Effect of dietary medium chain fatty acids on nursery pig growth performance, fecal microbial composition, and mitigation properties against porcine epidemic diarrhea virus following storage.

Gebhardt, Jordan T; Thomson, Katelyn A; Woodworth, Jason C; Dritz, Steve S; Tokach, Michael D; DeRouchey, Joel M; Goodband, Robert D; Jones, Cassandra K; Cochrane, Roger A; Niederwerder, Megan C; Fernando, Samodha; Abbas, Waseem; Burkey, Thomas E

An experiment was conducted to evaluate the effect of dietary medium chain fatty acid (MCFA) addition on nursery pig growth performance, fecal microbial composition, and mitigation of porcine epidemic diarrhea virus (PEDV) following storage. A total of 360 pigs (DNA 400 × 200, Columbus, NE; initially 6.7 ± 0.07 kg) were randomized to pens (5 pigs per pen) on the day of weaning (approximately 20 d of age), allowed a 6-d acclimation, blocked by body weight (BW), and randomized to dietary treatment (9 pens per treatment). All MCFA (Sigma Aldrich, St. Louis, MO) were guaranteed ≥ 98% purity, including hexanoic (C6:0), octanoic (C8:0), and decanoic (C10:0) acids. Treatment diets were formulated in two phases (7 to 11 and 11 to 23 kg BW) and formulated to meet or exceed NRC requirement estimates. Treatments (n = 8) were a dose response including 0, 0.25, 0.5, 1.0, and 1.5% added MCFA blend (1:1:1 ratio C6:0, C8:0, and C10:0), as well as treatments with individual additions of 0.5% C6:0, C8:0, or C10:0. Fecal samples were collected from pigs fed control and 1.5% MCFA blend diets on d 0 and d 14 and analyzed using 16s rDNA sequencing. Following feed manufacture, feed was stored in bags at barn temperature and humidity for 40 d before laboratory inoculation with PEDV. Subsamples of retained feed were inoculated with PEDV to achieve a titer of 104 TCID50/g and separate sample bottles were analyzed on 0 and 3 days post-inoculation (dpi). Overall, average daily gain (ADG) and average daily feed intake (ADFI) were increased (linear, P ≤ 0.010) and feed efficiency (G:F) improved (linear, P = 0.004) with increasing MCFA blend. Pigs fed 0.5% C8:0 had greater (P = 0.038) ADG compared to pigs fed the control diet, and G:F was improved (P ≤ 0.024) when pigs were fed 0.5% C6:0, 0.5% C8:0, or 0.5% C10:0 compared to control. An inclusion level × day interaction was observed (quadratic, P = 0.023), where PEDV Ct values increased (quadratic, P = 0.001) on 0 dpi with increasing levels of MCFA blend inclusion and also increased on 3 dpi (linear, P < 0.001). Fecal microbial diversity and composition were similar between control and 1.5% MCFA blend. In summary, the use of MCFA in nursery pig diets improves growth performance, provides residual mitigation activity against PEDV, and does not significantly alter fecal microbial composition.