What is CLOSTAT®?

CLOSTAT® contains a proprietary, patented strain of Bacillus subtilis PB6. PB6 is a unique, naturally occurring, spore-forming microorganism, which Kemin has identified and selected as an active substance that helps maintain the balance of microflora in the intestinal tract of livestock (Figure 1).

Bacillus subtilis PB6 in the intestine

Figure 1. Bacillus subtilis PB6 in the intestine.


  • Contains PB6, a unique, patented strain of Bacillus subtilis
  • Stable during processing and packaging
  • Stable when blended with other feed ingredients
  • Stable under normal commercial pelleting conditions
  • Compatible with antibiotics, coccidiostats and organic acids commonly used in the animal feed industry
  • Proven efficacy in research


  • Mineral premix concentrate (oxides, sulfates) for three weeks
  • Long-term: temperatures ranging from 5°C (41°F) to 65°C (149°F) for one year
  • Short-term: 194°F (90°C) for 10 minutes
  • Resistant to acid conditions of pH 2.0 for 90 minutes
  • Stable during processing and packaging, when blended with other feed ingredients and under normal commercial pelleting conditions

Mode of Action

Bacillus subtilis PB6 secretes molecules that are inhibitory toward various strains of bacteria including ClostridiumSalmonella and E. coli spp1 (Figure 2). In vitro studies have shown that PB6 is efficacious in inhibiting bacterial growth, such as Clostridium, in swine, poultry, cattle and equine.1,2 Inhibition or reduction of bacterial growth can decrease the animal's overall susceptibility to primary and secondary intestinal challenges that can affect overall production efficiency.

Pathogen cell
Pathogen cell wall disruption

Figure 2. Pathogen cell wall disruption.

Reducing the Negative Impact of Pathogenic Salmonella typhimurium in Weaned Holstein Steers

A research trial conducted with the United States Department of Agriculture at the Livestock Issues Research Unit in Lubbock, TX, evaluated the potential for CLOSTAT, a patented strain of Bacillus subtilis active microbial, to reduce the severity of salmonellosis in weaned Holstein steers challenged with Salmonella typhimurium.2 Calves were fed either control diets (no CLOSTAT) or 13 g/h/d CLOSTAT in a starter ration for 35 days. Calves were then assigned to one of four treatments consisting of CLOSTAT or no CLOSTAT and Salmonella (1.6 x 106 Salmonella typhimurium) or no Salmonella. The CLOSTAT calves displayed decreased rectal temperatures (P < 0.001) after the study compared to the control calves challenged with Salmonella.

Mounting an immune response to a pathogen challenge requires a significant amount of energy. It has been estimated that an increase in core body temperature by 1°C requires an increase of 10-13 percent in an animal’s metabolic rate.3 Mediating this change in body temperature would potentially spare glucose, allowing energy to be put towards other productive functions.

Effect of CLOSTAT on rectal temperature of weaned Holstein steers challenged with Salmonella