289 Sperm Quality Assessments Using Flow Cytometry do not Differ between Angus and Charolais Breeds of Yearling Bulls Meeting Breeding Soundness Exam Threshold Requirements

Flow cytometry has been used as a reliable and objective tool for bull sperm quality assessments and identification of sub-fertility. Our objective was to determine if breed differences exist in sperm quality assessments using flow cytometry when evaluating semen from yearling Angus and Charolais bulls that passed breeding soundness exam (BSE) semen evaluation thresholds. Ejaculates were collected via electroejaculation on one of three consecutive days from yearling (403.15 ± 11.19 d age) Charolais (n=23) and Angus (n=23) bulls as part of a BSE. BSEs were conducted by one veterinarian and all bulls met all requirements as set by the Society for Theriogenology. An additional sperm motility analysis was conducted with the iSperm analyzer. Ejaculates were diluted in BoviFree to 70 million cells/mL and sent overnight for flow cytometry analyses. Sperm flow cytometry analyses included: acrosome and cell membrane integrity, mitochondrial energy potential, and oxidation status. The GLIMMIX procedure of SAS with bull as experimental unit, bull breed as the main effect and collection date as a random variable was used to assess potential differences in sperm quality variables. Neither iSperm (P = 0.26) nor visual assessment (P = 0.66) of sperm motility differed among breeds. Bull breed did not influence (P = 0.83) total percentage of viable cells, nor percentage of viable cells with intact acrosomes (P = 0.83). When evaluating oxidation status by measuring reactive oxygen species, bull breed did not influence (P = 0.92) percentage of live sperm cells with positive reactive oxygen species status. There was a tendency (P = 0.10) for a greater percentage of sperm from Charolais bulls (31.1% ± 3.35) to have positive mitochondrial energy potential as compared with Angus bulls (17.6% ± 3.35). Bull breed appears to have little influence on sperm quality assessments among yearling bulls meeting threshold requirements for passing BSEs.

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PSII-A-2 Correlations between Reactive Oxygen Species and Functional Measurements of Spermatozoa from Beef Bulls

Reactive oxygen species (ROS) have effects on characteristics of spermatozoa, including mitochondrial membrane potential, acrosomal integrity, and structural abnormalities that can influence spermatozoa function. The objective was to determine correlations between sperm response to ROS and functional sperm measurements using ejaculates collected as part of bull breeding soundness exams (BSE). Semen samples were collected from Angus and Charolais bulls (403 ± 11 d of age; n=46) over three days during yearling BSEs. A veterinarian evaluated spermatozoa for percent motility and normal morphology, and percentage progressive motility was measured using an iSperm® analyzer. If ejaculates met minimum thresholds for passing a BSE, they were diluted to 70 million cells/mL using BoviFree® and sent overnight for flow cytometry evaluation. Flow cytometry assays including acrosome and cell membrane integrity, mitochondrial energy potential, and oxidation status. Data were analyzed using Pearson’s correlation coefficients in SAS. Percentage live spermatozoa with positive ROS status was correlated (r = 0.53; P < 0.001) with percentage progressive motility. Percentage live spermatozoa with negative ROS status was moderately correlated with percentage spermatozoa exhibiting secondary abnormalities (r = 0.33; P = 0.02) and tended to be lowly correlated (r = 0.28; P = 0.06) with percentage spermatozoa exhibiting primary abnormalities. Percentage live spermatozoa that had disrupted acrosomes was strongly correlated (r = 0.66; P < 0.001) with percentage live spermatozoa with negative ROS and also moderately negatively correlated (r = -0.31; P = 0.04) with percentage live spermatozoa with positive ROS. Percentage live spermatozoa with positive ROS status was correlated (r = 0.58; P < 0.001) with percentage of spermatozoa with active mitochondrial membranes. Live spermatozoa with positive ROS were strongly correlated (P< 0.001) with live spermatozoa (r=0.94) and live spermatozoa with intact acrosome (r=0.92). These data confirm previous research that shows the detrimental effects of ROS on spermatozoa function.

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179 Sire Distribution of Calves in a Herd with use of Fixed Time Artificial Insemination Followed by Immediate Bull Exposure for Natural Service

Use of fixed time AI followed by immediate exposure of females to bulls for natural service can be a useful management strategy for commercial cow-calf producers to limit labor and time related to bull turnout as well as increase pregnancy rates earlier in the breeding season. Considering potential influence of factors such as bull fertility and time to and length of estrus in females, expectations for outcomes in natural service sire versus AI sire parentage is relatively unknown. We hypothesized that of calves born in the first 14 d of the calving season, less than 5% would be sired by natural service bulls exposed to females immediately following fixed time AI. Heifers (n = 191) and cows (n = 156) were synchronized and inseminated using the 7-d CO-Synch + CIDR fixed time AI protocol. All females were inseminated by the same AI technician using a single sire for heifers and a different single sire for cows. All females were exposed to bulls immediately following insemination. DNA was collected from a random subset of calves (Calves born from heifers n = 59; Calves born from cows n = 89) born in the first 14 d of the calving season for parentage analysis to estimate the overall percentage of calves sired by AI and natural service. Chi-Square tests were used to determine if the percentage of calves actually sired by natural service differed from the hypothesized 5% or less. Among calves born from heifers, the actual percentage sired by natural service (5.1%; n = 3/59) was similar (P = 0.98) to our hypothesized percentage. Among calves born from cows, the actual percentage sired by natural service (14.6%; n = 13/89) was greater (P < 0.001) than our hypothesized percentage of 5%. If commercial producers use fixed time AI followed by immediate bull exposure in cows, natural service bulls may sire more calves early in the calving season than expected.

PSV-5 Effect of Breed and Barn Location on Semen Quality at an Artificial Insemination Facility

A better understanding of the factors that influence collection and semen quality for AI sires is needed. Our objectives were to evaluate the effect of breed and environmental factors on semen characteristics from 49,086 ejaculates analyzed by a single technician at a beef semen collection facility. Bulls were housed in one of 5 barns based on health testing and purpose of semen collection. Multiple ejaculate characteristics were evaluated using regression models; fixed effects included breed, age, and barn. Ejaculate volume differed (P < 0.001) between Angus (8.5 ml) and Horned Hereford (7.5 ml). Concentration of spermatozoa was lower (P < 0.001) for Angus compared with Simmental, Charolais, and Horned Hereford (1009, 1100, 1252, and 1197 x 106/ml, respectively). Horned Hereford had greater (P < 0.01) concentration of spermatozoa compared with Red Angus (1197 and 1046 x 106/ml, respectively). Simmental had greater (P < 0.01) pre-freeze motility when compared with Angus, Red Angus, and Horned Hereford (54, 50, 49 and 49%, respectively). Average production of 0.5 CC frozen straws per collection was greater (P < 0.001) for Simmental (244) when compared with Red Angus (205) and Angus (223). Pre-freeze motility (% motile) varied from 48% to 53% between the five barns (P < 0.001). The average concentration of spermatozoa varied from 1000 (x 106/ml) to 1155 (x 106/ml), with Barn 1 producing the lowest per ejaculate (P < 0.001). Bulls in Barn 1 produced a greater amount (P < 0.001) of primary abnormalities than Barn 4 and more (P < 0.001) secondary abnormalities than Barn 3. Overall, Simmental, when compared with Angus bulls, produced the greatest number of straws per collection, with the highest pre-freeze motility. Recognizing breed differences and the effect of barn location may help improve overall efficiency, and producer expectations of semen collection at this facility.

