Search

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.

Foot soundness is essential for optimum performance in beef cattle. When evaluating foot soundness, emphasis is placed on foot angle (FA) and claw set (CS). The objective of this study was to investigate the effects of foot angle and claw set scores on cowherd performance. Data were collected on 491 crossbred Angus-based cows over a three-year period. At weaning, FA and CS were evaluated according to American Angus Association guidelines. Scores are based on a nine-point scale, where a score of one indicates straight pasterns and short, divergent toes, and nine indicates weak, sunken pasterns and long, curled toes. Cows that exhibited scores ranging from four to six were considered acceptable. If either score fell outside this range, the cow was considered undesirable. Acceptable and undesirable cows were evaluated for performance traits including pre-breeding body weight (PBW), pre-breeding body condition score (PBCS), cow body weight at weaning (CWW), cow body condition score at weaning (WBCS), pregnancy rate, 205 d adjusted weaning weight (AWW), and weaning performance (WP). Data were analyzed using the GLIMMIX procedure of SAS. Significance was declared at P ≤ 0.05. There were no differences (P ≥ 0.19) for WP, PBW, PBCS, CWW, or pregnancy rate. Cows with acceptable foot scores had a WBCS 5.49% greater (P < 0.001) than undesirable cows. Acceptable cows possessed an average WBCS of 4.9 compared to 4.6 in undesirable cows. Acceptable cows weaned calves 3.39% heavier (P = 0.024) compared to undesirable cows. Acceptable cows weaned calves with a mean AWW of 216.67 kg compared to undesirable cows with a mean of 209.56 kg. The results from this study suggest that cows with acceptable foot scores may maintain more desirable BCS and wean heavier calves. These results could be used to help predict cow performance based on FA and CS.

The purpose of this study was to evaluate the efficacy of extended-release eprinomectin against horn flies, face flies, and fecal egg counts of parasitic nematodes in crossbreed replacement beef heifers. Fifty-four heifers were randomly placed into three treatment groups (n = 18 heifers/treatment). Group 1 was administered the labeled dosage of extended-release eprinomectin at the onset of fly season (day 0). Group 2 acted as the negative control. Group 3 received the anthelmintic injection once a quarter of the heifers in the group reached the threshold treatment level for horn flies (n = 200 flies/animal; day 41). All cattle were separately pastured for the duration of the study. Throughout the study, nematode infections were measured via fecal egg counts while horn and face flies were visually monitored. Evaluation of pregnancy status was recorded at the conclusion of the study (day 144). Due to the high number of face flies, heifers were treated with insecticide dusts twice during the study (day 54 and 69). Group 1 averaged a fecal egg count of (2.3), group 2 (7.4), and group 3 (9.1) (day 111). Low egg counts for all treatment groups reflected minimal parasite burden which likely had little effect on treatment groups. Extended release eprinomectin had little influence on face flies given that all groups were above threshold at days 40, 48, and 54. At study conclusion, horn fly population was lower (P < 0.05) for group 1 (405.6) compared to group 2 (680.6) and group 3 (680.6). Conception rates were greater (P < 0.05) in group 1 (89%) compared to the control heifers (56%) and group 3 exhibited an intermediate rate (72%). Results indicate that although treatment with extended-release eprinomectin did not decrease the face fly burdens, it did have an effect on fecal egg counts, horn fly burdens, and subsequent pregnancy status at the conclusion of the study

