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Impact of porcine respiratory and reproductive virus on behavior and welfare of growing pigs
The Porcine respiratory and reproductive virus (PRRSv) is one of the leading causes of negative pig welfare and substantial loss of profits in the US swine industry. Little is known about the effect of PRRSv on the sickness behavior of growing pigs. Therefore, in the current study we investigated the effects of PRRSv on the behavior and welfare of growing pigs. A total of 20 PRRS negative gilts (BW 9.4 ± 0.9 kg ) from a commercial line were fed restricted (550 g/d) a corn and SBM based diet, individually housed in metabolism crates and then inoculated intramuscularly with a live PRRSv (d 0). Blood samples were collected via the jugular vein at 0, 2, 4, 6, 8, and 9 days post inoculation (dpi), and assayed for blood urea nitrogen (BUN), glucose (Glu), creatinine, hematocrit (Hct), hemoglobin Hb, anion gap (AGap) and serum viral load. A video monitoring system was used to collect behavior data before (pre-challenge, d -3 to 0 dpi) and after the PRRSv challenge (post-challenge, d 0 to 9 dpi). Eye temperature of pigs was measured on a daily basis using an infrared imaging technique. All pigs became PRRSv-positive within 2-4 dpi as assessed by qPCR titers. Serum viral load was highest at 4 dpi and remained elevated until 9 dpi. Relative to d 0, the 9 d PRRSv challenge increased eye temperature from 37.7 to 38.7 °C (SE 0.12), AGap (from 13 to 17 mEq/L, SE 0.7), and creatinine concentrations (from 0.7 to 0.8 mg/dl, SE 0.03). However, PRRSv infection decreased the levels of blood Glu (from to 93 to 85 mg/dl, SE 6.0) and Hb (from 12 to 8 g/dl, SE 0.9; P < 0.05). No effect of PRRSv was seen on BUN and Hct (P > 0.05). During the post-challenge period pigs displayed an increase in lying frequency (pre- vs. post-; 77 vs. 85 % of time, SE 3.3; P < 0.05), a decrease in eating and drinking frequency (11 vs. 7 %, SE 1.1; P < 0.05), and a tendency to decrease overall activity (13 vs. 9 %, SE 2.5; P < 0.09) compared to the pre-challenge period. During the post-challenge period pigs consumed 55 % of their daily feed allowance (P < 0.05). Collectively, these results suggest that the porcine respiratory and reproductive virus alters physiology and directly impacts the behavior and welfare of growing pigs. NPB project #13-082
Keywords: PRRS, behavior, pig