Prevalence of ergot derivatives in natural ryegrass pastures: detection and pathogenicity in the horse.

: FEDERICO PONT LEZICA, V.D.; R. FILIP; GORZALCZANY SUSANA; GRACIELA FERRARO, PH.D.;

Theriogenology

Año: 2007

0093-691X

We prospectively studied the toxicity of endophyte-infected ryegrass (EIR) in horses, characterized the pharmacological mechanism of the toxin, and carried out trials on prevention. We recorded prevalence and seasonal/weather variations of clinical manifestations of EIR toxicity, carried out chemical detection and pharmacological bioassays on ryegrass extracts; and completed blind, randomized, placebo controled trials on (i) effects of domperidone or metochlopramide on EIR-induced ovarian inactivity (ii) efficacy of buspirone or dihydrochloro phenyl piperazine (m-CPP) on preventing EIR-induced suppression of milk production and (iii) effects of domperidone on physiological Winter anoestrum. Mares with toxicosis showed prolongation of gestation, embryo resorptions, dystocias and poor development of mammary glands. Mares had low milk production, prolongation of the uterine involution time, and low ovarian activity with low progesterone (< 4 ng/ml) and high estrogens (> 150 pg/ml) in blood. Foals showed respiratory failure, abnormal skin, umbilical abnormalities, ostheomuscular abnormalities, maladaptation syndrome, blindness, testicular atrophy and decreased serum inmunoglobulins. A linear correlation existed between EIR and prevalence of toxicosis (Pearson´s r=0.861, p=0.03). We did not detect ergot alkaloids on extracts of EIR by either thin layer chromatograpy or spectrophotometry, but were able to demonstrate its presence in the extracts by bioassay (dose-related increase in the contractile response of the isolated uterus to endophyte infested grass). Metoclopropamide treated mares (0.6 mg/kg/day p.o. each 8 hs) were induced to ovulate faster than domperidone treated mares (1.1 mg/kg/day p.o.). Buspirone and mCPP resulted in induction of milk production. Domperidone did not induce ovarian cycling in healthy inactive (Winter) mares.