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Cattle in some parts of the world graze pastures that consist of tall fescue that may contain ergot alkaloid contamination. Those ergot alkaloids are associated with reduced reproductive rates in cattle. Our objective was to determine if ergot alkaloids [dihydroergotamine (DHET), ergonovine (EN), and ergotamine (ET)] directly affect bovine sperm characteristics. Spermatozoa were collected from mature Angus (n = 2) and Balancer (n = 4) bulls. Within bull, treatments were structured as a 3 × 5 factorial with three alkaloids (DHET, EN, and ET) and five concentrations of each alkaloid (0, 33, 66, 100, or 200 μM). Spermatozoa (25 × 106) were incubated (39˚C) in 1 mL of modified sperm medium. Sperm motility characteristics were evaluated using CASA (Hamiliton Thorne IVOS, Beverly, MA) at 0, 3, and 6 h after initial alkaloid exposure. Initial sperm motility was (69% ± 1.1%) and declined (P = 0.01) to (35% ± 2.6%) at 6 h. Sperm motility decreased (P < 0.05) with increasing concentrations of DHET and ET, but not EN. As concentration of ET or DHET increased all CASA sperm characteristics were altered. The interaction of alkaloid concentration and incubation length affected sperm velocity and head size; exposure to 200 μM of ET or DHET for six hours decreased (P < 0.05) both characteristics. Our results demonstrate that ergot alkaloids (ET and DHET) can directly alter bovine sperm motility and morphology, which adds to our understanding of how ergot alkaloids may hinder cattle reproductive rates.

This study evaluated sperm viability over time, after dilution and refrigerator storage of fresh semen extended in either synthetic cauda epididymal plasma (CEP2), or in a low sodium medium (CJ2) supplemented with either AlbuMAX or egg yolk. Semen collected weekly for 4 weeks from 4 bulls and assigned within bulls, across treatments. After extension in either CEP2, or CJ2 containing either egg yolk or AlbuMAX, semen was cooled to 4°C, and evaluated for 7 days. A computer assisted sperm analysis (CASA) system was used for sperm evaluation. Particular emphasis was placed on sperm motility since it is the single most important sperm parameter influencing bull fertility. Total and progressive motility of sperm in CEP2 and CJ2-AlbuMAX were similar (P = 0.85 and P = 0.23, respectively), but both were lower (P < 0.01) when compared to CJ2-yolk. Fewer sperm had rapid motility in CEP2 and CJ2-AlbuMAX compared to CJ2-yolk (P < 0.01). Sperm straightness and linearity were greater in CJ2-AlbuMAX and CJ2-yolk than in CEP2 (P < 0.01). Mean velocity (VAP) and linear velocity (VSL) were greater (P < 0.01) in CJ2-AlbuMAX than either CEP2 or CJ2-yolk. The calculated curvilinear velocity (VCL) of spermatozoa in CEP2 was lower than CJ2-AlbuMAX (P = 0.01), but similar with CJ2-yolk (P = 0.54). Overall, every sperm parameter measured by the CASA system was equal to or higher for sperm stored 7 days in CJ2 medium as compared with CEP2. The CJ2 extender supplemented with egg yolk is a viable alternative for storing fresh bovine semen.

Charolais × Balancer heifers (n = 65; BW = 179 ± 30 kg; 255 ± 12 d of age) were used to determine the influence of growth-promoting implants on growth, reproductive development, estrous behavior, and pregnancy rate. Heifers were assigned to 1 of 4 implant treatment groups: (1) control, no implant (n = 16); (2) trenbolone acetate (TBA; 200 mg of TBA; n = 15); (3) trenbolone acetate plus estradiol (TBA+E2; 40 mg of TBA and 8 mg of E2; n = 17); or (4) zeranol (ZER; 36 mg of ZER; n = 17). Reproductive-tract scores (RTS) were determined via ultrasonography on d 106 and 195 (d 0 = implant treatment). Estrous behavior was monitored by radiotelemetry. Average daily gain was greater (P 0.10) among treatments (72%). Implanting with TBA+E2 after weaning resulted in heavier heifers at breeding, and reproductive development was delayed in ZER heifers. Implant strategies after weaning may alter heifer growth and development on forage systems, but overall fertility was not affected in this experiment.

