Kajian Penggalak Tumbesaran

https://umexpert.um.edu.my/file/publication/00010306_141757.pdf

1. Introduction

The contamination of veterinary drugs in the environment has been an important issue because their residues could result in the increase of drug resistance bacteria and antibiotic-resistance infection (Lombardo-Agüí et al., 2015). In Malaysia, sulfonamides have been detected in effluents from swine farms (Malintan andMohd, 2006), and the residues have been detected in chicken meat products (Cheong et al., 2010). Additionally, broiler manure and manure-amended agricultural soils have been contaminated by veterinary antibiotics and progesterone (Ho et al., 2014). These facts indicate that veterinary drugs are commonly used in Malaysia, and drug resistance bacteria or antibiotic-resistance infection could become a serious environmental issue. Beta-agonists are one of the most common veterinary drugs to treat cardiogenic shock, acute heart failure, bradyarrhythmias, asthma and chronic obstructive pulmonary disease for livestock as well as to treat diseases and infections for humans (Yu et al., 2011). However, they have been abused as a growth promoter for live-stock, which could lead to a considerable muscle mass increase as well as a decrease in fat accumulation (Mersmann, 1998). In Malaysia, swine farms had been alerted to the possibility of abusing beta-agonists for producing leaner meat by the Ministry of Health Malaysia (Ponniah et al., 2004). Beta-agonist residues produced via improper use could lead to adverse effects as a long-term treatment of beta-agonists in patients with obstructive airway disease, including an increased risk for adverse cardiovascular events (Salpeter et al., 2004). All drugs approved for use in food-producing animals have a withdrawal time to prevent residues in food of animal origin that are potentially harmful to consumers (Gehringa et al., 2004). The withdrawal time is defined as the time that should be elapsed after the administration of a pharmacologically active substance to the time when treated animals can be slaughtered for the production of safe food stuff (Damte et al., 2012). In other words, a residual concentration in a tissue must be below a given maximum residue limit (MRL) when the animals are slaughtered and sold on the market. Beta-agonists, except ractopamine for swine, are listed as prohibited drugs for food in Malaysia (Din et al., 2015); however, beta-agonist residues (terbutaline, salbutamol and clenbuterol) have been detected in swine liver specimens (Ponniah et al., 2004). Regular inspections of veterinary drug residues in animal products are conducted in certified poultry processing plants and slaughter houses by the Department of Veterinary Services Malaysia, whereas those in wet markets are under jurisdiction of the Ministryof Health Malaysia (personal communication). Therefore, it is a concern that beta-agonists and other veterinary drugs could be abused among some livestock farms. Given the illegal use of beta-agonists among livestock farms, their waste water could be contaminated by the abused drugs and discharged from the farms. There is no specific regulation or federal law for livestock effluent standards except for the regulations that are enforced through various state enactments and by-laws (Sakaiet al., 2016). Waste water treatment depends on livestock farms, except for swine farms that have been obliged to attach at least 3 retention ponds. There are a number of livestock farms in the Langat River basin; this basin has a major role in supplying tap water to the capital region, whereas the contamination of beta-agonists in their waste water has not been elucidated. To scruti-nize a potential for their environmental impacts, their occurrence and spatial distribution in the Langat River basin need to be clarified. In the present study, cattle, chicken and swine liver specimens were purchased at 14 wet markets in Kuala Lumpur and Selangor state, and 14 beta-agonists were analyzed to identify their residues and elucidate the health risks caused by them in local consumers. Four wastewater samples were collected at swine and cattle/cow farms, and the 14 compounds were analyzed to spatially assess their environmental impacts in the Langat River basin using a geographic information system (GIS). The main objective of thisstudy is to holistically elucidate the environmental and human health risks caused by the use of beta-agonists.

