Probiotics are said to offer potential as an alternative to antibiotics for pigs, both as a means of controlling enteric pathogens and improving growth rate and feed conversion.
Writing in the journal Plos One, the researchers say the Bacillus pumilus use in their experiment decreased ileal E. coli counts in a manner similar to a medicated treatment but without the adverse effects on growth performance.
Weaning is a stressful event for young pigs characterized by gastrointestinal disturbances caused by physiological, immunological and microbiological changes within the gastrointestinal tract.
During this period, say the authors, pigs are highly susceptible to enteric diseases, and those caused by E. coli are responsible for considerable economic losses in the pig industry.
As a result, in-feed antibiotics have long been used for the elimination or reduction of pathogenic bacteria, in particular E. coli, during the post-weaning period.
While their routine use has been banned in the EU since 2006, antibiotics are still permitted in feed under veterinary prescription as the need arises.
In-feed zinc oxide, at pharmacological concentrations, is also commonly used for enteric disease prevention in weaned pigs but there are concerns about its accumulation in the environment.
Marine probiotic potential
The marine environment is largely untapped as a source of probiotics but should not be overlooked given that it is a potential source of novel microorganisms and that antimicrobial production is common amongst marine microflora, said the researchers,
They noted that one strain of Bacillus pumilus showed most promise for animal feed “as it satisfies a number of probiotic criteria and has activity against E. coli without being cytotoxic.
However, as with any potential feed additive, observations made in vitro need to be substantiated with in vivo data and, to date, this marine B. pumilus strain has not been tested in vivo."
The objective of the present study, said the authors, was thus to evaluate this pre-screened Bacillus strain for use as an in-feed probiotic for weaned pigs in comparison to a negative control treatment without antibiotic or pharmacological levels of zinc oxide (non-medicated and a positive control treatment with apramycin and pharmacological levels of zinc oxide (medicated).
Key parameters including growth performance and health indicators were investigated in order to evaluate safety and efficacy in vivo.
Forty eight individual pigs weaned at 28 days of age were evaluated over 22 days to determine the effect of oral administration of a Bacillus pumilus spore suspension on growth.
The authors found that final body weight and average daily gain tended to be lower and feed conversion ratio was worsened for the medicated treatment compared to the B. pumilus treatment.
Ileal E. coli counts were lower for the B. pumilus and medicated treatments compared to the non-medicated treatment perhaps as a result of increased ileal propionic acid concentrations.
However, the medicated treatment reduced fecal and cecal Lactobacillus counts and tended to reduce the total cecal short chain fatty acid (SCFA) concentration, said the team.
Liver weights were lighter and concentrations of liver enzymes higher in pigs on the medicated treatment compared to those on the non-medicated or B. pumilus treatments.
Pigs on the B. pumilus treatment had lower overall lymphocyte and higher granulocyte percentages and higher numbers of jejunal goblet cells than pigs on either of the other two treatments or the non-medicated treatment, respectively.
However, histopathological examination of the small intestine, kidneys and liver revealed no abnormalities.
Overall, the B. pumilus treatment decreased ileal E. coli counts in a way similar to the medicated treatment but without the adverse effects on growth performance, Lactobacillus counts, cecal SCFA concentration and possible liver toxicity occurring with the medicated treatment.
Journal: PLoS One. 2014; 9(2): e88599.
Published online Feb 26, 2014. doi: 10.1371/journal.pone.0088599
Title: Evaluation of the Efficacy and Safety of a Marine-Derived Bacillus Strain for Use as an In-Feed Probiotic for Newly Weaned Pigs
Authors:Prieto ML et al