Spray-dried plasma (SDP) of bovine origin

Plasma of porcine origin often contains PEDV RNA which raises some concerns about biosecurity and transmission of viruses within pig populations. In contrast, it is well recognized that the addition of plasma to pig feed enhances immune reactions and also has some intrinsic inhibition on virus survival. The objective of this study was to determine if there is any benefit to the diet containing spray-dried plasma (SDP) of bovine origin during acute PEDV infection.

Three groups of five 3-week-old conventional pigs were used. For the inoculation, commercial raw porcine plasma positive for PEDV neutralizing antibodies and PEDV RNA (PORCINE-RAW-PLASMA) was used and was either left unspiked (negative control group) or was spiked with a PEDV stock and stored at 19°C for 1 h. The negative control group received 10 ml unspiked PORCINE-RAW-PLASMA orally, the PEDV group received 10 ml PEDV-spiked PORCINE-RAW-PLASMA orally, and the PEDV-bovine-SDP group received 10 ml PEDV-spiked PORCINE-RAW-PLASMA orally and was also fed SDP of bovine origin at 5% of the ration for the study duration. Fecal swabs were collected every day and tested for presence of PEDV RNA. Serum samples were collected at inoculation (dpi 0) and at dpi 7 and 14 and tested for PEDV IgA and IgG antibodies. Necropsy was done on dpi 14 and intestinal sections were collected and microscopically evaluated for PEDV lesions and antigen by IHC stains.

PEDV was not detected in the negative control group. In the PEDV and the PEDV-bovine-SDP groups, clinical signs were mild; a few pigs in both groups developed mild-to-moderate diarrhea or vomiting for 1-3 days. The average fecal PEDV RNA shedding time ± SEM was 7.2±1.0 days for the PEDV-bovine-SDP group and 9.4±1.7 days for the PEDV group. While PEDV RNA was no longer detectable after day 11 in the PEDV-bovine-SDP group it was still present up to termination of the study at day 14 in the PEDV group. By day 7, 3/5 PEDV-bovine-SDP pigs had IgA antibodies whereas 0/5 pigs of the PEDV pigs were IgA positive. By day 14 all pigs in the PEDV and PEDV-bovine-SDP groups were IgA and IgG positive. One PEDV pig had moderate enteric lesions at day 14 and PEDV antigen was present in enteroctyes in the small intestines of that pig.

The results of this study indicate a positive effect of bovine SDP on acute PEDV infection as the addition of bovine SDP to the diet resulted in a faster IgA response and also reduced the PEDV shedding time compared to pigs that didn’t receive bovine SDP. This could be important for disease outcome and transmission. Furthermore, the commercial raw porcine plasma used for inoculation didn’t contain infectious PEDV.

Disclosure of Interest: None Declared.