Fusarium mycotoxins in cows
The effect of feed-borne Fusarium mycotoxins on reproductive efficiency in dairy cows, sows and broiler breeders
Mycotoxins are fungal metabolites that can reduce performance and alter metabolism of livestock and poultry (Wannemacher et al., 1991). The pathological states arising from the consumption of feeds contaminated with mycotoxins are referred to as mycotoxicoses.
Mycotoxins can be formed in the field preharvest and may continue to be formed under suboptimal storage conditions post-harvest. High moisture content often predisposes feedstuffs to fungal growth and mycotoxin formation. Temperature is another key factor.
Some fungi, such as Aspergillus flavus, are usually found in tropical and semi-tropical climates. This mold produces the carcinogenic hepatotoxin aflatoxin. Fusarium fungi, however, are more common in temperate climates and Fusarium mycotoxins are likely the most common mycotoxins on a global basis (Wood, 1992).
There are many reports of the effects of Fusarium mycotoxins on growth rates and metabolism in livestock and poultry but less research has been devoted to the effects of Fusarium mycotoxins on reproduction. This is no doubt a reflection of the complexity of such experiments.
Ruminant animals have been considered more resistant to the effects of feed-borne mycotoxins because of the detoxifying potential of rumen microorganisms. Charmley et al. (1993), Ingalls (1996) and Trenholm et al. (1985) reported few adverse effects of deoxynivalenol (DON, vomitoxin)-contaminated feed on performance of lactating and non-lactating dairy cows. Friend et al. (1983) fed diets containing 3.45 mg DON/kg to gestating sows and noted a significant reduction in feed intake, body weight gain, fetal length and fetal weight at 20-54 days of gestation.
Chavez (1984) fed sows naturally-contaminated wheat-based diets to provide up to 3.29 mg DON/kg for the last 90 days of gestation. No effect was seen on litter size or piglet weight at birth but reduced feed intake and weight gain were observed. There have been even fewer reports of the effect of feed-borne Fusarium mycotoxins on reproduction in broiler breeder chickens. Brake et al. (2002) fed up to 20 mg diacetoxyscirpenol (DAS)/ kg feed to broiler breeder hens and roosters and observed decreased fertility in broiler breeder males.
Experiments were conducted, therefore, to determine the effect of feed-borne Fusarium mycotoxins on reproduction and metabolism in sows, broiler breeder hens and roosters and lactating dairy cows.
Materials and methods
FEEDING TRIAL WITH DAIRY CATTLE
A study was conducted to determine the effect of feeding lactating dairy cows total mixed rations (TMR) containing wheat, corn and hay naturally-contaminated with Fusarium mycotoxins.
A total of 18 mid-lactation Holstein cows (six cows per diet) with an average milk production of 30 – 35 kg/day were fed for 56 days.
Treatments included: (1) control (2) contaminated grains (3) contaminated grains + 0.2% Mycosorb® (Alltech, Inc.), a polymeric glucomannan mycotoxin adsorbent. DON was the major contaminant and was found at up to 3.6 mg/kg in TMR dry matter.
Zearalenone and 15- acetyl DON were found in lesser concentrations. Body weight, body condition score, milk production, milk composition, somatic cell count (SCC), blood serum chemistry, hematology, total immunoglobulin (Ig) count and coagulation profile were measured.
FEEDING TRIAL WITH SOWS
A study was conducted to determine the effects of feeding a blend of corn and wheat naturally-contaminated with Fusarium mycotoxins to gestating and lactating sows.
A total of 36 first parity Yorkshire gilts (12 per treatment) were housed in individual stalls for 21 days before farrowing and 21 days after farrowing. During gestation, feed was restricted to 2.4 kg/pig/day.
Treatments included 1) control, 2) contaminated grains, and 3) contaminated grains + 0.2% Mycosorb®. DON was the major contaminant and was present at 5.7 mg/kg in contaminated diets and 0.2 mg/kg in the control diet.
Zearalenone and 15-acetyl DON were found in lesser concentrations. Parameters measured included body weight change, feed consumption, numbers and weights of piglets born, numbers of stillborn and mummified piglets, milk composition, viability of piglets until weaning, blood chemistry and weaning to estrus interval.
FEEDING TRIAL WITH POULTRY
A study was conducted to determine the effects of feeding a blend of corn and wheat naturally-contaminated with Fusarium mycotoxins to broiler breeder hens and roosters.
Forty-two 26-wk-old broiler breeder hens and nine roosters (Ross 308) were weighed and randomly assigned to individual wire cages with replicates of 14 and 3, respectively, for each of the three treatment groups. Feed consumption of hens was restricted to 133 g/bird/d increasing to 155 g/bird/d at the end of the experiment.
Diets included 1) control, 2) contaminated grains, and 3) contaminated grains + 0.2% Mycosorb®. The major contaminant was DON, which was found at about 13 mg/kg in contaminated diets and 0.2 mg/kg in the control diet.
Zearalenone and 15-acetyl DON were again found in lesser concentrations. Contaminated rooster diets contained an average of 7.8 mg/kg DON with the control diet containing 0.9 mg/kg. Hens were individually inseminated three times during the week before egg collection with 50 μL of fresh pooled semen from roosters fed corresponding diets.
Experimental parameters measured included feed consumption, body weight change, egg production, egg weight, shell deformity, albumin height, yolk weight, shell weight, shell thickness, weights of liver, spleen and kidney, blood biochemistry, hematology, serology, hatchability, progeny performance and rooster fertility.
