Beyond 30-60 days into lactation, the most important factor to influence performance of dairy cows is quality of the roughage fed. In case of grass silage, haylage or corn silage, quality can be influenced at harvesting but also at feeding when TMR is being prepared.
Milk quality is increasingly becoming important. Traditionally, somatic cell count has been a very common quality parameter, with a potential negative impact on milk price if too high.
More recently, the potential presence of aflatoxins has become an issue. Incorrect preservation of silage can result in exposure of dairy cows to mycotoxins. Some of these mycotoxins cause problems in cows after exposure. Cows are relatively resistant to the effects of aflatoxins. Exposure of humans to aflatoxins can however cause health issues. The EU has stricter regulations than the US regarding allowable aflatoxin concentrations in milk for human consumption. According to EU legislation, aflatoxin level in milk must be below 50 ng/kg in milk, whereas 500 ng/kg is acceptable for the US authorities84.
Lastly, concerns about a possible correlation between Johne’s disease in dairy cows and Crohn’s disease in humans have resulted in increased concerns about contamination of milk with Mycobacterium para-tuberculosis (MAP)85.
