Abstract
Selection of sheep that are unresponsive to bitter flavors may allow for a wider variety of forages to be utilized. Therefore, accurate and efficient classification of sheep according to taste sensitivity of bitter flavors is needed. Phenylthiocarbamide (PTC; bittering agent)-laced water and feed have been used to classify bitter taste sensitivity in sheep, but differences in classification between the methods remain unclear. Accordingly, the objective was to estimate the agreement between classification methods using water vs. feed as a PTC carrier. Using a validated approach, we classified 116 rams based on voluntary intake of PTC-laced water in a side-by-side free-choice scenario with tap water. From this test, 42 rams classified as either bitter supertaster (n = 14), taster (n = 14), and non-taster (n = 14) were further evaluated for voluntary intakes of PTC-laced feed pellets in a side-by-side free-choice scenario with control pellets. Correlations between PTC-laced water and PTC-laced feed were made. ANOVA between bitter sensitivity classifications and PTC feed intake were additionally performed. Finally, ANOVA were performed to see if PTC feed and PTC water intake differed by day. PTC feed intake was negatively correlated with PTC water intake (r = -0.31, P = 0.02). Consistent with this, the most bitter-sensitive super-tasters as determined by PTC water intake ate more PTC feed than the least sensitive non-tasters (P = 0.02). During the acclimation period for both trials, carrier intake did not differ from the test periods (P > 0.05). Results indicated that PTC-laced feed and PTC-laced water were consumed differently by the same rams, suggesting inconsistencies in classification between the two PTC carrier methods. Overall, test method improvements are needed to increase the efficiency and accuracy of classifying bitter taste sensitivity in sheep.