Anthelmintic efficacy of pour-on Eprinomectin against gastrointestinal strongyles and relationships with milk production parameters in lactating goats

The aims of this study were (i) to evaluate the efficacy of pour-on eprinomectin (EPM) in lactating goats naturally infested with gastrointestinal strongyles, and (ii) to assess the related effects on their milk quanti-qualitative performance. Forty-two multiparous Camosciata delle Alpi goats reared in two semi-extensive farms (F1, n = 20; F2, n = 22) were included in the trial. In both farms, the goats were divided into two groups, which were balanced based on their infestation from gastrointestinal strongyles (number of eggs per gram of faeces, EPG), milk yield and gross composition. In each farm, the goats were then randomly assigned to a control (CTRL) or a treated (EPM) group. The EPM goats were treated with Eprinex® Multi Pour-On 5 mg / mL at the dosage of 1 mg / kg body weight (BW), while the CTRL goats did not receive any antiparasitic treatment. Starting on the day of drug treatment, and then once a week for the following 28 days, milk yield was recorded, and faeces and milk samples were collected individually. Faeces were subjected to copromicroscopic analysis, while milk samples were analysed for fat, protein, and lactose contents. Data were subjected to two-way ANCOVA using R software; the model included the effects of treatment, time (as a repeated measure), their interaction, and initial values as a covariate. Lower EPG values were found in EPM than CTRL goats in F1 (3316 vs 5485; p < 0.001), while no differences were found between groups in F2 (2864 vs 2986; p = 0.637). Coprocultures allowed to identify L3 larvae belonging to the genera Haemonchus, Teladorsagia and Trichostrongylus. In both farms, the treatment determined a reduction of Teladorsagia and Trichostrongylus larvae (p < 0.001). However, EPM goats showed significantly higher percentages of Haemonchus larvae when compared to CTRL ones (F1: 98.4% vs 92.3%; F2: 97.6% vs 92.5%; p < 0.001). In both farms, the treatment did not significantly affect milk yield and composition (fat, protein and lactose contents and yields). An exception was observed for milk lactose and protein contents, which were approximately 1 g / kg lower in EPM goats compared to CTRL goats in F1 and F2, respectively (p < 0.001). The obtained results suggest that pour-on EPM at the recommended dosage of 1 mg / kg BW is not effective in reducing Haemoncus in multiparous lactating goats. Further studies should identify the dosage able to reduce the parasite load, to avoid impairments of the short-term productive performance of dairy goats.