Is exposure to endocrine disrupting compounds during fetal/post-natal development affecting the reproductive potential of farm animals?

Concerns have been raised about the potential adverse effects on reproductive health and immune status of farm animals following exposure to a range of natural and synthetic environmental compounds that disrupt normal hormonal actions. These compounds range from natural plant oestrogens (e.g. genistein, coumesterol) and mycoestrogens (e.g. Aflatoxins, zearalenone) to growth promoting pharmaceuticals (e.g. trenbolone acetate, melengastrol acetate) to chemicals spread in water, sewage sludge or the atmosphere such as detergents and surfactants (e.g. octylphenol, nonylphenol), plastics (e.g. bisphenol-A, phthalates), pesticides (e.g. methoxychlor, dieldrin, DDT) and industrial chemicals (e.g. PCB, TCDD). These compounds are commonly termed 'endocrine disrupting compounds' (EDCs) or 'endocrine disruptors' due to their ability to act as either hormone agonists or antagonists or the ability to disrupt hormone synthesis, storage or metabolism. A similar group of compounds are called 'immunotoxicants' and are thought to affect the immune system mainly by disrupting B and T cell homeostasis. As more studies are performed it is becoming clear that many compounds can directly or indirectly affect both the endocrine and immune systems. The susceptibility of target tissues is related to the stage of development, the cumulative exposure dose and the immune status of the individual. While some of the effects of the EDCs on the endocrine and immune systems are quite distinct, many are subtle and identifying the causative agent from the vast array of environmental challenges including EDCs, nutrition, temperature, etc. can be problematic. Identifying the causative agent is confounded by the possibility that effects that are observed in the adult may be due to exposure to EDCs during fetal life. This has major implications for the determination of universal end-point measurements to assess exposure to EDCs in farm animals.     

Are Endocrine Disrupting Compounds a Threat to Farm Animal Health,Welfare and Productivity?

Contents The sources and characteristics of endocrine disrupting compounds (EDCs) are reviewed and discussed with respect to their potential effects on farm animal health, welfare and productivity. The importance of certain properties of these compounds in relation to the expression of their biological effects is addressed together with potential routes of exposure. It is concluded that little is known of factors affecting the tissue concentrations of EDCs in farm animals, the concentrations that are required to perturb physiological function in these species, the effects of prolonged exposure to low doses, the effect of cocktails of EDCs and other pollutants or the responses of specific organs and physiological systems that are affected by EDCs. Much of the available information pertaining to EDCs is derived from epidemiological studies of wildlife species and from laboratory animal studies and while these studies have significant limitations, they are considered to be valuable indicators of potential effects in farm animal species. The results of such studies, together with the small amounts of data from studies of ruminants, indicate that there may be significant effects of exposure to environmental levels of EDCs on farm animal health, even although effects are not generally apparent in practice, at this time.     

Ochratoxin A in feed of food-producing animals: an undesirable mycotoxin with health and performance effects

Mycotoxins are secondary fungal metabolites, whose presence in feed- and foodstuffs is unavoidable. Ochratoxin A (OTA) is one of the known mycotoxins with greatest public health and agro-economic significance. Several toxic effects have been ascribed following exposure, namely nephrotoxicity, as well negative impacts in the performance of farm animals, resulting in major economic implications. Of no less importance for the route of human exposure that can also embody the carry-over of OTA from feed into animal-derived products is also a concern. For all these reasons the present article updates the worldwide occurrence of OTA in different raw ingredients and finished feed destined to food-producing animals. After that a brief characterization of specie susceptibility and the major rationales is made. An historical overview of field outbreaks linked to OTA exposure in farm animals, concerning the implicated feeds, contamination levels and major clinical and productivity effects is presented. Finally a review of the major animal health and performance potential impacts of animals being reared on contaminated feed is made allied to a perspective regarding its co-occurrence with other mycotoxins, and simultaneous parasitic and bacterial infections. Ultimately, this article aims to be instructive and draw attention to a mycotoxin so often neglected and elapsed from the list of differential diagnosis in farm practice. For the unpredictability and unavoidability of occurrence, OTA will definitely be an enduring problem in animal production.     

