Unlike what is perceived in the animal industry, the risk of mycotoxin exposure is the highest for dairy cows. Their TMR contains not only grains and protein sources, but many unconventional by-products, silages, hay, haylage, and green grass/pasture. The consumption of such TMR induces multiple mycotoxin toxicity and therefore, the intervention strategy must be holistic, practical, and multi-pronged.
Global Programme Manager Mycotoxin Risk Management
Selko Feed Additives
The global animal industry considers mycotoxins as a major threat to the health and performance of pigs and poultry. Does everyone in the animal industry believe the same for dairy cows? Probably not, as there is a myth in the animal industry that dairy cows can handle mycotoxins effectively due to their rumen microbial activity.
Why can dairy cows succumb to mycotoxins?
Although rumen microbes can reduce the toxicity of some mycotoxins, they cannot eliminate the problem completely. Not all mycotoxins are equally degraded in the rumen. Modern high-yielding dairy cows are fed with high-starch diets which compromises the detoxification capacity of rumen microbes. For some mycotoxins, like zearalenone (ZEN), rumen degradation may increase the toxicity. Among mycotoxins not completely inactivated in the rumen, only aflatoxin (AF) B1 is transferred into dairy milk as AFM1 in levels that create a public health concern. Research has demonstrated that cows genetically selected for high milk production may also excrete higher levels of AFM1 into milk.
The global dairy industry must also be aware that among all production animals, dairy cows are exposed to a greater number of mycotoxins. How is that possible? Looking at the diets of poultry and pigs, it is mainly comprised of grains such as wheat and corn, and protein sources such as soybean meal, and sunflower meal. What about dairy cows? In addition to the feed ingredients mentioned above, TMR of dairy cows contains silages, hay, haylage, green grass/pasture and many other unconventional ingredients. Such complex TMR composition results in multiple mycotoxin challenges in dairy cows. Although it varies across the globe, in general high-quality raw materials are prioritized for humans, pets, pigs, poultry and dairy cows, in that order.
What else can make dairy cows more susceptible to mycotoxins? It is very well known that dairy cows are exposed to low levels of multiple mycotoxins for an extended period. Acute toxicity due to mycotoxins such as ergot toxins and T-2 toxin is lower now but chronic toxicity due to relatively lesser toxic mycotoxins such as DON, fumonisins and silage mycotoxins is on the rise. The chronic multiple mycotoxin toxicity is comparable to cancer as it is very difficult to diagnose the problem at the early stages.
What are so called “Silage” mycotoxins?
Many new names for mycotoxin classification have been used lately. “Big 6” mycotoxins refer to the major six mycotoxins that are analysed regularly at feed mills and labs using rapid tests. These are aflatoxins (AF), ochratoxin A (OTA), T-2 toxin, DON, zearalenone (ZEN) and fumonisins (FB) and are measured as “marker mycotoxins” and their presence indicates the potential presence of another 30 to 40 mycotoxins. These mycotoxins along with ergot toxins in the total mixed ration (TMR) can cause health concerns when present in the ration at high concentrations. All these mycotoxins are mainly produced at the pre-harvest stage.
What are “Silage” mycotoxins then? “Silage” mycotoxins are those that are predominantly produced during the process of silage fermentation. A well-managed silage will have less production of such mycotoxins as the anaerobic condition will not allow moulds to overgrow and produce mycotoxins. More than 80 micro-aerobic fungal species can grow in silages producing diverse mycotoxins. Penicillium roqueforti, Aspergillus fumigatus and Bysspchlamus are the major moulds in silages and the mycotoxins produced by them have antibacterial and anti-protozoic activity. Since most of the mycotoxins produced during silage fermentation are from the genus “Penicillium”, “Silage” mycotoxins are often referred as “Penicillium” mycotoxins. Some of the examples are roquefortine C, mycophenolic acid, and penicillic acid.
What are “Emerging” and “Masked” mycotoxins?
