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

Abstract

Abstract 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.