Effects of Endocrine Disrupting Compounds in Animal Feed on Reproductive Health in Farm Animals*Euroconference Wageningen, The Netherlands, 20–22nd November 1998

This Euroconference was a follow-up to the Euroconference held in Halle, April 1997. The programme of the conference in Halle had an exploratory character with respect to accumulation of endocrine disrupting compounds (EDCs) in the environment and in animal tissues and their effects on animal physiology and reproduction. Many questions arose from the first Euroconference, such as: What are biologically meaningful levels of environmental contamination? Is there a risk for farm animals’ health and reproduction? What assays are available and which are the most appropriate to be used? These questions formed the basis for the programme of the second Euroconference held in Wageningen in November 1998. Taking these questions into consideration, the programme of the Wageningen Euroconference was divided into four main topics. In the first session an overview was given on sources and levels of EDCs in the environment. The second session addressed chemical nature and metabolism of EDCs including phytoestrogens. In the third session the effects of EDCs on ovarian function and embryo development were discussed and in the last session the advantages and disadvantages of different in vivo as well as in vitro assays were debated.     

Consequences of endocrine disrupting chemicals on reproductive endocrine function in birds: establishing reliable end points of exposure

It has been difficult to establish reliable indices of exposure to endocrine disrupting chemicals (EDCs) appropriate for a variety of avian species because of a vast array of reproductive strategies. Data from mammals, reptiles and fish provide insight on likely mechanisms of action for EDCs. However, many of the effects of EDCs are weaker than the actions of the native hormones, making it difficult to assess adverse effects in domestic and wild birds. It is clear that differential sensitivity to EDCs exists across species, due to the timing and mode of exposure, compound toxicity and age of the individual. Our studies on EDCs are conducted in the quail model system, with focus on reproductive endocrine, neuroendocrine and behavioral responses. Studies have included EDC exposure, either by egg injection or via diet. Results from egg injection studies showed the following: (1) estradiol administered by embryonic day 12 demasculinized male sexual behavior, altered hypothalamic neurotransmitters and reduced hen day production and fertility in a dose dependent fashion, (2) methoxychlor (MXC) or vinclozolin impaired male sexual behavior in adult quail and (3) DDE exposure impaired reproductive and immune related end points. Two-generation studies were conducted on Japanese and northern bobwhite quail with dietary methoxychlor (MXC) exposure (0, 5 and 10 ppm) beginning in adults (P1), continuing in their offspring (F1), with F2 offspring raised on control diet. MXC exposure impaired male sexual behavior, hypothalamic catecholamines and plasma steroid hormones. Moreover, MXC exposure had reproductive consequences observable at both the lower and higher doses of MXC in F1 and F2 generations. These data demonstrate that embryonic EDC exposure interferes with sexual differentiation of neural systems that direct reproduction.     

Contaminants in feed for food-producing animals

Outbreaks of Bovine Spongiform Encephalopathy (BSE) and food borne microbial infections, dioxin contaminated animal products, the presence of veterinary drug residues, microbial resistance to antibiotics, mycotoxins, agricultural and industrial chemicals, etc. are serious concerns for the food industry in many countries. Since the direct links between feed safety and safety of foods of animal origin are obvious, feed production and manufacture should be considered as an integral part of the food production chain. Industry is responsible for the quality and safety of food and feed that is produced. This paper is a brief review of some microorganisms as source of infections for farm animals that could result in human illnesses. These include Salmonella enterica, Bacillus anthracis, Toxoplasma gondii, Trichinella spiralis, prions, Listeria monocytogenes, EHEC, Campylobacter, Clostridium botulinum, Hog Cholera virus, Foot and Mouth Disease virus, etc. as well as other contaminants associated with animal feed such as mycotoxins, veterinary drugs, dioxins and PCB and Genetically Modified Organisms.     