Osteopontin (OPN) is a protein found at higher concentrations in the seminal plasma of bulls with above average fertility. Polymorphisms have been reported within the OPN gene promoter that can affect production of this protein and thus, affect fertility. Therefore, Angus (n = 5) and Angus x Gelbvieh (Balancer, n = 14) and Angus x Brahman (n = 15) bulls were evaluated for presence of single nucleotide polymorphisms (SNP) in the Bos taurus OPN gene (GenBank: AY878328.1) promoter region, and their possible effects on bull semen quality as evaluated by computer-assisted semen analysis (CASA). Semen was collected by electroejaculation 6 to 9 times from each bull, and each semen collection was evaluated by CASA for motile, progressive and rapid sperm within 5 mins of ejaculation. The bulls were genotyped for reported single nucleotide polymorphisms (SNP) in the promoter region of the OPN gene through amplification of two 700 base pair (bp) DNA fragments and sequencing of the resulting PCR products. Seven SNP sites were identified, at bp 3379, 3490, 3492, 5075, 5205, 5209, and 5263 of the OPN gene. The SNP identified at bp 5205, 5209 and 5263 had not been previously reported. Individual SNP sites were evaluated as the main effect on CASA sperm motility variables in a SAS MIXED model for repeated measures. A thymine to guanine substitution at bp 3379 was associated with increased (P ≤ 0.02) percentage of motile, progressive and rapid sperm in Angus x Brahman bulls, and tended (P ≤ 0.10) to increase the same sperm motility parameters in Angus, and Angus x Gelbvieh bulls. The percentages of motile, progressive and rapid sperm were similar (P ≥ 0.05) among genotypes for the other 6 SNP identified. These results suggest that identification and genotyping of polymorphisms within the promoter region of the bovine OPN gene may be useful for selecting bulls with improved sperm motility parameters.

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.

This study investigated whether Estrotect estrous-detection patches could be used as a simple, cost-effective reproductive-management tool to identify cyclic animals before breeding, to distinguish between cows or heifers conceiving to AI versus natural service, and to determine seasonal pregnancy rate after bull removal. A secondary objective was to determine whether altering the timing of gonadorelin (GnRH) treatment in a 14-d progesterone-Select Synch synchronization protocol could reduce labor costs without reducing protocol effectiveness. Compared with cyclic status determined via ultrasonography, Chi-square analysis indicated that estrous-detection patches monitored for a 4-wk period were able to correctly identify 79% of cyclic and 86% of noncyclic heifers (P 0.10), regardless of timing of GnRH treatment. Treatment with GnRH at CIDR removal reduced labor costs and animal handling.

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.

Sixteen (mean age = 1.1 ± 0.1 yr; mean BW = 478 ± 34 kg) Brahman-influenced bulls were used to determine the influence of fescue type on sperm characteristics and serum concentrations of prolactin, cortisol, and testosterone. Bulls were blocked by BW, scrotal circumference (SC), and pregrazing sperm characteristics and randomly assigned to graze toxic endophyte-infected (EI; 4 bulls/pasture; 2 pastures) or novel endophyte-infected (NE; 4 bulls/pasture; 2 pastures) tall fescue for 121 d. Semen was collected by electroejaculation, and SC was measured and blood samples collected monthly. Sperm were evaluated for motility and morphology with an integrated visual optical system. Overall mean concentration of prolactin was decreased more (P 0.10) influenced by fescue type. Semen from bulls grazing EI had reduced motility and morphology than bulls grazing NE. Detrimental effects of toxic fescue may not be mediated by cortisol, testosterone, or both. Semen quality of bulls grazing toxic EI tall fescue was decreased with increased maximum ambient temperatures.

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.

This study examined the relationship between serum anti-Müllerian hormone (AMH) concentration at weaning and breeding to determine if either or both measures could predict subsequent fertility of beef heifers. Blood was collected from 71 Angus based heifers at ~7 and 14 months of age and serum stored frozen (−20°C) until analysis for AMH, using bovine AMH ELISA kits (AL115; Ansh Laboratories, Webster, TX, USA). Before breeding, transrectal ultrasonography was used to determine cyclic status of heifers. Heifers received 25 mg of prostaglandin F2α (PGF) and those detected in oestrus were AI ~12 h after detected oestrus. Heifers not detected in oestrus after 7 days received a second PGF injection and oestrus detection and AI continued for 4 days. Ten days later, the heifers were exposed to fertile bulls for a 45-days breeding season. At 50 to 60 days after insemination, transrectal ultrasonography was used to identify pregnant heifers and to confirm conception date based on fetal size. At 60 days after bull removal, ultrasonography was performed to determine pregnancy in heifers conceiving during the breeding season and confirm continuing pregnancy in heifers previously identified as pregnant. Based on fetal size at ultrasonography, the oestrous cycle after initiation of breeding when conception occurred was estimated. For comparison, AI pregnancies were considered cycle 1, and pregnancies initiated during subsequent 21-day intervals of the breeding season were classified as cycles 2, 3, and 4, respectively. For analysis, frequency distribution was used to assign serum AMH concentration measured at weaning, breeding, and the change from weaning to breeding, into quartiles. Comparisons were then made via Chi-squared analysis for heifers in each quartile that were cyclic at synchronization, detected in oestrus, conceived after AI, pregnant at the end of the breeding season, and the estimated cycle that conception occurred. Comparison of heifers based on serum AMH quartiles at weaning failed (P ≥ 0.35) to detect any effect of AMH on subsequent heifer cyclicity at breeding, oestrous response after synchronization, AI conceptions, overall pregnancy rate, or estimated oestrous cycle of the breeding season when conception occurred. Based on AMH concentration at breeding, heifers in the lowest quartile (Q1) had a lower (10%; P = 0.02) AI conception rate than heifers in other quartiles (43 to 73%), and conceived at a later oestrous cycle (P = 0.03) in the breeding season. Comparison of heifers based on the change in AMH concentrations from weaning to breeding revealed that none of the heifers in the lowest quartile (Q1) conceived after AI, compared with 80% in the highest quartile (Q4; P

