试验选用360头仔猪（初重6.7 ± 0.07 kg），在断奶当天根据体重随机分至各圈，每圈5头，每个处理9圈，适应期6天。所有中链脂肪酸保证98%的纯度，包括己酸（C6：0），辛酸（C8：0）和癸酸（C10：0）。共有两阶段（7-11kg、11-23kg）饲料日粮，日粮营养指标均达到或超过NRC推荐量。试验共8个处理，中链脂肪酸混合物（己酸、辛酸、癸酸比例为1:1:1）添加量为0、0.25、0.5、1.0、1.5%，还有三个处理为己酸、辛酸、癸酸分别添加0.5%。在试验第0和14天收集对照组、1.5%中链脂肪酸混合物组的猪粪便，用16s rDNA测序。饲料制作完成后放置于袋中在谷仓温度和湿度条件下储存40d，然后在实验室进行猪流行性腹泻病毒接种。存留的饲料接种猪流行性腹泻病毒，滴度为104 TCID50/g，然后在第0、3天检测。
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
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 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 2 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 days 0 and 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 withPEDV. 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 d post-inoculation (dpi). Overall, ADG and 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 with 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 with 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.