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1117
Comparison of follicular dynamics and subsequent progesterone profiles in Brahman cows with either two or three ovarian follicular waves
The objective of this study was to identify differences in follicular dynamics in a Bos indicus bovine estrous cycle with 2 or 3 follicular waves (2FW or 3FW) and the subsequent progesterone profiles. Daily ultrasonography was performed on 15 multiparous Brahman cows through a complete estrous cycle. Blood samples were collected daily from the coccygeal vein throughout the subsequent estrous cycle to determine serum progesterone concentrations by RIA. The ultrasound images were collected using a SonoSite M-Turbo© ultrasound with a 7.5 MHz L52X transducer. Follicular data were analyzed using Proc Mixed procedures and serum progesterone data were analyzed using Proc Mixed procedures specific for repeated measures using SAS v9.3. The first FW from cows with 2 or 3 FW estrous cycles were compared and the ovulatory FW were compared. Size and day (d) of the dominant and largest subordinant follicle did not differ between 2 or 3 FW estrous cycles during either the first or ovulatory FW. As expected the length of the FW differed (P< 0.01) during the first (2FW=11.90 ± 0.73; 3FW=7.00 ± 1.03) and ovulatory FW (2FW=10.80 ± 0.90; 3FW=6.00 ± 1.27) between groups, respectively. The d the largest follicle appeared differed (P< 0.01) in the first (2FW= 9.5 ± 0.48; 3FW= 5.6 ± 0.67) and ovulatory FW (2FW=9.8 ± 1.05; 3FW=5.6 ± 1.47). The greatest number of antral follicles found differed during the first (2FW=14.20 ± 1.60; 3FW=6.00 ± 2.25) (P< 0.01) and ovulatory FW (2FW=21.0 ± 2.00; 3FW=12.5 ± 2.83) (P=0.025). The serum progesterone profile of the following estrous cycle was normalized by analyzing the first 10d after estrus (CL growth phase) and the 10 d prior to the succeeding estrus (CL regression phase). There was a tendency (P=0.08) for an interaction between day and number of FW for the CL regression phase of the estrous cycle. The 3FW cows tended to have greater progesterone concentrations during the last 7d of the regression phase compared with the 2FW. These results suggest that cows with 2FW have greater a number of antral follicles within the first and ovulatory FW and the 3FW cows had increased serum progesterone concentrations during the CL regression phase of the subsequent estrous cycle.
Keywords: Brahman cows; follicular dynamics; serum progesterone.