001) monocyte counts compared to YCW-supplemented pigs. This study suggests that YCW supplementation decreases intraperitoneal temperature and specific WBC subtypes after oral Salmonella challenge, similar to pervious results observed in cattle, and indicates YCW may be a viable supplement for weaned pigs in order to reduce the negative effects of Salmonella-induced illness.