Trichinae certification in the United States pork industry

Control of Trichinella infection in U.S. pork has traditionally been accomplished by inspection of individual carcasses at slaughter or by post-slaughter processing to inactivate parasites. We propose that an alternative to individual carcass testing or processing can be used when pigs are raised in production systems where risk of exposure to Trichinella spiralis has been mitigated. Declines in prevalence of this parasite in U.S. domestic swine during the last 30 years, coupled with improvements in pork production systems, now allow Trichinella control to be shifted to the farm through implementation of specific pork production practices. Knowledge of risk factors for exposure of swine to T. spiralis was used to develop an objective audit of risk that can be applied to pork production sites. In a pilot study, 461 production site audits were performed by trained veterinary practitioners. The on-farm audit included aspects of farm management, bio-security, feed and feed storage, rodent control programs and general hygiene. Of the 461 production site audits, 450 audits (97.6%) indicated compliance with the required good production practices. These sites are eligible for certification under the U.S. Trichinae Certification Program and will be audited regularly to maintain that status. The described trichinae certification mechanism will establish a process for ensuring the Trichinella safety of swine, and ultimately food products derived from swine, at the production level.     

Impact of Endocrine‐Disrupting Chemicals on Reproductive Function in Zebrafish (Danio rerio)

The prevalence of endocrine‐disrupting chemicals (EDCs) in the aquatic environment has been associated with the wide detection of alterations in the development and physiology of vertebrates. Zebrafish, as a model species, has been extensively used in toxicological research. In this review, we focus on recent published evidence of the harmful effects of EDCs on reproductive function in zebrafish, including skewed sex ratio, immature gonads, diminished sexual behaviour, decreased sperm count, reduced spawning and fertilization. These impairments mostly result from disruption to sex‐steroid hormones induced by endocrine disruptors. We also discuss other effects of exposure to EDCs. In EDC exposure research, despite incomplete assessments of altered gonad histopathology and sexual behaviour, these present potential effective biomarkers or pathways for evaluating the reproductive function in zebrafish on EDC exposure. To date, the pernicious effects of some EDCs on the reproductive performance in laboratory zebrafish are well understood; however, similar alterations remain for further determination in wild‐type fish and more kinds of EDCs. More studies should be performed under established scientific regulatory criteria to investigate the impact of EDCs on reproduction in zebrafish. Moreover, further research is required to explain the definite mechanism of sexual differentiation, which helps in understanding the shift of sexual phenotype with EDC exposure.     

Research Progress on Safety Assessment of Transgenic Bt Rice as Animal Diets

Rice is one of the major food crops for humans.It is also an important feed source of animals.In recent years,several transgenic Bacillus thuringiensis (Bt) rice were bred by domestic and international research institutes.These varieties of transgenic Bt rice can kill insect pests such as rice stem borer,yellow rice borer and rice leaf roller.They can also reduce the use of pesticides and boost rice yields.People pay much attention to safety of transgenic Bt rice as it is one of the major food crops.As yet there is no definite evidence that the transgenic Bt rice has safety issues.But we still need to monitor the results of long-term consumption of the rice continuously.This article mainly reviews the development,potential risk and safety assessment method,nutritional value and toxicity of transgenic Bt rice,the impact of growth and immune of animals,the foreign gene and the foreign protein in vivo residual.     

转Bt基因水稻饲用安全性评价的研究进展

水稻是世界主要的粮食作物之一,同时也是重要的饲料原料.近年来国内外研究机构培育出数种转苏云金芽孢杆菌(Bacillus thuringiensis,Bt)基因水稻,可有效杀灭二化螟、三化螟、稻纵卷叶螟等虫害,减少水稻种植过程中农药的使用,提高水稻产量.由于水稻是人类主要的粮食作物,转Bt基因水稻的安全性受到广泛的关注.截至目前尚未有确切证据证实转基因水稻存在饲用安全性问题,但仍需对其长期饲用结果进行持续监控.作者现就转Bt基因水稻的发展、潜在风险和安全评价方法,营养价值、毒理性,对动物生长、免疫、肠道微生物的影响,以及外源基因和外源蛋白的残留等方面进行简要综述.     

