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Internal parasitism inevitability prompts economic loss in beef cattle production by decreasing growth performance and reproductive traits. Previous studies have conflicting results on the macrocyclic lactones (ML) efficacy against internal parasitism. The objective of this study was to evaluate the efficacy of milbeymycin and avermectin sub groups of ML on cow performance. Multiparous fall calving, crossbred beef cows (n = 106) were allocated randomly to 1 of 3 anthelmintic treatments: 1) Negative control (CON), in which cows did not receive an anthelmintic, 2) Injectable moxidectin (MOX) and 3) Injectable extended release eprinomectin (ERE). Body weights (BW), body condition scores (BCS), and fecal egg counts (FEC) were taken throughout the duration of the calving season to weaning on d0, d80, d162, and d217, with weaning occurring on d217. Performance data were analyzed using the MIXED procedures of SAS, and pregnancy data were analyzed using the GENMOD procedures of SAS. Significance was fixed at P < 0.05 and tendencies were established from 0.05 ≤ P ≤ 0.10. There was no effect of anthelmintic treatment on cow BW (P ≥ 0.57) or cow BCS (P ≥ 0.22) during the 217 d study; however, CON cows tended to have lower BCS (P = 0.08) throughout the duration of the study. Cows treated with ERE had fewer FEC compared to MOX and CON groups (P ≤ 0.001), and tended to improve pregnancy rates (c2 = 0.0546). Calf weaning weight was similar among treatments averaging 216, 225, and 223 kg regarding CON, MOX, and ERE cow treatments, respectively.

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.

The objectives of this study were to explore the usefulness of blood-based traits as indicators of health and performance in beef cattle at weaning and identify the genetic basis underlying the different blood parameters obtained from complete blood counts (CBCs). Disease costs represent one of the main factors determining profitability in animal production. Previous research has observed associations between blood cell counts and an animal's health status in some species. CBC were recorded from approximately 570 Angus based, crossbred beef calves at weaning born between 2015 and 2016 and raised on toxic or novel tall fescue. The calves (N = ∼600) were genotyped at a density of 50k SNPs and the genotypes (N = 1160) were imputed to a density of 270k SNPs. Genetic parameters were estimated for 15 blood and 4 production. Finally, with the objective of identifying the genetic basis underlying the different blood-based traits, genome-wide association studies (GWAS) were performed for all traits. Heritability estimates ranged from 0.11 to 0.60, and generally weak phenotypic correlations and strong genetic correlations were observed among blood-based traits only. Genome-wide association study identified ninety-one 1-Mb windows that accounted for 0.5% or more of the estimated genetic variance for at least 1 trait with 21 windows overlapping across two or more traits (explaining more than 0.5% of estimated genetic variance for two or more traits). Five candidate genes have been identified in the most interesting overlapping regions related to blood-based traits. Overall, this study represents one of the first efforts represented in scientific literature to identify the genetic basis of blood cell traits in beef cattle. The results presented in this study allow us to conclude that: (1) blood-based traits have weak phenotypic correlations but strong genetic correlations among themselves. (2) Blood-based traits have moderate to high heritability. (3) There is evidence of an important overlap of genetic control among similar blood-based traits which will allow for their use in improvement programs in beef cattle.

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

Disease incidence and feed costs are two main drivers in cattle production operations. Frequently environmental stressors such as fescue toxicosis have negative effects on livestock performance and health. Low-cost methods to measure these types of health and stress response phenotypes are needed to capture their impact on production traits. Previous research has correlated white blood cell parameters to disease resistance in beef cattle. Based on this, blood parameters at weaning may be candidates that could be a proxy for selection and identification of high-performance animals in commercial settings. To identify candidate blood parameters, blood samples were collected at weaning on approximately 500 crossbred animals (Angus background crossed with Hereford, Charolais, Sim-Angus, Brangus) born between 2015 and 2016 and raised on toxic fescue. The animals were also genotyped at an approximate density of 50,000 SNPs. Complete blood counts (CBC) were obtained the blood samples and heritabilities for 15 peripheral blood parameters were estimated. For the CBC traits that were measured, heritabilities ranged from low to moderate (0.02 to 0.35). Based on current findings, a substantial genetic component for some CBC parameters exists and selection could be effective at improving these traits. Further research will estimate genetic correlations between peripheral blood parameters, weaning weight and average daily gain (ADG) with the intention of identifying correlated traits to be used in commercial selection programs.

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.