A study investigated the effect of AI timing on pregnancy rate when using X sorted semen, and whether prostaglandin F2α (PGF2) injection on Day 7 of a modified 14-day progesterone (P4) protocol improved oestrous response in beef cows. Angus-based cows were allotted across treatment groups by cyclicity, parity, weight, body condition, and days postpartum. Treatment 1 (n = 132) cows received a CIDR P4 insert (Eazi-Breed CIDR, Pfizer Animal Health, Groton, CT, USA) on Day 0, with CIDR removal on Day 14, followed by 100 μg of gonadotropin-releasing hormone (GnRH; Factrel, Pfizer) on Day 16, and 25 mg of PGF2 (Lutalyse, Pfizer) on Day 23. Treatment 2 (n = 132) cows received the same synchronization treatment, except for an additional 25 mg dose of PGF2 given on Day 7 of CIDR treatment. Cows were observed for oestrus over an 84-h period and inseminated with X-sorted semen at 9 to 14, 15 to 17, 18 to 21 or 22 to 24 h after detected oestrus, followed 10 days later by exposure to fertile bulls for 45 days. Ultrasonography was used to determine pregnancy status ~45 days after AI and again 45 to 55 days after bull removal. Chi-squared analysis was used to determine the effects of treatment on oestrus response, AI pregnancy, and seasonal pregnancy rates, and the effect of AI timing on pregnancy rate. Analysis of variance was used to determine the effects of treatment on the interval from PGF2 dosing to detected oestrus. Oestrus response to synchronization treatment was similar (P = 0.33) at 76.5 and 71.2% for cows in Treatments 1 and 2, respectively. The mean interval from PGF2 to the onset of oestrus was extended (P = 0.03) ~3 h for cows in Treatment 2 (57.4 v. 54.3 h, respectively). About two-thirds of the cows in each treatment were cyclic at the start of synchronization. The extended interval from PGF2 to observed oestrus was due to an effect on cyclic, but not acyclic, cows in Treatment 2. Of the cows expressing oestrus, 69 and 89% expressed oestrus 48 to 72 h post-PGF2 in Treatments 1 and 2, respectively. Pregnancy rates after AI with sorted semen were similar (P = 0.64) at 63.3 and 66.7% for Treatments 1 and 2, respectively. No differences (P = 0.98) were detected in AI pregnancy rates for insemination intervals ranging from 9 to 24 h after detected oestrus. At the end of the breeding season, seasonal pregnancy rates were also similar (P = 0.74), at 83.3 and 84.9% for cows in Treatments 1 and 2, respectively. The addition of a PGF2 treatment on Day 7 of our 14-day CIDR-based protocol was expected to ensure all cows has sub-luteal P4 concentrations and would develop a persistent follicle capable of ovulation in response to GnRH given on Day 16. Whereas the Day 7 PGF2 treatment had no effect on oestrus response or pregnancy rate, it did result in a more synchronous oestrus within a 24-h period. Results indicate that acceptable pregnancy rates can be achieved in lactating beef cows when using sorted semen over a range of insemination times.