DETERMINATION OF DIETARY MYCOTOXIN CONCENTRATIONS
Dietary contents of 19 mycotoxins including DON, 3-acetyl DON, 15-acetyl DON, nivalenol, T-2 toxin, iso T-2 toxin, acetyl T-2 toxin, HT-2 toxin, T-2 triol, T-2 tetraol, fusarenone-X, diacetoxyscirpenol (DAS), scirpentriol, 15-acetoxyscirpentriol, neosolaniol, zearalenone, zearalenol, aflatoxin and fumonisin were analyzed by gas chromatography and mass spectrometry (Raymond et al., 2003).
The detection limits were 0.2 mg/kg with exception of aflatoxin and fumonisin, which were detected at 0.02 and 2 mg/kg respectively.
Results and discussion
DAIRY CATTLE RESPONSE
There was no effect of diet on feed consumption, body weight change, body condition score, milk production, milk composition or milk somatic cell count.
Total serum protein and globulin concentrations were increased after 42 days in cows fed the contaminated TMR while albumin:globulin ratio decreased compared to controls (Table 1). Cows fed contaminated TMR + Mycosorb® were not significantly different from controls.
These changes might reflect the beginning of liver damage due to mycotoxin exposure. The changes in serum proteins do not appear to be a sign of acute inflammation as there was no elevation in other markers of inflammation.
Table 1. Effect of feeding a TMR naturally-contaminated with Fusarium mycotoxins on production, somatic cell count, serum IgA and urea of dairy cows.
1Not significant (P>0.05).
Feeding the contaminated TMR resulted in a continuous elevation in serum urea concentrations throughout the experiment, which was prevented by dietary supplementation with Mycosorb®.
It is not clear whether the elevated blood urea concentrations are due to the effect of DON and other trichothecene mycotoxins in inhibiting protein synthesis in rumen microbes or in inhibiting hepatic protein synthesis.
The contaminated TMR also significantly reduced serum IgA concentrations after 36 days of feeding and this was prevented by dietary supplementation with Mycosorb®.
This likely reflects the immunosuppressive effects of Fusarium mycotoxins as has been described in monogastric species.
It was concluded that feed naturally contaminated with Fusarium mycotoxins, even in low concentrations, can affect metabolic parameters and immunity of dairy cows and supplementation with Mycosorb® can prevent many of these effects.
RESPONSES IN SOWS
There was no effect of diet on average daily feed intake of gilts in gestation (Table 2).
Weight gain and gain:feed ratios, however, were reduced by feeding contaminated grains, which was prevented by supplementation with Mycosorb®.
Serum chemistry was unaffected by diet. The percentage of stillbirths was higher and the total piglets born was lower for gilts fed contaminated grains compared to those fed contaminated grains + Mycosorb®. There was no effect of diet on number of mummified piglets, total piglets born or piglet birthweight.
In the lactation period, feed intake and weight gain were reduced by diets containing contaminated grains (Table 3). Blood chemistry, milk composition and piglet weights at weaning were not affected by diet. There was a strong trend, however, toward increased weaning-to-estrus interval when sows were fed contaminated grains.
Table 2. Effect of feeding blends of grains naturally-contaminated with Fusarium mycotoxins on performance of gestating gilts.
a,b,cMeans differ (P<0.05).
Table 3. Effect of feeding blends of grains naturally-contaminated with Fusarium mycotoxins on performance of lactating sows.
a,b,cMeans differ (P<0.05).
It was concluded that feeding grains naturally contaminated with Fusarium mycotoxins to gestating and lactating sows increased numbers of stillborn piglets, however piglets that were born alive thrived throughout the lactation period. This is achieved, however, by a marked depletion of sow body reserves resulting in a trend towards increased weaning-to-estrus intervals.
RESPONSES IN BROILER BREEDERS
There was no effect of diet on feed consumption or feed efficiency (feed consumed/egg produced) and body weights were also not affected (Table 4).
There was a trend toward reduced egg production in birds fed the contaminated grains and this was significant in week 6. Feeding contaminated grains did, however, reduce egg shell thickness after 4 weeks; and this was accompanied by an increase in early (1-7 d) embryonic mortality.
These effects were prevented by dietary supplementation with Mycosorb®. It has been demonstrated that shell thickness affects moisture loss during incubation, prompting early embryonic mortality.
There was no effect of diet on other egg parameters including weight, yolk weight, albumen height, egg shell deformity or egg shell weight. Weights of liver, spleen and kidney were also not affected by diet. There was no effect of diet on weight or viability of newly hatched chicks.
Table 4. Effect of feeding blends of grains naturally-contaminated with Fusarium mycotoxins on performance of broiler breeder hens.
1Not significant (P>0.05).
Feeding contaminated grains decreased serum antibody titers against infectious bronchitis virus after 12 weeks, which was prevented by supplementation of contaminated diets with Mycosorb®.
There was no effect of diet, however, on serum antibody titers against Newcastle disease virus. The absence of the effect of diet on titers against Newcastle disease virus is likely due to the fact that Newcastle disease is not endemic in Canada.
Reduced antibody titers against infectious bronchitis is a reflection of the immunosuppressive properties of the trichothecene mycotoxins.
Rooster semen volume and sperm concentration, viability, motility and relative weights of testes were not significantly affected by diet.
| Conclusions It can be concluded that there are adverse effects of feed-borne Fusarium mycotoxins on reproduction in swine, poultry and dairy cows with the severity declining in that order. These effects can largely be prevented by dietary Mycosorb® supplementation. This has important economic consequences when widespread contamination of the feed supply forces use of contaminated grains or when favorable pricing prompts the intentional feeding of contaminated materials. |
References
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