Characterizing the Role of Animal Exposures in Cryptosporidiosis and Shiga Toxin‐producing Escherichia coli Infections: South Dakota, 2012

Cryptosporidium spp. and Shiga toxin‐producing Escherichia coli strains (STEC) are important causes of human illness. Incidence rates of these illnesses are high in South Dakota compared to the USA as a whole. Direct animal contact has been identified as a possible route of exposure for these illnesses. Ruminant animals may carry STEC subclinically, while young ruminants are common sources of zoonotic strains of Cryptosporidium. South Dakota patients with either STEC or cryptosporidiosis during 2012 were interviewed regarding seven categories of animal exposure: (i) petting zoo/fair attendance, (ii) animal event/rodeo attendance, (iii) feed/pet store visits, (iv) farm visits, (v) employment or residence at a farm, (vi) residence with pets and (vii) visiting other households with pets. Of the 50 STEC cases, 78.0% reported animal exposure prior to illness onset, with 23.3% having lived or worked on a farm. Farm visitors in particular had high degrees of animal contact and infrequently practiced personal protective measures. Of the 115 cryptosporidiosis cases, 87.8% reported animal exposures, with 45.6% having lived or worked on a farm and 29.0% having visited a farm prior to illness. Cases with farm exposures reported a high degree of direct animal contact and inconsistent use of personal protective measures. Cryptosporidiosis patients were significantly more likely than STEC patients to have lived or worked on a farm prior to their illness and were older on average. Patients with these illnesses had high rates of animal contact prior to illness. Animal contact on farms emerged as an important exposure route. Educational messages about personal protective measures should be directed at these individuals.     

Feedstuffs as a vehicle of cattle exposure to Escherichia coli O157:H7 and Salmonella enterica

Feed has been reported as a vehicle for transmission of Salmonella enterica in cattle and several lines of evidence suggest that feed can be a vehicle for transmitting Escherichia coli O157:H7 as well. To show whether microbial contamination of feeds could contribute to the populations of S. enterica and E. coli O157:H7 on a farm, we compared isolates from feed samples to bovine fecal isolates from the same farm using pulsed-field gel electrophoresis (PFGE). Four of 2365 component feed samples (0.2%) and 1 of 226 feed mill samples (0.4%) were positive for E. coli O157:H7. Twenty of 2405 (0.8%) component feed samples and none of 226 feed mill samples were positive for Salmonella. PFGE profiles from E. coli O157:H7 isolated from a component feed sample closely resembled that from a fecal isolate collected later from the same farm, and a similar observation was made of a Salmonella Tyhpimurium isolate from component feed on another farm. There were indistinguishable PFGE profiles from component feed Salmonella Tyhpimurium DT104 isolates and fecal isolates from the same farm. These results provide evidence for a role of cattle feed in transmission of E. coli O157:H7; S. enterica; cattle-bacteria.     

Food safety achieved through herd management

Most animal-derived food products originate from production chains consisting of a series of well-defined, separate production steps. Undesired events affecting food safety can principally occur at any point within the production chain. The principle of integrated food safety assurance from stable to table has therefore been established. The livestock holding has thus to be understood as a fix element of the production chain, and the producer has to accept a part of the responsibility for food safety. On a farm, food safety can be negatively affected by animal feed (microbiological or toxicological contamination), management (hygiene, stocking density, cleaning and disinfecting), veterinary treatments (use of antibiotics) and recycling of slurry. Most relevant practices can be summarised under the standard of "good farming practice". HACCP programmes as they are applied in the processing industries could in principle also be used at the farm level. Influential management steps would need to be identified and controlled. This approach is, however, still in its infancy at present. Using the current monitoring systems, microbiological and toxicological problems in food are difficult to be identified before the end of the production chain. As the cause of a problem can be found at the farm level, traceability of products through the production chain is essential. In Switzerland, traceability of animals is realised using compulsory animal identification and the animal movement database. Using this link, information on the health status of a herd could be made available to the slaughterhouse in order to classify animals into food-safety risk categories. This principle is a key element in the ongoing discussion about visual meat inspection in Europe and elsewhere.     

