Impact of gonadotropin-releasing hormone administration at the time of artificial insemination on conception risk and its association with estrous expression.

Cows with reduced estrous expression have compromised fertility. The aim of this study was to determine whether the administration of GnRH at the time of artificial insemination (AI) would affect ovulation rates and the fertility of animals expressing estrous behavior of lesser intensity. Cows were enrolled at the time of estrus from 3 farms (n = 2,607 estrus events; farm A: 1,507, farm B: 429, farm C: 671) and randomly assigned to receive GnRH at AI or not (control). The intensity of estrous expression, monitored through leg-mounted activity monitors, was determined using the maximum activity during estrus; estrous expression was categorized as greater or lower relative to the farm median. On farm A, cows were assessed at alert, and 24 h, 48 h, and 7 d post-alert for ovulation using ultrasonography. Pregnancy per AI was confirmed at 35 ± 7 d post-estrus for cows that were inseminated. Differences between treatments were tested using the GLIMMIX procedure of SAS. Treatment with GnRH at the time of AI increased pregnancy per AI (41.3 ± 1.6 vs. 35.7 ± 1.7%). An interaction between treatment and estrous expression on pregnancy per AI was found. Control cows with greater estrous expression had greater pregnancy per AI than those with lesser expression, whereas GnRH administration increased pregnancy per AI for cows with lesser estrous expression but not those with greater expression (GnRH, greater intensity: 43.5 ± 2.1; GnRH, lesser intensity: 37.8 ± 2.2; control, greater intensity: 42.6 ± 2.2; control, lesser intensity: 31.0 ± 2.2%). A higher proportion of cows with greater estrous expression that were administered GnRH at AI were found to ovulate by 48 h and 7 d post-estrus; however, ovulation of cows with lesser estrous expression was unaffected by GnRH administration. In conclusion, fertility of cows with reduced estrous expression may be increased using GnRH at the time of AI; however, increased ovulation rates do not seem to be the direct mechanism behind this relationship.

Plasma concentrations of progesterone in the preceding estrous cycle are associated with the intensity of estrus and fertility of Holstein cows.

The aim of this study was to determine the association between concentrations of progesterone (P4) during previous the estrous cycle with the intensity of spontaneous or estrogen-induced estrous expression and pregnancy per artificial insemination (P/AI). A total of 1,953 AI events from lactating Holstein cows were used, consisting of 1,289 timed AI events from experiment 1 (Exp. 1) and 664 AI events from experiment 2 (Exp. 2). In Exp. 1, cows were bred after a timed AI protocol based on estradiol and P4. In Exp. 2 animals were bred upon spontaneous estrus detection. In both experiments cows were continuously monitored by an automated activity monitor (AAM), in Exp.1 a relative increase of activity was calculated (i.e., percentage of increase activity at estrus compared to cow's baseline activity) and in Exp.2, activity data from each cow were computed into an index value that ranged from 0 to 100. In Exp.2 duration (hours) of estrus were calculated and defined as the total time above the threshold (35 index). The intensity of estrous expression was determined for each event and classified as either high or low intensity using the median of each experiment. Blood samples were collected for P4 analysis in Exp. 1 at -4 d, 0 d, and 7 d relative to timed AI, and in Exp. 2 immediately following estrus (0 d), 7 d, 14 d, and 21 d post-AI. Concentration of P4 was classified as greater or lower according to the median value in each experiment. Cows with lower concentrations of P4 at AI had greater estrous expression in Exp. 1 (363.6 ± 5.2 vs. 275.9 ± 8.0% relative increase) and Exp. 2 (76.7 ± 1.9 vs. 67.4 ± 4.7 index; and 12.5 ± 0.5 vs. 9.3 ± 1.8 hours). Cows with a greater intensity of estrous expression at timed AI had greater concentrations of P4 at -4 d than cows with lower intensity estrus or no estrous expression (4.6 ± 0.2 vs. 3.6 ± 0.2 vs. 3.7 ± 0.2 ng/mL). Cows with greater concentrations of P4 at -4 d had greater P/AI (32.8 ± 4.4 vs. 22.4 ± 4.5%), whereas cows with lesser concentrations of P4 at d0 for either timed AI (35.2 ± 3.4 vs. 19.6 ± 4.6%) or spontaneous estrus (31.8 ± 2.8 vs. 23.4 ± 3.2%) had greater P/AI. Cows with greater concentrations of P4 7 d post-timed AI had greater P/AI compared with cows that had lower concentration of P4 (39.1 ± 2.9 vs. 24.7 ± 2.6%). Similarly, cows that had lower concentrations of P4 at 7 d, 14 d and 21 d post-spontaneous estrus tended to have lower P/AI when compared with cows with greater concentrations of P4. Overall, concentrations of P4 prior to and at AI were associated with greater estrous intensity and P/AI at both spontaneous and timed AI events.