50 Long-term Motility of Semen Following Breeding Soundness Exams for Yearling Beef Bulls

To find an in vitro predictor of in vivoM/em> semen motility prompted this study. Our objective was to evaluate semen motility for an 8-hour period immediately following a breeding soundness exam. Ejaculates from 52 Angus and 56 Charolais bulls were evaluated. Motility, morphology, scrotal circumference and pH of ejaculate were evaluated at the time of collection. Ejaculates were then extended using a one to one ratio and incubated in a water bath held at 37 degrees Celsius and evaluated hourly. Motility was evaluated hourly for 8 hours, or until motility of the sample reached zero. Data were analyzed for breed and hourly effects using the GLIMMIX procedure of SAS. There was statistical evidence for difference (P < 0.0001) between breeds for motility over time. Angus ejaculates had higher pH values than Charolais ejaculates showing an association between breed and pH (6.82 vs 6.76, respectively). Primary spermatozoa abnormalities were greater (P < 0.0001) for Angus bulls compared to Charolais bulls (13.33% vs. 10.91%, respectively). Scrotal circumference between breeds tended to be different (P < 0.07), with Charolais bulls having a larger scrotal circumference compared to Angus bulls (38.29 vs. 38.03 centimeters, respectively). There was no difference (P > 0.05) between breeds for secondary abnormalities. There was a significant interaction (P < 0.01) between breed and time of motility measurement. Angus bull’s motility decreased drastically until hour 4, it then had a more gradual decrease until hour 8. Charolais bulls had a more gradual decrease in the percentage of motile sperm over time. In conclusion, there was evidence for difference between breeds for pH, primary spermatozoa abnormalities, and long-term motility, and a scrotal tendency. Understanding the effects of breed and individual biological factors may help producers adjust BSE expectations and lead to future research in long term semen motility.

Genetic parameter estimation for beef bull semen attributes

Improvements in bull reproductive performance are necessary to optimize the efficiency of cattle production. Female fertility has been enhanced through assisted reproductive technologies as well as genetic selection; however, improving beef bull fertility has been largely ignored. Phenotypes routinely collected at bull semen collection facilities are believed to affect fertility and provide the phenotypes necessary for a genetic evaluation. The first objective of this study was to determine the significant fixed effects for modeling beef bull fertility using data from bull semen collection facilities. The second objective was to estimate variance components, heritabilities, repeatabilities, and correlations between beef bull semen attributes. Beef bull fertility phenotypes including volume (VOL), concentration (CONC), number of spermatozoa (NSP), initial motility (IMot), post-thaw motility (PTMot), 3-h post-thaw motility (3HRPTMot), percentage of normal spermatozoa (%NORM), primary abnormalities (PRIM), and secondary abnormalities (SEC) were obtained from two bull semen collection facilities. A total of 1,819 Angus bulls with 50,624 collection records were analyzed. Of the fixed class and covariate effects tested, the significant class effects were collection location and collection day within year and the significant covariate effects included age at collection, days since previous collection, and cumulative comprehensive climate index (CCI). For this study, the CCI was calculated for a 75-d period including the 61-d spermatogenesis cycle and 14-d epididymal transit time. The 75 d prior to collection accounted for the environmental stress a bull may have experienced over the course of development of the spermatozoa, which was more significant than the CCI calculated for collection day or spermatogenesis start date. Pre-thaw beef bull semen traits had low heritability estimates of 0.11 ± 0.02 (VOL), 0.09 ± 0.02 (CONC), 0.08 ± 0.02 (NSP), and 0.12 ± 0.03 (IMot). Heritabilities of post-thaw beef bull semen attributes were more variable at 0.10 ± 0.02 (PTMot), 0.05 ± 0.04 (3HRPTMot), 0.10 ± 0.04 (%NORM), 0.03 ± 0.03 (PRIM), and 0.18 ± 0.04 (SEC). Correlations of breeding values for these traits with scrotal circumference (SC) expected progeny difference (EPD) are low. The low to moderate heritability estimates indicate that genetic improvement can be made in beef bull semen quality traits if new tools are developed to augment the scrotal circumference EPD that are currently available within the industry.

Pre-synchronization of ovulation timing and delayed fixed-time artificial insemination increases pregnancy rates when sex-sorted semen is used for insemination of heifers

This study was conducted to determine effects of pre-synchronization of ovulation timing among heifers and delayed fixed-time artificial insemination (TAI) with sex-sorted semen on proportion of heifers pregnant after TAI (PR/AI). Heifers were assigned to one of eight treatments: 1 and 2), 7-d CO-Synch + CIDR treatment regimen with administration of gonadotropin-releasing hormone and a CIDR insert on Day 0, prostaglandin F_2α (PGF) at CIDR removal on Day 7, and TAI occurring 54 h later with conventionally processed (CTRL54-CNV) or sex-sorted semen (CTRL54-SEX); 3 and 4), same as CTRL54 but TAI delayed to 72 h with conventionally processed (CTRL72-CNV) or sex-sorted semen (CTRL72-SEX); 5 and 6), same as CTRL54 but additional administration of PGF on Day -7 and TAI with conventionally processed (PRE54-CNV) or sex-sorted semen (PRE54-SEX); 7 and 8), same as PRE54 treatments but TAI delayed to 72 h with conventionally processed (PRE72-CNV) or sex-sorted semen (PRE72-SEX). Proportion of heifers pregnant after TAI was greater (P ≤  0.02) with conventionally processed semen compared with sex-sorted semen, yet PR/AI did not differ (P =  0.14) between heifers in PRE72-CNV and PRE72-SEX groups. There were greater PR/AI in the PRE72-SEX (P =  0.03) than CTRL54-SEX group (46.1 % and 36.9 %) and there was no difference (P =  0.31) in PR/AI between CTRL54-CNV and PRE72-SEX groups (50.4 % and 46.1 %). In conclusion, pre-synchronization of ovulation timing among heifers combined with delayed TAI resulted in increased PR/AI with sex-sorted semen compared with the 7-d CO-Synch+CIDR treatment regimen.

96 Estimation of the genetic parameters of beef bull semen attributes

Fertility is a critical factor in cattle production because it directly relates to producing offspring to offset production costs. A number of semen attributes are believed to affect fertility and are frequently measured as part of routine breeding soundness exams or semen collection procedures. The objective of this study was to estimate the variance components for different semen quantity and quality traits that may influence fertility using phenotypes collected on 369 Simmental bulls. A total of 7,436 bull collection records including volume and concentration were obtained from two bull studs and evaluated utilizing a linear univariate animal model with repeated records. The five-generation pedigree used in the analysis consisted of 3,336 sires and 7,225 dams. Volume is the total amount of ejaculate and measured as milliliters of total ejaculate. Volume measurements ranged from 0.100 to 41.30 milliliters, with an average of 7.599 milliliters. Concentration is a measurement of millions of spermatozoa per milliliter. Concentration measurements ranged from 10 to 3,651 with an average of 1,053 million spermatozoa per milliliter. Fixed effects were included in the model if the effect was significant (P ≤ 0.05) for either backward or forward selection. Fixed effects included bull owner, collection center, location within center, collection day within year as a Julian day, collection year fit as class variables. Fixed effects fit as covariates included age of bull at collection (linear and quadratic), days since previous collection (linear and quadratic), and scrotal circumference (quadratic). Heritability estimates of volume and concentration were 0.43 ± 0.14 and 0.40 ± 0.15. These moderate heritability estimates indicate genetic improvement can be made in beef bull semen quality traits through selection.

71 Imitating the dynamic bovine cervix with 3D printing technology to teach artificial insemination in cattle

The process of artificial insemination in cattle is commonly taught using excised reproductive tracts. Excised reproductive tracts can be difficult to collect, and often require freezing and thawing prior to use; however, they are an effective tool to teach artificial insemination (AI) techniques. As an alternative tool, 3D printed cervixes were created using NinjaFlex filament in a Flashforge Creator Pro Dual Extrusion Printer. Designs of cervixes were created with a 3D CAD software while MATLAB was used to generate the random placement of the cervical ring openings to model biological diversity. The objective was to determine the effectiveness of using a 3D printed cervix compared with an excised reproductive tract to teach AI in cattle. Data were collected via surveys for 120 students from 2016 through 2019. Students were divided in two groups prior to entering live animals: 1) Excised reproductive tract and 2) 3D Cervix. The excised reproductive tracts were previously collected, preserved, and confirmed passable by instructors. The 3D cervix group included 3D cervixes mounted in a bovine pelvis inside a box. Overall, 88% of students had success passing the cervix in the cow by the third day. Eighty-seven percent of students thought the excised tracts felt somewhat similar to a live cow, compared with 54% who thought the 3D cervixes alone felt similar to a live cow. When the 3D cervixes were mounted in the box, 17/20 students thought they felt similar to a live cow. For learning AI techniques, 12/21 students thought the excised tracts were more helpful than the 3D cervixes alone (5/21); however, when the 3D cervixes were mounted in the pelvic boxes, 11/21 students preferred this setup compared with the excised tracts (6/21 students). Student feedback suggests the 3D cervixes mounted in pelvic boxes are a useful tool for teaching artificial insemination techniques.

