This study was conducted to determine the effects of the antimicrobial peptide cecropin on performance and intestinal health in piglets. Twenty-four, newly weaned barrows (Large White x Landrace; initial BW = 6.76 ± 0.54 kg; 21 ± 3 d of age) were randomly assigned to one of three treatments (n = 8) according to their initial body weight in a randomized complete block design. Diets were corn-soybean based or similar diets supplemented with antibiotics (100 mg/kg kitasamycin plus 800 mg/kg colistin sulfate) or 400 mg/kg cecropin AD. On day 13, all piglets were orally challenged with 109 CFU/mL of Escherichia coli K88. On day 19, all piglets were euthanized and sampled.
Before challenge, piglets fed antibiotics had greater weight gain (328 vs. 354 g/day), feed efficiency (0.72 vs. 0.77) than the control (P < 0.05). E. coli challenge decreased weight gain, feed intake and feed efficiency for the control piglets (P < 0.05) but not for the antibiotic or cecropin AD treated piglets. Antibiotic supplementation resulted in higher nitrogen (P < 0.04) and energy retention (P < 0.04) (11.5 g/day and 3.0 MJ/kg/day) compared with the cecropin AD (10.7 g/day and 2.8 MJ/kg/day) and control (10.1 g/day and 2.5 MJ/kg/day) groups. The incidence of diarrhea post-challenge in the antibiotic and cecropin AD treatments decreased 52.4% and 47.6%, respectively, compared with the control piglets. The total viable counts of cecal E. coli (3.09 vs. 3.22 vs. 3.37 log CFU/g digesta) were lower while the Lactobacilli (9.47 vs. 9.23 vs. 8.89 log CFU/g digesta) counts were higher in the antibiotic and cecropin AD treatments compared with the control (P < 0.05). Cecropin AD treatment vs. the control group, decreased total aerobes (6.43 vs. 6.69 log CFU/g of digesta) while increasing total anaerobes (10.12 vs. 9.36 log CFU/g of digesta) in the ileum (P < 0.05). A higher villus height to crypt depth ratio in the jejunum and ileum as well as a deeper crypt depth in the jejunum and higher villus height in the ileum were observed in piglets fed antibiotics or cecropin AD compared with control piglets (P < 0.05). Piglets fed the control diet had lower levels of secretory IgA in their jejunum (65.1 µg/g in the control group to 71.5 and 74.5 µg/g in the antibiotic and cecropin AD treatment, respectively) and lower serum IgA (167.8 vs. 165.1 vs. 185.4 µg/ml), IgG (868.4 vs. 925.3 vs. 1020.7 µg/ml), interleukin-1 (4.58 vs. 7.88 vs. 9.77 pg/ml) and interleukin-6 (1.97 vs. 2.84 vs. 5.04 pg/ml) compared with the other treatments (P < 0.05).
Overall, these data suggest that cecropin AD enhances pig performance through increasing immune status and nitrogen and energy retention as well as reducing intestinal pathogens in weaned piglets.
S Wu, F Zhang, Z Huang, H Liu, C Xie, J Zhang, PA Thacker, S Qiao. 2012. Effects of the antimicrobial peptide cecropin AD on performance and intestinal health in weaned piglets challenged with Escherichia coli. Peptides, 35:225-230. http://dx.doi.org/10.1016/j.peptides.2012.03.030.