sou · GLB3132d2 · 1998-01-01 00:00:00 — Animal species from which the manure originates and dry matter content is of prime importance, but feed composition, management factors and geographic area may also influence the composition of the manure. Other factors that may affect the outcome of degradation studies are temperature, light, oxygen concentration, microbial composition in soil and manure, and sampling procedures. The methods for analysing the substance in question, as well as its major metabolites, must also be standardised. When all these requirements are fulfilled, it will still be very difficult to apply the results of experimental studies to the environment as a whole. Antimicrobial substances that are released into the environment via faeces will disperse through a number of transport mechanisms. A model for this was presented by (1984), in which volatilisation, degradation, diffusion, adsorption to sediment, losses to ground water and streams etc. is calculated. This model clearly illustrates the complexity of the matter and how difficult it is to predict the exact fate of antimicrobials that are released into the environment. Various studies have been reported on aerobic degradation in soil of substances used as including bacitracin, tylosin spiramycin and flavomycin (Bewick, 1978; Jagnow, 1978; Bewick and Tribe, 1980; Gavalchin and , 1994). Most study designs are fairly simple; the substance under investigation is mixed with soil or soil/manure mixes and the decline in concentration under different conditions is measured over time. Most substances appear to have a half life in soil of about 2-3 weeks at , while lower temperatures generally cause a slower degradation. In sterile soil, no degradation occurs, indicating that microbes are essential for the process (Gavalchin and , 1994). Two studies have been found that demonstrate no uptake of tylosin (Bewick, 1979b) or bacitracin (Vogtmann ET AL , 1978) by vegetables from soil fertilised with AFA-containing manure. For the quinoxalines, no information has been found. Being synthetic substances, they are of special interest as they might not be as easily degradable by existing soil microflora. Some losses to surface or ground water are to be expected. Bewick (1979a) demonstrated a notable difference in adsorptive capacity of different clays. When release from soils was studied, the concentration in leakage was related to the amount of tylosin applied. Under practical conditions, the degree of leaching will depend, among other things, on fertilising practices, weather conditions and type of soil. In view of the large variation of such factors within Union, experimental data are especially difficult to interpret. No data on degradation in water has been found. Larger standardised studies would be necessary to draw firm conclusions on the environmental burden (Bouwman and Reus, 1994). As light and temperature are important variables regarding degradation times, it may be necessary to conduct separate studies for application to different geographic areas. Most antibiotic appear to have a half life in soil of about 2-3 weeks at . Information is lacking on the synthetic substances (quinoxalines). to the complexity of the matter, it is difficult to predict the exact fate of antimicrobials that are released into the environment. 6.3Effects of on the environment Many ecosystems depend on complex microbial interactions. Soil is a heterogeneous system with a mixed biota and fluctuating local conditions. The microbiota is essential for supplying nutrients to crops, stimulating plant growth, control or inhibition of the activity of plant pathogens and improvement of soil structure. Microbes are also important in the degradation of pollutants. Disruption of these microbial populations is detrimental for agriculture as well as for the society as a whole. Antibacterial substances such as , if present in animal wastes in inhibitory concentrations, are expected to affect the environmental microflora. Bewick (1978), in one of a series of experiments on waste from tylosin production, investigated the effects of added tylosin on various parameters for soil activity. At concentrations corresponding to 37 ppm or more, nitrogen mineralisation was reduced. A decrease in microbial respiration could be noted for 5 to 7 weeks after the addition of the antibiotic. Degradation of most would be expected during composting (Vogtmann ET AL , 1978). Other microbial systems could be affected. Treatment of wastewater from animal production facilities and slaughterhouses, as well as sewage, often includes a microbial process. This may be impaired by low concentrations of antimicrobial substances in the wastewater. No information has been found on this subject. Source separated municipal