26 Factors effecting collection characteristics in beef bulls at an artificial insemination facility

Increased genomic information available for young bulls has decreased age at time of semen collection. Factors effecting collection characteristics include collection method (electro ejaculate (EE), or artificial vagina (AV), and the number of ejaculates collected. The objective of this study was to determine the effect of managerial factors on collection characteristics. From 2008 to 2018, 11,642 individual ejaculates were analyzed by a single technician at the Kansas Artificial Breeding Service Unit. Bulls that were not receptive to the AV after 3 or 4 attempts, were subject to EE. Collection characteristics were evaluated using multiple regression models; fixed effects included collection method, sequence of ejaculates collected per day, and were evaluated for their impact on collection characteristics. Progressive motility before freezing was greater (P< 0.0001) for bulls collected with EE compared to AV. Ejaculate volume for EE collections was greater (P< 0.0001) than those collected with AV. Percent spermatozoa with secondary abnormalities was greater (P< 0.05) for bulls collected with EE compared to AV. Concentration of spermatozoa per mL was less (P< 0.0001) for bulls collected with an EE (514 x106) compared to AV (617 x106). Total number of straws frozen per ejaculate were less (P< 0.001) for bulls collected with EE (94) compared to AV (108). The number of ejaculates collected per day was significant for the percent of spermatozoa with secondary abnormalities (P< 0.001). As ejaculate number per day increased, the concentration of spermatozoa decreased (713, 580, 535, and 434 x 106 per ml respectively; P< 0.0001) and the number of straws frozen per ejaculate decreased (123, 107, 93, and 82 respectively; P < 0.0001). In conclusion, AV collections resulted in a higher number of straws frozen. The method of collection could cause a significant impact when collecting young high demand bulls.

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147 Presynchronization and delayed fixed-time artificial insemination increases pregnancy rates with sex-sorted semen in replacement beef heifers

To determine effects of presynchronization and delayed fixed-time artificial insemination (TAI) on pregnancy rates to TAI (PR/AI) with sex-sorted semen, 2,855 Bos taurus beef heifers were enrolled in a completely randomized design. Within location, heifers were randomly assigned to one of eight treatments: 1 and 2), heifers were exposed to the 7-d CO-Synch+CIDR protocol wherein they received gonadotropin-releasing hormone (GnRH) and a CIDR insert on d 0, prostaglandin F2α (PGF) upon CIDR removal on d 7, and were TAI 54 ± 2 h later with conventional (CTRL54-CNV; n = 359) or sex-sorted semen (CTRL54-SEX; n = 356); 3 and 4), same as CTRL54 but were TAI at 72 ± 2 h with conventional (CTRL72-CNV; n = 366) or sex-sorted semen (CTRL72-SEX; n = 360); 5 and 6), same as CTRL54 but also received PGF 7 d prior to initial injection of GnRH (d -7) and were TAI with conventional (PRE54-CNV; n = 355) or sex-sorted semen (PRE54-SEX; n = 353); 7 and 8), same as PRE54 but had TAI delayed to 72 ± 2 h and were inseminated with conventional (PRE72-CNV; n = 351) or sex-sorted semen (PRE72-SEX; n = 355). All heifers received estrus detection patches on d 7, which were evaluated for activation at TAI. Ultrasonography was performed 30–45 d after TAI to determine PR/AI. Estrus expression was greater (P < 0.01) in the CTRL72 heifers compared to CTRL54, PRE54, and PRE72 heifers (73.0 vs 55.4, 43.4, and 65.7%, respectively). Moreover, estrus expression was greater (P < 0.01) in PRE72 heifers compared to CTRL54 and PRE54 heifers. Within treatment pairs, PR/AI were greater (P ≤0.04) when conventional semen was utilized compared to sex-sorted semen. Furthermore, PR/AI were greater (P = 0.02) in PRE72-SEX heifers than CTRL54-SEX heifers (45.8 vs. 37.5%). No difference (P = 0.20) was determined in PR/AI between CTRL54-CNV and PRE72-SEX heifers (50.5 vs. 45.8%). In conclusion, presynchronization in combination with delayed TAI increased estrus expression and PR/AI with sex-sorted semen in replacement beef heifers.

Selection for bull fertility: a review

Fertility is a critically important factor in cattle production because it directly relates to the ability to produce the offspring necessary to offset costs in production systems. Female fertility has received much attention and has been enhanced through assisted reproductive technologies, as well as genetic selection; however, improving bull fertility has been largely ignored. Improvements in bull reproductive performance are necessary to optimize the efficiency of cattle production. Selection and management to improve bull fertility not only have the potential to increase conception rates but also have the capacity to improve other economically relevant production traits. Bull fertility has reportedly been genetically correlated with traits such as average daily gain, heifer pregnancy, and calving interval. Published studies show that bull fertility traits are low to moderately heritable, indicating that improvements in bull fertility can be realized through selection. Although female fertility has continued to progress according to increasing conception rates, the reported correlation between male and female fertility is low, indicating that male fertility cannot be improved by selection for female fertility. Correlations between several bull fertility traits, such as concentration, number of spermatozoa, motility, and number of spermatozoa abnormalities, vary among studies. Using male fertility traits in selection indices would provide producers with more advanced selection tools. The objective of this review was to discuss current beef bull fertility measurements and to discuss the future of genetic evaluation of beef bull fertility and potential genetic improvement strategies.

Two split-time artificial insemination programs in suckled beef cows

Our objective was to determine which of 2 split-time AI programs applied to suckled beef cows would result in greater pregnancy risk. Suckled beef cows (n = 1,062) at 12 locations in 4 states (CO, KS, MY, and WA) were enrolled. Cows were treated on d -7 with a progesterone insert concurrent with 100 µg GnRH and on d 0 with 25 mg PGF plus removal of the insert. Estrus-detection patches were affixed to cows at insert removal. The study was designed as a completely randomized experiment of 2 treatment combinations. Within location and balanced for parity (primiparous vs. multiparous), cows were assigned randomly to 2 treatment times (55 vs. 65 h after CIDR insert removal) at which time estrus-detection patches were assessed. Estrus was defined to have occurred when an estrus-detection patch was > 50% colored (activated). Cows determined to be in estrus were inseminated at either 55 or 65 h, whereas the residual nonestrous cows in both treatment times received GnRH at 55 or 65 h but were inseminated 20 h later at 75 or 85 h, respectively. Pregnancy outcomes were determined at 36 d after AI and at the end of the breeding season. Thus, pregnancy outcomes of interest were compared between the 55 + 75-h treatment combination and that of the 65+85-h combination. Expression of estrus was greater ( = 0.001) by 65 h after PGF than by 55 h (62.0% vs. 41.9%), respectively, and this proportion was influenced by parity (time x parity interaction; = 0.006). As a result, proportionally more ( < 0.001) cows received the timed AI at 75 than 85 h (59.4% vs. 40.6%). Similar proportions of cows not in estrus by 55 or 65 h were detected in estrus by 75 or 85 h (40.1% vs. 39.3%), respectively. The cumulative proportion of cows in estrus by 75 h was less ( < 0.001) than that by 85 h (66.7% vs. 76.7%), respectively. Pregnancy risks at 36 d differed among treatments, with cows detected in estrus and inseminated at 55 or 65 h having greater pregnancy risks than their time-inseminated herd mates at 75 or 85 h (62.3% vs.49.7%), respectively. Overall pregnancy risk for cows in the 65+85-h treatment combination was greater at 36 d than for cows in the 55 + 75-h treatment combination (61.0% vs. 51.4%), respectively. We conclude that the 65 + 85-h treatment combination produced more pregnancies than the 55 + 75-h combination, but its implementation may be somewhat less convenient in terms of cow handling times.

