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Relatively, little is known about the corpus luteum (CL) function in early pregnancy after the successful treatment of luteal phase deficiency in repeat-breeder dairy cows when exposed to extreme environments under tropical climate. To investigate the influence of increased tissues of corpora lutea (CLs) by inducing secondary CL based on progesterone (P4) concentration and fertility in repeat-breeder dairy cows undergoing the fixed-time artificial insemination (FTAI) protocol, 32 cows were treated with gonadotropin releasing hormone (GnRH) on day 5 post-induction (experiment 1). In experiment 2, 213 cows were bred using the short-term FTAI protocol. On day 5 post-FTAI, cows were divided into two groups: treatment with (GnRH5-treated group) or without (GnRH5-untreated group) GnRH. The temperature-humidity index ranged from 77.3 to 82.8. Cows bearing two CLs had greater P4 concentrations than cows bearing only one CL on their ovaries (P 0.05). Pregnancy rates were greater in GnRH5-treated group than the GnRH5-untreated group (P 0.01). Moreover, repeat-breeder cows bearing two CLs had a greater likelihood of pregnancy (odds ratio = 20.86) than cows bearing only one CL on their ovaries (P 0.01). Under heat stress condition, the results highlighted that increasing luteal tissues by creating secondary CL leads to enhanced peripheral P4 concentrations and improved pregnancy outcomes in repeat-breeder dairy cows.

Background: Lower concentrations of endogenous progesterone (P) after fertilization, due to corpus luteum (CL) dysfunction, leads to an increased embryonic loss and reduced pregnancy outcomes not only in female cattle but also in women. Therefore, an increase in the number of corpora lutea (CLs) may improve fertility in infertile bovine females. The aim of the current study was to investigate the influence of increased number of CLs by creating accessory CL on plasma P concentration and fertility in bovine repeat-breeder females undergoing the short-term fixed-time artificial insemination (FTAI) protocol.Methods: In experiment 1, 32 female cattle had induced ovulation with the short-term (5-day) P-based protocol. To induce additional CL, cows were treated with gonadotropin releasing hormone (GnRH) on day 5 post-induction. On day 14, only female cattle with at least one CL on their ovaries were classified into two groups: 1CL (original CL; n = 14) and 2CLs groups (original CL + accessory CL; n = 8). In experiment 2, 213 bovine repeat-breeder females were bred using the short-term FTAI protocol. On day 5 post-FTAI, cows were divided into two groups: treatment with (GnRH5-treated group; n = 113) or without (GnRH5-untreated group; n = 100) GnRH. On day 14 post-FTAI, cows were sub-divided into two groups: 1CL (n = 115) and 2CLs (n = 39) groups.Results: In experiment 1, the ovarian luteal diameter, area, and volume per total CLs were greater in 2CLs group compared with 1CL group (P < 0.001). On days 12 and 14 post-induction, female cattle bearing two CLs had greater P concentrations than female cattle bearing only one CL on their ovaries (P < 0.05). In experiment 2, CL number and pregnancy rates were greater in GnRH5-treated group compared with GnRH5-untreated group (P < 0.01). Pregnancy rates were greater in 2CLs cows compared with 1CL cows (P < 0.01). Moreover, female cattle bearing two CLs had a greater likelihood of pregnancy (odds ratio = 20.86) than female cattle bearing only one CL on their ovaries (P = 0.001). Conclusions: In bovine model, our findings confirmed a beneficial effect of an additional CL on ovarian hormone and fertility in infertile female cattle. The results highlighted that increased number of CLs by creating additional CL leads to enhanced peripheral P concentrations and improved pregnancy outcomes in bovine repeat-breeder females undergoing the short-term FTAI protocol.