In recent times there is a lot of reference to “Emerging” and “Masked” mycotoxins and these mycotoxins add further toxicity to the regular mycotoxins in TMR. “Emerging” mycotoxins such as enniatins and fusaric acid can also have antimicrobial effects in the rumen and this can be one of the reasons for a reduced rumen function and a reduced mycotoxin degradation capacity of the rumen. Some mycotoxins like conjugates of DON, ZEN and T-2 toxin are difficult to detect in feed when routine extraction methods are applied. These so-called “Masked” mycotoxins remain active and are often released by enzymatic and/or microbial activity in the digestive tract.
How does mycotoxicosis manifest in dairy cows?
Alone and in combination, mycotoxins can threaten dairy cows’ health, rumen function, feed intake, milk yield, milk quality, lameness, and reproductive abilities. Many “mouldy silage syndrome” cases in the field have shown incidences of increased somatic cell counts, undigested faecal feed particles, laminitis, mastitis and ruminitis cases. The reproductive challenges range from increased number of inseminations per conception to retention of placenta or even abortions. Many cases of vaccination failures have been reported with multiple mycotoxins in TMR.
How can mycotoxin issues be diagnosed?
The major challenge of mycotoxin risk management lies in the diagnosis of the problem and the ability to establish the cause-and-effect relationship. Mycotoxin symptoms in dairy cows can be confounded with that of pathogen challenge, nutritional deficiency, and management related challenges. Although feed mycotoxin analysis has its own sampling error issues, it is the most used diagnostic tool at feed mills and bigger dairy farms.
As part of its mycotoxin risk management programme, Selko uses the Mycomaster+ system to check raw materials, feeds, and milk for the “Big 6” mycotoxins and AFM1. Selected feed samples can also be analysed for multiple mycotoxins using LC-MS/MS. Based on the mycotoxin concentrations, NutriOpt Mycotoxin Adviser provides customer-specific interpretations on what those concentrations mean and how the toxicity can be managed with the use of right dose of mycotoxin mitigation product (TOXO Range).
Is mycotoxin binding strategy good enough?
Mycotoxin mitigation strategies in dairy cows demonstrate the importance of an integrated approach. It starts from optimal crop management, includes harvesting and storage of raw materials and finally the management of TMR (Figure 1). Innovations in organic acid application (Selko Fylax range) are allowing for better storage of raw materials in silos, leading to optimal silage production and face management, and preventing heating of TMR (Selko-TMR). Mycotoxin mitigation products (Selko TOXO range) can be added to TMR directly or via concentrate to effectively reduce mycotoxin risk for animal health and human health, by keeping AFM1 levels within statutory limits.
As mycotoxins differ in their structure, scientific research has shown that all mycotoxins cannot be bound by a mycotoxin binder. Addressing this limitation, Selko developed the TOXO portfolio, using four modes of action to reduce the absorption of mycotoxins and to protect the animal against toxin damage. Based on the main objective of the feed mills or dairy farms, a selection of the right TOXO product can help in meeting those objectives.
How to manage Aflatoxin M1 in dairy cows?
Milk AFM1 management should be based on HACCP approach. This means all the critical control points of AFB1 entry into the dairy feed must be given proper attention and efforts should be made to prevent such entry. Regular feed mill audits and hygiene management will help in controlling unwarranted levels of AFM1 in milk. Since moulds are ubiquitous, irrespective of the efforts made there still be a chance of AFM1 appearing in the milk. The U.S. Food & Drug Administration (FDA) has set an upper limit of 0.5ppb AFM1 in milk while for the European Union has set this limit to 0.05ppb, ten times more stringent than FDA. Depending on the country the feed mills or dairy farms are in, these regulations should be followed both for milk used for domestic consumption as well as export. AFM1 requirements in the importing countries should be studied thoroughly before planning the export of milk and milk products. There are many instances of milk being rejected at the port of entry due to higher than stipulated AFM1 concentrations in milk.