solid waste and agricultural waste can be utilised for biogas production. Substances with an antimicrobial effect against anaerobic bacteria could disturb this process. Thaveesri (1994) found that monensin negatively affected the performance of UASB (upflow anaerobic sludge blanket) reactors. Contrary to this, in studies on manure from pigs and poultry fed avilamycin, (1989) reported efficient operation of experimental and large mesophilic digesters. The presence of avilamycin appeared to alter the metabolism of the microflora, increasing the efficiency to degrade volatile solids. Considerable research and investments are currently spent on optimising biogas plants in order to meet with the requirements for more sustainable systems. In such highly efficient, modern anaerobic digestion plants, the processes are strictly controlled. The effects of on such sensitive systems must therefore be carefully evaluated. Albeit transient, the deleterious effects of antibiotics on environmental microflora cannot be ignored. The beneficial effect of on nitrogen excretion and total amount of animal manure has been widely discussed (and Kirchgessner, 1993; Lindermayer and Propstmeier, 1994; , 1994; Verbeke and Viaene, 1996). This effect is a consequence of the improved feed efficiency associated with use. The amounts of nutrients excreted in faeces and urine are lowered in proportion to the decreased amount of feed consumed by the animals, i.e. by approximately (Thomke and Elwinger, 1997). In combination with , high protein diets are often used. Dietary manipulations can also reduce nitrogen excretion while maximum growth is maintained (, 1995; Cromwell ET AL , 1996; , 1996). Multiphase feeding, where the daily supply of nutrients is adjusted as closely as possible to the requirements of the animals, will substantially reduce nitrogen excretion while supporting maximum growth (, 1996). Appropriate feeding strategies will not only affect nitrogen excretion, but also reduce pollution by other substances, such as phosphorus and trace elements. Investments in feed storage, feed preparation and feed distribution with computerised automated systems may be costly but adjustment to the physiological requirements of the animals may still be a beneficial alternative to costly waste treatments and the risk of future environmental damage. It appears logical that the amount of nitrogen in the feed will affect the amount of nitrogen excreted in faeces and urine. A pig feed with a protein content of with added amino acids will result in similar or smaller nitrogen excretion per animal than feed with protein content supplemented with (and Kirchgessner, 1993; , 1995; Verbeke and Viaene, 1996). Supplementations of feed with enzymes and probiotics also aim at a situation in which a greater share of the nutrients supplied in the feed is made available for absorption by the animal. The higher rate of nutrient absorption leads to a lowered output with animal voiding. The protein content of both pig and broiler feed in was reduced as a consequence of the ban of enforced in 1986 (Wierup, 1996). This has been possible since several crystalline amino acids are available at competitive price levels. Although the alteration in feed composition was primarily aimed at avoiding intestinal disturbances, there were also benefits in terms of lowered nitrogen excretion. When discussing nitrogen load it is also important to remember that inorganic fertilisers added to agricultural soil contain a substantial amount of nitrogen. As an example, the amount of nitrogen fertilisers used in , and expressed in kg/hectare cultured land in 1995 was 120, 140 and 70 respectively (SCB, 1997). Finding ways of a better utilisation of the nitrogen in manure as a fertiliser, thereby reducing the need for inorganic fertilisers, would perhaps be a better way of reducing total nitrogen load than reducing the nitrogen content of manure. Presence of non degraded in manure or wastewater will impair the microbial activity in the recipient habitats, lowering the turnover capacity of the microbiota. The usage of leads to lower excreta nutrient discharges in pigs and poultry. given diet that improves nutrient absorption will also reduce nutrient losses with animal voiding. 6.4Antimicrobial resistance genes in the environment Faeces from animals fed contains not only bacteria carrying genes coding for resistance against these substances, but also the substance itself, thereby providing a selective pressure that may further the spread of the genes. This is not primarily a problem for the environment, although some possible implications will be discussed in 6.4.4. 