Reducing bacterial and mould loads
by Sakchai Himathongkham and Hans Reimann, University of California Davis, CA 95616. USA and Ram Saini, Preserve International, POÂ Box 3135, Turlock, CA 95381,USA
In some countries poultry litter is not always removed between cycles and, therefore, needs to be disinfected in situ.
Most of the pathogenic microorganisms do not survive well in the deeper layers of old litter.
This is probably because of an accumulation of ammonia and a reduction of oxygen resulting from the activity of saprophytic microorganisms.
The surface of the litter represents a risk. Here pathogenic bacteria are deposited and moulds can produce spores.
The application of a liquid acid complex to the surface of litter is a potentially effective method of reducing the numbers of pathogenic microorganisms.
Most of the disinfectants approved for use in poultry houses cannot efficiently kill microorganisms in the litter because of the high load of organic matter.
Formaldehyde is a very potent disinfectant. However, it causes irritation and is a potential carcinogen. Dyno-0-Might seems to be aÂ good alternative to formaldehyde. It is composed of organic acids that are recognized by FDA a, GRAS (General Recognized As Safe) and are not carcinogenic.
In a study undertaken by scientists from the University of California and Preserve International, the manufacturers of the disinfectant, its effect onmicroorganisms on the surface of broiler chicken litter was measured.
Two poultry houses with litter of wood shavings on which three flocks of broilers had, been raised were used in this study.
Sterile drag swabs moistened with double strength skimmed milk were used for surface sampling of litter and walls. Approximately 0.84m' was covered by each swab.
Forty swabs were used to sample the floor (152 x 12m) and 10 swabs to sample the walls just above the floor. The swabs were combined in numbers of five and placed in sterile Whirl-pak bags.
To each bag was then added 100ml sterile 1% protease pep- tone which, after shaking, was plated on nutrient agar (for total plate count), eosinmethylene blue agar (for E. coli), brilliant green novobiocin agar (for salmonellae), tryptose-sulphite cycloserin egg yolk agar (for Clostridium perfringens) and Sabouraud agar for yeasts and moulds.
10ml of the liquid in the Whirl-pak bags was transferred to two Whirl-pak bags with 90ml protease peptone and two more 10-fold dilution's were made in duplicate for most probable number estimation.
The Whirl-pak bags were incubated for 20 hours at 37'C.
The pre-enrichment broth was cultured in tetrathionate broth for 24 hours at 37'C and then streaked on brilliant green novobiocin agar that was incubated for 48 hours at 37'C for detection of salmonellae.
Â Suspect colonies were inoculated on triple sugar iron agar for confirmation.
The two houses were sampled for bacteria on 4th March 1994 and again on 15th March, three days after spraying with Dyne-O-Might solution. A second test for moulds was done on 19th May. On this occasion only floors were sampled and only one hour or less elapsed between spraying and sampling for mold and acidity test (pH)
There was a consistent decrease in. microbial counts after spraying with Dyne-0-Might. The counts of E. coil were low, only around 100 per swab, even before spraying and the counts of salmonellae were too low, 1-3 per swab, to permit conclusions.
However, total aerobic viable counts (over 100 million) and C. perfringens counts (between 1000 and 10,000) before spraying were high enough to demonstrate a significant reduction.
Spraying reduced pH temporarily to very low values, which probably explains the killing effect (Fig. 2)