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Strategic supplementation of P4 may be used to increase conception rates in cattle, but timing of supplementation in relation to ovulation, mass of supplementary P4 and formulation of the P4-containing supplement has not been determined for beef cattle. Effects of supplementation of long-acting progesterone (P4) on Days 2 or 3 post-ovulation on development, function and regression of corpus luteum (CL) were studied in beef cattle. Cows were synchronized with an oestradiol/P4-based protocol and treated with 150 or 300 mg of long-acting P4 on Day 2 or 3 post-ovulation (6-7 cows/group). Colour-doppler ultrasound scanning and blood sample collection were performed from Day 2-21.5. Plasma P4 concentrations were greater (p < 0.05) from Day 2.5-5.5 in the Day 2-treated groups and from Day 3.5-5.5 in the Day 3-treated cows than in the control group. CL area and blood flow during Day 2-8.5 did not differ (p > 0.05) among groups, suggesting no effect of P4 treatment on luteal development. The frequency of cows that began luteolysis before Day 15 was greater (p < 0.04) in cows treated with 300 mg than in the controls, but there were no differences between non-treated and 150 mg-treated cows. The interval from pre-treatment ovulation to functional and structural luteolysis was shorter (p < 0.01) in the combined P4-treated groups than in the control cows. In conclusion, was showed for the first time that long-acting P4 supplementation on Day 2 or 3 post-ovulation increases P4 concentrations for ≥3 day, has no effect on luteal development, but anticipates the beginning of luteolysis in beef cattle.

This short communication reports the impact of endometrial biopsies, uterine flushings and follicular fluid aspiration procedures at day 6 post artificial insemination (AI) on pregnancy rates. In Experiment 1, cows were timed AI (TAI) and assigned to the following treatment groups: control (n = 37), uterine flushing (n = 35) and endometrial biopsy (n = 38). On day 30 post AI, pregnancy rates were 40.5%, 33% and 28.5%, respectively (p > 0.1). Pregnancy rate on day 60 was lower (p < 0.004) in flushed cows than in the controls. In Experiment 2, oestrus was detected and cows were assigned to flushing (n = 32) or biopsy (n = 33) treatments 6 days after AI, which resulted in pregnancy rates of 31% and 36%, respectively (p > 0.1). In Experiment 3, cows were, 6 days after TAI, randomly assigned to the following treatments: control (n = 84) or aspiration of the largest follicle (n = 73). Pregnancy rates on day 30 post AI were 63.5% for the control group and 53% for the aspirated group (p > 0.1). In conclusion, uterine flushing and endometrial biopsy negatively affect pregnancy rates, but neither procedure can be considered to be incompatible with pregnancy maintenance. Follicular aspiration during pregnancy does not interact with pregnancy success. The amount and quality of samples obtained are compatible with the use of cellular and molecular analysis of uterine variables from cows that failed or succeeded on maintaining pregnancy.

Accurate estrus detection is an essential component of a successful AI program in modern swine operations. It is necessary to establish efficacious means of estrus detection and optimize reproductive performance in the herd. Measurement of physiological traits such as body temperature, vaginal electrical resistance, and vulva reddening have been investigated as methods to aid in estrus detection in swine. The relationship between vulvar skin temperature (VST) and ovulation has not been previously investigated. Therefore, the objective of this study was to assess changes in VST that occur during the periovulatory period using digital infrared thermography (IRT). The experiment group consisted of a total of 25 gilts and 27 multiparous sows, and the control group consisted of 30 sows that were 60 days of gestation. All Yorkshire-Landrace females were housed individually in a temperature and humidity controlled environment. VST were measured twice daily at 8-h intervals using the infrared digital thermocamera (Fluke IR FlexCam® Thermal Imager, Fluke Corporation, Everett, WA) while the animals were standing and eating prior to estrus detection. Estrus detection was performed twice daily (at 8-h intervals) with the aid of an adult boar. Once standing estrus was observed, transrectal real-time ultrasound was performed twice daily at 8-h intervals to monitor follicle development and determine the time of ovulation. Ovaries were visualized using an Aloka 500 V ultrasonics machine (Aloka Inc., Tokyo, Japan) fitted with a transrectal 7.5-MHz linear transducer, which was fitted into a rigid, fixed-angle PVC adapter. Average VST and hours were reported in mean ± SEM and compared using an ANOVA and Student’s t-test using SAS software (SAS Institute Inc., Cary, NC, USA). Additionally, pairwise comparisons were performed to compare VST at different times during estrus. Significant differences were reported at P ≤ 0.05. Evidence of CL formation and ovulation was detected at 38 ± 9.3 h after onset of estrus in gilts, and 43 ± 12 h in sows. The mean VST of sows during estrus was significantly higher (P ≤ 0.05) than that of gilts. During estrus, the mean VST of gilts reached a peak of 35.6 ± 0.24°C and then decreased significantly to 33.9 ± 0.32°C 12 h prior to ovulation. This marked change in mean VST was detected between 36 and 12 h prior to ovulation. There was a similar trend in sows with a peak mean VST of 36.1 ± 0.25°C at 24 h prior to ovulation and then dropping to 34.6 ± 0.31°C 12 h prior to ovulation. There was no significant difference (P ≥ 0.05) between VST in gilts and sows at the time of ovulation. This study demonstrated that VST of sows and gilts measured by IRT change significantly during the periovulatory period. Additionally, there are distinct times that VST rises and then falls precipitously in sows compared with gilts. Digital IRT as a predictor for ovulation in swine appears to be a promising tool. Further studies involving predictor models and hormonal assays need to be performed.

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