Mycotoxin contamination of pig feeds may have a considerable impact on health and productivity of the enterprise. This article focuses on the effect of feed naturally contaminated with mycotoxins on reproductive performance and lactation of the sow, as well as on the development of piglets.
Mycotoxins are harmful metabolites produced by molds (fungi). They can be produced before harvesting (due to factors such as extreme weather), and continue after the harvest, in suboptimal storage conditions.
Currently, there seems to be an increase in the frequency of challenges caused by animal feed contaminated with mycotoxins. This is probably due, in part, to extreme climatic conditions lately verified in agricultural areas around the world.
The UN Intergovernmental Panel on Climate Change recently informed that, due to global warming, extreme climatic conditions are becoming increasingly frequent.
Higher humidity due to increased rainfall. The increase in humidity before harvest, due to excess in rainfall and floods, promotes mould growth and increases the risk of mycotoxin contamination.
Droughts. Extremely dry conditions also can increase the chances of mycotoxin contamination. Smaller, cracked grains may allow mould spores to cross mechanic fibrous barriers and grow inside the layers of the endosperm.
Mycotoxins can be produced in:
The growing utilisation of the LC/MS/MS method to measure mycotoxins in animal feed constitutes a great advancement in the fight against mycotoxin contamination.
Analysis of historical data of LC/MS/MS tests have pointed out the frequency of feed contamination with several mycotoxins at one time. This method has also shown the presence of mycotoxins rarely measured before, mostly due to the unavailability of ELISA kits to test for them. These mycotoxins are known as “emerging mycotoxins” (Table 1) (Gruber-Dorninger et al., 2016). Little is known about their toxicity to pigs and other species.
A good example of the utilisation of LC/MS/MS is the work by Blandino et al. (2017). Those researchers analysed maize samples cultivated in natural conditions in Italy, throughout several years. They detected 37 different mycotoxins and metabolites. All samples contained fumonisins, fusaric acid, fusaproliferin, DON, DON-3-glucose, culmorin and zearalenone.
Such multiple co-contamination suggests the possibility of additive and synergic effects of mycotoxins. Such interactions could exaggerate the response in the pig when comparing it with individual mycotoxins.
The administration of diets contaminated with only one mycotoxin showed a 14% drop in feed intake, and a 17% drop in average weight gain.This concept was backed up by the studies performed by Andretta et al. (2016). They did a metanalysis on data obtained from 85 published papers on the effect of feeding diets contaminated with mycotoxins to growing pigs.
These values, once again, emphasise the importance of additive and synergistic effects when diets are contaminated with multiple mycotoxins.
It seems that some plants have the ability of chemically modifying the mycotoxins produced by invading fungi. This can be a natural defence mechanism if one considers that some mycotoxins are also phytotoxic.
However, the relative toxicity of these compounds for pigs have not yet been clarified. The difficulty of the task is given by the fact that bacterial enzymes of the gastrointestinal tract may hydrolyse the mycotoxins conjugates, generating free mycotoxins that can enter the bloodstream to reach the target tissues. Researchers believe that such undetectable conjugates contribute to an unexpectedly high toxicity in pigs, if estimations were based on resuots of conventional analytical techniques.
A series of trials were performed, in which first-time pregnant sows were given diets consisting of a mix of maize and wheat, naturally contaminated with mycotoxins. Feeding took place during 21 days before farrowing (Diaz-Llano and Smith, 2006) and during the first 21 days of lactation (Diaz-Llano and Smith, 2007).
During the trials, the following variables were measured:
It was concluded that the lower body weight gain by the end of pregnancy, observed in sows eating contaminated feed, was due to a lower intestinal absorption caused by DON-mediated damage of intestinal mucosa.
The reduction of arterial blood pressure caused by fusaric acid should have affected the transference of nutrients to the foetuses. However, the lack of effect of the contaminated diet on the piglets may have been the result of the sow mobilizing its own energy and protein reserves to compensate for the deleterious effect of mycotoxins.
It was again concluded that the sows compensated the toxic effects of the contaminated diets, by mobilising their own body reserves.
Contaminated diets affected the reproductive function.
This supports the theory that a prolonged return to oestrus in sows eating contaminated feed was due to a longer time needed to replenish body reserves.
In a later stage, researchers posed the question of whether body weight loss was due to a direct effect of the mycotoxin, or due to a reduction in feed consumption. A second study was performed (Diaz-Llano et al., 2010) to find an answer to that question. It also aimed to determine the mechanisms whereby the toxin binder reduces the number of stillborn piglets.
The experimental design of the first study was repeated, but with the addition of a fourth treatment. In it, the sows were fed a restricted amount of control diet to emulate the effect of reduced feed intake during lactation, but in absence of mycotoxins. Muscular biopsies were taken to analyse DNA, RNA and proteins.
The results suggested that stillbirths in sows eating contaminated diets was due to an increase in the blood concentration of ammonium. The mycotoxin binders probably adsorbed the ammonia in the digestive tract, preventing the developing foetus from being intoxicated.
Based on the results of muscular biopsies, the severe weight loss during lactation, verified in sows eating contaminated feed, was due to the reduction in feed intake and not because of a direct toxic effect of the mycotoxins.
Gestating and lactating sows are negatively affected when consuming diets naturally contaminated with mycotoxins of Fusarium spp. The greatest economic losses are probably related to the prolonged time needed to restore body condition before entering the new oestrus.
This article was originally published in nutriNews Spain with the title Contaminación por micotoxinas de los alimentos para cerdos
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