Effect of dietary mineral source on the clearance time of porcine epidemic diarrhea virus in the saliva of commercial gilts

Novel inorganic trace mineral sources, like hydroxychlorides (IntelliBond, Micronutrients, Indianapolis, IN), are now commercially available. Hydroxychloride trace minerals (HTM) have covalent bonds similar to organic mineral sources and better bioavailability than sulfate mineral sources (SUF). Moreover, it is well established that trace minerals like Zn, Cu, and Mn significantly influence immune function. Therefore, trace mineral source might affect how gilts respond to being acclimated to porcine epidemic diarrhea virus (PEDV). Currently, there is little commercial field research investigating the effect of mineral source on PEDV clearance from gilt saliva. Therefore, a study was conducted to determine how feeding different sources of trace minerals to developing gilts affected PEDV saliva concentrations at different time points. In the nursery, gilts were divided into two groups of at least 20,000 pigs. Once separated, 34 rooms were fed diets supplemented with Cu, Zn, and Mn hydroxychloride, and 45 rooms were fed diets supplemented with the same concentration of SUF. Mineral source, day, and their interaction were used as fixed effects. Farm was used as a random effect. Room was the experimental unit. Gilts received treatment diets at the start of the 3^rd nursery phase (12.5 to 25 kg BW) and continued for 15 weeks after they were transferred to the gilt developer unit (GDU). Gilts were fed practical, industry-type diets that changed with feeding phase and were formulated to contain 15 ppm Cu, 120 ppm Zn, and 50 ppm Mn. Mineral source was the only difference between treatments. Upon arrival to the GDU, pigs were orally acclimated to PEDV (day 0) through the water line using a water medicator. Beginning at day 7, ropes were placed into each room to collect saliva. After 7 days, ropes were tested for PEDV via real-time PCR (RT-PCR). The virus was deemed clear when 32 RT-PCR cycles were required to detect PEDV. When first measured (14 days), there was a trend (P = 0.066) for HTM fed gilts to require more cycles to detect PEDV than SUF fed gilts. After 42 days, HTM fed gilts required significantly more (P < 0.05) cycles to detect PEDV. Gilts fed diets with HTM reached the clearance threshold of 32 cycles by 42 days, whereas SUF fed gilts reached that threshold one week later. In conclusion, replacing SUF with HTM reduced the time it took the immune system of commercial gilts to clear PEDV from their saliva.