Using estrus detection patches to optimally time insemination improved pregnancy risk in suckled beef cows enrolled in a fixed-time artificial insemination program

A multilocation study examined pregnancy risk (PR) after delaying AI in suckled beef cows from 60 to 75 h when estrus had not been detected by 60 h in response to a 7-d CO-Synch + progesterone insert (CIDR) timed AI (TAI) program (d -7: CIDR insert concurrent with an injection of GnRH; d 0: PGF injection and removal of CIDR insert; and GnRH injection at TAI [60 or 75 h after CIDR removal]). A total of 1,611 suckled beef cows at 15 locations in 9 states (CO, IL, KS, MN, MS, MT, ND, SD, and VA) were enrolled. Before applying the fixed-time AI program, BCS was assessed, and blood samples were collected. Estrus was defined to have occurred when an estrus detection patch was >50% colored (activated). Pregnancy was determined 35 d after AI via transrectal ultrasound. Cows ( = 746) detected in estrus by 60 h (46.3%) after CIDR removal were inseminated and treated with GnRH at AI (Control). Remaining nonestrous cows were allocated within location to 3 treatments on the basis of parity and days postpartum: 1) GnRH injection and AI at 60 h (early-early = EE; = 292), 2) GnRH injection at 60 h and AI at 75 h (early-delayed = ED; = 282), or 3) GnRH injection and AI at 75 h (delayed-delayed = DD; = 291). Control cows had a greater ( < 0.01) PR (64.2%) than other treatments (EE = 41.7%, ED = 52.8%, DD = 50.0%). Use of estrus detection patches to delay AI in cows not in estrus by 60 h after CIDR insert removal (ED and DD treatments) increased ( < 0.05) PR to TAI when compared with cows in the EE treatment. More ( < 0.001) cows that showed estrus by 60 h conceived to AI at 60 h than those not showing estrus (64.2% vs. 48.1%). Approximately half (49.2%) of the cows not in estrus by 60 h had activated patches by 75 h, resulting in a greater ( < 0.05) PR than their nonestrous herd mates in the EE (46.1% vs. 34.5%), ED (64.2% vs. 39.2%), and DD (64.8% vs. 31.5%) treatments, respectively. Overall, cows showing estrus by 75 h (72.7%) had greater ( < 0.001) PR to AI (61.3% vs. 37.9%) than cows not showing estrus. Use of estrus detection patches to allow for a delayed AI in cows not in estrus by 60 h after removal of the CIDR insert improved PR to TAI by optimizing the timing of the AI in those cows.

Phenotypic relationships between docility and reproduction in Angus heifers

The objective of this study was to elucidate the phenotypic relationships between docility and first-service AI conception rate in heifers. Data ( = 337) collected from 3 cooperator herds in Kansas at the start of synchronization protocol included exit velocity (EV), chute score (CS), fecal cortisol (FC), and blood serum cortisol (BC). Data were analyzed using logistic regression with 30-d pregnancy rate as the dependent variable. The model included the fixed effect of contemporary group and the covariates FC, BC, EV, CS, BW, and age. Correlation coefficients were calculated between all continuous traits. Pregnancy rate ranged from 34% to 60% between herds. Blood cortisol positively correlated with EV ( = 0.22, < 0.01), negatively correlated with age ( = -0.12, < 0.03), and tended to be negatively correlated with BW ( = -0.10, = 0.09). Exit velocity was positively correlated with CS ( = 0.24, < 0.01) and negatively correlated with BW ( = -0.15, < 0.01) and age ( = -0.12, < 0.03). Chute score negatively correlated with age ( = -0.14, < 0.01), and age and BW were moderately positively correlated ( = 0.42, < 0.01), as expected. Older, heavier animals generally had better temperament, as indicated by lower BC, EV, and CS. The power of our test could detect no significant predictors of 30-d pregnancy for the combined data from all ranches. When the data were divided by ranch, CS ( < 0.03) and BW ( < 0.01) were both significant predictors for 30-d pregnancy for ranch 1. The odds ratio estimate for CS has an inverse relationship with pregnancy, meaning that a 1-unit increase in average CS will reduce the probability of pregnancy at ranch 1 by 48.1%. Weight also has a negative impact on pregnancy because a 1-kg increase in BW will decrease the probability of pregnancy by 2.2%. Fertility is a complex trait that depends on many factors; our data suggest that docility is 1 factor that warrants further investigation.

Follicular expression of follicle stimulating hormone receptor variants in the ewe

BACKGROUND

Several alternatively-spliced mRNA transcripts of the follicle stimulating hormone receptor (FSHR) have been identified in sheep, including FSHR-1 (G protein-coupled form), FSHR-2 (dominant negative form), and FSHR-3 (growth factor type-1 form). Our objective was to determine which of these variants is predominantly expressed in follicles collected from ewes at various times after estrus.

METHODS

Suffolk-cross ewes (n = 8) were allowed to come into estrus naturally and were euthanized 24 (n = 3), 36 (n = 3), or 48 (n = 2) hours after the onset of estrus. All visible follicles were measured, aspirated and pooled according to follicular diameter: small (<= 2.0 mm), medium (2.1-4.0 mm), large (4.1-6.0 mm), and preovulatory (> = 6.1 mm). Aspirated cells were separated from follicular fluid by centrifugation. Total RNA was extracted from cell pellets and reverse transcribed. The resulting cDNA was subjected to qPCR, using primer sets designed to amplify each variant specifically. Gene expression was normalized to that of beta-actin within samples, and compared by analysis of variance with the level of significant differences set at p < .05.

RESULTS

Relative expression of FSHR-3 exceeded that of both FSHR-1 and FSHR-2 in medium follicles, and tended to be higher in small follicles (p = .09) regardless of time after onset of estrus, and thus results from different time points were pooled. Expression of FSHR-3 was greater than that of FSHR-2 and luteinizing hormone receptor (LHR) in small and medium follicles. Expression of LHR was greatest in preovulatory follicles.

CONCLUSIONS

These experiments show that in addition to the well characterized G protein-coupled form of the FSHR, alternatively spliced variants of the FSHR may participate in follicular dynamics during follicular waves of the sheep estrous cycle. Furthermore, these results indicate that an "alternatively" spliced form of the FSHR (FSHR-3) is the predominant form of the FSHR in the sheep.

PVD9902, a porcine vas deferens epithelial cell line that exhibits neurotransmitter-stimulated anion secretion and expresses numerous HCO3(-) transporters

Epithelial ion transport disorders, including cystic fibrosis, adversely affect male reproductive function by nonobstructive mechanisms and by obstruction of the distal duct. Continuous cell lines that could be used to define ion transport mechanisms in this tissue are not readily available. In the present study, porcine vas deferens epithelial cells were isolated by standard techniques, and the cells spontaneously immortalized to form a porcine vas deferens epithelial cell line that we have titled PVD9902. Cells were maintained in continuous culture for >4 yr and 200 passages in a typical growth medium. Frozen stocks were generated, and thawed cells exhibited growth characteristics indistinguishable from their nonfrozen counterparts. Molecular and immunocytochemical studies confirmed the origin and epithelial nature of these cells. When seeded on permeable supports, PVD9902 cells grew as electrically tight (>6,000 ohms x cm2), confluent monolayers that responded to forskolin with an increase in short-circuit current (I(sc); 8 +/- 1 microA/cm2) that required Cl-, HCO3(-), and Na+, and was partially sensitive to bumetanide. mRNA was expressed for a number of anion transporters, including CFTR, electrogenic Na+-HCO3(-) cotransporter 1b (NBCe1b), downregulated in adenoma, pendrin, and Cl-/formate exchanger. Both forskolin and isoproterenol caused an increase in cellular cAMP levels. In addition, PVD9902 cell monolayers responded to physiological (i.e., adenosine, norepinephrine) and pharmacological [i.e., 5'-(N-ethylcarboxamido)adenosine, isoproterenol] agonists with increases in I(sc). Unlike their freshly isolated counterparts, however, PVD9902 cells did not respond to glucocorticoid exposure with an increase in amiloride-sensitive I(sc). RT-PCR analysis revealed the presence of both glucocorticoid and mineralocorticoid receptor mRNA as well as mRNA for the alpha- and gamma-subunits of the epithelia Na+ channels (alpha- and gamma-ENaC), but not beta-ENaC. Nonetheless, PVD9902 cells recapitulated most observations in freshly isolated cells and thus represent a powerful new tool to characterize mechanisms that contribute to male reproductive function.

