Typical Levels of Mycotoxin Contamination Impact the Performance of High-Producing Dairy Cows
The effects of mycotoxins on high-producing dairy cows are well established, but the levels at which contamination affects cow health and performance are still being debated. A new study finds that commonly occurring levels of mycotoxins may be significantly impacting commercial dairy operations around the globe.30.09.2021
• A diet with typical levels of DON (700 ppb) and FUM (1000 ppb) markedly affected rumen fermentation and milk production.
• Three-week exposure to common DON and FUM levels was enough to significantly affect digestion, productivity and liver health of dairy cows.
• Within a three-week of treatment period, Mycofix® Plus counteracted the adverse effects of a diet contaminated with regular levels of DON and FUM.
Setting mycotoxin contamination thresholds for high-producing dairy cows
High-producing dairy cows are thought to be more sensitive to mycotoxicosis because of their higher feed intake. This higher intake leads to faster passage through the digestive tract and, consequentially, lower time for mycotoxin detoxification by rumen microbes. Moreover, high-producing cows are often fed diets containing high amounts of fermentable carbohydrates in order to meet their energy requirements, which increases the risk of subacute ruminal acidosis. Time with low rumen pH has been associated with lower mycotoxin detoxification by rumen microbes, because of shifts in rumen population at the expense of those having the higher mycotoxin detoxifying activity.
The synergistic effects of mycotoxins may also exacerbate the negative effects on cow health and performance, as mycotoxin co-contamination is much more frequent than single contamination.
A new in vivo trial examines effects of commonly occurring mycotoxin levels
To address this issue and provide useful guidelines for the industry, prof. Antonio Gallo and his team from the Animal Science department at the University of Piacenza (Italy), in cooperation with Biomin® Research Center (Austria), recently led an experiment to explore the effect of typical levels of deoxynivalenol (DON) and fumonisins (FUM) on the performance and diet digestibility of high-producing dairy cows.
The trial involved 12 multiparous and lactating Holstein cows, producing 42.2 kg milk/cow per day with an average of 114 days in milk at the onset of the trial. Cows were fed a total mixed ration composed of corn silage, hays, soybean meal, dehulled sunflower meal and water. Corn meal (contaminated or not with DON and FUM) was supplied individually according to trial groups. The total diet averaged (DM basis) 17% crude protein, 26% starch, 37% aNDFom and 4% ether extract.
The trial design was a three-treatment Latin square with 21 days treatment periods followed by 14 days washout. The three treatments were:
- Control (CTR): cows receiving the non-contaminated corn meal
- Mycotoxin-contaminated TMR (MTX): cows receiving the DON and FUM contaminated corn meal
- Mycotoxin-contaminated TMR + Mycofix® Plus (MPL): cows receiving the DON and FUM contaminated corn meal and supplemented with 35 g Mycofix® Plus/cow per day
The DON and FUM contamination levels of the MTX and MPL diets were typical mycotoxin levels commonly found in feeds and forages delivered to dairy cows, as reported by the European Food Safety Agency (EFSA, 2013). These levels also correspond to ‘realistic’ doses (as opposed to ‘occasional’ and ‘unrealistic’ doses), as defined by Grenier and Applegate (2013), based on worldwide mycotoxin surveys of Binder et al (2007) and Rodrigues and Naehrer (2012).
A trend for a lower dry matter intake was observed for the MTX group (25.02 vs 25.41 kg/d for control group), which is consistent with previous experiments using typical levels of DON and FUM.
The MTX group showed a significantly lower DM digestibility: 67.3%, vs. 71.0% for CTR group (P < 0.05). This difference was mainly explained by a markedly lower NDF digestibility: 42.8% for the MTX group vs 52.3% for the CTR group (P < 0.05).
Several in vitro studies have shown detrimental effects of mycotoxin on rumen fermentation (Gallo et al., 2015), but those findings are still controversial because of the diversity of protocols, doses and toxin origins used (purified vs natural). Furthermore, those in vitro trials tested the effect of mycotoxin by adding the targeted mycotoxins to the rumen fluid after rumen fluid collection, which may fail to reflect on-farm conditions. In the current study, both mycotoxin and Mycofix® Plus were fed to the cows in the diet before rumen fluid collection. Rumen fluid was collected from all cows at day 21 of each treatment period, and an in vitro gas production test was performed.
