Commercially produced spray-dried porcine plasma contains increased concentrations of porcine circovirus type 2 DNA but does not transmit porcine circovirus type 2 when fed to naïve pigs

摘要

The porcine circovirus type 2 (PCV2)antibody and DNA status of porcine plasma productscollected during the commercial spray-drying processwere evaluated. Samples evaluated included 52 pooledliquid plasma (fresh) samples collected at 14 regionalabattoirs before transport to 1 of 2 spray-drying facilities,32 pooled liquid plasma (concentrated) samplescollected after arrival at the spray-drying facilities atdifferent stages before the spray-drying process, and 32samples in powdered form (spray-dried) collected afterspray drying. All 116 samples were positive for PCV2antibody, with PCV2 ELISA sample-to-positive ratiosranging from 9.2 to 13.6 on a DM basis. Porcine circovirustype 2 DNA (4.5 to 7.9 log PCV2 copies/mL,DM basis) was present in 82.7% (43/52) of the freshplasma samples, 71.9% (23/32) of the concentratedplasma samples and 78.1% (25/32) of the spray-driedplasma samples, with a greater prevalence of PCV2bthan PCV2a. To determine the infectivity of PCV2DNA-positive commercial spray-dried plasma, nine10-wk-old 68-kg PCV2-naive pigs were randomly assignedto 1 of 3 treatment groups and rooms: 1) a negativecontrol (no plasma in the feed, not inoculated withPCV2); 2) a positive control (no plasma in the feed,inoculated with PCV2); and 3) plasma-fed pigs (4%porcine plasma in the feed for 42 d, not inoculated withPCV2). All positive control pigs became viremic by 7 dpostinoculation and seroconverted by 42 d postinoculation,whereas pigs in the negative control group and inthe spray-dried plasma group were PCV2 PCR negativeand did not seroconvert to PCV2 for the durationof the study. The results indicate that PCV2 DNA andantibodies are commonly found in commercial spraydried plasma. However, no evidence of infectivity of the PCV2 DNA was found in naive pigs when commercial spray-dried plasma was included in the diet under the conditions of this study. © 2011 American Society of Animal Science. All rights reserved.