Supplemental norgestomet, progesterone, or melengestrol acetate increases pregnancy rates in suckled beef cows after timed inseminations

In Exp. 1, 187 lactating beef cows were treated with injections of GnRH 7 d before and 48 h after prostaglandin F2alpha (PGF2alpha; Cosynch) or with Cosynch plus a 7-d treatment with an intravaginal progesterone (P4)-releasing insert (CIDR-B; Cosynch + CIDR). In Exp. 2, 183 lactating beef cows were treated with the Cosynch protocol or with Cosynch plus a 7-d treatment with norgestomet (Cosynch + NORG). In Exp. 1 and 2, blood samples for later P4 analyses were collected on d -17, -7 (first GnRH injection), 0 (PGF2alpha injection), and at timed artificial insemination (TAI; 48 h after PGF2alpha). In Exp. 3, 609 lactating beef cows were treated with the Cosynch + CIDR protocol or were fed 0.5 mg of melengestrol acetate (MGA) per day for 14 d before initiating the Cosynch protocol 12 d after the 14th d of MGA feeding (MGA + Cosynch). Blood samples were collected as in Exp. 1 and 2, plus additional samples on d -33 and -19 before PGF2alpha. In Exp. 4, 360 lactating beef cows were treated with a Cosynch + CIDR protocol, with TAI occurring at either 48 or 60 h after PGF2alpha, while receiving either GnRH or saline to form four treatments. Blood samples were collected as in Exp. 1 and 2. In Exp. 1, addition of P4 reduced the ability of the first GnRH injection to induce ovulation in anestrous cows with low P4 before PGF2alpha but improved (P = 0.06) pregnancy rates (61 vs 66%). In Exp. 2, the addition of NORG mimicked P4 by likewise increasing (P < 0.01) pregnancy rates (31 vs 51%) beyond those after Cosynch. In Exp. 3, the Cosynch + CIDR protocol increased (P < 0.001) pregnancy rates from 46 to 55% compared to the MGA + Cosynch protocol. In Exp. 4, administration of GnRH at TAI improved (P < 0.05) pregnancy outcomes (50 vs 42%), whereas timing of TAI had limited effects. We conclude that a progestin treatment concurrent with the Cosynch protocol improved pregnancy outcomes in all experiments, but pretreatment of cows with MGA was not as effective as the CIDR insert or NORG implants in this Cosynch-TAI model. Most of the improvement in pregnancy rates was associated with the increase in pregnancy rates of anestrous cows, regardless of whether ovulation was successfully induced in response to GnRH 7 d before PGF2alpha. Injection of GnRH at TAI following the Cosynch + CIDR protocol increased pregnancy rates in cycling cows with high P4 before the PGF2alpha injection and in anestrous cows with low P4 before PGF2alpha injection.

Retinol and estradiol regulation of retinol binding protein and prostaglandin production by porcine uterine epithelial cells in vitro

Secretion into the uterine lumen follows a precise pattern during early pregnancy. Near the end of the second week of pregnancy and coincident with elongation of conceptuses, retinol, retinol binding protein (RBP), estradiol (E2), and prostaglandins E (PGE) and F (PGF) increase in the uterine lumen, and RBP mRNA increases in the endometrium. In the present studies the potential for E2 (0.1 microM) and retinol (10 microM) to regulate RBP and PG production by cultured luminal (LEC) and glandular (GEC) epithelial cells collected from postpubertal females and LEC from prepubertal gilts was examined. Endometrial tissue was collected surgically from cyclic and pregnant females (n = 8) on d 10 and 13 postestrus (first day of estrus = d 0) and from 120- and 150-d-old prepubertal gilts that were treated with progesterone (P4) (2.2 mg x kg(-1) x d(-1), n = 6) or corn oil (n = 6) for 14 d prior to tissue collection. The LEC from postpubertal females responded to retinol with increased (P < 0.05) RBP, PGE, and PGF in culture medium and increased (P < 0.07) RBP mRNA but E2 decreased (P < 0.05) RBP and RBP mRNA and had no effect on prostaglandins. No E2 or retinol effects on secretions of GEC occurred in vitro, but a day x pregnancy status interaction (P < 0.06) affected PGE output by the GEC. Secretion of PGE was greater when GEC were collected on d 10 of pregnancy than from d-10 cyclic or d-13 pregnant or cyclic females. Both E2 and retinol stimulated (P < 0.05) secretion of RBP by LEC isolated from prepubertal gilts, but their effects were not additive. In vivo treatment of prepubertal gilts with P4 increased (P < 0.05) RBP and decreased (P < 0.05) PG production by LEC in vitro. Therefore responses to E2 and retinol differ between pre- and post-pubertal females, and retinol may function in the regulation of endometrial RBP and PG secretion.

Glucocorticoid regulation of type 1 and type 2 cytokines in cultured porcine splenocytes

Glucocorticoids are reported to bias cytokines to a Th2 phenotype. However, this dogma has been advanced largely from studies utilizing potent glucocorticoid analogs. The current study was conducted to revisit the issue of glucocorticoid modulation of Th1/Th2 cytokine production and evaluate migration inhibitory factor (MIF) mRNA expression in cultured pig splenocytes treated with physiologically relevant concentrations of cortisol (CORT). Dexamethasone (DEX) was included for comparison. In Experiment 1, DEX, at 150 and 300 nM, suppressed concanavalin (ConA)-stimulated IFNgamma at both 12 and 24 h in culture, and IL-10 at 24h (P<0.05). Both 150 and 300 nM CORT suppressed IL-10 at 24 h (P<0.05), but neither concentration affected IFNgamma at 24 h. In Experiment 2, cells were cultured with a broader range of CORT for 48 h following ConA. Parallel cultures with identical treatments also were conducted in separate plates for evaluation of glucocorticoid regulation of MIF mRNA. IFNgamma was reduced by 300 nM DEX at 12, 24, and 48 h (P<0.05), whereas 150 and 300 nM CORT blunted IFNgamma at 24 h (P<0.05), but not 48 h. ConA increased IL-2 (P<0.01), but none of the steroid treatments affected IL-2. At both 12 and 24 h, IL-10 was reduced by 300 nM DEX and by 150 and 300 nM CORT (P<0.05). ConA increased relative abundance of MIF mRNA (P<0.001), but no steroid treatment affected MIF mRNA. In Experiment 3, steroid additions were delayed by 24 h after ConA, and cytokine concentrations evaluated 48 h later. Again, separate cultures were used for determination of effect of treatments on MIF mRNA. None of the steroid treatments affected IFNgamma, but 300 nM DEX reduced IL-10 (P<0.05). All of the CORT treatments (75-300 nM) reduced MIF mRNA (P<0.05), whereas DEX did not affect MIF mRNA in this experiment. The current experiments suggest that both DEX and high physiological concentrations of CORT can suppress both type 1 and type 2-like cytokines in cultured pig splenocytes. But, IL-10 was generally more sensitive to CORT suppression with increased time in culture than was IFNgamma. In addition, MIF mRNA could be suppressed by delayed addition of CORT to porcine splenocytes. Taken together, the data do not support the hypothesis that CORT directs the cytokine milieu toward a type 2 bias in cultured pig splenocytes.

