Preliminary Results on the Efficacy of Gel Microencapsulated Acaricides in the Control of Tick Infestations in Dairy Cows and Their Impact on Milk Yield

The castor bean tick (Ixodes ricinus) is a widespread European ectoparasite and vector of multiple diseases that can impair cattle health and productivity. This study evaluated whether a single application of a gel microencapsulated acaricide (α-cypermethrin and permethrin) reduces I. ricinus infestation in dairy cows and affects milk yield. Twenty cows were allocated to treated and control groups; treated animals received one spray at the start of the grazing season, and tick counts were recorded daily for 196 days with monthly milk-yield measurements. Two activity peaks were observed (June and September–October) with reduced abundance in July–August; all control cows were parasitised, with daily counts of 1–18 ticks (median = 2). During the first month after treatment, the acaricide reduced tick numbers by around 80% versus controls (p < 0.001); efficacy declined over the ensuing months, and differences were negligible after about five months. No adverse effect on milk yield was detected (p = 0.38), and seasonal variation (p < 0.0001) and lactation stage (p < 0.001) were the primary determinants of production. Primiparous and young cows, as well as cows in mid-to-late lactation, tended to show higher levels of tick infestation. A single application of the gel microencapsulated product provided a significant reduction in tick burden during the first month after treatment in grazing dairy cows, without a negative impact on milk production, supporting its use in endemic areas.