The goal of every nutritionist is to ensure that the fermented/digested ration is as close as possible to the formulated ration, but aside from the dry matter (DM) content of the feed, another major factor that can lead to a wide difference in rations is the presence of mycotoxins. Mycotoxins are toxic compounds that are naturally produced by certain types of molds (fungi). Hundreds of mycotoxins have been identified, but the most common ones that affect human and livestock health include aflatoxins, ochratoxin A, patulin, Fumonisins, zearalenone and nivalenol/deoxynivalenol. These mycotoxins are produced by molds that grow on various foodstuffs including cereals, dried fruits, nuts and spices. Specifically, they can be found in feed ingredients including corn and other grains used in dairy cow feeds. The growth of molds can occur before or after harvest and during storage, usually under warm and humid conditions.
During one of the breakout sessions at the just-concluded Penn State Dairy Nutrition Workshop in Hershey, PA, Caroline Knoblock (Agrarian Solutions) shed some light on the effect of mycotoxins on the productivity and health of dairy cows. Plants are more susceptible to mold growth when they are exposed to stressors like drought, high moisture, and physical damage. Mycotoxins are becoming more frequent, and their presence in feeds lead to several health and production problems. The table above summarizes the major mycotoxins found in the US and Canada, and the main effects they exert.
Mycotoxins can be controlled in the field by full tillage, and by the use of fungicides (at full silking and with the drop nozzle method). To prevent the growth of molds during storage (or ensiling), the pH should be reduced as quickly as possible, and proper packing, covering, and complete oxygen removal should be ensured. Inoculants (lactic acid bacteria) can also be used. Feed additives like binders, enzymes, and probiotics can also be fed to the animals to tackle the impact of ingested mycotoxins if it cannot be controlled at the field level.
A very insightful part of her session was the result of the mycotoxin survey that was done from March to September 2024 in the US. According to her, the Northeast, Pennsylvania, Virginia, and Georgia are contributing high Vomitoxin (DON) total mixed ration (TMR) samples for 2023 and 2024. For Zearalenone, there’s an indication that this mycotoxin will not be a problem in the Great Lakes area in 2024, although it is still showing up in the Northeast and Pennsylvania, with new occurrences in Virginia and North Carolina. For T2, even though this mycotoxin was low in 2023, it’s becoming higher in the 2024 crop, especially in Virginia, while samples from Southeast Pennsylvania show a medium to high risk level for it. There is every likelihood that 2024 would show more Fumonisin contamination in some parts of the country, with higher incidences in Virginia, North Carolina, and Pennsylvania.
In my opinion, these results can help to project the outlook of mycotoxin contamination for 2025, and the more feed and TMR samples that are tested, the more accurate the predictions to ensure timely interventions. If there is a concern about the feed you have grown, bought, or have in the bunk, it’s worth testing such feeds to understand the potential impact of any mycotoxins present, and to decide on changing your feeding strategy or consider including a binder in the diet. These efforts will guarantee that our cows are fermenting and digesting the feed we formulate on paper, and save us the cost of curative measures.
— Gift Omoruyi