The threat from mycotoxins has become an increasing cause for concern. Historically, ruminant animals have been thought less susceptible to the negative effects of mycotoxin ingestion from the point of view of modification of the mycotoxins by rumen microbes. Controlled experiments investigating susceptibility of ruminants to mycotoxins have invariably used individual compounds, in contrast to the practical, field situation where the reality is exposure to multiple mycotoxins simultaneously. Additionally, many mycotoxins are able to adversely modify the rumen environment by anti-microbial, anti-fungal and anti-protozoal activity. The ability to degrade and inactivate many mycotoxins varies with diet, health status and has a finite capacity. Essentially, the more contaminated the diet or the less healthy the animal the lower the capacity to deal with a mycotoxin challenge, resulting in some toxins escaping the rumen unaffected to be absorbed in the small intestine. The immediate culprits that spring to mind are deoxynivalenol (DON) and zearalenone (ZEA).

Often, signs of mycotoxin challenge are non-specific, such as reduced intake, feed conversion efficiency and performance and, therefore, not immediately associated with a mycotoxin problem and may continue to persist while other avenues are investigated.

Mycotoxins are produced by moulds, a number of which can result in rumen dysfunction, reduced feed intake, significant drops in milk output, infertility, and decreased immune response to diseases. When analysed, it is clear that mycotoxins are a common problem in forage and more often than not, multiple mycotoxins are present. These have a synergistic effect, meaning that the presence of one exaggerates the effect of another, increasing the overall risk to the dairy and beef animal.

Farmers may think that only those feeds showing visible evidence of mould growth contain mycotoxins. Unfortunately, this is not true. Mycotoxins will remain even after the moulds responsible for producing them have been removed and are often present even when no visible mould exists.

Mycotoxins compromise animal health and performance. Signs of mycotoxin challenge include reduced milk yield, poor growth, swollen joints, ‘dull’ appearance and lethargy. It’s important to note that many of the symptoms associated with mycotoxicosis are non-specific often meaning that a mycotoxin issue is ‘last in the queue’ when diagnosing.

Symptoms of mycotoxins on ruminant:

• Fertility
  • Irregular heats
  • Low conception rates
  • Ovarian cysts
  • ketosis
  • Embryonic loss
  • Abortions
  • Low sperm production low semen quality
• Young animals
  • Early development of mammary gland in prepubertal heifers
  • Low testicular development
  • Death due to poor immune system at birth
• Vital organs
  • Kidney lesions
  • Liver lesions
  • Hepatocellular injuries
• Gastrointestinal
  • Gastroenteritis and diarrhoea
  • Gastrointestinal lesions
  • Impaired rumen function
  • Decrease rumen motility
  • Shifts in rumen pH and volatile fatty acids production
  • Decrease dry matter and nutrient digestibility
• Production
  • Mastitis and laminitis
  • Decrease milk production
  • Low milk solids
  • Low animal growth

Author: Denis Dreux