No abstract

Porcine reproductive and respiratory syndrome (PRRS) virus is an economically significant pathogen that antagonizes production in all stages of the swine industry. In nursery pigs, it increases the risk of mortality and reduces growth performance parameters. Thus, the objective of this study was to further understand how PRRS virus infection and its associated viremia and serology levels related to febrile response and performance in nursery pigs. Over two replicates, 37 three-week post-weaned PRRS naïve gilts (11.2 ± 2.56 kg BW) were randomly assigned to one of two treatments: Control (CON, n = 16) or PRRS virus-inoculated (PRRS+, n = 21). All pigs were housed individually in a BSL2 facility for the 21 d test period. PRRS serology, BW, ADG, ADFI, and G:F were determined at 0, 7, 14 and 21 days post inoculation (dpi). Core body temperatures were collected daily using a biosensor microchip. Data was analyzed using mixed procedure of SAS with dpi as a repeated effect and CON or PRRS+ as a treatment effect. Treatment, dpi and their interactions were assessed. As expected, viremia and antibody titers in PRRS+ pigs were significantly different compared to CON pigs, which remained negative (P < 0.001). The lowest PRRS Ct was observed at dpi 7, while antibody titers were highest between dpi 14 to 21 (P < 0.001). Compared with the CON, PRRS+ reduced BW gains by 17, 33 and 42% at dpi 7, 14 and 21 respectively (P < 0.001). The PRRS challenge also reduced ADFI by 30, 67 and 68% at dpi 7, 14 and 21 respectively, compared to CON (P < 0.001). The febrile response in the PRRS+ pigs peaked between dpi 7 and 14 then returned to CON baseline level by dpi 21 (P < 0.001). Overall, PRRS virus challenge induced a sustained febrile response that contributes to the attenuated performance of nursery pigs.

No abstract

Reductions in voluntary feed intake during disease, or disease hypophagia, is a common phenotype observed in nearly all species. However, the extent to which disease hypophagia explains attenuated pig performance during disease is poorly defined. The objective of this study was to describe the extent to which hypophagia explains pig performance during a Porcine Reproductive and Respiratory Syndrome (PRRS) virus challenge. Twenty-four PRRS naïve barrows (12.8 ± 0.73 kg BW; Landrace x Large White, PIC) were selected, blocked by body weight, and allotted across three treatments (n=8/trt): 1) PRRS-naïve, ad libitum fed (Ad), 2) PRRS-inoculated, ad libitum fed (PRRS), and 3) PRRS-naïve, pair-fed daily to the PRRS pigs (PF) to mimic disease feed intake. All pigs were individually penned and after a 4-day acclimation, on days post inoculation (dpi) 0, PRRS pigs were inoculated with PRRS virus. Over 7 dpi, daily feed intake and body temperatures (BT), and 7 day ADG, ADFI, and G:F were assessed. Over the 7-day challenge period, a treatment x time interaction (P &lt; 0.0001) was reported for ADFI in which PRRS and PF pigs’ ADFI was reduced by 51% compared with Ad pigs. Compared with Ad pigs, PRRS and PF pigs end BW was reduced by 23% (P = 0.004). The Ad pigs had greater ADG compared with PF and PRRS pigs (0.64, 0.12, -0.04 g/d, respectively, P &lt; 0.0001). Overall G:F was reduced by 112% and 53% in the PRRS and PF pigs, respectively, compared with Ad pigs (P &lt; 0.0001). A treatment x dpi effect was reported in core BT, in which PF pigs; BTs reduced over time compared with Ad and PRRS pigs (38.7, 39.4, 39.6 °C, respectively, P = 0.001). In summary, disease hypophagia explains much of the reduced growth observed during PRRS challenge.