361 - Methods for Identification and Classification of Phenylthiocarbamide Sensitivity in Mature Rams

Rams exhibit varying levels of sensitivity to phenylthiocarbamide (PTC), which has been correlated with the ability to perceive bitter-tasting foods. Previously, the only procedure for measuring PTC-sensitivity in rams involved a 9-d test phase with 5 PTC concentrations. The objective of this experiment was to develop a more streamlined approach for identifying and classifying rams on extreme ends of the bitter-tasting spectrum. Mature Targhee, Rambouillet, Polypay, and Composite-breed rams (n = 44), housed in three separate barns, and subjected to 4-d acclimation, 2-d sham, and 2-d testing phases. The 2-d sham phase was conducted to determine if ethanol-spiked water (delivery vehicle for PTC) influenced voluntary fluid intake; no effect (P = 0.16) was observed. The 2-d test phase was a side-by-side preference study between water (control; 3.0 kg) and 1 of 2 concentrations (0.2 and 2.0 mM) of PTC solution (3.0 kg) delivered on alternate days. Average consumption of PTC as a percentage of total test fluid intake was used determine taster status. No PTC-treatment effect (P ≥ 0.23) was observed, but within each treatment level, PTC intake was less (P < 0.001) than water intake. Classification levels of PTC consumption were determined by ± 1.0 standard deviation of the mean and used to classify rams into non- (n = 9; 61.5 ± 3.9%), intermediate- (n = 29; 40.7 ± 1.8%), or super- (n = 6; 15.6 ± 3.3%) PTC tasting groups, which were different (P < 0.001) from each other. Likewise, water consumption intakes were different (P< 0.001) between the non- (38.5 ± 3.9%), intermediate- (59.3 ± 1.8%), and super- (84.4 ± 3.3%) PTC tasting groups. The methods outlined in this study will facilitate further research focused on the influence of bitter tasting sensitivities on the dietary preferences of sheep.