The impact of mycotoxin in cattle feed on rumen health and productivity of dairy cattle

We don't always fully understand where and when molds produce mycotoxins, but conditions that are stressful for the mold certainly play a role. Molds produce mycotoxins to defend themself against other microorganisms. The direct impact of mycotoxin contamination on animal health and production are well known, but next to that, several mycotoxins can have an indirect effect on dairy health and milk production of dairy cows as well. During the 2023 EAAP congress in Lyon, Professor Gallo from the University of Piacenza shared his latest insights on the impact of mycotoxins in feed.

Problems with aflatoxins that are related to Aflatoxin M1, a metabolite of Aflatoxin B1, are well understood. Aflatoxin M1 is carcinogenic and and is one of the regulated mycotoxins, with tolerance levels of Aflatoxin and its secondary metabolites being 10 times lower in the EU compared to the US and other countries. Health problems in dairy cows caused by Aflatoxin B1 are less commonly known. Aflatoxin B1 can cause a reduction of rumen function and mastitis. A recent trial showed a significant reduction of rumen fermentation at aflatoxin B1 levels between 300 and 900 ng, but these levels are much higher compared to what can be expected on a commercial dairy farm in Europe.  

A recent trial with mycotoxin analysis showed that exposure to feed with Aflatoxin B1 concentrations below the European Union (EU) limit for regulation of mycotoxins results in Aflatoxin M1 excretion in milk that exceeded the EU regulatory limit of 0.05 ppb (see Figure 1). In the same trial, Selko Toxo MX significantly reduced the transfer of Aflatoxin B1 in feed to Aflatoxin M1 in milk and also significantly improved feed efficiency measured as milk production per kilogram of dry matter ingested (see Figure 2).

Various mycotoxins in silage are nowadays causing serious problems in ruminants. Effects of fusarium toxins on gastro-intestinal epithelium are well studied. Recent trials show that levels of mycotoxins of concern such as aflatoxin, deoxynivalenol (DON), zearalenone (ZEA), ochratoxin, T2 mycotoxin produced by fusarium and fumonisins in feed for dairy and beef cattle are significantly above tolerance levels for regulated mycotoxins that were agreed within the EU. Presence of mycotoxins in commodities is not uncommon. A mycotoxin analysis of maize meal used in dairy cattle nutrition showed elevated mycotoxin concentrations of aflatoxin and fumonisins. A trial in dairy heifers showed that feeding a commodity with these mycotoxins levels had significant negative effect on growth and fertility (see Figure 3).

A very important class of products that can be used to neutralise common mycotoxins of dairy cattle are the aluminosilicates:

• Bentonites
• Montmorillonites
• Zeolites
• Illites
• HSCAS

Next to that, other options to reduce mycotoxin contamination of dairy feed such as activated carbon, yeast walls, micronized fibres and bacteria such as lactobacillus exist. In-vitro trials show that for mycotoxins that produce different toxins, there is also a difference in binding capacity for mycotoxins between environments with a pH of 3 vs a pH of 7. These different mycotoxin neutralising compounds can be screened with in-vitro tests in which they should bind at least 80% of a mycotoxin to pass the screening. Compounds that pass the screening should be tested in in-vivo experiments with multiple mycotoxins.

Once a certain binding agent is found to be suitable, it greatly matters how it will be applied. In an experiment in which cattle were fed corn contaminated with Aflatoxin B1, the most effective way to reduce the risk of contamination of the milk with Aflatoxin M1 was to add the toxin binder to the complete feed (see Figure 4).

Mycotoxin binders can reduce the negative effects of mycotoxins in feedstuffs on systemic inflammation, rumen microflora and rumen function of dairy cows. This results in an increase of milk production and a positive impact on the cheese making properties of milk. The adverse effects of commonly found levels of Fusarium mycotoxins and the effect of animal feed decontamination with Selko Toxo HP-R on dairy cow performance after a long period of exposure (54 days) were tested. During the experiment, dairy cows were fed moderate levels of Deoxynivalenol (DON), Zearalenone (ZEA), Fumonisins B1 and Fuminisins B2 (FB) from feeds naturally contaminated with multiple mycotoxins. Rumination time and production of ECM of the dairy cattle included in the study were reduced in the dairy cows on the contaminated diet compared to the negative control cows with no mycotoxins in feed. The dairy cattle treated with Selko Toxo-HP-R had an increase of rumination time and produced more milk compared to both the negative control cows and the cows on the contaminated diet (see Figures 5 and 6). Cheese making properties of the milk from dairy cows treated with Selko Toxo HP-R were also improved.

Ruminants are less sensitive to mycotoxicosis compared to monogastrics, but due to the diversity in diet ingredients, it is hard to completely control mycotoxins in the dairy diet. Corn silages from 66 different dairy farms in Italy were tested for the presence of aspergillus, penicillium and fusarium produced mycotoxins and grouped in 5 different clusters. A high correlation between the type of mycotoxin contamination and the metabolic profile of milk from the 66 different dairy farms was found.

Many factors are involved in enhancing the formation of mycotoxins. They are plant susceptibility to fungal infestation, suitability of fungal substrate to support mold growth, climate conditions, moisture content and physical damage of seeds due to insects and pests. Toxin-producing fungi may invade at pre-harvesting period, during harvesting, during post-harvest handling and in storage. According to the site where fungi infest grains, toxinogenic fungi can be divided into three groups: field fungi, storage fungi and advanced deterioration fungi. Various indexes are being used to classify the quality of fermentation of a corn silage (see Figure 7). These different indexes seem to have a poor correlation. 

Preliminary work with Near Infrared Spectroscopy looks like a promising alternative to testing for mycotoxins in corn. A mycotoxin analysis was carried out to test levels of different  common mycotoxins in 120 samples of corn silage. Subsequently, these samples were tested with  Near Infrared Spectroscopy. 97% of the samples with less than 31 mycotoxins were correctly classified as having low levels of contamination with mycotoxins, whereas 100% of the samples with more than 31 mycotoxins were correctly classified as having high levels of contamination with mycotoxins.

A survey was carried out to characterize the different feeding strategies adopted on dairy cow farms in the Po Valley in Italy using corn silage rations. The aim of the study was to characterize the chemical composition of the diets, the fermentation profile of the diets, methane production, the ability to meet nutrient requirements, herd feed efficiency, milk production and quality, and fecal fermentation profile. 66 dairy farms were included in the survey which could be divided into 6 clusters with similar approaches. Huge variations were found between the different clusters of dairy farms, but it was found that starch digestibility of the diet could strongly influence farm profitability and intestinal health status of dairy cows.

Agronomical aspects will also have to be taken into account. A trial was carried out in which corn was planted at two different seed densities:

• 13.0 seeds m2 (smart or NANO)
• 8.2 seeds m2 (conventional or DC)

Both the corn with the normal seeding density and the corn with the higher seeding density were ensiled and fed to 2 different groups of dairy cattle. Dry matter intake and milk yield were increased in the group of dairy cows fed the corn at higher seeding density, resulting in a significant increase of feed efficiency (see Figure 8).