Ovulation and artificial insemination rates have been observed to decrease in sheep and cows when exposed to dietary phytoestrogens at concentrations greater than 25 mg/kg DM. A grazing trial was undertaken to investigate the effects of coumestrol and other key phytoestrogens on the superovulatory response, embryo numbers and quality in beef cows grazing legume pastures. A 7-week controlled grazing trial was conducted with legume and ryegrass pasture treatments, with cows exposed to legumes at two timed treatments, 4 and 7 weeks. Twenty Angus cows were subjected to a conventional estrus synchronization and superovulation protocol. Embryos were recovered via conventional uterine body flushing 7 days post artificial insemination (AI). Numerous phytoestrogens were identified in both pasture and plasma samples, including coumestrol and formononetin. Concentrations of phytoestrogens in the pasture ranged from 0.001 to 47.5 mg/kg DM and 0 to 2.6 ng/mL in plasma. Approximately 50% of cows produced viable embryos 7 days post AI. A significant interaction between the effect of treatment groups on the embryo stage was observed (p < 0.05). The results suggest that concentrations of >25 mg/kg DM of phytoestrogens less than 20 days preceding AI may negatively affect oocyte developmental competence, reduce progesterone production and thus contribute to early embryonic loss.

Altrenogest is a synthetic progestin that suppresses reproductive behaviours and assists pregnancy maintenance in female horses. Two formulations are available, a 'weekly' intramuscular injection and a daily oral formulation. Altrenogest administration has returned positive swabs for steroids; consequently, using injectable altrenogest in racing mares is prohibited. Oral administration may be permitted in race mares if there is one clear day between dosing and racing. The only pharmacokinetic data available were generated from geldings. Therefore, to assist veterinarians and analysts in determining accurate dosing and detection intervals, pharmacokinetic analysis using mares is required. Blood samples were taken from 10 mares pretreatment to obtain baseline concentrations. Mares were administered altrenogest, either oral (PO; 0.044 mg/kg; daily for 15 days) or intramuscular (IM; 0.3 mg/kg; twice; Days 0 and 7). On the first and last treatment day, blood samples were taken at designated times post dosing. After a 3‐week washout, mares received the alternative treatment with sampling repeated. At the initial dose, for IM administration mean (± SD) plasma altrenogest C_max was 18.0 ± 6.6 ng/mL at 7.9 ± 3.9 h compared with PO dosing 13.2 ± 5.8 ng/mL at 0.8 ± 0.8 h. Plasma C_max on the final day was significantly higher (p = 0.002 [IM]; p = 0.006 [PO]). At 24 h post final oral treatment, mean (± SD) plasma altrenogest was 1.0 ± 0.8 ng/mL and at 48 h were 0.65 ± 0.5 ng/mL. Plasma concentrations well exceeding this may indicate that the one clear day rule or dosage recommendations have not been adhered to.

Detecting the use of bisphosphonates (BPs) in equine athletes is of interest to regulators and laboratories due to the threat to welfare issues for the potential to provide analgesic effects and manipulating bone structure. The detection of BPs in biological matrices is challenging due to erratic biological elimination and inconsistent analytical recoveries. Therefore, complementary approaches are needed to provide evidence of their misuse in racehorses. BPs have two sub‐classes: nitrogenous and non‐nitrogenous. This study investigated plasma elimination following administration of one example from each sub‐class, together with changes in endogenous eicosanoid and corticosteroids. Zoledronic acid (ZA) and tiludronic acid (TA) were administered by IV infusion to 8 thoroughbred horses with an 11‐month washout period between each administration. Sample preparation for quantification of BPs by liquid chromatography–tandem mass spectrometry (LC–MS/MS) utilised a two‐step solid phase extraction (SPE) consisting of polymeric reversed‐phase followed by weak anion exchange prior to derivatisation using trimethyl orthoacetate. Endogenous biomarkers were analysed after protein precipitation and SPE with polymeric reversed‐phase prior to liquid chromatography–high resolution mass spectrometry (LC‐HRMS) using data independent acquisition. The LC–MS/MS analysis showed ZA was undetectable after 8 h post‐administration while TA was detected up to the final collection point of 28 days post‐administration. The LC‐HRMS analysis utilised targeted (i.e., prior inclusion list of compounds) approaches to monitor level changes of eicosanoid and corticosteroid biomarkers. Putative biomarkers were identified and now subject to validation for translation into routine sample analysis for improved retrospectivity to detecting BP misuse in equine plasma.

Altrenogest is a synthetic progestogen widely used in equine reproductive management. Adverse effects to altrenogest have been reported in people with cutaneous exposure reported as the highest exposure pathway. Despite these reports, there has been no quantitative research to determine the capacity for altrenogest to be absorbed through skin. This study aimed to determine if cutaneous application of oral altrenogest results in systemic absorption in mares and to evaluate the influence of application site. A randomized, two‐period, two‐treatment crossover study was undertaken in eight mares. Mares received a topical application of oral altrenogest (0.044 mg/kg) onto clipped skin on either the neck or back for five consecutive days, with blood sampling immediately before and 1 h after each treatment. Following the final dose, blood samples were taken at 0.08, 0.16, 0.3, 0.5, 0.66, 0.83, 1, 1.5, 2, 4, 6, 8, 12, 24 and 48 h. After a 3‐week washout period mares underwent treatment on the alternative site, sampling at the same intervals. Plasma samples were analysed for altrenogest using LC–MS/MS and pharmacokinetic variables were estimated using noncompartmental analysis. Altrenogest was detectable in plasma following application at both sites. Peak plasma concentrations (C _max ) were significantly higher following neck application (1.7 ± 0.7 ng/mL) compared to the back (0.6 ± 0.3 ng/mL; p = 0.002). Concentrations remained quantifiable throughout the 48‐h post‐treatment period. As altrenogest is absorbed through equine skin of varying thickness, there is a need for cautious use and handling, especially given that human skin is thinner than equine skin.