6.4.1 Persistence of resistant bacteria in the environment In order to have an influence on the environmental pool of resistance genes, bacteria carrying the genes must persist for some time in the environment. Animal bacteria would be expected to disappear from the soil surface under the influence of sunlight, but they may persist deeper in the soil for some time. Around farm , enterococci and % COLI can be isolated from soil (Parrakova and Fratric, 1980). Mackey and Hinton (1990) investigated the survival of streptococci and enterococci on straw. After 4 weeks, the inoculated bacteria could still be isolated although their numbers were reduced. and (1996) found that salmonellae from infected calf carcasses could diffuse into soil and persist for up to 21 months, while bacilli and clostridia from the same source could persist in soil for more than two years. The salmonellae could also be isolated from wild-bird droppings, maggots and surface water for 4 weeks after burial of the carcasses. Hinton and (1982) reported survival of multiresistant salmonellae and % COLI in slurry for at least 7 weeks. Thus, bacteria of animal origin (both gram- positive and gram-negative) appear to be able to contaminate soil for prolonged periods of time. 6.4.2 transfer in the environment transfer occurs readily in almost any environment. It has been shown that gene transfer can occur in soil between different bacteria, by various mechanisms (Bale ET AL , 1988; and , 1990; Top ET AL , 1990; Cresswell and , 1992; Lilley ET AL , 1994). and Sørum (1994) demonstrated the transfer of multiple drug resistance plasmids between various bacterial species in diverse household microenvironments. Timoney and (1982) showed that transfer of a specific plasmid between different strains of % COLI from calves in faeces occurred at but not at . This indicates that some transfer systems in animal bacteria are adapted only to environmental conditions. transfer to soil bacteria can occur from bacteria that will not themselves survive for long in the soil. The addition of nutrients, as when manure is spread on farmland, and the presence of plant roots, provide a favourable environment in which an increased bacterial metabolism and gene transfer would be expected (Cresswell and , 1992; Lilley ET AL , 1994). When studying gene transfer in the soil microenvironment, many factors may influence the result. For example, temperature, humidity and pH are important, as well as the bacterial species used in the experiments. Soil micro-organisms such as pseudomonads, bacilli and streptomycaetes are well adapted to growth in the soil environment and may transfer and maintain resistance genes in these environments better than do coliforms (Cresswell and , 1992). Methodological problems such as detection of transfer when the genes are not properly expressed and the vast amount of non-described or non-cultivable bacteria present in soil suggest that the observed transfer frequencies may only be the tip of the iceberg. agricultural soil can contain more than 100 000 different bacterial species (Cresswell and , 1992). It seems obvious that studies on just a few of those cannot provide a basis for conclusions regarding the whole microenvironment. 6.4.3Persistence of resistance genes in environmental bac teria Resistance genes in soil microbes may persist for a long time, even without a selective pressure from antimicrobial substances. transfer from % COLI to soil pseudomonads in a non-sterile, unamended, soil system has been demonstrated, with a persistence of the introduced gene in the recipient bacterium for 100 days (Cresswell and , 1992). If the expression of resistance genes is costly from a metabolic point of view, resistant bacteria are likely to disappear in the absence of a selective pressure. However, this competitive disadvantage may be overcome (see 4.4.5). Bacteria may adjust to the expression of resistance, lowering the metabolic cost. Bale and co- workers (1993) studied the survival of % COLI and its nalidixic acid resistant mutants on dry surfaces. Out of seven resistant mutants, five survived longer compared to the sensitive parent strains. Further, transferable genetic elements carrying resistance genes may also carry other traits of advantage. If so, the resistance genes will still be able to persist in the environment. 