High levels of soybean meal reduces medical treatment in nursery pigs affected by PRRS

Abstract Text: High levels of soybean meal (SBM) may modulate the response to a respiratory disease challenge by reducing systemic viral replication and modulating the immune system. A total of 2,112 pigs (BW 5.99±0.10 kg) were placed into 2 nursery rooms of 48 pens each (22 pigs/pen) under commercial conditions to evaluate the potential of SBM levels (low, medium, or high) in combination with phytase (Quantum Blue, AB Vista; 560 or 1,415 analyzed FTU/kg) to improve growth and health of weaned pigs originating from a porcine reproductive and respiratory syndrome (PRRS) affected sow farm. Pigs were fed a 3-phase feeding program, with each period being 10, 10 and 22 d, respectively. Inclusion of SBM was 15.0, 22.5 and 30.0% (1.50% SID lysine; 23.6, 25.8, and 28.0% CP) for phase 1 and 20.0, 27.5 and 35.0% (1.42% SID lysine; 23.1, 24.9, and 26.6% CP) for phase 2 for low, medium, and high SBM, respectively. For phase 3, pigs were fed a common diet. Stool firmness (0=normal; 1=soft; 2=fluid; and 3=completely liquid) was determined during the first 10 d of the study. Oral fluid samples were collected on d 20 and 42 and analyzed by PCR to assess viral load of PRRS. Data were analyzed as a RCBD in a 3×2 factorial arrangement of treatments with pen as experimental unit. No significant interactions or main effects (P>0.05) were observed for ADFI, ADG or gain:feed. The percentage of pigs pulled for medical treatment declined linearly with increasing SBM levels (11.09, 9.15, 8.42%; P=0.04). However, there was no reduction in mortality or improvement in the percentage of full value pigs (97.3, 97.4, and 97.3%; P=0.97). Stool firmness decreased with increasing SBM during d 1 to 5 (linear, P=0.01) and tended to decrease for d 1 to 10 (P=0.13; 0.60, 0.60 and 0.71). Phytase tended to improve stool score for d 1 to 5 (P=0.06) and d 1 to 10 (P=0.14; 0.67 vs. 0.61). Soybean meal levels did not affect (P≥0.31) viral load of PRRS when determined on d 20 (Ct values of 30.1, 30.3, and 32.0) or d 42 (Ct values of 29.3, 30.1, 29.1). In conclusion, increased levels of SBM may be beneficial in health challenged pigs by reducing labor and cost associated with treatment for disease without impacting performance or viral load of PRRS. The tendency for high levels of SBM to cause stool looseness can be countered with a high phytase level.

 Keywords: phytase, porcine reproductive and respiratory syndrome, soybean meal