Impact of PRRSV infection and dietary soybean meal on ileal amino acid digestibility and endogenous amino acid losses in growing pigs

Authors: SCHWEER, WES - Iowa State University; PATIENCE, JOHN - Iowa State University; BURROUGH, ERIC - Iowa State University; Kerr, Brian; GABLER, NICHOLAS - Iowa State University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/7/2018
Publication Date: 5/18/2018
Citation: Schweer, W.P., Patience, J.F., Burrough, E.R., Kerr, B.J., Gabler, N.K. 2018. Impact of PRRSV infection and dietary soybean meal on ileal amino acid digestibility and endogenous amino acid losses in growing pigs. Journal of Animal Science. 96:1846-1859. https://doi.org/10.1093/jas/sky093.
DOI: https://doi.org/10.1093/jas/sky093

Interpretive Summary: Fat and protein accretion rates and the performance efficiency are reduced in health challenged pigs, suggesting an alteration in nutrient utilization and resource allocation within the body of the animal. Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the most economically significant swine diseases in the world, costing the US pork industry more than $660 million annually. In growing pigs, PRRSV infected pigs have been shown to have reduced growth performance and feed efficiency, and reduced apparent total tract digestibility of nutrients and energy. It is not known, however, if basal endogenous losses of amino acids or the standardized ileal digestibility of amino acids are affected in relation to a PRRSV challenge. The current study was conducted to determine if PRRSV infection affects the basal endogenous losses of amino acids and consequently impacts the standardized ileal digestibility of amino acids in growing pigs fed diets containing either high or low levels of soybean meal. Data from this experiment suggests that PRRSV infection in growing pigs had little impact on basal endogenous losses of amino acids, and therefore, the standardized ileal digestibility of most amino acids were not different, but the nonessential amino acids of arginine and proline appear to be conditionally essential during a PRRSV challenge. This information is important for nutritionists at universities, feed companies, and pig production facilities for the determination of the impact of a PRRSV health challenge on growth performance and production efficiency, and on any changes necessary in the requirement of amino acids in growing pigs during a PRRSV health challenge.

Technical Abstract: Porcine reproductive and respiratory syndrome virus (PRRSV) is a significant disease in the swine industry and increasing soybean meal (SBM) during this disease challenge may improve performance. Our objectives were to determine the impact of SBM level on apparent total tract (ATTD) and ileal (AID) digestibility during PRRSV infection, and to determine ileal (BEL) and total tract basal endogenous losses during PRRSV infection. Forty PRRSV negative gilts (38.6 ± 0.70 kg BW) were fitted with a T-cannula in the distal ileum. Treatments were arranged in a 2 × 2 factorial with high and low SBM (HSBM, 29% vs. LSBM, 10%), with and without PRRSV (n=6/treatment). The remaining pigs (n=8/PRRSV status) were fed a N-free diet. Chromic oxide was used as an indigestible marker. On day post inoculation (dpi; day 0), 20 pigs were inoculated with live PRRSV; 20 control pigs were sham inoculated. Infection was confirmed by serum PCR in inoculated pigs. Feces were collected at dpi 5-6 and 16-17, and ileal digesta was collected at dpi 7-8 and 18-19. Feed, feces, and digesta were analyzed for DM, N, and GE. Digesta and feed were also analyzed for AA. Data were analyzed in a 2 × 2 factorial design to determine main effects of diet and PRRSV and their interaction. Data from N-free fed pigs were analyzed separately to determine BEL and hindgut disappearance due to PRRSV infection. All control pigs remained PRRSV negative. There were no interactions for AID of AA; however, diet impacted AID of DM, GE, Arg, Lys, Met, Thr, Asp, Gly, Ser, and Pro (P < 0.05), while PRRSV reduced AID of DM and GE (P < 0.05) at dpi 7-8 only. At 7-8 dpi, BEL of Arg, Ala, and Pro were reduced (P < 0.05) due to PRRSV by 64, 39, and 94%, respectively. At dpi 18-19 there was a tendency (P = 0.06) for Thr to be increased in PRRSV infected pigs; however, no other differences were observed. Pigs fed LSBM had increased SID of Lys, Met, Thr, Trp, and Pro, primarily at 7-8 dpi. At 7-8 dpi, PRRSV pigs had reduced SID of Arg, Gly, and Pro (P < 0.01), and SID Pro continued to be reduced by 17% at dpi 18-19. Hindgut disappearance of DM and GE was reduced in LSBM pigs compared to HSBM at dpi 5-8 and 16-19 while N disappearance was reduced at dpi 5-8. There were no differences between control and PRRSV N-free fed pigs. Altogether, SBM inclusion impacts SID of AA and hindgut disappearance of nutrients, regardless of PRRSV. In contrast, there is minimal impact of PRRSV on BEL, and therefore, SID of most AA are not different.