The MTX group showed:
- A trend for reduced volume of gas production: 147.8 vs 161.7 mL/g OM for the CTR group
- A significantly reduced concentration of acetic acid: 67.9 vs 71.0 mmol/L for the CTR group (P < 0.05)
Taken together, those results confirm the direct and negative effect of mycotoxin, through their antimicrobial, anti-protozoal and anti-fungal effects, on rumen fermentation and nutrient digestibility.
The reduction in rumen fermentation intensity, and the subsequent reduction in total-tract DM and NDF digestibility, likely lead to a lesser flow of available nutrients for milk production, as suggested by the 1.34 kg milk production drop observed in the MTX group: 36.39 vs 37.73 kg/d for the CTR group (P < 0.05).
Decreased NDF and fiber digestibility has been reported before with DON contamination, but with higher contamination levels (i.e. 4,400 ppb, Hildebrand et al., 2012). This experiment is the first to show impaired rumen function with regular levels of DON and FUM contamination.
If not fully detoxified, mycotoxins have the potential to harm and cross the intestinal epithelium barrier and reach the portal vein. In this experiment, significant increases in AST (117.07 vs 106.62 U/L for CTR group, P < 0.05) and GGT (30.726 vs 29.604 U/L for CTR group, P < 0.05) liver enzymes suggest a liver damage following toxin translocation to the blood stream.
It is worth noticing that a brief three-week period of exposure to mild levels of DON and FUM was enough to produce negative and significant effects in high-producing cow’s health and productivity. A longer exposure to those contamination levels, as frequently observed in commercial farms, would lead to exacerbated negative consequences on both productivity and health.
The addition of Mycofix® Plus to the DON and FUM contaminated diet showed:
- Trend for increased DMI: 25.52 vs 25.02 kg/d for the MTX group
- Significant increase of DM and NDF total-tract digestibility: 72.4 vs 67.3% DMd for the MTX group (P < 0.05), and 53.6 vs 42.8% NDFd for the MTX group (P < 0.05)
- Significant increase of rumen fluid total gas volume production: 172.6 vs 147.8 mL/g OM for the MTX group (P < 0.05)
- Significant increase of rumen fluid gas production rate: 7.8% vs 6.3%/h for the MTX group (P < 0.05)
- Trend of recovery of the energy-corrected milk production: 38.36 vs 37.86 kg/d for the MTX group, reaching a value very close to the one of control diet (38.50 kg/day)
- Significant decrease of AST and GGT liver enzymes: 110.0 vs 117.1 U AST/L for the MTX group (P < 0.05), and 29.5 vs 30.7 U GGT/L for the MTX group (P < 0.05)
- Additionally, Mycofix® Plus restored milk coagulation parameters that ensure a good cheese:milk ratio
Improvements in rumen fermentation, diet digestibility and liver enzymes indicate an efficient DON and FUM deactivation that enabled MPL group to recover similar digestive parameters to the CTR group.
Interestingly, the increase of DM and NDF digestibility in the MPL group were slightly, but significantly higher than those of the control group. This might have been due to the mild DON and FUM contamination observed in the control group.
This trial provides insight into how mycotoxins impact rumen fermentation, total-tract digestibility and productivity of high-producing dairy cows ingesting a diet contaminated with typical levels of DON and FUM. As the contamination levels used in this experiment are commonly observed in commercial dairy operations around the globe, and as the three-week treatment period used in the experiment is a much shorter period of exposure than what is observed in the field, one may conclude that regular contamination levels of DON and FUM have significant impacts on dairy herd’s productivity and health worldwide. Further investigation is needed, but this experiment brings interesting insights on how moderate mycotoxin contamination levels can impact dairy cow health and productivity. Those insights may be useful for the industry when it comes to setting mycotoxin contamination thresholds for risk evaluation in high-producing dairy cows.
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