The weakest link: medroxyprogesterone acetate in pig feed

Medroxyprogesterone acetate (MPA)-contaminated feed arrested the onset of farrowing, and induced post-lactational anoestrus in sows. Sixty percent of the sows developed cystic ovaries after weaning following exposure to pharmaceutical waste of MPA in glucose syrup. This waste ended up in acidified feed of by-products of a sow farm, and proved to be the cause of the disorders. Analysis by thin layer chromatography and Gas Chromatography/Mass Spectrometry of renal fat from 10 slaughter sows demonstrated residues of 2.5-8 ppb of MPA. Within the European Union use of MPA is illegal as growth promoter in production animals, and therefore MPA-exposed farms were placed under official control by the general inspection service. Clinical signs and diagnostic procedures of the initial case are presented and the role of the veterinary practitioner in detecting potential food safety hazards is discussed.     

Enhancing the profitability of pasture-based dairy production in the humid tropics through improved nutrition

Dairy production in the tropics represents a major challenge, especially when reliant on grazed forages, because of the conflicting factors of a high nutritional demand to sustain lactation on the one hand, and the relatively low quality of tropical grasses and a stressful environment, on the other. This paper focuses primarily on those tropical situations where grazed pasture is the cheapest feed resource. Effective management of the pasture as well as the animals that graze it is required in order to maximize economic viability of the farming enterprise. Feed planning helps to ensure that pasture use is maximized, either directly by grazing or, where profitable, indirectly by cutting for conservation. High rates of pasture utilization at each grazing minimize pasture senescence and decay and ensure that pasture remains in a vegetative state of the highest possible nutritional quality. Total annual feed requirements of the grazing herd must therefore be matched as closely as possible to the total annual pasture production on the farm. Stocking rate is critical in this regard, and is the single most important determinant of productivity in pastoral farming. Periods of pasture surplus or deficit will inevitably arise, but can be minimized by matching the monthly feed requirements of the herd as closely as possible to the monthly feed production on the farm. Herd requirements can be influenced, for example, through altering calving patterns and drying off dates. Even with good pasture management practices, it is highly likely that tropical pasture quality will be low for part of the year. Utilization of low-quality forages can be improved through the appropriate use of feed supplements, and the key principles are discussed. Firstly, conditions for optimum fermentative digestion in the rumen must be promoted through adequate provision of fermentable energy and nitrogen as well as essential minerals, such as phosphorus and sulfur. Further supplementation with metabolizable energy or protein, depending on what limits animal production, may be profitable. Various practical supplementation strategies for tropical forages are discussed. Finally, some suggestions for future research and development for enhancing the profitability of pasture-based dairy production in the humid tropics are made.     

Environmental endocrine disruptors in farm animal reproduction: research and reality

In this review, possible comparative advantages of studying endocrine disruption in farm animals vs laboratory rodents are discussed. First, using farm animals, the generality of findings in laboratory rodents are challenged. Farm animals may in certain aspects be better models for humans than laboratory rodents, and sometimes there might be methodological advantages in using farm animals. Second, there are several in vitro studies based on cell-culture systems from sows and cows where the effects of chemicals on sex steroid secretion can be measured and maturation and fertilization of oocytes may be assessed. These in vitro systems are powerful tools for dissecting the mechanisms of action for endocrine-disrupting chemicals. Third, in a set of recent in vivo studies using sheep, goats and pigs, in which very different exposure regimens to endocrine-disrupting chemicals have been used, a full panel of reproductive parameters pertinent to farm animals were assessed. Clinically, it is suggested that endocrine disruption in farm animals should be considered when impaired reproduction could be linked to change in source of feed or pasture. Finally, epigenetic and toxicogenomic approaches can be particularly rewarding in elucidating endocrine disruption in future farm animal studies.     