Prolactin (PRL) is a pleiotropic protein hormone synthesized and released from the anterior pituitary. Concentrations of PRL can serve as a biomarker of cattle exposure to ergot alkaloids. Our objective was to determine relationships among prolactin concentrations, hair coat score, and body weights of non-lactating crossbred beef cows (n = 71). Cows were weighed, hair coat scored (1 = 100% shed, and 5 = 0% shed), and blood samples collected in May, June, and July. Cows were grazing mixed grass pastures that included native endophyte-infected tall fescue. Serum PRL concentrations were determined by validated RIA. Based on May samples, cows were categorized as high (n = 11; 159 ± 29 ng/mL PRL), medium (n = 48; 51 ± 4 ng/mL PRL), or low (n = 12; 21 ± 4 ng/ mL PRL). Data were analyzed with Pearson correlations, and repeated measures ANOVA with month and prolactin category (PRLCAT) as main effects. Concentrations of PRL were correlated (r > 0.53; P < 0.0001) over the three months, and May PRL concentrations were correlated (r > 0.29; P < 0.02) with cow body weights in May, June, and July. Cows in the low PRLCAT had lower (P < 0.01) concentrations of PRL in all three months. Hair coat score decreased (P < 0.0001) each month (4.3, 2.7, and 1.3; respectively, May, June, July), and was higher (P < 0.05) for cows with low PRLCAT (3.3 vs. 2.7 and 2.4 for low, medium, and high, respectively). Cow body weight increased (P < 0.0001) from May to July. Cows in the low PRLCAT had lower (P < 0.05) body weights than medium and high PRLCAT cows (484 vs. 555, and 575 kg; respectively). Concentrations of PRL in May could be useful in identifying cattle with slick hair coats and heavier body weights.

A study was conducted to evaluate variation in the ratio of X- to Y-bearing sperm of individual ejaculates and to determine any relationship between skewed sex ratio and either routine morphological evaluation or computer assisted sperm analysis (CASA). Semen was collected from bulls weekly for 6 consecutive weeks, sperm DNA was recovered and quantitative, and real-time PCR was used to determine the ratio of X- to Y-bearing sperm in each ejaculate. The overall mean of X-bearing sperm within ejaculates was 54.7% over the 6 weeks of semen collections. The percentages of X-bearing sperm were similar (P > 0.5) across all collections. Between bulls, there were differences (P < 0.05) in the mean percentage of X-bearing sperm. No significant correlations were found between CASA parameters and percentage of X-bearing sperm across bulls, so analysis was done within each bull. Different combinations of CASA and/or morphological parameters were found to correlate with the percentage of X-bearing sperm but the prediction equations were specific for individual bulls and unlikely to be of use across bulls. These results confirm that the ratio of X- to Y-bearing sperm may be skewed in some ejaculates of bull semen. Some sperm parameters measured by CASA or routine morphological evaluation were associated with semen sex ratio.

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.

Crossbred beef steers (n = 106; body weight (BW) = 96 ± 3.9 kg; age = 74 ± 2.0 d) were blocked by parity of dam (≤ 2 or > 2 parities), stratified by BW, age, and sire, and assigned randomly to 1 of 4 implant treatments on d 0: 1) RAL, administered Ralgro (36 mg zeranol) at branding (d 0), and Ralgro at weaning (d 156), 2) COM, administered Component E-C (100 mg progesterone and 10 mg estradiol with 29 mg tylosin tartrate) at branding (d 0), and Component TE-G (40 mg trenbolone acetate, 8 mg estradiol, and 29 mg tylosin tartrate) at weaning (d 156), 3) N-REV, no growth-promoting implant at branding (d 0), and administered Revalor-G (40 mg of trenbolone acetate and 8 mg estradiol) at weaning (d 156), and 4) CON, no growth-promoting implants administered during any phase of production. Body weights were recorded on d 0, 57, 98, 156, 198, 233, 268, 303 and 323 (feedlot shipment). Data were analyzed using the MIXED procedures of SAS with calf serving as the experimental unit for all dependent variables with α = 0.05. Weaning BW on d 156 tended to be greater (P = 0.08) in calves implanted during branding. Stocker phase average daily gains were greater (P < 0.01) in N-REV and COM compared to CON while RAL was intermediate. At time of feedlot shipment on d 323, there was an increase (P = 0.02) in BW in RAL (330 kg), COM (324 kg), and N-REV (318 kg) compared to CON (297 kg). Calves implanted at branding and weaning (RAL and COM) were 33 and 27 kg heavier; whereas calves implanted first at weaning (N-REV) were 21 kg heavier compared to never implanted calves indicating profitability in implanted calves regardless of timing of that implant.

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

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 (P0.01) in EI bulls than NE bulls from May to August. Scrotal circumference was not affected by fescue type (P = 0.58); overall SC averaged 36.7 +/- 2.3 cm. Percentage of live sperm was not different (P = 0.24) between NE bulls (80%) than EI bulls (67%) in July and August. Bulls grazing NE fescue had more (P0.06) motile sperm than EI bulls in July and August. Percentages of progressive (57 vs. 38%, NE and EI, respectively; P0.06) and rapid (67 vs. 46%, NE and EI, respectively; P = 0.04) sperm were greater from bulls grazing NE than EI bulls in July and August. Average velocity of the smoothed sperm path and progressive velocity in a straight line from the beginning to the end of the sperm track were slower (P0.09) in EI bulls than NE bulls and were slower (P = 0.04) in August compared with July. Mean width of head oscillation as the sperm swims was less (P0.06) in August than July. Concentrations of cortisol and testosterone were not (P0.10) 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.

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.