Science & Technology Asia, 24, 3, 67-79

The objectives were to evaluate effects of tropical seasons on thermal biology, preovulatory follicle (POF) diameter, POF and luteal vascularities, and estradiol (E2) and progesterone (P4) concentrations; and to determine the associations among the values for these variables during preovulatory and postovulatory periods in Thai native cows in tropical climates: cold, hot, and rainy seasons. Development and vascularity of the POF and corpora lutea (CL) were evaluated using color Doppler ultrasonography. The temperature-humidity index (THI) was greater when the preovulatory period occurred during the rainy season when compared with the occurrence during the hot and cold seasons of the year. Furthermore, POF diameter was less when the THI was greater. The THI was greater when the postovulatory period occurred during the rainy season when compared to the occurrence of the postovulatory period during the hot and cold seasons of the year. Furthermore, the CL vascularity and P4 concentration were less when the THI was greater. The THI was inversely correlated with CL vascularity and P4 concentrations. When the THI was greatest during the hot and rainy seasons of the year, there were the greatest negative effects on POF size, POF and CL blood flow, and concentrations of E2 and P4 during the preovulatory and postovulatory periods. While native Bos indicus are capable of adapting to tropical conditions, there are still negative effects, such as impaired POF and CL functions, when the THI induces heat stress.

A greater understanding of the uterine artery's (UtA) biology is essential to the increase in female reproductive abilities. The UtA flow velocity waveform, blood flow volume (BFV), pulsatility and resistance indices (PI and RI), blood flow velocities, dynamics of the dominant follicle (DF), and estradiol (E2) and progesterone (P4) levels in an induced ovulatory cycle were evaluated in Thai native cattle. Twenty cows were induced with synchronized ovulation through a P4-releasing device, from Day -9 to Day -4, concurrent with the administration of two doses of a gonadotropin-releasing hormone on Day -9 and Day -1, and two doses of prostaglandin F2α on Day -4 and 8 h later. Day 0 was designated as the day of ovulation. The cows underwent Doppler sonographic determination and blood collection from Day -4 to Day 0. The cows were classified in the non-ovulating (n = 5) and ovulating groups (n = 15). The ovulating cows presented higher BFV values, blood flow velocities, DF growth rates, and E2 levels; yet lower PI values and P4 concentrations, than those of the non-ovulating cows. The BFV values and the blood flow velocities were greater, but the RI and PI values were lower in the ovulatory side UtA than in the contraovulatory side UtA. The BFV values were positively correlated with blood flow velocities, DF growth rates and E2 concentrations in the ovulating cows; confirming the importance of UtA blood flow, follicular growth, and E2-vasodilation during preovulatory phase in the induced ovulatory cycle of Bos indicus beef cows.

The present study aims to determine the impact of differences in the locational relationship between the previous corpus luteum (CL) and the further ovulatory follicle (OF) on follicular dynamics and progesterone (P4) concentrations in Thai indigenous beef cows (White Lamphun) exhibiting two follicular waves. Twenty-one cows, exhibiting the two-wave follicular pattern, were studied through interovulatory intervals (IOI), and classified according to the relationship between the previous CL and the further OF on the cattle model ovaries. Classifications were outlined as either an ipsilateral (same ovary) relationship (n = 12), or a contralateral (opposite ovaries) relationship (n = 9). Ultrasound monitoring, which evaluated the follicular diameter, and collection of blood for determining the P4 concentration were performed each day throughout the IOI. The IOI was longer (P < 0.05) in the contralateral cows than in the ipsilateral cows (19.7 ± 0.33 days vs 18.5 ± 0.29 days). Cows with an ipsilateral relationship were found to have further OFs with greater (P < 0.05) diameters than were cows with a contralateral relationship (13.9 ± 0.31 mm vs 12.1 ± 0.21 mm). The mean growth rate of the further OF was greater (P = 0.05) in the ipsilateral cows than in the contralateral cows (1.1 ± 0.11 mm/day vs 0.8 ± 0.04 mm/day). On Day 17 of the IOI, the ipsilateral cows demonstrated their lowest concentration of P4 (P < 0.05). On Day 18 of the IOI, the concentrations of P4 tended to be lower (P = 0.09) in the ipsilateral cows than in the contralateral cows (0.6 ± 0.04 ng/mL vs 1.1 ± 0.12 ng/mL). The interval from the luteinisation until the end of the luteolysis was longer (P < 0.05) in the contralateral group than in the ipsilateral group (18.5 ± 0.50 days vs 16.7 ± 0.33 days). Thus, we conclude that in Thai indigenous beef cows, the growth rate and diameter of the further OF during luteolysis increases more in the ipsilateral relationship than in the contralateral relationship.