2.5. Health risk assessment of beta-agonist residues in meat 

The health risks of ractopamine and clenbuterol residues incattle, chicken and swine meat were assessed at an estimated maximum daily intake by a local consumer using an average weight (62.65 kg) (Azmi et al., 2009). The observed maximum concentra-tions in liver specimens (i.e., parent compound) were converted tothe total residue concentrations (i.e., parent compound and its metabolites) based on the percentage of their parent compounds in liver after oral administration (Joint FAO/WHO Expert Committeeon Food Additives, 2004). Their concentrations in muscle were estimated by the biodistribution data in liver and muscle after oral administration (Joint FAO/WHO Expert Committee on Food Additives, 2004). The maximum daily intake of these residues from cattle, chicken and swine meats was calculated from the estimated concentrations in muscle multiplied by a daily con-sumption of the respective meat in Malaysia (Ministry of HealthMalaysia (2014a)). The estimated maximum daily intake wasdivided by an acceptable daily intake (ADI) of ractopamine (JointFAO/WHO Expert Committee on Food Additives, 2004) and clen-buterol (Joint FAO/WHO Expert Committee on Food Additives,1998) to calculate a hazard quotient, which indicates health risks if its value exceeds 1.

3.1. Beta-agonist residues in cattle, chicken and swine livers 

Table 3 shows concentrations of residues of beta-agonists detected in cattle, chicken and swine liver specimens collected at 14 wet markets. Ten beta-agonists (salbutamol, cimbuterol, ractopamine, clenbuterol, brombuterol, tulobuterol, mabuterol, hydroxymethyl clenbuterol, clenpenterol and mapenterol) were detected in the specimens (Tables S1eS3). In particular, ractopamine was detected in almost all swine liver specimens, and its maximum concentration (21.6mg/kg) was much higher than that of the other detected compounds. The wide range of residual con-centration (0.42e21.6mg/kg) of ractopamine was derived from its rapid excretion and was dependent on the withdrawal period because 84.7% was excreted during the first day after the oral administration of 14C-ractopamine hydrochloride (Dalidowiczet al., 1986). Chicken liver specimens had the most positive detection of 9 compounds; ractopamine and mabuterol were detected in more than half of the specimens. In Malaysia, ractopamine is permitted for swine, and its MRLs are established by the Ministry of Health Malaysia (2014b), whereas ractopamine for other live stockand any other beta-agonists are a prohibited treatment (Din et al.,2015). Therefore, the compounds other than ractopamine detected in swine liver were suspected to be illegally abused among livestock farms. Tulobuterol is used as a feed supplement to increase feed efficiency to induce the production of leaner meat (Huang et al., 2016), and brombuterol and mabuterol had been detected in cattle urine and feed samples in the Netherlands (Kuiper et al., 1998). Therefore, all the prohibited compounds with similar chemical structures could be abused for producing leaner meat without considering their withdrawal period.3.2. Health risk assessment of beta-agonist residues in meat. A health risk assessment of ractopamine and clenbuterol was carried out based on ADIs set by the Joint FAO/WHO Expert Committee on Food Additives (1998, 2004). Their hazard quo-tients calculated from the estimated maximum intakes from cattle, swine and chicken meats were 7.82104 and 2.71103, respectively, which means that the observed concentrations in the liver specimens were 3e4 digits lower than health risk levels (Table 4). An ADI for zilpaterol (0.04mg/kg body weight/day) has also been set by the Joint FAO/WHO Expert Committee on Food Additives (2013), but there was no detection in all the liver specimens. There are neither ADIs nor MRLs for the other 8 compounds (salbutamol, cimbuterol, brombuterol, tulobuterol, mabuterol, hydroxymethyl clenbuterol, clenpenterol and mapenterol) set by international commissions such as the 38th session of the Codex Alimentarius Commission (2015), Joint FAO/WHO Expert Committee on Food Additives (2004) and Health Canada (2015). Alternatively, no-toxic-effect dosages of salbutamol, tulobuterol and mabuterol by subacute administration in rats have been re-ported at 20 mg/kg/day, 5 mg/kg/day and 2.5 mg/kg/day, respectively (Gopinath and Gibson,1987; Fort et al.,1984; Amemiya et al.,1983). The values are higher than that of clenbuterol, which has been reported at 1 mg/kg/day (Joint FAO/WHO Expert Committeeon Food Additives, 1998), suggesting that health risks caused by these compounds would be minimal in the observed concentrations as the hazard quotient of clenbuterol was 3 digits lower than the health risk level (i.e., hazard quotient>1). Health risks caused by the other 5 compounds were difficult to assess because there was no toxicological evaluation report. Their detections in the present study recommend further investigations to elucidate their adverse effects.

