Aspectos fisiopatológicos da reprodução de novilhas submetidas a dietas contendo zearalenona com e sem aditivo anti-micotoxina

Abstract

Zearalenone (ZEA) is a mycotoxin produced by several fungi species of the genus Fusarium spp., which can interferes with the physiology of endogenous hormones and affects the reproductive system of production animals. Since diets are contaminated with ZEA, the possibility of reducing exposure is through adoption of decontamination strategies such as use of anti-mycotoxin additive (AAM). Therefore, the aim of the present study was to evaluate whether the modified bentonite-based anti-mycotoxin additive would reduce the negative effect of zearalenone-contaminated diets on the clinical, cyclical and conception rate of beef heifers submitted to Fixed- Time Artificial Insemination (FTAI). Twenty-four heifers (n=24) with average age of 2 years and 271 ± 11.14 kg of body weight were evaluated through a general and complete gynecological examination. Healthy and cyclic females were selected and randomly assigned to compose four experimental groups with 6 animals each: T1 - basal diet (control), T2 - basal diet + 5 mg/kg ZEA, T3 - basal diet + 5 mg/kg ZEA + 2.5 kg/ton AAM and T4 - basal diet + 5 mg/kg ZEA + 5.0 kg/ton AAM. The research had a total duration of 37 days, being 11 days of adaptation period, 21 days of experimental period and 5 days of regression period. In the adaptation period, all heifers received a hormonal protocol for estrus synchronization and ovulation. During the experimental and regression period were evaluated body weight, vulvar volume, mammary gland edema, blood collection for estradiol and progesterone hormone dosage, and ultrasonography of the reproductive tract for frequency of uterine edema and number and diameter of follicles and corpus luteum on days 0, 5, 10, 15, 20 and 25. At the reproductive season (D67) the heifers were submitted to a FTAI protocol to analyze conception rate after intoxication. Body weight averages were similar between treatments on the different days evaluated. There was no significant vulvar edema between treatments on the different days evaluated. The edema of the mammary gland was absent in all treatments on the different days evaluated. In the assessment of uterine edema, it was observed that at day 0, all heifers presented uterine edema regardless of the treatment. And on days 5, 10 and 25 uterine edemas were absent in all heifers regardless of the treatment. On days 15 and 20, uterine edema occurred randomly between treatments. In the evaluation of the ovaries the averages were similar between treatments, regarding the number and diameter of follicles and corpora lutea corpus luteum on the different days evaluated. Serum estradiol concentration was similar between treatments on the different days evaluated. The progesterone levels revealed that there was no significant difference between treatments on days 0, 5, 10, 15 and 25, except for day 20 (P=0.03), where concentration was higher in T4. Conception rates after intoxication was 83% for T1, 60% for T2, 67% for T3, 83% for T4, and the overall rate between treatments was 74%. The use of an anti-mycotoxin additive at a dose of 5 kg/ton reduced the negative effect of diets contaminated with zearalenone by preventing the effects of mycotoxin on conception rate of heifers submitted to FTAI protocol. The contamination of the diets with 5 mg/kg zearalenone did not affect the clinical aspects and the cyclicity during days evaluated in the beef heifers, but reduced conception rate.