A series of preference assays were conducted, using 2-month old 135 Holstein calves (65±0.3d of age), to develop an experimental method aimed at evaluating oro-sensory preferences in weaned calves. First, 35 calves (65±0.7d of age) were used to describe the typical eating pattern to determine the optimum moment to conduct preference assays. It was observed that maximum feed consumption coincided with the morning liquid feeding, and thus, the optimum time to initiate the oro-sensory preference assays was 1h after that maximum intake had been reached. Subsequently, two different experiments, involving 30 naive calves (65±0.5d of age) in each experiment, were conducted to evaluate a double-choice experimental method that compared feed intake every 60min for 6h of a control feed (CF) vs. the same feed supplemented with sucrose (SF), 10% (SF10) in the first and 5% (SF5) in the second experiment. The proposed method allowed to detect oro-sensory preferences for the sugar-supplemented feeds, with a clear preference for SF10 (72.5%) and SF5 (69.2%) over CF. After, in Exp. 4, the same method was further evaluated for its ability to discern oro-sensory preferences for novel feeds using 20 calves (65±1.1d of age) that were confronted with ground barley and ground oats. Exp. 5 was a replicate of Exp. 4 to determine the reproducibility of the results obtained with the method. The proposed experimental method effectively discerned oro-sensory preferences of calves presented with novel feeds, with ground barley being preferred (8% and 80%, in Exps. 4 and 5, respectively) over ground oats. Last data from Exps. 2–5 were used to determine the minimum sample size required for detecting significant differences. In Exp. 3 (where the oro-sensory differences between the two contrasted feeds were the least), only 17 animals would have been sufficient to detect statistical differences in calf preferences. It is concluded that a valid and consistent method to assess oro-sensory preferences consists of conducting a double choice assay in which feed consumption of two feeds that are simultaneously offered (1h after the morning peak of feed consumption) ad libitum to a minimum of 20 naive calves is monitored for a 6-h period.
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