animal endo 2011 zearalenone, phytoestrogens

Bos bovis

The effects of Zearalenone on ovarian function in dairy cows

Uzi Moallem, Moshe Kaim  Volcani Institute

It is well documented that compounds similar to estrogen in containing a phenol group can cause disturbances in the reproductive organs of various species. These estrogen-mimetics may exert their effects by two major actions: 1) binding to the estrogen receptor as an agonist; 2) binding to the estrogen receptor and preventing estrogen action (antagonist). Zearalenone is a well-known estrogen-mimetic which binds to the estrogen receptor and can decrease reproductive function in pigs, cattle and chickens.  Zearalenone has been reported to decrease conception rates and increase abortion incidence in cattle.  Similarly zearalenone is suspected to cause cyst formation in the bovine ovaries. One report was that in heifers fed 12.5 ppm of zearalenone/day, there was a reduction in the inception rate. A similar problem was reported in a milk herd which was feed with moldy hay with high concentration of zearalenone. The goal of the present experiment was to examine the effect of a known amount of zearalenone on the bovine reproductive system.  The experiment was undertaken using the experimental barn of the Volcani Institute using 12 cows which had at least one milking cycle.  Six cows were given feed containing 5 mg/day of zearalenone (Sigma) while six other cows served as a control. The zearalenone was mixed with 20 grams of ground corn and feed to the individual cows. The cows were synchronized and the ovaries were scanned for 2 consecutive cycles.  The scans recorded the follicles, corpora lutea and any ovarian abnormality. During the third cycle, follicular fluid was suctioned form the pre-ovulatory follicles. Samples of blood were taken at least once a week and more frequently in the peri-ovulatory period for estradiol determinations. No difference was observed between the groups in the size of small and intermediate follicles but the number of follicle greater than 15 mm was higher in the treated group compared to controls. Similarly the diameter and volume of pre-ovulatory follicles was greater in the treated over the control but this did not reach significance.  Analysis of the follicular fluid did not find significant differences in progesterone, androstenedione or estradiol concentrations. However the total estradiol/follicle was twofold higher in the treated compared to control (P<0.1). Similar observations were made for androstenedione and progesterone. The concentration of progesterone in the plasma on day 14 of the cycle was lower in the zearalenone treated than control (3.25 vs 6.55 ng/ml, respectively).  Examination of plasma estradiol in the peri-ovulatory showed no differences between the groups.  The data suggest that there were differences in steroid hormone production in the ovaries feed 5 mg/day zearalenone.  This was reflected in lower plasma progesterone but not plasma estradiol. Because of the high cost of the material and the intensive work schedule required, this experiment was limited to only 12 cows.  We suggest that if a larger group of cows were used, a statistical robust effect would be obtained for most of the parameters reported here.

Hebrew report  http://www.halavi.org.il/info/research/1/362-0159-08.htm

Zearalenone in the feed is sometimes associated with abortion in cows. In this unusual case, there were nearly 50 abortions in the time observed.  The peak in abortions was in second trimester.

Phytoestrogens - effects on fertility

Structure of the phytoestrogens 

Genistein and daidzein are converted to the more potent phytoestrogen equol by the intestinal bacteria.

Structure of the phytoestrogens

Plasma estrogen concentrations in cows on day of insemination in a herd feed vetch and three months after the vetch was discontinued Winter 1996).  Higher plasma estrogen was associated with higher resorption rates.

Legumes and resorption in dairy cows

Fetal resorption percentages in cows fed legumes.

Vicia sativa  vetch

Vigna unguiculata  cow peas

Resorption was determined as described in Shore, L.S., Rios, C., Marcus, S., Bernstein, M. and Shemesh, M. (1998). Relationship between peripheral estrogen concentrations at insemination and subsequent fetal loss in cattle. Theriogenology 50:101-107.  Cows were fed 1 to 3 KG of legumes/dy.  The principle phytoestrogen in cowpeas is formonentin but the phytoestrogen in vetch  could not be identified.

Here is a chart indicating that feeding vetch (a legume) to bull calves results in smaller scrotal circumference.