A study investigated whether prostaglandin injection on d 7 of a modified 14-d progesterone protocol improved estrous response in beef cows, and the effect of insemination timing on conception rate when using X-sorted semen. Treatment 1 (control; n = 132) cows received a CIDR progesterone insert from d 0 to 14, gonadorelin treatment on d 16, and prostaglandin F2α treatment on d 23. Treatment 2 (n = 132) cows received the same synchronization treatment, except an additional dose of prostaglandin F2α was given on d 7 of CIDR treatment. Cows were observed for estrus over an 84-h period and inseminated with X-sorted semen either 9 to 15 h or 16 to 24 h after detected estrus, followed 10 d later by exposure to fertile bulls for 45 d. Percentage of cows exhibiting estrus did not differ (P = 0.33) at 76.5 and 71.2% for treatments 1 and 2, respectively. Conception rates after AI with X-sorted semen were similar (P = 0.64) at 63.3 and 66.7% for treatments 1 and 2, respectively. Time of insemination had no effect (P = 0.72) on conception rate. At the end of the breeding season, overall pregnancy rates were also similar (P = 0.74) at 83.3 and 84.9% for cows in treatments 1 and 2, respectively. Results demonstrated no benefit to addition of prostaglandin F2α on d 7 to the estrous synchronization protocol and that acceptable conception rates can be achieved in lactating beef cows when using X-sorted semen over a range of insemination times.

This study evaluated the effectiveness of a modified long-term progestin-Select Synch estrous-synchronization protocol in beef cows and heifers. Experiment 1 evaluated the effect of reducing the interval from progesterone insert (CIDR) removal to gonadotropin releasing hormone (GnRH) administration in 72 postpartum cows. Treatment (TRT) 1 cows received a CIDR from d 0 to 14, GnRH on d 26, and prostaglandin F2α (PG) on d 33. Cows in TRT 2 received a CIDR from d 10 to 24, GnRH on d 26, and PG on d 33. Cows assigned to TRT 2 exhibited a shorter (P 0.10) among treatments. In Exp. 2, beef heifers (n = 64) and cows (n = 74) received progestin from d 0 to 14, GnRH on d 16, and PG on d 23. Cows and heifers in their respective groups were evenly divided to receive either CIDR or melengestrol acetate as the progestin source. Cows receiving CIDR exhibited increased estrous response and AI pregnancy rate (P 0.10) among progestin treatments. Final pregnancy rate was similar (P = 0.12) for cows receiving CIDR compared with those receiving melengestrol acetate. Regardless of progestin source, heifers exhibited similar (P > 0.10) estrous response, mean interval to estrus following PG, AI conception rate, and final pregnancy rate.

This study evaluated the use of melengestrol acetate ( MGA ), prostaglandin F 2α ( PGF 2α ) and gonadotropin-releasing hormone ( GnRH ) in a timed AI ( TAI ) protocol in postpartum beef cows. One hundred twenty-one Angus-crossbred cows in two herds were ranked by parity, days postpartum, body condition score ( BCS ), and BW and then randomly assigned to one of two treatments. Cows in both treatments received 1.8 kg of supplement containing 0.5 mg/d of MGA for 14 d, then received supplement without MGA for 17 d. After MGA withdrawal, cows in both groups received an injection of PGF 2α . Cows receiving the MGAPGF 2α ( MPG ) treatment were subjected to estrus detection and AI for 8 d. Cows receiving the MGA-PGF 2α -GnRH ( MPGG ) treatment were injected with GnRH 48 h after PGF 2α , followed by TAI 16 to 18 h after PGF 2α . There was a difference (P CR ) and pregnancy rate to AI ( PR ) and overall pregnancy rate ( OP ). The CR was not different between treatments (P≥0.24), but PR was greater in MPGG vs MPG (P≤0.08). There was no difference in OP between MPG and MPGG treatments (P≥0.25). The TAI procedure described in this study yielded results that were equal to those obtained with cows in a standard 14- to 17-d MGA-PGF 2α with estrus detection and AI protocol and similar to previously described TAI procedures.