6.4.4Possible implications for the environment Co-transfer of resistance genes and virulence genes has been demonstrated, not only in animal and human pathogens, but also in plant pathogens (Amuthan and Mahadevan, 1994). Certain virulence genes in plant and animal pathogens are similar enough to suggest a horizontal spread (Alfano and Collmer, 1996). Theoretically, in the presence of a selective pressure for resistance genes, virulence of plant and wildlife pathogens might increase and non-pathogenic bacteria might acquire virulence. Although purely speculative, this merits further investigation. Similarly, possible co-transfer of resistance to pesticides such as copper or sulphur should be considered. Transfer of genes occurs readily in the environment. Resistance genes can persist in the environment both in their original bacterial hosts and in environmental organisms. Possible co-transfer of resistance genes and other genes in plant pathogens should be investigated. information is publicly available on environmental effects of . According to accessible data, antibiotic present in soil are degraded by microbes. , no major toxic effects on terrestrial or aquatic fauna or on terrestrial plants are expected. Presence of in soil will transiently disrupt the microflora with potentially negative consequences on nutrient mineralisation etc. Further, more information is needed concerning possible effects on modern biogas plants. Presence of and genes encoding for resistance to in manure is not primarily a problem for the environment. Such genes will form part of the resistance gene pool available for animal and human bacteria. !DDISON * " , 1984. Antibiotics in sediments and run-off waters from feedlots. 2ESIDUE 2EVIEWS 1-28. !LFANO * 2 AND #OLLMER ! Bacterial pathogens in plants: life up against the wall. 4HE 0LANT #1683-1698. !MUTHAN ' AND -AHADEVAN ! Plasmid and pathogenecity in 8ANTHOMONAS ORYZAE pathovar ORYZAE. *OURNAL OF !PPLIED "ACTERIOLOGY 529-538. "ALE - * "ENNET 0 - "ERINGER * % AND (INTON - , 1993. The survival of bacteria exposed to dessication on surfaces associated with farm . *OURNAL OF !PPLIED "ACTERIOLOGY 519-528. "ALE - * &RY * # AND $AY - * , 1988. Transfer and occurrence of large mercury resistance plasmids in river epilithon. !PPLIED AND %NVIRONMENTAL -ICROBIOLOGY "EWICK - 7 - , 1978. Effect of tylosin and tylosin fermentation waste on microbial activity of soil. 3OIL "IOLOGY AND "IOCHEMISTRY 403-407. "EWICK - 7 - , 1979a. The adsorption and release of tylosin by clays and soils. 0LANT AND 3OIL 363-372. "EWICK - 7 - , 1979b. The use of antibiotic fermentation waste as fertilizers for tomatoes. *OURNAL OF !GRICULTURAL 3CIENCES #AMBRIDGE 669-674. "EWICK - 7 - AND 4RIBE ( 4 , 1980. The decomposition of tylosin fermentation waste in soil at four temperatures. 0LANT AND 3OIL 249-258. "OUWMAN ' - AND 2EUS * ! Persistence of medicines in manure.CLM 163-1994, pp. CLM, , . AND 7ELLINGTON % - ( EDS , 1992. $ETECTION OF GENETIC EXCHANGE IN THE TERRESTRIAL ENVIRONMENT. Pergamon Press, . #ROMWELL ' , #ARTER 3 $ ,INDEMANN - $ AND 4URNER , 7 , 1996. the excretion of nitrogen and phosphorus in growing and finishing pigs by dietary manipulation. )N PROCEEDINGS OF TH )063 #ONGRESS 7-10 , . $AVIES 2 ( AND 7RAY # , 1996. Seasonal variations in the isolation of 3ALMONELLA TYPHIMURIUM, 3ALMONELLA ENTERITIDIS, "ACILLUS CEREUS and #LOSTRIDIUM PERFRINGENS from environmental samples. *OURNAL OF 6ETERINARY -EDICINE " 119-127. 'AVALCHIN * AND +ATZ , 1994. The persistence of fecal-borne antibiotics in soil. *OURNAL OF THE !SSOCIATION OF /FFICIAL !NALYTICAL #HEMISTS 481-485. (9 , 1996. Feeding strategies for pollution control in pig production. )N PROCEEDINGS OF TH )063 #ONGRESS 7-10 , . (ENSCHKE 2 " AND 3CHMIDT & 2 * , 1990. Plasmid mobilization from genetically engineered bacteria to members of the indigenous soil microflora IN SITU. #URRENT -ICROBIOLOGY 105-110. (INTON - AND ,INTON ! ( , 1982. The survival of multi-antibacterial drug-resistant %SCHERICHIA COLI and 3ALMONELLA TYPHIMURIUM in stored static slurry from a veal calf unit. *OURNAL OF (YGIENE 557-565. *AGNOW ' , 1978. Microbial degradation of the feed antibiotics zinc-bacitracin, flavophospholipol, spiramycin, and of tetracycline in chicken manure, damp-stored and mixed with soil. ,ANDWIRTSCHAFTLICHE &ORSCHUNG 3ONDERHEFT 227-234. +RUSE ( AND 3¸RUM ( , 1994. Transfer of multiple drug resistance plasmids between bacteria of diverse origins in natural microenvironments. !PPLIED %NVIRONMENTAL -ICROBIOLOGY 4015-4021. + &RY * # $AY - * AND "AILEY - * , 1994. )N SITU transfer of an exogenously isolated plasmid between 0SEUDOMONAS spp. in sugar beet rhizosphere. -ICROBIOLOGY 27-33. ,INDERMAYER ( AND 0ROPSTMEIER ' , 1994. Leichtungsförderer über die gesamte Mastdauer? +RAFTFUTTER .O 479-481. -ACKEY % 4 AND (INTON - , 1990. The survival of streptococci and enterococci in animal feed and on straw with particular reference to 3TREPTOCOCCUS . *OURNAL OF !PPLIED "ACTERIOLOGY 345-348. 0ARRAKOVA % AND &RATRIC ) , 1980. Soil contamination in the environment of intensive farming units. !GRICULTURAL 7ASTES 161-170. 2OTH & 8 AND +IRCHGESSNER - , 1993. Influence of avilamycin and tylosin on retention and excretion of nitrogen in growing pigs. *OURNAL OF !NIMAL 0HYSIOLOGY AND !NIMAL .UTRITION 175-185. 