УДК 502.53 + 504.064 + 591.13
К. В. Опалинский*, Е. Дмовская*, С. Г. Пиржиновский**
* Центр экологических исследований Польской академии наук, Дзиканов/Варшава, Польша
E-mail: firstname.lastname@example.org, email@example.com
**Университет Лунда, Лунд, Швеция, E-mail: firstname.lastname@example.org
Ключевые слова: пищевые добавки, антибиотики, почва, микрофлора, фауна
THE REVERSE OF THE MEDAL: FEED ADDITIVES AND SOIL SYSTEM
K. W. Opaliński*, E. Dmowska*, S. G. Pierzynowski**
*Center for Ecological Research Pol. Acad. Scis, Dziekanów/Warsaw, Poland,
E-mail: email@example.com, firstname.lastname@example.org
**LundUniversity, Lund, Sweden, E-mail: email@example.com
Key words: feed additives, antibiotics, soil, microflora, soil fauna
Present-day livestock production uses antibacterials (antibiotics) not only as therapeuticals in veterinary medicine, but also as growth promoters, which results in high production of meat, milk, eggs and animals health too.
Antimicrobial Growth Promoters (AGP), or Antimicrobial Feed Additives (AFA) were added to the feed of all kinds of domestic animals – from piglets and poultry to fish, since 1949 in USA and since 1952 in Europe. There are probiotics and prebiotics, coccidiostats but first of all antibiotics: avilamycin, bacitracin, flavomycin, avoparcin, spiramycin, tylosin, virginiamycin, carbadox and some others. In European Union all those substances can be used in livestock production in accordance with the procedures laid down in article 7 of the directive 70/524/EEC concerning additives in feedingstuffs and medicinal feed additives.
The wonderful averse of the antibiotic medal there is higher animal growth rate and lower death rate of infants, better feed utilization and carcass quality, better welfare and health of animals, and benefits for livestock producers.
Antibiotics are poorly or not at all absorbed from the alimentary tracts of an animal, a substantial quantity of the administered doses are excreted with faces and urine as active substances and ends up in the environment – in fields (as manure) and in pastures and other grass–lands – in their soils.
But there is also the black reverse of the medal – the hazards and risks associated with potentially genotoxicity of some antibiotics, their toxicity for target species, and therapeutic effect on human health. The last effect, practically not known, there is effect on the environment – on the soil, on its flora and fauna and on functioning of soil ecosystem.
The aim of the present study was to compare the effect of application of pig manure from animals fed on standard forage with antibiotics and without antibiotics, on selected processes and organisms in a soil system. We hypothesized that changes in soil ecosystem after application of manure with antibiotics would differ from those found after application of manure without them.
In experimental farm two groups of piglets were fed with special forage without antibiotic (prepared by Gramminer AB, Sweden) and on standard forage with antibiotic. Manure from both groups were transported to the experimental fields. Measurements and experiments were made on two types of experimental fields: first one fertilized with manure from animals fed on special forage without antibiotics, and the second one fertilized with manure from animals fed with standard forage with antibiotic.
In the field experiment we have measured: microbial (fungi and bacteria) biomass, activity of decomposition processes, abundance and population structure of soil nematodes and enchytraeids, biomass and structure of higher plants community.
The maximum effect of antibiotics on soil community was observed four weeks after the treatment. After fourteen weeks all effects fall down to the control level, but some of them can be observed even after forty six weeks (in the next growing season).
After four weeks the biomass of bacteria (measured by Substrate Induced Respiration method) in soil with antibiotics was by 17 % lower in comparison with soil without antibiotics, and the biomass of fungi in soil with antibiotics growth up. This effect was reduced in subsequent weeks and was not visible in the fourteenth week of exposition.
The rate of organic matter (cellulose) decomposition by litter bag method was slightly lower in soil with antibiotics. The rate of nitrification of ammonia to nitrate in soil with antibiotics was lowering too.
Nematode population in soil without antibiotics was more numerous than in soil with antibiotics, but the difference was not statistically significant.
Significantly more bacterial-feeding nematode were found in soil without antibiotics – this difference was observed also forty six weeks after the treatment, i.e. in subsequent growing season. Density of plant-feeding and fungal-feeding nematodes was higher in soil with antibiotics. The abundance of other ecological groups of nematodes (predatory and omnivorous) in both soils was low and the difference between them was not significant.
The answer of soil mesofauna on antibiotics was not clear – in the beginning of exposition the density of enchytraeids in soil with antibiotics significantly growth up. But after twelve weeks the abundances of mesofauna in both soils were lowered.
Eight weeks after the treatment the species biodiversity of vascular plants in the soil with antibiotics fall down – the lack of characteristic species for meadow community was observed, and density of nitrophilous and ruderal plant species growth up.
The above-ground biomass of plants, specially of monocotyledons, on soil with antibiotics was by 1/3 higher than in soil without antibiotic.
The results of this study confirm our hypothesis. Some of studied microbial, micro- and mesofaunal and plant community parameters in soil with antibiotics differ from those from «clear» soil, fertilized without antibiotics. The result showed that the rate of two very important soil processes: organic matter decomposition and ammonia nitrification are checked by antibiotics– probably antibiotics had negative effect on the bacteria responsible for those processes. In the other hand antibiotics provide better conditions for development of fungi. The supposition can be made that mycorrhizal fungi also grew better in presence of antibiotics – it could explain the higher biomass of vascular plants.
The changes in bacteria / fungi balance in the soil under influence of antibiotics affect the function of mesofauna structure and its activity – under influence of antibiotics the grazing food web pathway predominate the detritus food web pathway.
On the basis of the obtained results one can conclude that manure from animals fed on forage with antibiotics affects soil environment and soil community, their structure and function. The effect of antibiotics is well visible on target organisms (bacteria) as well as on non target organisms, such as fungi, micro- and mesofauna, and also higher plants.
The reverse of the antibiotic medal is rather black. Can we throw antibiotics away from our livestock production as a growth promoters? Yes, we can. Than death rate in piglets will grow up two times, body mass production falls down by 16 %, and feed utilization by 7 %. Than prices of pork will grow up by 8 %, of poultry by 3 %, eggs by 11 %, etc. etc. etc.
This work was funded in part by Svenska Institutet (Visbyprogrammet 390/4968/1977 no 39) and in part by Polish Committee for Scientific Research (KBN 6 PO4G 050 16).
Zoocenosis — 2005
Біорізноманіття та роль зооценозу в природних і антропогенних екосистемах: Матеріали ІІІ Міжнародної наукової конференції. – Д.: Вид-во ДНУ, 2005. – С. 205-207.