Effect of increasing proportion of supplemental N from urea in prepartum supplements on range beef cow performance and on forage intake and digestibility by steers fed low-quality forage

Four experiments were conducted to evaluate the influence of changing the proportion of supplemental degradable intake protein (DIP) from urea on forage intake, digestion, and performance by beef cattle consuming either low-quality, tallgrass prairie forage (Exp. 1, 2, and 4) or forage sorghum hay (Exp. 3). Experiments 1, 2, and 3 were intended to have four levels of supplemental DIP from urea: 0, 20, 40, and 60%. However, refusal to consume the 60% supplement by cows grazing tallgrass prairie resulted in elimination of this treatment from Exp. 1 and 2. Levels of supplemental DIP from urea in Exp. 4 were 0, 15, 30, and 45%. Supplements contained approximately 30% CP, provided sufficient DIP to maximize digestible OM intake (DOMI) of low-quality forage diets, and were fed to cows during the prepartum period. In Exp. 1, 12 Angus x Hereford steers (average initial BW = 379) were assigned to the 0, 20, and 40% treatments. Forage OM intake, DOMI, OM, and NDF digestion were not affected by urea level. In Exp. 2, 90 pregnant, Angus x Hereford cows (average initial BW = 504 kg and body condition [BC] = 5.0) were assigned to the 0, 20, and 40% treatments. Treatment had little effect on cow BW and BC changes and calf birth weight, ADG, or weaning weight. However, pregnancy rate tended to be lowest (P = 0.13) for the greatest level of urea. In Exp. 3, 120 pregnant, crossbred beef cows (average initial BW = 498 kg and BC = 4.6) were assigned to the 0, 20, 40, and 60% treatments. Prepartum BC change tended (P = 0.08) to be quadratic (least increase for 60% treatment), although BW change was not statistically significant. Treatment effect on calf birth weight was inconsistent (cubic; P = 0.03), but calf ADG and weaning weight were not affected by treatment. Pregnancy rate was not affected by prepartum treatment. In Exp. 4, 132 pregnant, Angus x Hereford cows (average initial BW = 533 and BC = 5.3) were assigned to the 0, 15, 30, and 45% treatments. Prepartum BC loss was greatest (quadratic; P = 0.04) for the high-urea (45%) treatment, although BW loss during this period declined linearly (P < 0.01). Prepartum treatment did not affect pregnancy rate, calf birth weight, or ADG. In conclusion, when sufficient DIP was offered to prepartum cows to maximize low-quality forage DOMI, urea could replace between 20 and 40% of the DIP in a high-protein (30%) supplement without significantly altering supplement palatability or cow and calf performance.

Synchronizing estrus and(or) ovulation in beef cows after combinations of GnRH, norgestomet, and prostaglandin F2alpha with or without timed insemination

Three experiments were conducted to induce estrus and(or) ovulation in 1,590 suckled beef cows at the beginning of a spring breeding season. In Exp. 1, 890 cows at three locations were allotted to three treatments: 1) GnRH on d -7 + prostaglandin F2alpha (PGF2alpha) on d 0 (Select Synch); 2) GnRH on d -7 + PGF2alpha on d 0 (first day of the breeding season) plus a norgestomet implant (NORG) between d -7 and 0 (Select Synch + NORG); or 3) two injections of PGF2alpha given 14 d apart (2xPGF2alpha). More (P < 0.05) cycling cows were detected to have been in estrus after both treatments that included GnRH, whereas, among noncycling cows, the addition of norgestomet further increased (P < 0.05) the proportion in estrus. Pregnancy rates were greater (P < 0.01) among noncycling cows after treatments that included GnRH. For cows that calved >60 d before the onset of the breeding season, conception rates were greater (P < 0.01) than those that calved < or =60 d regardless of treatment, whereas days postpartum had no effect on rates of detected estrus. When body condition scores were < or =4 compared with >4, rates of detected estrus (P < 0.05) and conception (P = 0.07) were increased. In Exp. 2, 164 cows were treated with the Select Synch + NORG treatment and were inseminated either after estrus or at 16 h after a second GnRH injection (given 48 h after PGF2alpha). Conception and pregnancy rates tended (P = 0.08) to be or were less (P < 0.05), respectively, for noncycling cows inseminated by appointment, but pregnancy rates exceeded 53% in both protocols. In Exp. 3, 536 cows at three locations were treated with the Select Synch protocol as in Exp. 1 and inseminated either: 1) after detected estrus (Select Synch); 2) at 54 h after PGF2alpha when a second GnRH injection also was administered (Cosynch); or 3) after detected estrus until 54 h, or in the absence of estrus, at 54 h plus a second GnRH injection (Select Synch + Cosynch). Conception rates were reduced (P < 0.01) in cows that were inseminated by appointment. An interaction of AI protocol and cycling status occurred (P = 0.05) for pregnancy rates with differing results for cycling and noncycling cows. Across experiments, variable proportions of cows at various locations (21 to 78%) were cycling before the breeding season. With the GnRH or GnRH + NORG treatments, ovulation was induced in some noncycling cows. Conception rates were normal and pregnancy rates were greater than those after a PGF2alpha program, particularly when inseminations occurred after detected estrus.

Twice daily suckling but not milking with calf presence prolongs postpartum anovulation

Two experiments were conducted to determine whether milking beef cows two or five times daily in the presence or absence of their own nonsuckling calves would alter postpartum interval to first ovulation. Multiparous Angus x Hereford cow-calf pairs were assigned randomly between 13 and 18 d postpartum to treatments for 4 wk. In Exp. 1, pairs were assigned to six treatments: 1) calf was weaned permanently from its dam (CW; n = 9); 2) same as CW, but dam was milked twice daily (CW+2xM; n = 9); 3) calf was present continuously with its dam but restricted from contact with the udder (CR; n = 9); 4) same as CR, but dam was milked twice daily (CR+2xM; n = 9); 5) same as CR, but calf was allowed to suckle twice daily (CR+2xS; n = 8); and 6) calf was present continuously with its dam and suckled ad libitum (CP; n = 9). The interval from onset of treatments to first postpartum ovulation was shorter (P<.05) in the CW (14.1+/-3.1 d), CR (14.2+/-3.1 d), CW+2xM (13.0+/-3.1 d), and CR+2xM (17.2+/-3.1 d) than in the CP (34.7+/-3.1 d) and CR+2xS (33.9+/-3.3 d) treatments. Daily milk yield during treatment was greater (P<.01) for CR+2xM cows (7.1+/-.6 kg) than for CW+2xM cows (3.5+/-.6 kg). In Exp. 2, cow-calf pairs were assigned to three treatments: 1) CR+2xM (n = 10); 2) same as CR+2xM but cows were milked five times daily (CR+5xM; n = 10); or 3) CP (n = 10). The interval to first postpartum ovulation was shorter (P<.05) in the CR+2xM (23.6+/-3.5 d) and CR+5xM (26.1+/-3.7 d) treatments than in the CP (37.7+/-3.7 d) treatment. Daily milk yield during treatment was greater (P<.05) for CR+5xM cows (7.7+/-.6 kg) than for CR+2xM cows (6.4+/-.6 kg) by 17%. We conclude that suckling twice daily was sufficient to prolong postpartum anestrus as much as suckling ad libitum. Furthermore, milk removal by suckling, but not by milking two or five times daily, even in the presence of the cow's own nonsuckling calf, is essential to prolong postpartum anovulation.

Follicular, hormonal, and pregnancy responses of early postpartum suckled beef cows to GnRH, norgestomet, and prostaglandin F2alpha

Cycling (n = 16) and noncycling (n = 24), early postpartum, suckled beef cows of three breeds were assigned randomly to three treatments: 1) 100-microg injection of GnRH plus a 6-mg implant of norgestomet administered on d -7 before 25 mg of PGF2alpha and implant removal on d 0 (GnRH+NORG); 2) 100 microg of GnRH given on d -7 followed by 25 mg of PGF2alpha on d 0 (GnRH); or 3) 2 mL of saline plus a 6-mg implant of norgestomet administered on d -7 followed by 25 mg of PGF2, and implant removal on d 0 (NORG). All cows were given 100 microg of GnRH on d +2 (48 h after PGF2alpha). Blood sera collected daily from d -7 to d +4 were analyzed for progesterone and estradiol-17beta, and ovaries were monitored daily by transrectal ultrasonography to assess changes in ovarian structures. Luteal structures were induced in 75% of noncycling cows in both treatments after GnRH, resulting in elevated (P < .01) progesterone on d 0 for GnRH+NORG-treated cows. Concentrations of estradiol-17beta (P < .01) and LH (P < .05) were greater on d +2 after GnRH for cows previously receiving norgestomet implants. Pregnancy rates after one fixed-time AI at 16 h after GnRH (d +2) were greater (P < .05) in GnRH+NORG (71%) than in GnRH (31%) and NORG (15%) cows. Difference in pregnancy rate was due partly to normal luteal activity after AI in over 87% of GnRH+NORG cows and no incidence of short luteal phases. The GnRH+NORG treatment initially induced ovulation or turnover of the largest follicle, induction of a new follicular wave, followed later by increased concentrations of estradiol-17beta and progesterone. After PGF2alpha, greater GnRH-induced release of LH occurred in GnRH+NORG cows before ovulation, and pregnancy rates were greater after a fixed-time AI.

