The impact of mycotoxins in dairy on health and performance

Assessing the risk of mycotoxins in cattle feed has always been challenging. If dairy cows are fed with a Total Mixed Ration (TMR) containing silages, grains and by-products. Each of these feed ingredients could lead to mycotoxins symptoms in cattle. Although mycotoxins in cattle feed with high-fiber ingredients can be analysed, test methods for mycotoxins in dairy are costly and not practical for routine analysis. On the other hand, more practical and affordable tests for mycotoxins in cattle feed, such as ELISA and Lateral Flow Devices, are not particularly suitable for testing high-fiber ingredients for mycotoxins in dairy. This problem can be solved by using rapid mycotoxin cattle tests that are practical for testing mycotoxins in ingredients with low amounts of fiber and using a combination of mould counts and mycotoxin analysis for ingredients with high levels of fiber and for TMR.

Making a correct assessment of the risk of contamination with mycotoxins in cattle feed in combination with understanding consequences of the presence of mycotoxins in cattle feed and negative effective effects of mycotoxins in dairy cows is very important to prevent mycotoxin symptoms in cattle that can lead to problems with health, performance and fertility of dairy cows. Next to these problems with mycotoxins in cattle, there can also be problems with residues of aflatoxins in milk as a result of contamination with aflatoxin mycotoxins in cattle feed.

Problems with mycotoxins in dairy and mycotoxin symptoms in cattle are not always easy to recognise

Traditionally, there are the so-called “big 6” mycotoxins in dairy (Aflatoxins, Zearalenone (ZEA), deoxynivalenol (DON), T-2 toxin, Fumonsins and Ochratoxin A (OTA)), sometimes also referred to as "AFOZET” mycotoxins in cattle, that are associated with several mycotoxins in cattle symptoms. More recently, new groups of mycotoxins in dairy, the so-called silage mycotoxins in dairy have been identified^108,109,110. Lastly, there are the Endophytes, moulds that grow inside plants and can cause mycotoxin cattle problems in grazing dairy cows. These Endophytes and silage mycotoxins in dairy can be different from the “big 6” mycotoxins in cattle and hence understanding the presence and potential mycotoxins symptoms in cattle of these silage mycotoxins and endophytes is very important.

Where do mycotoxins in dairy come from and what are the mycotoxins symptoms in cattle that they can cause?

Table 1 shows which feed ingredients can contain the various AFOZET mycotoxins in dairy cattle and what the mycotoxins in cattle symptoms can be.

Table 1: Feed sources of important mycotoxins in dairy cows and mycotoxins symptoms in cattle. Most of the mycotoxins in cattle included in the table have an effect on health, performance, and reproduction of dairy cattle.

Aflatoxins are mainly associated with feed safety issues

Aflatoxins can cause problems with health fertility and performance of dairy cows at high concentrations, but as they are very toxic for humans, tolerance levels in milk are relatively low. Aflatoxins in dairy cows are mainly related to problems with rejection of milk due to concerns about safety for human consumption. Thus, if there is an aflatoxin risk, particularly aflatoxin M1, a Hazard Analysis Critical Control Points (HACCP) approach will be required.

Mycotoxins cause problems with health, performance, and fertility of dairy cows

The symptoms caused by mycotoxins are mainly related to poor rumen fermentation, systemic immune activiation leading to poor immunity, hormonal imbalance and sometimes liver and kidney toxicity, all leading to poor health, performance and reproduction. There are many other causes for these types of problems, as a result, recognising a problem with mycotoxins isn’t always easy.

The risk of mycotoxins in dairy is much bigger in dairy cows than in monogastric animals because the chances of exposure to mycotoxins in cattle feed through various ingredients is much higher (see Figure 1). There is no doubt that microbes in the rumen of the cows, particularly protozoa, can help to lower toxicity of mycotoxins in dairy feed, particularly in case of a mycotoxin cattle challenge with ochratoxin A (OTA). Some mycotoxins in dairy can however have a negative effect on the ability of rumen flora to detoxify mycotoxins in cattle feed. Next to that, modern dairy cows do have an increased passage rate of feed through the rumen, leaving less time for microorganisms to detoxify mycotoxins to rescue the risk of mycotoxins symptoms in cattle. In case of sub-acute ruminal acidosis (SARA), the number of protozoa in the rumen declines, having a negative effect on the ability to detoxify mycotoxins in dairy. As a result, the awareness of farmers, nutritionists, and veterinarians that issues with mycotoxins in cattle feed are increasing.

How to assess the risk of mycotoxins in cattle feed causing problems with mycotoxins symptoms in cattle?

