Over the past 15 years the incidence of in-transit losses in swine during transportation to harvest has tripled. These losses (non-ambulatory and dead animals) are associated with the rapid accumulation of lactic acid in blood and the development of metabolic acidosis in transport-stressed swine. As pigs have become more efficient and muscular, they have modified muscle fiber type (more glycolytic fibers) which has increased the potential for rapid lactic acid generation from muscle during handling. Modification of electrolyte balance of the pig just prior to transportation has the potential to provide the pig greater buffering capacity to more effectively withstand this acidogenic load. The current proposal will evaluate the effect of increased dietary electrolyte balance (dEB) on total in-transit losses under commercial conditions in approximately 90 truckloads of finisher swine. Preliminary laboratory data indicate that increasing dEB prior to transport could reduce in-transit losses by 50%. If the commercial feeding test is effective, subsequent work will focus on development of a water soluble cation-rich electrolyte that can be administered in medicator systems in the finishing barn prior to transportation to the packing plant. OBJECTIVES: Over the past 15 years the incidence of in-transit losses in swine during transportation to slaughter has tripled. These losses (non-ambulatory and dead animals) are associated with the rapid accumulation of lactic acid in blood and the development of metabolic acidosis in transport-stressed swine. Modification of dietary electrolyte balance prior to handling in a laboratory trial significantly reduced the number of non-ambulatory fatigued animals. Therefore, the research in this study has been designed to explore the relationship between acid-base balance in swine and the incidence of in-transit losses during transportation to harvest under practical real-world conditions. The principal objective of the research is to determine the effect of increasing dietary electrolyte balance by 400 meq/kg feed for 4 days prior to transportation on the pigs ability to combat metabolic acidosis, often a consequence of the stressful events surrounding handling, transport and slaughter. By providing pigs with electrolyte supplementation to maintain an increased electrolyte balance, it is hypothesized that pigs will have the ability to more successfully buffer the lactic acid accumulation associated with periods of high stress and subsequently prevent the onset of the fatigued pig syndrome and in-transit losses. In addition to reducing loss attributed to fatigued pig syndrome, the alteration of electrolyte balance prior to slaughter may have positive effects on pork meat quality. APPROACH: Approximately 90 truckloads of finisher swine will be used to determine if increasing dEB by 400 meq/kg feed for 4 days prior to transport will reduce in-transit losses. The incidence of in-transit losses is affected by many environmental factors such as human interaction, pig mixing, climate and truck environment. Throughout the research study, these factors will be equalized across treatments to effectively evaluate the effect of electrolyte supplementation on the incidence of in-transit losses. The study will be conducted during the months of June to November, 2007 with the highest number of replicates during July/August, 2007. We will work through the packers to identify producers that are able to effectively switch feeds during the last 4 days prior to transport. Approximately four days prior to harvest, half the pigs in each barn to be evaluated will be fed a low electrolyte diet and the other half a high electrolyte diet produced by increasing the standard dietary cation electrolyte content by approximately 400 meq/kg feed. Throughout the course of the study, in-transit loss will be defined as dead on arrival (DOA), non-ambulatory non-injured (NANI) or non-ambulatory injured (NAI). The number of pigs in each category will be recorded at the barn, truck, and packing plant as well as signs of stress such as dyspnea (open mouth breathing), skin blotchiness and muscle tremors. Blood will be obtained via jugular venipuncture prior to transportation to document that pigs received the appropriate electrolyte in the feed. The blood samples will be analyzed using a portable iSTAT blood analyzer to obtain pH, base excess, lactate and bicarbonate concentrations. Blood samples will also be obtained at the plant to determine the persistence of the electrolyte treatment. Ninety truckloads of finisher pigs, transported under commercial conditions, will be required in the study based on previously published data as well as power calculations of required replication. We predict that increasing dEB by 400 meq/kg feed for 4 days prior to transport will cut in-transit losses in half. If the commercial feeding test is effective, subsequent work will focus on development of a water soluble cation-rich electrolyte that can be administered in medicator systems in the finishing barn a few days prior to transportation to the packing plant