Suckling reinitiated milk secretion in beef cows after an early postpartum hiatus of milking or suckling

We determined whether milk secretion in beef cows could be reinitiated by renewed suckling after a hiatus from milking or suckling. Fifty-three Angus x Hereford cows were suckled ad libitum by their own calves for 13 to 18 d postpartum and then assigned to treatments for 4 wk in which cows were 1) neither milked nor suckled (weaned; n = 18), 2) milked 2 x daily (milked; n = 18), or 3) suckled by their own calves (suckled; n = 17). Thereafter, all calves (including earlier weaned calves) suckled their own dams until permanent weaning at 203 d of age, except when their dams were milked once after receiving (i.m.) 40 IU of oxytocin at reinitiation of suckling (0 wk) and again 1 and 5 wk later. Prolactin was increased in milked and suckled cows during 20 min after milking or suckling at the termination of treatments (0 wk). Concentrations of insulin-like growth factor-I were greater for weaned than suckled cows; milked cows had intermediate concentrations. At 0 wk, milk yield was greater for suckled than milked or weaned treatment cows. After 1 wk of renewed suckling, milk secretion of weaned treatment cows increased, and by 5 wk, composition of milk was normal, but yield was still reduced. We concluded that milk secretion was renewed by suckling in early postpartum cows after they were neither suckled nor milked for 4 wk.

Pituitary function in the acute phase response in domestic farm animals: cytokines, prostaglandins, and secretion of ACTH

Contained in this report is a review of available data on pituitary cytokines in domestic species of agricultural importance. The concept is advanced that the pituitary gland is essential to appropriate generation of host defense mechanisms and thus should be considered among other tissues contributing to innate immunity. The functions of these intrapituitary cytokines, principally IL-6, are discussed in the context of potential regulation of the pituitary-adrenal axis (ACTH secretion) via intrapituitary PGE2 generation during the acute-phase response to infectious/inflammatory stimuli. Data from other species are cited as appropriate for comparative purposes and elaboration of proposed mechanisms. However, the scope of the review is not intended to comprehensively cover the vast literature on proinflammatory cytokines and prostaglandins generated peripherally and centrally during host responses to inflammatory stimuli.

Uterine and ovarian responses to puberty induction and pregnancy in prepubertal gilts

We evaluated the effect of age on response to puberty induction in gilts. Sequential treatment with a commercial gonadotropin mixture (400 IU PMSG, 200 IU hCG) followed 96 h later with hCG (500 IU) was used to induce follicular growth and ovulation, respectively. In the first experiment, gilts (84, 104, 124, 144, and 164 d old) were used. Peripheral blood was collected on d 0 (before treatment) and on d 2, 3, 4, 8, and 16 after treatment. On d 16, all gilts were hysterectomized, uterine flushings were collected, and uterine weight (UTWT) and length (UTLG) were measured. For treated gilts, UTWT, UTLG, number of corpora lutea (CL), peripheral progesterone (P4) on d 16, and estradiol (E2) on d 4 increased (P < .05) linearly with age. Uterine luminal PGE (P < .05) and PGF (P = .07), expressed per UTWT, responded quadratically with age; gilts treated at 124 d of age or older showed decreased amounts. Overall, the number of CL correlated positively (P < .01) with UTWT and P4 on d 8 and 16. Peripheral P4 on d 4, 8, and 16 (P < .10) and E2 on d 0 and 4 (P < .01) were correlated positively with uterine weight on d 16. Gilts induced to ovulate at 104 and 144 d of age had heavier and longer uteri (P < .01), more P4 on d 8 and 16 (P < .05), and more E2 on d 2 (P < .1) and 4 (P < .05) than controls at the same age. The second experiment evaluated pregnancy success for gilts induced to ovulate at 116 vs 151 d of age. The effects of induction of two consecutive estrous cycles also were evaluated. Two of seven (28.6%) and four of nine (44.4%) gilts first treated when 116 and 151 d old but none of seven gilts treated at 96 and 116 d of age were pregnant 60 d after insemination. Results indicate that induction of a prior cycle did not improve pregnancy rates. However, some gilts in this population maintained pregnancies to 60 d when induced to ovulate and inseminated at 120 d of age.

Ad libitum suckling by an unrelated calf in the presence or absence of a cow's own calf prolongs postpartum anovulation

Our objective was to determine whether onset of first postpartum ovulation would be altered in suckled cows nursing an unrelated calf in the presence or absence of their own nonsuckling calf. In a 2-yr study, Angus x Hereford cows were assigned randomly to five treatments between d 13 and 18 postpartum for 4 wk: 1) own calf was weaned (OCW, n = 9); 2) own calf was present continuously (OCP, n = 12); 3) own calf was present continuously but restricted from udder contact (OCR, n = 9); 4) unrelated calf was present continuously after own calf was removed (UCP, n = 10); and 5) unrelated calf was present continuously and own calf was present but restricted as in the OCR treatment (OCR + UCP, n = 10). Interval to the first increase in progesterone (ovulation) was less (P < .05) in OCW (14.7 +/- 3.4 d) and OCR (19.9 +/- 3.4 d) than in the OCP (35.0 +/- 2.9 d), UCP (38.0 +/- 3.4 d), and OCR + UCP (37.6 +/- 3.4 d) treatments. The OCW cows showed no maternal bond with their own calves after 4 wk of treatment, whereas OCR, OCP, and OCR + UCP cows were bonded to their own natural calves. Cows in the UCP treatment, suckled by unrelated calves, formed new maternal bonds with those calves, resulting in prolonged anovulation. Further, OCR + UCP cows had prolonged anovulation because maternal bonds were maintained with their own restricted calves while milk was removed by unrelated calves. We conclude that milk removal preceded by a continuously reinforced cow-calf bond (original or reestablished) is essential to prolong anovulation in beef cows.

Uterine response to progesterone in prepubertal gilts

During early pregnancy, progesterone stimulates the secretion of proteins and other molecules that support the developing conceptus. Some gilts are able to support conceptus development as early as 110 days of age. The objective of this study was to evaluate the onset of responsiveness of the prepubertal uterus to progesterone. Thirty gilts were assigned to receive 2.2 mg progesterone kg-1 body mass per day or corn oil daily for 14 days starting at 6, 46, 76, 106, and 136 days of age. Hysterectomies were performed the day after the last treatment of progesterone, and the uterine horns were weighed and flushed with sterile saline (0.85% NaCl). Recovered flushings were analysed for total luminal protein, retinol binding protein, uteroferrin, prostaglandin E and prostaglandin F. An interaction between age and progesterone occurred for uterine wet mass (P < 0.001). Progesterone did not affect the uterine mass of gilts that underwent hysterectomy at 20 days of age, but did increase the uterine mass (P < 0.05) in other age groups. Progesterone increased (P < 0.01) the amount of total luminal protein in all but the youngest gilts. An increase in the amounts of retinol binding protein and uteroferrin (P < 0.001) by progesterone was first observed in 90-day-old gilts. Prostaglandins exhibited a different age-related pattern. The amount of prostaglandin E was increased (P < 0.001) by progesterone treatment in gilts aged 90-150 days, with a greater (P < 0.05) response at 120 days than at 90 days old. The response at 150 days old decreased (P < 0.05) to that observed at day 90. The response of prostaglandin F to progesterone followed a similar age-related pattern. Therefore, uterine responsiveness to progesterone develops between 20 and 90 days after birth, and uterine mass responds earlier than the secretory responses measured in our study.

