Impact of mycotoxins on dairy farming
The objective of this work is to know the main aspects of mycotoxicosis and its repercussions in dairy cattle.
The objective of this article is to analyze the main aspects of mycotoxicosis and their impact in bovine milk production. The most relevant mycotoxins in dairy cattle are Aflatoxins, Zearalenone, T-2 toxin, Ochratoxin, Vomitoxin or Deoxynivalenol. All of them can cause productive losses, decreased milk production and feed intake, reduced weights and inefficient feed conversion ratio and also show specific clinical signs.
Amongst them, Aflatoxins are more relevant on dairy farming due to their negative effect on nutrition and transmission of this toxin into the milk which compromises the welfare of the animal and its productivity.
Cattle are able to protect themselves from the mycotoxin’s harmful effect, due to the degradative effect of ruminal bacteria that deactivate mycotoxins.
This ability is directly related with the time the feed spends within the rumen which allows microorganisms to work properly. This explains why in intensive production systems, where animals digest higher quantities of feed in little time in order to increase milk production, the risk of exposure to mycotoxins is higher.
Changes on the feed ration and a diet high on concentrates also affect the ruminal bacteria’s ability to break down pathogen microorganisms.
This allows mycotoxins to pass through the ruminal wall and be absorbed in the intestine. Then they will be spread into different organs where will disrupt the enzymatic activity and therefore the health of the animal.
Different types of mycotoxicosis have been found: acute and chronic. The latter causes decreased feed intake and milk yields. One of the challenges can be identifying feed rations that contain low levels of mycotoxins. Subclinical mycotoxicosis reduces productivity on farms due to a drop in milk yields and milk quality. Also because of the cost to treat secondary conditions.
Aflatoxins are a group of mycotoxins mainly synthesized by the moulds Aspergillus flavus and A. parasiticus which are present in numerous raw materials used for animal feed.
Greater attention has been paid to aflatoxin B1 since, after being metabolized in the rumen, it passes to the milk as aflatoxin M1. There is strict regulation in place to control this toxin due to its harmful effect on both humans and livestock. This toxin is classified as a carcinogenic agent to humans.
Besides losses on milk quality and production, fertility can also be compromised.
The liver is the target organ for mycotoxins therefore hepatic lesions are observed, with congestion and haemorrhages. Also, fat deposits are seen on the liver, kidneys, heart, producing encephalopathies and limb oedema, down cows, abdominal pain and ruminal stasis.
The most relevant trichothecenes due to their clinical significance are DON (deoxinivalenol, also called vomitoxin) and T-2. Detoxification can be reduced by a low ruminal pH.
Clinical signs derived by trichothecenes include fertility issues, diarrhoea, gastro-enteritis and intestinal haemorrhages.
DON affects the liver and its ability to detoxify. It also produces a significant drop of milk production, fat in the milk and increased somatic cell count.
T-2 and its hydroxy and acetyl metabolites produce cytotoxic immunosuppressive effects, thus they are a risk for the animal health.
In dairy cows, the presence of T-2 can be related with anorexia, low milk yield, gastroenteritis, intestinal haemorrhages and death. T-2 has been associated with a notorious reduction of the immune response in calves and fresh (periparturient) cows.
Due to their estrogenic activity, Zearalenone and its metabolites are responsible for reproduction issues such as abnormal oestrus cycles that can disrupt fertility and mammary glands.
When the intoxication is a chronic one, long anoestrus cycles will appear in addition to chronic endometritis with hypertrophy of the uterine muscle.
Fumosin B1 and B2 are the most important and they are relatively slowly and inefficiently metabolised within the rumen.
Damaged organs in ruminants include liver and kidneys which leads to neurotoxic and nephrotic syndromes, brain and lung oedema, and hepatotoxicity and heart lesions.
They are produced by several types of mould so that they are present in mild and tropical areas.
Ochratoxin A is more widespread and has a nephrotoxic activity. It can affect ruminants; however, it is rapidly broken down within a healthy rumen so that it is not considered a major risk for dairy cattle.
Therefore, mycotoxin binders have been widely used in feed intended for ruminants in the last decade.
Biovet S.A. has developed a patented process in which the structure of natural silicates is modified in order to synthesize a patented molecule, named Silicoglycidol. Its structure improves the adsorption of mycotoxins and widens the binding spectrum. Thus, mycotoxins are not absorbed in section of the digestive tract and they are expelled with faeces.