Compared to poultry and pigs, it has always been difficult to assess the risk of mycotoxins in cattle feed causing problems with mycotoxins in dairy. Most dairy cows are fed a Total Mixed Ration (TMR) containing forages, grains (including high moisture grains), protein meals, by-products and sometimes green grass or hay. Two methods to measure the level of mycotoxins in cattle feed exist. Next to measuring the actual amount of mycotoxins in cattle feed, the risk of contamination with mycotoxins in cattle feed can be indirectly assessed by mould analysis of high moisture ingredients and TMR. Out of the 2 methods available for analysis of mycotoxins in dairy feed samples, rapid analysis for mycotoxins in cattle feed samples is recommended for raw materials having less than 15% moisture and a low fiber content. Mould analysis is recommended for raw materials or TMR with more than 15% moisture and high fiber content.

HPLC and LC-MS/MS methods to measure levels of mycotoxins in cattle feed samples

Both HPLC and LC-MS/MS methods can be used to measure mycotoxins in cattle feed samples of TMR and high-fiber ingredients, but these methods are not practical due to the time consumed to obtain results as well as the high cost per sample analysis.

Rapid tests for mycotoxins in dairy

Rapid tests to analyse mycotoxins in cattle feed samples, such as ELISA and Lateral Flow Devices (including Mycomaster), are excellent for testing levels of important mycotoxins in dairy feed samples rapidly and at an affordable cost. Unfortunately, these tests for mycotoxins in cattle feed are not particularly suitable for testing high-fiber ingredients.

The alternative to measuring levels of mycotoxins in cattle feed with expensive tests is mould analysis. Depending on the extent of information needed, further identification of mould species is possible in some commercial labs. Such identification helps in understanding whether the mould identified can produce mycotoxins and if yes, which mycotoxins symptoms in cattle are to be expected based on the presence of these mycotoxins in cattle feed (see Table 2).

Table 2: Relation between moulds and mycotoxins in dairy. Mycotoxins in cattle produced by Penicillium species in silages are highly volatile and mycotoxins in cattle feed samples hard to analyze by conventional methods.


Because there is no cheap and practical way to measure the levels of mycotoxins in cattle feed samples of TMR or high-fibre feed ingredients, the alternative to testing all feed samples for mycotoxins in dairy is to combine two methods. Mycotoxins in cattle feed ingredients with a low amount of fibre should be analysed for mycotoxins using a rapid test for mycotoxins in dairy such as the Mycomaster, whereas mould analysis should be used to assess the risk for mycotoxins in cattle of the total TMR or ingredients with high fibre content (see Table 3). Lastly, there is the option to test feacal samples of dairy cows for moulds. This method is not very accurate, as the presence of moulds only indicates there has been a problem mycotoxins in dairy in the recent past. It does not provide any information as to where the contamination with mycotoxins in cattle feed is coming from. It is however a simple method that can be used to find out if mycotoxins symptoms in cattle are likely or unlikely to be related to problems with health, performance and fertility in a dairy herd.

*Table 3: Diagnostic tools for understanding the risk of problems with mycotoxins in dairy*


### What are the tolerance levels for moulds and mycotoxins in dairy cattle?
Based on the combined knowledge of both peer-reviewed research and field experience, Selko has developed “Practical Mycotoxin and Mould Guidance Values” to asses the risk of problems with mycotoxins in cattle feed (see Table 4). These values should be considered as a guide to manage raw material and TMR quality in such a way that mycotoxins symptoms in cattle can be prevented. Managing the risks of contamination of mycotoxins in cattle feed ultimately protects animal performance and bottom line of farm operations.


*Table 4: Guidance values for mould values and values for mycotoxins in cattle feed and mould for TMR for dairy cows. Recommended values for aflatoxins in cattle feed are based on FDA regulation and these values are much lower for EFSA regulation.*

A robust programme to reduce the risk of mycotoxins symptoms in cattle should comprise of many actions:

• Identify which ingredients of the ration carry a risk to increase problems with mycotoxins in cattle
• Avoid feeding ingredients that can cause mycotoxins symptoms in cattle if possible
• Reduce growth of moulds while crops are on the field or in storage to reduce the risk of problems with mycotoxins in dairy
• Add mould inhibitors and silage inoculants while making the silage
• Spray liquid mould inhibitors to the face of the silage after cutting
• If there is a serious risk of presence of mycotoxins in cattle feed, add toxin binder for cattle into TMR directly or through concentrate portion
  
  

Irrespective of the source and the type of mycotoxins in dairy, overall health, performance, and reproduction of dairy cows are significantly affected by mycotoxins in cattle feed, resulting from poor quality raw materials and TMR. The impact of mycotoxins in dairy has increased in recent times as rumen health and the immune system of high yielding dairy cows is relatively compromised. The risk of exposure to mycotoxins in cattle is much higher as compared to monogastric animals and hence an integrated approach to managing mycotoxins in dairy should be in place when procuring raw materials, producing feed and silages, and rearing dairy cows. In terms of milk quality, aflatoxin M1 residues in milk is a global concern that requires an HACCP-like approach as this problem with mycotoxins in dairy ends in compromising human health.