3.3. Contamination of beta-agonists in wastewater from livestockfarms

All the waste water samples contained high nutrients, and the dissolved oxygen was exhausted because of high microbial activities (Table S4). In the swine farms, the waste water was channeled to 3 retention ponds comprising an anaerobic and 2 facultative ponds in series, and the effluent from the last pond was discharged into a drain outside the farms. This treatment system is applied to all swine farms in Malaysia that had been enforced by the Department of Veterinary Services Malaysia. In contrast, the waste water from the cattle/cow farms was temporarily retained ata solid trap, and the supernatant was discharged into a drain outside their farms without further treatments. This is a common system of ruminant farms in Malaysia, and the simply treated waste water is discharged into the environment. Five beta-agonists (ractopamine, clenbuterol, brombuterol, tulobuterol and mabuterol) showed values over the limit of detection in the 4 waste water samples (Table 5). The waste water at the first swine farm contained 30.1mg/L of ractopamine, while other compounds were not detected except for a detection of brombuterol from the second farm. In the cattle/cow farms, ractopamine was the highest contamination (0.138 and 0.498mg/L) followed by clenbuterol (0.019mg/L), tulobuterol (0.004mg/L) and mabuterol (LOQ). It is difficult to generalize the illegal use of beta-agonists in livestock farms from such a limited number of samples, but the detection of these beta-agonists could be associated with the residues in the liver specimens (Table 3). Ractopamine detected in the swine farms was also detected in most of the swine liver specimens, and ractopamine, tulobuterol and mabuterol detected in the cattle farm were also detected in some cattle liver specimens. Likewise, the 9 compounds detected in the chicken liver specimens could also be abused at chicken farms. Beta-agonists are usually administered as feed additives to stimulate skeletal muscle growth,and many feed additive products containing beta-agonists exist, such as Optaflexx and Paylean containing ractopamine hydro-chloride and Zilmax containing zilpaterol hydrochloride (Centneret al., 2014; Shelver et al., 2005). Therefore, different animal feeds among chicken, cattle and swine farms could be a significant factorof the different residual levels. The contamination source, partic-ularly animal feeds, needs to be investigated to elucidate the res-idue of 10 beta-agonists detected in liver at the wet market.

4. Conclusions 

In the present study, 10 beta-agonists were detected in cattle,chicken and swine liver specimens purchased at 14 wet markets. Ractopamine is permitted for swine by the Malaysia government, and the residual concentration in swine liver was in an admissible range. In contrast, another 9 compounds that are not permitted by the government could be illegally abused among livestock farms for producing leaner meats. Health risks of ractopamine and clenbu-terol were assessed to be minimal, but the detection of the 10 compounds should be not overlooked, and regular inspections by the government are recommended to minimize the health risksdue to their illegal use. The detection of these beta-agonists in the liver specimens was associated with the contamination in the waste water collected from swine and cattle/cow farms. The envi-ronmental impacts of the detected beta-agonists were concluded to be minimal in the Langat River basin. However, negative impacts due to the contamination of ractopamine in coastal areas near the swine farms were concerning, and environmental impacts of chicken droppings sold off as organic manure or fertilizer need further investigation. Thus, we conclude that some beta-agonists were illegally abused among livestock farms in Selangor State, and the meats sold at the wet markets contained their residues. The detection of beta-agonists in liver specimens was associated with the contamination in waste water, and its insufficient treatment at the livestock farms should be improved to minimize environmental impacts.

Acknowledgments

This study was funded by UM/MOE HIR Grant (E000005-20001)and JSPS Bilateral Programs entitled “Human health risk assessment of endocrine disrupting chemicals based on multi-racial as-pects in Malaysia”. Additionally, this work was supported under the framework of “Research and Education Center for Risk Based Asian Oriented Integrated Watershed Management” funded by the JSPS Asian CORE Program and Ministry of Education Malaysia. We would like to give special thanks to Marni SAPAR, Roslan MOHD YUSOF and Marzura MD RODZI in the Veterinary Public Health Laboratory in Malaysia for rendering help in this project.

https://umexpert.um.edu.my/file/publication/00010306_141757.pdf

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