Abstract: The objective of this study was to investigate the follicular dynamics by B-mode ultrasonography during spontaneous estrous cycles in 6 river buffaloes and 6 swamp buffaloes. 2 patterns of follicular waves were discovered in one estrous cycle in river buffaloes, and 2 follicular waves were the most frequent (66.7%, 4/6) in swamp buffaloes. During the two patterns of follicular waves, the 1st and 2nd wave of river buffaloes emerged on 1.3 and 12.2 d，respectively, and swamp buffaloes emerged on 1.1 and 11.0 d. The number of recruited and selected follicles in 1st wave was 14.8, 2.5 d, and 2nd wave was 14.2, 3.2 d in river buffaloes, while 1st wave was 8.0, 1.0 d, and 2nd wave was 7.8, 1.5 d in swamp buffaloes. There were significant differences between river buffaloes and swamp buffaloes(P<0.05) in the number of follicles recruited and the number of follicles selected.

Key words: B-mode ultrasonography; river buffaloes; swamp buffaloes; follicular wave