Figure 2 - Mycotoxin risk level for sows and calves based on Alltech’s REQ metric.
Moderate: 14.5%
% of samples at lower, moderate or higher risk REQ for Sows/Gilts
Lower: 44.9%
Average REQ
94 Maximum REQ
Higher: 40.6%
797
% of samples at lower, moderate or higher risk REQ for Calves/Heifers
Moderate: 14.5%
Lower: 42.0%
Average REQ
40 Maximum REQ
Higher: 43.5%
344
in 2021 straw samples, this could potentially lead to serious negative impacts for animals. With such high average and maximum DON levels present, and considering that the European Commission recommen- dation (2006/576/EC) clearly defines that feeding DON at a concentration higher than 900 ppb to pigs will result in significant effects of this mycotoxin on their health and per- formance, pig producers must consider the potential myco- toxin risk in straw to livestock health and performance. DON is one of the mycotoxins produced by the Fusarium mould. It belongs to the type B-trichothecene mycotoxins group, a group of 100 compounds with the same basic chemical structure produced by various Fusarium moulds. A common symptom of DON toxin consumption in animals is reduced feed intake. While this is certainly a significant problem, the reality is that the negative effect of trichothecene mycotox- ins on livestock is much more complex. Pigs are considered the species most sensitive to DON, with the effects amplified by the presence of fusaric acid. Many of the impacts of the trichothecene mycotoxins, such as DON, occur as a result of increased levels of oxidative stress, which is caused by an imbalance of antioxidants. Fusaric acid is produced by many species of Fusarium mould, such as Fusarium sporotrichiodes, Fusarium oxy- sporum and Fusarium moniliform. These can produce numerous mycotoxins, including fusaric acid. Fusaric acid appears to be produced at a wide range of temperature and moisture values and may be produced in the field or
during storage of feedstuffs. Fusaric acid competes with the amino acid tryptophan at binding sites, which leads to an increase in free tryptophan in the blood. This elevated free tryptophan can enter the brain, where it increases serotonin production. Fusaric acid also plays a role in reducing blood pressure. Together, these effects can lead to lower feed intake, vomiting, lethargy and swelling of the legs or mam- mary glands. These symptoms are often not observed until higher levels of fusaric acid are present in feedstuffs/feeds. Lower levels of fusaric acid still play a role in mycotoxin risk, however. Calves are typically offered long fibre roughage (straw or hay) to help develop their stomach and encourage cudding, especially where they are eating a pelleted ration. They also require some dietary fibre to minimise problems with bloat and reduce issues with acidosis, especially with diets formulated with elevated levels of starch. In a survey of com- mercial farms in Northern Ireland it was found that straw and hay were offered to calves by 59% and 33% of farms, respectively. Due to their rumen not being fully developed, calves tend to have low levels of immunity at this young age. With this reduced immunity, levels of DON or any other mycotoxin in straw or hay may have a significant impact on calves’ health and performance with these impacts at an early age also impacting performance as they transition to become productive animals.
References available on request. ▶ ALL ABOUT FEED | Volume 30, No. 3, 2022 27
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