Abstract
Due to antimicrobial properties, nisin is one of the most commonly used and investigated bacteriocins for food preservation. Surprisingly, nisin has had limited use in animal feed as well as there are only few reports on its influence on microbial ecology of the gastrointestinal tract (GIT). The present study therefore aimed at investigating effects of dietary nisin on broiler chicken GIT microbial ecology and performance in comparison to salinomycin, the widely used ionophore coccidiostat. In total, 720 one-day-old male Ross 308 chicks were randomly distributed to six experimental groups. The positive control (PC) diet was supplemented with salinomycin (60 mg/kg). The nisin (NI) diets were supplemented with increasing levels (100, 300, 900 and 2700 IU nisin/g, respectively) of the bacteriocin. The negative control (NC) diet contained no additives. At slaughter (35 days of age), activity of specific bacterial enzymes (α- and β-glucosidases, α-galactosidases and β-glucuronidase) in crop, ileum and caeca were significantly higher (P<0.05) in the NC group, and nisin supplementation decreased the enzyme activities to levels observed for the PC group. A similar inhibitory influence on bacterial activity was reflected in the levels of short-chain fatty acids (SCFA) and putrefactive SCFA (PSCFA) in digesta from crop and ileum; no effect was observed in caeca. Counts of Bacteroides and Enterobacteriacae in ileum digesta were significantly (P<0.001) decreased by nisin and salinomycin, but no effects were observed on the counts of Clostridium perfringens, Lactobacillus/Enterococcus and total bacteria. Like salinomycin, nisin supplementation improved broiler growth performance in a dose-dependent manner; compared to the NC group, the body weight gain of the NI900 and NI2700 groups was improved by 4.7 and 8.7%, respectively. Our findings suggest that dietary nisin exerts a mode of action similar to salinomycin and could be considered as a dietary supplement for broiler chickens.
Highlights
Lactic acid bacteria (LAB) of the genera Lactococcus, Streptococcus, Pediococcus, Leuconostoc, Lactobacillus and Carnobacterium are the most commonly used starter cultures in food industry. Their mode of action is mainly based on the antimicrobial effect of lactic acid and pH reduction in combination, but certain LAB are capable of producing different types of bacteriocins, which are small peptides, lethal to bacteria other than the producing strain, but most often with a rather narrow target spectrum in comparison to antibiotics
The highest counts were observed in the negative control (NC) group, whereas significant reductions were observed with salinomycin and nisin supplementation; for nisin in a dose-dependent manner
A similar trend was observed in ileum, statistically lower short-chain fatty acids (SCFA) and putrefactive SCFA (PSCFA) levels were observed only in the NI300, NI900 and NI2700 groups in comparison to the NC group (Table 4)
Summary
Lactic acid bacteria (LAB) of the genera Lactococcus, Streptococcus, Pediococcus, Leuconostoc, Lactobacillus and Carnobacterium are the most commonly used starter cultures in food industry. Their mode of action is mainly based on the antimicrobial effect of lactic acid and pH reduction in combination, but certain LAB are capable of producing different types of bacteriocins, which are small peptides, lethal to bacteria other than the producing strain, but most often with a rather narrow target spectrum in comparison to antibiotics. In a series of our studies, we have recently demonstrated significant effects of bacteriocin - divercin AS7 - on the broiler chicken GIT microbiota and fermentation status as well as bird performance [2,3,4,5]. To our knowledge there are no available data on in vivo usage and effects of nisin; probably the most explored and commonly used bacteriocin in many types of human foodstuffs
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