At the animal level, fortunately there are effective strategies to bind AFB1 in the intestine thereby preventing its entry into blood circulation. Selko has incorporated a high quality smectite binder in their product TOXO-MX and this product has shown to significantly lower AFM1 levels by 65%. Such effect was achieved at very low concentrations of AFB1 in TMR indicating product’s high affinity towards AFB1 (Figure 2).
Can the TOXO range bind multiple mycotoxins?
A series of in vitro trials conducted at independent labs have shown that TOXO range can bind multiple mycotoxins. In addition to more than 90% binding to AFB1, TOXO range can bind T-2 toxin, ZEN, and OTA to the tune of 35 to 45%. Other two “Big 6” mycotoxins are hard to bind, and hence different modes of action need to apply. On the other hand, TOXO range has shown to bind ergot toxins up to 93.6% at pH 3 and 7. Given the increased emphasis on emerging mycotoxins, a study done in 2021 in Germany looked at the TOXO range ability to bind emerging mycotoxins at a pH of 3 or 6.5. All three of the emerging mycotoxins (roquefortine C, sterigmatocystin and enniatin) showed to be bound at more than 74% (Figure 3).
How to manage the effects of multiple mycotoxins on milk production?
TOXO-XXL is Selko’s most broad-spectrum mycotoxin mitigation product encompassing four mode of actions – reduction in mycotoxin bioavailability, strengthening gut barrier function, modulation of immune response, and enhanced antioxidant status. Controlled research was carried out at University of Cattolica in Italy to understand the efficacy of TOXO-XXL in reducing the negative impact of multiple Fusarium mycotoxins on the dry matter intake (DMI), milk production, and rumination time. A total of 31 Holstein lactating cows were enrolled in the study, where 16 cows were used for a trial in the spring period and the trial was repeated in the following summer period with another 15 cows. Each period consisted of a 7-day of adaptation and a 54-day intoxication, where cows were blocked based on days in milk (DIM) and parity, and randomly assigned to specific treatments. Treatments are listed in Table 1. The daily milk production and milk composition was measured by AfiLab system. Cows were milked twice a day and weighted after each milking.
During a 54-day exposure to moderate levels of Fusarium mycotoxins, DMI (expressed as a percentage relative to body weight) reduced from 4.02 to 3.99%. Rumination time saw a reduction as well from 513 to 505 minutes. Additionally, milk yield decreased from 38.29 to 37.55 kg/cow/day (Figure 4). Supplementation of TOXO-XXL at 100 g/cow/day, however, was able to increase DMI, rumination time and milk yield to 4.09%, 525 minutes and 39.28 kg/cow/day, respectively.
CONCLUSIONS
• Unlike the perception, dairy cows can succumb to the negative effects of low levels of multiple mycotoxins originating from wide variety of raw materials in TMR. Negative effects can be manifested on their health, milk production, reproductive capacity and milk quality.
• Many organs and organ systems are compromised by mycotoxins in dairy cows. Moreover, mycotoxin binding approach alone is not sufficient for the effective management of mycotoxins. It takes combination of mycotoxin binder with ingredients capable of supporting gut, immune system and anti-oxidant system to protect the high-yielding dairy cows. Mycotoxin mitigation methods should be based on the specific objective of feed mills or dairy farms in question.
About Dr. Swamy Haladi, PhD
Dr. Haladi is Selko’s Global Programme Manager for the Mycotoxin Risk Management programme. He obtained his Bachelor and Master degrees in veterinary science in India, and then moved to Canada to obtain his PhD in animal and poultry science. During studies and career, he continued to gain more interest and knowledge in the area of mycotoxins, especially the global challenges around this topic.
He published various articles in both peer-reviewed journals as well as industry magazines and he truly understands the global challenge of mycotoxins. Furthermore, he developed practical guidance values for mycotoxins in various species.
