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We have long thought that the only problem mycotoxins can cause in milk stem from the presence of the potent carcinogenic metabolite aflatoxin M1. In terms of food safety this is true, but what about quality parameters? Here's a look at how milk properties are affected by mycotoxins in cow diets.
When talking about mycotoxins and milk, the only concern that comes in our minds is aflatoxin M1. This is certainly an issue of great importance due to its direct impact on human health. We also know that carry-over of other mycotoxins is possible. Traces of other fungi metabolites have been detected in milk although at much lower carry-over rates than aflatoxin (Fink-Gremmels, 2008) (Table 1). So far none of these detectable mycotoxins represents a real threat to human health. Contamination of dairy milk with mycotoxins might also impair quality and use of milk which undergoes typical fermentation processes (e.g. yoghurt). Several mycotoxins do exert strong antimicrobial effects even at very low concentrations, and could affect milk technology with consequent economic losses.
Table 1 - Products of ruminal bioconversion and transfer of mycotoxins from feed to milk
The impact of mycotoxins on milk quality has been poorly investigated. In 2016, a Czech study found a correlation between the load of the main mycotoxins in feedstuffs (particularly DON, FUM and ZEN) and several milk parameters including physical and technological properties. In particular, a higher mycotoxin load was associated with a lower curd firmness and quality (Krížová et al., 2016). Despite this interesting outcome, there are only a handful of studies looking into this topic.
Curd firmness was significantly altered in the group of cows fed the contaminated diet, suggesting a substantial effect of mycotoxins on milk coagulation.
A recent study conducted by Gallo et al. (2021) at the University of Piacenza (Italy), also produced interesting insights. The objective was to analyze the effects of two different contamination levels in Holstein cows’ diets. The control diet, or “low contaminated” total mixed ration, contained about 300 ppb of deoxynivalenol (DON) and 100 ppb of fumonisins (FUM) per kg of dry matter, while the “high contaminated” diet had an average concentration of about 700 ppb of DON and 1000 ppb of FUM. The experiment was designed to reproduce field conditions, since both low and high contamination levels are regularly found in daily practice. After only 21 days of exposure, the group of cows fed with the higher mycotoxin load experienced:
The scientists then compared the milk produced by cows fed the different diets, focusing also on milk coagulation properties. Time to curd firmness at 20 mm (K20) and curd firmness at 30 min (A30) were significantly altered in the group of cows fed the more highly contaminated diet (figure 1), suggesting a substantial effect of mycotoxins on milk coagulation.
Figure 1 – Effect of diet mycotoxins contamination on milk coagulation properties (adapted from Gallo et al. 2020)
The most common approach to evaluate the coagulation capacity of milk is to monitor the viscosity of milk samples, following addition of rennet (enzymes). The “formograph”, widely used in the dairy industry, records changes of firmness over time of the milk mass. The result is a graph with a characteristic “Y” shape (figure 2). Three parameters are usually determined:
Figure 2 - Formograph output: graphical representation of milk coagulation properties
In 2013, Pretto et al. published a work assessing the effect of chemical and coagulation properties of milk on cheese yield of Grana Padano (a popular Italian cheese), under field conditions. As expected, they found out that milk fat, protein and casein content were highly correlated with cheese yield. In addition, milk that coagulated earlier and had a stronger A30 was also associated with greater yield (figure 3). A higher cheese yield means more cheese produced per unit of fluid milk, resulting in a more profitable cheesemaking process.
Figure 3 – Positive correlation between A30 and cheese yield (adapted from Pretto et al. 2013)
First of all, we have to bust a myth. Some dairy farmers who process their own milk are not inclined to use mycotoxin-controlling products unless aflatoxin is out of control. This stems from the misconception that mycotoxin binders have detrimental effects on milk coagulation.
This is certainly not true, at least not for Mycofix®. Thanks to its capability to both bind and biotransform mycotoxins, it also has beneficial effects on milk coagulation properties. In the above-mentioned study, Mycofix® added to the higher contaminated diet restored A30 values at the same level of control group (Figure 4). Therefore, counteracting mycotoxins could be beneficial not only for cows’ performance and health, but could also have positive implications for the dairy industry.
Figure 4 – Effect of Mycofix Plus® fed in addition to the high contaminated diet on milk coagulation properties (adapted from Gallo et al. 2020).
The mechanisms underlying the effect of mycotoxins on milk coagulation are still unknown and further investigation is necessary. Yet, the potential of Mycofix® proves to go beyond dairy farm performance and animal welfare. In fact, the dairy industry increasingly requires an integrated approach across the whole supply chain. Promoting on-farm practices that can positively impact milk quality and process optimization will be crucial for an industry committed to becoming more efficient and sustainable.
References
Johanna Fink-Gremmels (2008). Mycotoxins in cattle feeds and carry-over to dairy milk: A review, Food Additives & Contaminants: Part A, 25:2, 172-180, DOI: 10.1080/02652030701823142
Křižova, L., O. Hanuš, M. Klimešova, J. Nedělnik, J. Kučera, P. Roubal, J. Kopecky, and R. Jedelska (2016). Chemical, physical and technological properties of milk as affected by the mycotoxin load of dairy herds. Arch. Tierzucht 59:293–300. https://doi.org/105194/aab-59-293-2016.
Gallo A., Minuti A., Bani P., Bertuzzi T., Piccioli Cappelli F., Doupovec B., Faas J., Schatzmayr D., Trevisi E. (2020). A mycotoxin-deactivating feed additive counteracts the adverse effects of regular levels of Fusarium mycotoxins in dairy cows. J. Dairy Sci., 103:12 11314-11331, https://doi.org/10.3168/jds.2020-18197
24 June 2021
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