Rumen-protected B vitamin complex supplementation during the transition period and early lactation alters endometrium mRNA expression on day 14 of gestation in lactating dairy cows.

Greater metabolic demands in high-producing dairy cows are believed to be a cause of sub-fertility in these animals. Previously, supplementation with vitamin B complex molecules has shown benefits in improving milk production, health, and reproductive efficiency of dairy cows. The primary aim of this project was to determine the effects of rumen-protected vitamin B complex supplementation of 100 g of Transition VB (Jefo, St. Hyacinthe, QC, Canada) and 4 g of Lactation VB (VB; Jefo), during the transition and early lactation periods, respectively, compared with a control diet containing no supplementation on d 14 endometrial outcomes of pregnancy. In the vitamin B supplemented cows, we expect to see a change in the mark-up of endometrial genes important for embryo survival before implantation. Multiparous Holstein cows were enrolled into the study 3 wk before parturition and were randomly assigned to either the VB or control treatment. Twice-a-week blood samples, weekly milk samples, and daily feed intake were collected. Cows were enrolled onto a double-ovsynch protocol at 33 ± 3 d postpartum and inseminated by timed artificial insemination. Milk production and components, concentrations of BHB, haptoglobin, and progesterone in serum, and ovarian dynamics were also measured, but no treatment effect was observed. The uterus was flushed on d 14 after artificial insemination (around 72 DIM) for conceptus collection, and endometrial samples were collected at the same time. Overall, 42 cows were flushed and 13 embryos were collected. Analysis of mRNA expression of genes related to embryo development, immune system, adhesion, and regulation of vitamin B molecules showed that OXTR, MUC5B, MUC1, IL1B, SPP, TRD, FZD8, and FOLR1 genes were significantly upregulated in the VB group. Vitamin B supplementation had no effect on the size of the embryo and ovulatory follicle or corpus luteum diameter at embryo collection. In conclusion, the benefits of strategic dietary VB supplementation during the transition and early lactation might be directly linked to endometrial functions required for embryo survival during the peri-implantation period.

Effect of estrous expression on timing and failure of ovulation of Holstein dairy cows using automated activity monitors.

