Osmotic pumps were evaluated for 7-d delivery of growth hormone-releasin g factor (GRF). In Exp. 1, 12 steers weighing 253 kg received hGRF(1-29)NH2 in H20 at rates of O, 3, 30 and 300 pmol, h -~ ,kg -I. Pumps were implanted s.c. on d 0 and removed at 1200 on d 7. Blood samples were drawn at 20-min intervals from 0800 to 1200 on d -1, 1, 3, 5, 7 and 9. Growth hormone levels were not altered by GRF treatment (P > .05). Solubility and volume limitations render hGRF(1-29)NH2 delivery via osmotic pumps problematical. Flow rate and duration of release of dimethyl sulfoxide (DMSO):H20 (1:1) from osmotic pumps incubated in vivo and in vitro were found to be consistent with manufacturer's specifications. Two hGRF(1-29) analogues, Ro23-7863 and 4SG-29, were dissolved in DMSO:H20. In Exp. 2, six 222-kg steers had pumps implanted and blood samples were taken as in Exp. 1. Three steers received each analogue at a rate of 300 pmol.h -1 .kg -1. Analogues had similar GH-releasing ability and GH levels differed (P < .001) among days, being approximately fourfold higher on d 3, 5 and 7 than on d -1, 1 and 9. Residual analogue solutions retained full bioactivity after 7-d implantation, and in vitro biopotencies of Ro23-7863 and 4SG-29 were similar (Exp. 3). In Exp. 4, 15 wethers (~ = 31.3 kg) received osmotic pumps delivering 0, 3, 15, 75 and 300 pmol.h -1.kg -1 Ro23-7863 in DMSO:H2Ofor7d. Lambs were bled at 0800 and 1400 from d -1 to 8. The latter two doses increased (P < .01) mean GH levels 2.7- and 4.3-fold over those in control animals during the treatment period. Results demon- strate that increased GH secretion can be elicited in steers and wethers for 1 wk by con- tinuous s.c. infusion of GRF analogues utilizing osmotic pumps.

The objective of the study was to determine the nature of ILA present in bovine plasma. Plasma samples collected from four bulls, steers, cows and ovariectomized (ovx) cows, which had been stored at -20°C, were processed. Plasma (2 mL) was immunoaffinity purified (IAP) using rabbit alpha-inhibin antibody (alphaAb) coupled to Affi-Gel. The alphaAb was raised against a synthetic alpha-peptide that matched in sequence the N-terminal 1-25 amino acids of the mature bovine inhibin alpha-subunit. Rabbit antiserum was IAP using Affi-Gel-alpha-peptide to obtain alphaAb for coupling to Affi-Gel. Bovine plasma and Affi-Gel-alphaAb were mixed overnight, washed extensively and eluded with glycine-HCl, pH 2.5. Eluates were neutralized, exchanged into PBS and concentrated up to 10-fold in an Amicon filtration device. Concentrates were denatured and reduced for SDS-PAGE and Western blotting. Specific alpha-bands were detected using biotinylated IAP alphaAb and beta-bands were detected using an ovine IAP betaAb against the C-terminal region (82-114) of the bovine inhibin beta-subunit. Control blots were developed using alphaAb and betaAb pre-incubated with an excess of respective peptide antigens. Processing procedures were tested using a pool of bovine follicular fluid (bFF). Specific alpha-bands of 19, 45 and 56 kD were detected in non-processed and processed bFF. Detected alpha-bands are similar to published values. Specific beta-bands were present at 14, 75 and 87 kD in non-processed and processed bFF. The 14 kD band stained more intensely than the larger bands. All processed plasma samples had prominent alpha-bands of 19 and 29 kD. The 29 kD alpha-band stained more intensely than the 19 kD alpha-band. These were the only specific alpha-bands detected in cow and ovx cow plasma samples. In 3 of the 4 bulls a less intense 47 kD alpha-band was present and in 3 of 4 steers a 57 kD alpha-band was present. Two strong specific beta-bands of 75 and 87 kD were present in all plasma samples. No other beta-bands were detected. Concentrates from bFF and steer plasma were tested in an ovine pituitary bioassay. Both preparations decreased (P < 0.01) FSH secretion in a dose-response manner. The same concentrates also were examined for the presence of dimeric inhibin using a two-site ELISA. The IAP alphaAb was used for capture and a monoclonal Ab against human recombinant activin was used for detection. Assay of the bFF concentrate yielded a positive signal, whereas the steer concentrate was negative. The bioassay and ELISA results confirm the presence of dimeric inhibin in bFF, but conflict in regard to steer plasma. In bFF the alpha-bands of 19, 45 and 56 kD and the beta-band of 14 kD are consistent with the presence of various forms of dimeric and monomeric inhibin. Presence of dimeric inhibin was supported by the ability of bFF concentrate to decrease FSH secretion in the bioassay and by its detection in the two-site ELISA. Bovine plasma contained prominent alpha-bands of 19 and 29 kD. The 19 kD alpha-band is consistent with the size of the mature alpha-subunit. The 29 kD alpha-band has been detected in human male serum and hFF. It may correspond to an alpha-inhibin precursor molecule that has been cleaved at a unidentified cleavage site. This molecule, together with the 19 kD protein, appear to constitute the bulk of ILA in bovine plasma. Unlike bFF, no beta-band of 14 kD was detected in bovine plasma. Previous reports have indicated that plasma ILA is due largely to monomeric forms of inhibin. The nature of the 75 and 87 beta-bands detected in bFF and plasma is unclear. As is their relationship with alpha-inhibin, which enabled them to be retained and eluded from alphaAb IAP columns. (poster)

