Abstract
Besides oral temperature, meteorological parameters are expected to be relevant for mouthpiece temperature, potentially influenced by the material, surface area and weight of the bit. This study measured the temperature of the mouthpieces at the corner of the mouth while they were in use on 58 carriage horses during the four 2024 seasons. Stainless steel, copper, and copper-steel bits were tested in three shapes: Butterfly Liverpool, Liverpool, and Loose Ring Snaffle with four rings. Additionally, surface temperatures of inner thighs, the ground, and buildings were measured using infrared thermography as well as meteorological parameters. Mouthpieces of copper bits reached the highest median temperatures of all materials over all months (31.9 °C) and in August (34.5 °C). In February, the air temperature (median 12.45 °C) was cooler than mouthpiece temperatures (steel median 21.8 °C, copper median 26.4 °C). Mouthpieces of copper-steel Liverpool bits were significantly warmer than those of steel Liverpool bits (+1.1 °C, p < 0.026) at wet bulb globe temperatures > 25 °C. Maximum mouthpiece temperatures of steel Butterfly Liverpool bits showed a weaker correlation (Spearman Rho 0.8) with wet bulb globe temperature categories than both steel Liverpool bits and steel Loose Ring Snaffle bits, which demonstrated a full correlation (Spearman Rho 1). Concerning mouthpiece temperatures, bit material, shape, and weather conditions should be considered when selecting bits to ascertain impacts on equine welfare.