2OTH & 8 7INDISCH 7 AND +IRCHGESSNER - , 1994. Influence of Avilamycin and Tylosin on fecal excretion of nitrogen and amino acids in growing pigs. !GRIBIOLOGICAL 2ESEARCH 147-155. 3#", 1997. Jordbruksstatistisk årsbok 1996. pp. , .YE * # 0ATTERSON * ! +ELLY $ 4 AND &URUMOTO %LKIN % * , 1989. Effects of avilamycin in swine and poultry wastes on methane production in anaerobic digesters. "IOLOGICAL 7ASTES 35-45. 4HAVEESRI * "OUCNEAU ' AND 6ERSTRAETE 7 , 1994. Effect of monensin on UASB- reactor performance. %NVIRONMENTAL 4ECHNOLOGY 491-496. 4HOMKE 3 AND %LWINGER + , 1997. Growth and feed efficiency responses to antibiotic growth promotants in pigs and poultry. Report to the Commission on Antimicrobial Feed Additives. 4IMONEY * & AND ,INTON ! ( , 1982. Experimental ecological studies on H2 plasmids in the intestine and faeces of the calf. *OURNAL OF !PPLIED "ACTERIOLOGY 417-424. 4OP % -ERGEAY - 3PRINGAEL $ AND 6ERSTRAETE 7 , 1990. escape model: transfer of heavy metal resistance genes from %SCHERICHIA COLI to !LCALIGENES EUTROPHUS on agar plates and in soil samples. !PPLIED AND %NVIRONMENTAL -ICROBIOLOGY 2471-2479. 6ERBEKE 7 AND 6IAENE * , 1996. Environmental impact of using feed additives. 7IERUP - , 1996. förbjöd antibiotika i tillväxtbefrämjande syfte 1986 - vad hände med djurhälsan och hur löstes problemen? +UNGLIGA 3KOGS OCH ,ANTBRUKSAKADEMIENS 4IDSKRIFT 69-78. 7ILLIAMS 6 , 1995. Animal production and European pollution problems. !NIMAL &EED 3CIENCE AND 4ECHNOLOGY 135-144. 6OGTMANN ( /BRIST 7 (AUSER + 0FIRTER ( 0 AND !UGSTBURGER & , 1978. Composting and plant growth: use of chicken manure containing antibiotics. #OMPOST 3CIENCE ,AND 5TILIZATION 22-25. Coccidiosis is a severe, world wide health and welfare problem in poultry. The disease is caused by unicellular parasites which grow and multiply in the intestinal mucosa of the birds. Commercially reared chickens are particularly vulnerable to the disease due to the intensive production systems. Since the early 1940s various drugs have been used to treat and/or prevent coccidiosis in poultry. Coccidiostats have in fact contributed substantially to the remarkable success of modern poultry production. In the EU coccidiostats are incorporated in the feed, as feed additives, while in , coccidiostats are regarded as pharmaceutical specialities (i.e. medicated feed) and are only available on veterinary prescription. Included among the coccidiostats used in poultry are the ionophoric antibiotics and various chemotherapeutic substances. Two of the ionophores, monensin and salinomycin are also used as growth promoters, in cattle and swine, respectively. 7.1.1 The parasite and the disease Several reviews of the coccidiosis problem in poultry have been published (and Long, 1963; Macpherson, 1978; Long and , 1982; Long, 1990). Since knowledge of the disease is essential for the discussion about coccidiostats in modern poultry production, some basic information about coccidia and coccidiosis will be presented in the following. Coccidiosis is caused by intestinal protozoa of the phylum Apicomplexa. Most coccidia of domestic fowl belong to the genus %IMERIA Each poultry species may be infected with several different %IMERIA species which are host specific and of varying pathogenicity. Seven different coccidial species can infect chickens. The parasites are transmitted via oocysts, shed in the faeces of infected hosts and ingested by uninfected birds. Coccidia multiply in epithelial cells in the intestinal mucosa and sometimes also in other organs of the host. The severity of the infection depends on the coccidial species, host immunity and on the dose of ingested oocysts. birds are highly susceptible to coccidiosis since they, to a large extent, lack passively transferred maternal immunity. Immunity is best developed by repeated exposure to small numbers of oocysts. Additionally, immunity to coccidia is species specific which means that resistance to one coccidial species does not confer resistance to another species. The symptoms of coccidiosis include mucoid to haemorrhagic diarrhoea, depression, emaciation and depressed growth rate. Sometimes mortality is high. The location and nature of the lesions in the host intestinal mucosa depend on the coccidial species. Birds with clinical coccidiosis can be treated with water-soluble sulphonamides, amprolium or toltrazuril. Coccidia are ubiquitous parasites which are easily introduced into poultry houses. to the persistent nature of the oocysts, and the propagation in the birds, a considerable population of oocysts will be established in the during the rearing period. As commercially reared young chickens, with insufficient immunity to coccidia, are kept in large numbers in high stocking density productions systems the disease becomes a severe problem if not prevented.