Active immunization of beef heifers against luteinizing hormone: III. Evaluation of dose and longevity

Objectives were to evaluate the dose (Exp. 1) and purity of LH preparations (Exp. 2) on the anti-LH antibody response in heifers. Experiment 3 evaluated the longevity of LH immunization on sterility in heifers. In Exp. 1, 115 crossbred heifers were injected every 3 wk for 6 wk with .1, .33, 1.0, 3.0 or 9.0 mg of LH-ovalbumin. Concentrations of anti-LH antibodies generated were quantified by determining the percentage of binding of [125I]LH in serum. Mena LH binding over wk 0 to 12 was greater in heifers immunized with 1.0 mg conjugate than in heifers immunized with other doses (P less than .05). In Exp. 2, LH-ovalbumin conjugates were made from either LH-1, LH-2 or LH-3, which had relative immunological potencies of 2.1, 1.5 and 1.2 x NIH-LH-S1 units/mg, respectively. Forty-eight crossbred beef heifers were immunized against one of these three LH-ovalbumin conjugates, against LH conjugated without ovalbumin (LH-LH), or against ovalbumin alone (Oval). Estrous cycle activity was monitored by measuring serum progesterone concentration. Potency of the LH preparation used in the LH-ovalbumin conjugate was correlated (r = .94) with its ability to produce LH antibodies. In Exp.3, heifers were injected with 1 mg antigen every 2 wk for 10 wk. Five LH-1 heifers and five control heifers were slaughtered for examination of ovaries 10 wk after the last booster injection. The remaining five LH-I and five control animals were placed with a bull 8 wk after the last booster. All five control heifers conceived by 4 +/- 1 wk after placement with the bull whereas the LH-immunized heifers remained acyclic for 42 to 96 wk.

Active immunization of beef heifers against luteinizing hormone: II. Evaluation of conjugation technique on antigenicity of LH

This study evaluated the antigenicity of LH-ovalbumin complexes produced using different conjugation techniques. Two homobifunctional cross-linkers, glutaraldehyde (Glut) and carbodiimide (ECDI), were evaluated together with one heterobifunctional reagent, m-maleimido-benzoyl N-hydroxysuccinimide ester (MBS). Polyacrylamide gel electrophoresis and Western transfer techniques were used to confirm conjugation of LH. Forty-four beef heifers were assigned randomly to seven treatment groups. Two groups of heifers were immunized against glutaraldehyde conjugates (Glut-I and Glut-II), two against MBS conjugates (MBS-I and MBS-II) and one against a carbodiimide conjugate (ECDI). Control animals were immunized against nonconjugated LH (LH-only) or ovalbumin alone (Oval). Heifers received one primary injection of antigen followed by two boosters at a 3-wk interval. The Glut conjugates induced the highest (P less than .05) LH antibody activity (Glut-II, 18 +/- 4%; Glut-I, 14 +/- 4%). The ECDI (11 +/- 4%), and MBS-I (11 +/- 2%) conjugates induced greater LH binding than MBS-II (4 +/- 1%), LH-only (4 +/- 1%) or Oval (2 +/- 1%). Glutaraldehyde produced an LH-ovalbumin conjugate of greater LH immunogenicity than either ECDI or the heterobifunctional reagent, MBS.

Vaccines against endogenous hormones: a possible future tool in animal production

Vaccines have been widely used by the livestock industry to control and prevent disease. New technologies now permit development of vaccines against hormones that control reproduction, growth, and lactation in domestic farm animals. Results of research projects studying passive and active immunization against such hormones as estrogen, testosterone, LH, FSH, and somatotropin have demonstrated that reproductive efficiencies and growth can be altered through vaccination. Although immunizations against most of the hormones studied have proven effective in most cases, there remain problems related to longevity, consistency, and efficiency of response both within and between animals. When these areas have been clearly defined for individual hormones, standardized immunization regimens can be developed that will optimize antibody production in the animal, thus providing the animal agriculture industry with a powerful and profitable production tool.

Effects of estradiol on secretion of LH, hypothalamic function and testicular development in bull calves

Two experiments were conducted in order to determine the effects of estradiol (E2) on the development of the hypothalamic-pituitary-testicular axis in bull calves. In experiment 1, calves were assigned randomly to one of the following groups: 1) intact, 2) intact E2-treated, 3) castrated, or 4) castrated E2-treated. Treatments began when the calves were 7.5 wk of age and continued for 16.5 wk. Samples of blood were collected once a week from 3 to 14 wk of age and every 10 min for 6 hr at 8, 12 and 16 wk of age. Concentrations of E2 in plasma decreased between 3 and 4 wk of age and were further reduced by castration. Maximum concentrations of E2 (24.3 pg/ml) were observed 72 hr after insertion of E2 implants, however, plasma E2 stabilized at 5.9 pg/ml by 2 wk after insertion of E2 implants. Treatment with E2 eliminated the pulsatile secretion of LH in intact and castrated calves and retarded testicular growth. In experiment 2, calves were assigned to a control (n = 4) or E2-treated (n = 6) group. Implants of E2 were inserted at 7.5 wk of age. At 24 wk of age, calves were bled and then sacrificed to collect hypothalamic and pituitary tissues. Age-related changes in testicular weight and secretion of LH were blocked by E2. Neither the morphology nor the intensity of immunostaining of GnRH nerve cell bodies in the preoptic area (POA) were affected by E2. However, the density of GnRH fibers and beads in the stalk median eminence (SME), and concentrations of pituitary GnRH receptors were greater (P less than .01) in E2-treated compared to control calves. In addition, concentrations of norepinephrine (NE) in the SME were lower in E2-treated calves when compared to controls. Based on these observations, it is concluded that administration of E2 at 7.5 wk of age causes profound alterations in hypothalamic function including, changes in metabolism of NE and suppression of GnRH release.

Hormonal patterns of boars exposed to natural or supplemental lighting during pubertal development

Thirty-two crossbred boars (Hampshire X Duroc X Yorkshire) were reared under natural lighting (35 lx) or supplemental lighting (1,400 lx) beginning at 4 wk of age. Boars received supplemental lighting from six 40-W fluorescent bulbs between 0530 and 2030 in a nursery unit. From 9 to 32 wk of age, boars received either natural lighting (30 lx) or supplemental lighting (100 lx) in a growing-finishing unit. Blood samples were collected from indwelling cannulae at 20-min intervals for 6 h every 2 wk from 2.5 to 7 mo of age. Libido scores were evaluated during alternate weeks when intensive blood samples were not taken. Libido scores were not different between natural and supplemental lighting treatments (P greater than .30). However, at 122 d of age, libido scores of boars exposed to supplemental lighting tended to be higher (P = .10) than those exposed to natural lighting. Although mean serum concentrations of luteinizing hormone (LH) were higher (P less than .05) in boars at 75, 89, 103 and 131 d of age reared under supplemental lighting than boars of the same age reared under natural lighting, the number of LH secretory spikes was similar between the treatment groups (P = .39). Serum concentrations of LH decreased in both treatment groups as boars became older (P less than .05). However, the incidence of LH spikes was similar across ages and between treatment groups from 2.5 to 7 mo of age. Mean serum concentrations of follicle stimulating hormone and testosterone were similar between treatments (P greater than .75).

Follicular fluid concentrations of estradiol-17 beta and progesterone and secretory patterns of LH and FSH in prepubertal gilts reared in confinement or outdoor lots

One-hundred-twenty crossbred gilts from two experiments were assigned randomly to a 2 X 5 factorial experiment. Gilts were reared in two environments (confinement or outside) and assigned to be slaughtered at 4, 5, 6, 7 or 8 mo of age. Beginning at 6 mo of age, blood samples were taken at weekly intervals from each gilt via venipuncture. Serum concentrations of progesterone were analyzed to determine when gilts attained puberty. On the day prior to slaughter, six pigs within a treatment group were cannulated and blood samples were taken at 20-min intervals for 4 h. At slaughter, follicular fluid (FF) was aspirated and the volume determined from those follicles having a diameter of at least 4 mm. No effect of environment was found on the proportion of gilts that attained puberty by 8 mo of age. For the 12 gilts that reached puberty during the study, the age at puberty for gilts reared in outdoor lots (202 +/- 5 d) was less (P less than .05) than those reared in confinement (224 +/- 8 d). Mean concentrations of serum luteinizing hormone (LH; P = 98) and number of secretory spikes of LH (P = .76) were similar between gilts reared in confinement and those reared in outdoor lots. No differences in average serum concentrations of follicle stimulating hormone (FSH) or number of secretory spikes of FSH were found between gilts subjected to these environments (P = .95). Concentrations of estradiol-17 beta in FF were not affected by environment or age (P greater than .25).(ABSTRACT TRUNCATED AT 250 WORDS)