Canary coloration of wools: breed differences and their possible causes

Abstract

The intensity of non-scourable yellow (canary) coloration, based on a visual score, was observed in a number of indigenous carpet-wool breeds, Rambouillet and Merino, and in the crosses of some of the indigenous breeds with Rambouillet. Among Indian breeds, those with dense fleeces showed more intense coloration than those with open fleeces. Exotic fine-wool breeds (Merino and Merino types) showed considerably less coloration than the native breeds. Rambouillet x Chokla crosses (half and three-quarter breeds) had less intense coloration (P < 0.05) than Chokla, the three-quarter breeds significantly (P < 0.05) less than the half-breeds. In contrast, the Rambouillet x Malpura half-breeds showed more intense coloration (P < 0.05) than the pure Malpura, though the three-quarter breeds showed coloration similar to that of the Malpuras. It is suggested that different modes of heat dissipation—a greater dependence on respiratory evaporative cooling in Merinos and on cutaneous evaporative cooling in native breeds—are responsible for the differences in intensity of fleece coloration between exotic and native breeds. Differences in coloration among native breeds appear to be due primarily to differences in fleece density. Differences between half-breeds and the respective native breeds appear to be due to the combined effect of the different modes of heat dissipation and diffcrences in fleece density: the increase in exotic inheritance results in greater dependence on respiratory evaporative cooling.