CUTANEOUS CIRCULATION IS CORRELATED WITH MERINO WOOL PRODUCTION

Laser Doppler velocimetry was used to investigate the cutaneous circul ation and its relationship to wool growth in Finewool and Strongwool M erinos. Skin blood flow measured with the laser Doppler velocimeter (L DV) was highly correlated with estimates of blood flow obtained using Co-57-labelled microspheres (R2 = 0.85; P < 0.01), although the absolu te values estimated by the microsphere technique were significantly hi gher (P < 0.001). Strongwool Merinos had a greater rate of blood flowi ng through the skin than Finewool Merinos, and this was associated wit h both wool production per unit area of skin (R2 = 0.27, P < 0.01) and with the total volume of germinative tissue in the skin (R2 = 0.54; P < 0.04). The relationship between the microvascular anatomy of the sk in and blood flow was also examined in four Finewool Merinos and four Strongwool Merinos. Silicone rubber was infused into the deep circumfl ex iliac artery within the abdominal flank, from which an index of the area of vascular tissue per unit volume of skin was estimated. This i ndex was not related to blood flow, wool growth or follicle density wi thin nor between strains of Merinos. Both the usefulness and limitatio ns of the LDV are discussed, and it was concluded that (a) blood flow has an important role in the level of wool produced both within and be tween strains of Merinos, and (b) laser Doppler velocimetry is a usefu l tool for the study of blood flow in the skin of sheep.