Evaluation of a Lactococcus lactis- based dried fermentation product administered through drinking water on nursery pig growth performance, fecal Escherichia coli virulence genes and pathotypes, antibiotic usage, and mortality.

A total of 34,749 pigs were used in two experiments to evaluate the effects of a postbiotic dried fermentation product ( DFP ) administered through drinking water on nursery pig growth performance, antibiotic injection frequency, morbidity, mortality, fecal consistency, and characterization of fecal Escherichia coli . The DFP is composed of bioactive molecules derived from Lactococcus lactis. In Exp. 1, 350 barrows (DNA Line 200 × 400; initial body weight [ BW ] 6.1 ± 0.01 kg) were used in a 42-d study with five pigs per pen and 35 pens per treatment. The DFP was supplied for 14 d at a target dosage of 24 mg/kg BW using a water medicator at a 1:128 dilution. On days 7 and 14, fecal samples were collected for dry matter ( DM ) and to determine, by a multiplex polymerase chain reaction ( PCR ) assay, prevalence of 11 virulence genes characteristic of E . coli pathotypes. There was no evidence ( P > 0.10) for differences for growth, incidence of diarrhea, number of antibiotic injections, removals, or fecal DM. On both fecal collection days, E . coli virulence genes were present with day 7 samples positive for genes that encode for hemolysins ( hlyA , exhA) , intimin ( eae) , and enteroaggregative heat-stable enterotoxin ( astA) . Prevalence of enterotoxin genes ( elt, estA , estB, astA ) increased on day 14, but DFP had no effects on the prevalence of any of the virulence genes. A total of 32 out of 72 E . coli isolates were identified as enterotoxigenic pathotype and all except one were from day 14 fecal samples. Fourteen isolates were positive for F4 fimbria and one isolate was positive for F4 and F18 fimbriae. In Exp. 2, 34,399 nursery pigs (initially 5.6 kg) were used in 20 nursery barns with 10 barns per treatment (control or DFP). The target dosage of the DFP for the first 14 d was 35 mg/kg BW. Following the 14-d supplementation period, pigs continued to be monitored for approximately 31 d. There was no evidence ( P > 0.05) for the DFP to influence the overall percentage of pigs that died or growth performance. From days 0 to 14, providing the DFP reduced ( P < 0.05) the percentage of pigs that were euthanized. However, providing the DFP increased ( P < 0.05) the overall percentage of pigs that were euthanized and total mortality. For the number of antibiotic injections (treatment interventions), providing the DFP reduced the number of injections for the common period ( P < 0.001) and overall ( P = 0.002). These results indicate that the DFP did not influence growth performance but providing the DFP in Exp. 2 led to increased total nursery pig mortality.