环境内分泌干扰物对睾丸间质细胞功能的影响

近年来,环境内分泌干扰物(environmental endocrine disrupting chemicals,EDCs)对雄性动物的生殖毒性引起了广泛的关注。大量资料显示EDCs可引起雄性生殖发育障碍,如隐睾、尿道下裂、睾丸癌、精液品质不良等。作者就几种典型的EDCs对睾丸间质细胞分泌睾酮的影响机制作一综述。     

Mycotoxins and reproduction in domestic livestock.

Molds are parasitic plants that are ubiquitous in livestock feedstuffs. Even though molds themselves reduce the quality of grains, their synthesis of chemical substances termed mycotoxins causes the greatest monetary loss to the animal industry. Five major mycotoxins that impair growth and reproductive efficiency in North America are aflatoxins, zearalenone, deoxynivalenol, ochratoxin, and ergot. Aflatoxins are produced by Aspergillus flavus and Aspergillus parasiticus. Consumption of grains containing aflatoxins by swine affects reproduction indirectly by reducing feed intake and growth. In swine, aflatoxins impair liver and kidney function, delay blood clotting, increase susceptibility to bruising, and interfere with cellular humoral immune systems. Ruminants are comparatively resistant to aflatoxicosis, but presence of aflatoxins in milk of dairy cows is closely monitored for human safety. Depending on environmental conditions, Fusarium roseum can produce either zearalenone or deoxynivalenol. Days 7 to 10 postmating seem to be a critical period of gestation for zearalenone to exert its detrimental actions on early embryonic development. Presence of deoxynivalenol in swine feedstuffs decreases feed intake, causes feed refusal, and induces occasional vomiting. Several species of Penicillium and Aspergillus produce ochratoxin, a mycotoxin that causes necrosis of kidney tissue. Ergot alkaloids produced by Claviceps purpurea on wheat can cause reproductive problems and are associated with lactational failure in swine. Various methods have been developed to remove mycotoxins from infected feedstuffs. Chemical analyses in laboratories as well as diagnostic kits suitable for use at the elevator or farm can be used successfully to identify which mycotoxins are present in suspect feedstuffs.     

Imbedding HACCP principles in dairy herd health and production management: case report on calf rearing

Driven by consumer demands, European legislation has suggested the use of HACCP (Hazard Analysis Critical Control Point) as the quality risk management programme for the whole dairy chain. Until now, an exception has been made for primary producers, but as regulations evolve, on-farm HACCP-like programmes should be ready to assure food safety as well as animal health and animal welfare. In our field experiment, the HACCP-concept was used to combine both optimal farm management and formalisation of quality assurance in an on-farm situation in the Netherlands. The process of young stock rearing was chosen, since its importance for the future of the farm is often underestimated. Hazards and their associated risk factors can be controlled within the farm-specific standards and tolerances, as targets can be controlled by corrective measures and by implementation of farm-specific worksheets. The veterinarian is pivotal for the facility-based HACCP team, since he/she has knowledge about on-farm risk assessment and relations between clinical pathology, feed and farm management. The HACCP concept in combination with veterinary herd health and production management programmes offers a promising approach to optimise on-farm production processes (i.e., young stock rearing) in addition to a structural approach for quality risk management on dairy farms.     

Perspectives for feed-efficient animal production

Modern animal breeding programs are largely based on biotechnological procedures, including AI and embryo transfer technology. Recent breakthroughs in reproductive technologies, such as somatic cell nuclear transfer and in vitro embryo production, and their combination with the emerging molecular genetic tools, will further advance progress and provide new opportunities for livestock breeding. This is urgently needed in light of the global challenges such as the ever-increasing human population, the limited resources of arable land, and the urgent environmental problems associated with farm animal production. Here, we focus on genomic breeding strategies and transgenic approaches for making farm animals more feed efficient. Based on studies in the mouse and rat model, we have identified a panel of genes that are critically involved in the regulation of feed uptake and that could contribute toward future breeding of farm animals with reduced environmental impact. We anticipate that genetically modified animals will play a significant role in shaping the future of feed-efficient and thus sustainable animal production, but will develop more slowly than the biomedical applications because of the complexity of the regulation of feed intake and metabolism.