The aim of this study was to determine if estrous expression, as measured by an automated activity monitor (AAM), affects timing and failure of ovulation of lactating Holstein dairy cows. Cows were equipped with 2 AAM, 1 neck-mounted (AAMC) and 1 leg-mounted (AAML), by 10 d postpartum and enrolled into the trial when their activity crossed the alert threshold on the AAMC. A total of 850 episodes of estrus from 293 different cows were used for this study. When cows were enrolled, their ovaries were scanned by transrectal ultrasonography and gait and body condition scored. Ovaries of cows detected in estrus were scanned twice daily for a maximum of 3 d to determine the disappearance of the preovulatory follicle (ovulation) and the interval from estrus to ovulation was calculated. Physical activity data recorded from the AAM were used to determine estrus behavior using 2 traits: (1) peak activity and (2) duration. Peak activity was only available for the AAML. Peak activity was defined as the maximum activity during an estrus episode. Duration of estrus was defined as the time the activity of the cow exceeded threshold values set by the AAM software. The AAMC correctly identified 87.8% of the estrus alerts, with 12.2% false positives. The average (±standard deviation) intervals from activity alert to ovulation were 25.8 ± 10.2 and 24.7 ± 9.3 h for the AAMC and AAML, respectively. Changes in estrous expression were associated with differences in the interval from alert to ovulation. Cows with short intervals to ovulation were found to have less intense estrous expression than cows with medium and long length intervals to ovulation using the AAMC, whereas using the AAML, cows with short intervals to ovulation exhibited less intense estrous expression than cows with medium but the same as those with long intervals to ovulation. Furthermore, irrespective of the AAM, estrus events with less estrous expression had increased odds of having a short interval to ovulation (below the median of 20 h) when compared with those having greater estrous expression (2.6 and 1.9 increased odds for the AAMC and AAML, respectively). Ovulation failure was affected by estrous expression because estrus events with greater peak activity or longer duration had reduced ovulation failure compared with those with less estrous expression (AAMC peak activity: 1.9 ± 1.4 vs. 9.5 ± 1.7%; AAML peak activity: 2.3 ± 1.4 vs. 6.2 ± 1.5%; AAMC duration: 2.1 ± 1.4 vs. 8.9 ± 1.7%). In addition, cows with more estrous expression had greater pregnancy per artificial insemination than those with less estrous expression with both the AAMC (42.3 ± 0.4 vs. 31.7 ± 0.4%) and the AAML (43.1 ± 0.4 vs. 36.3 ± 0.4%). Pregnancy per artificial insemination results were consistent even when removing cows that failed to ovulate. In conclusion, expression of estrus was highly associated with ovulation timing, ovulation failure, and fertility when using 2 different AAM. Cows with greater estrous expression have longer intervals from activity alert to ovulation, experience less ovulation failure, and have greater pregnancy per artificial insemination.

Integrating an automated activity monitor into an artificial insemination program and the associated risk factors affecting reproductive performance of dairy cows.

The aim of this study was to compare 2 reproductive programs for the management of first postpartum artificial insemination (AI) based on activity monitors and timed AI, as well as to determine the effect of health-related factors on detection and expression of estrus. Lactating Holstein cows (n = 918) from 2 commercial farms were enrolled. Estrous cycles of all cows were presynchronized with 2 injections of PGF2α administered 2 wk apart. Treatments were (1) first insemination performed by timed AI (TAI) and (2) first insemination based upon the detection of estrus by activity monitors (ACT; Heatime, SCR Engineering, Netanya, Israel) after the presynchronization, whereas cows not inseminated by the detection of estrus were enrolled in the Ovsynch protocol. Body condition score (BCS; scale 1 to 5), hock score (scale: 1 to 4), gait score (scale: 1 to 4), and corpus luteum presence detected by ovarian ultrasonography were recorded twice during the presynchronization. On the ACT treatment, 50.5% of cows were inseminated based on detected estrus, whereas 83.2% of the cows on the TAI treatment were inseminated appropriately after the timed AI protocol. Pregnancy per AI did not differ by treatment (30.8 vs. 33.5% for ACT and TAI, respectively). Success of pregnancy was affected by parity, cyclicity, BCS, milk production, and a tendency for leg health. In addition, treatment × cyclicity and treatment × parity interactions were found to affect pregnancy success, where anovulatory cows and older cows had compromised pregnancy outcomes on the ACT treatment but not on the TAI treatment. Factors affecting pregnancy outcomes varied among farms. Hazard of pregnancy by 300 DIM was affected by farm, parity, BCS, a treatment × cyclicity interaction, and a tendency for an interaction between leg health and farm. Detection of estrus was affected by farm, parity, cyclicity, and leg health, but not BCS or milk production. Expression of estrus was compromised in anovular and older cows, and by the timing of the estrus event, but not by gait score, BCS, or milk production. Increased duration of estrus, but not intensity of estrus, improved pregnancy per AI. In conclusion, using an automated activity monitor for the detection of estrus within a Presynch-Ovsynch program resulted in similar pregnancy per AI and days open compared with a reproduction program that was strictly based on timed AI for first postpartum AI. In contrast, notable variations in reproductive outcomes were detected between farms, suggesting that the use of automated activity monitors is prone to individual farm management.