Twenty-five ram lambs were immunized against alpha-inhibin peptide emulsified in Freund's adjuvant (FRA), Emulsigen (EML) containing an oligodeoxynucleotide as an immunostimulant, or adjuvant without alpha-inhibin antigen (control). Four immunizations were administered during an 85-d period, after which testes were obtained for determination of daily sperm production (DSP) and histological evaluation. alpha-Inhibin antibody (Ab) titers were 70-fold greater in lambs treated with FRA than in EML-treated ram lambs. alpha-Inhibin immunization had no effect on testes weight or on plasma concentrations of follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone. Mean DSP/g tended (P=0.1) to be greater in alpha-inhibin-immunized (EML=17.6x10(6); FRA=15.8x10(6)) ram lambs than in control animals (14.4x10(6)). One of the 8 control ram lambs had an elevated DSP/g, which was a statistical outlier. Without data from this lamb, DSP/g was increased (P<0.01) in alpha-inhibin-immunized ram lambs by 28% over controls. No association was found between the titer of alpha-inhibin Ab developed and DSP/g. Histologically, the percentage of testicular area occupied by seminiferous tubules differed (P=0.01) by treatment and was greatest (82%) in EML-treated ram alpha-inhibin-immunized lambs and lowest (74%) in control animals. Percentage tubular area and DSP/g were correlated (r=0.57, P=0.003). Findings show that (1) the extent of the increase in DSP/g is not dependent on the titer of alpha-inhibin Ab; (2) the increase in DSP/g is achieved through an increase in the mass of seminiferous tubules; and (3) FRA elicits a greater alpha-inhibin Ab titer than EML containing an oligodeoxynucleotide.

Experiments were conducted to determine the ability of exogenous L-dihydroxyphenylalanine (L-dopa) and 17/3-estradiol to alter the concentrations of hypothalamic biogenic amines and affect the release of luteinizing hormone (LH) in the ewe. A single iv injection of L-dopa (7 mg/kg) into ewes on day 3 of the estrous cycle failed to elicit an LH release during the 32-hr sampling period in three of four animals. In one ewe, however, elevated serum LH concentrations of 19.6 and 91.3 ng/ml were detected at 24 and 32 hr post-injection of L-dopa, respectively. A single im injection of 750 lag of 1713-estradioI into ewes at the same stage of the estrous cycle caused an increase in serum LH concentration in each ewe (range, 20 to 30 ng/mt) within 16 hr following treatment. A similar injection of estradiol into ewes 8 hr prior to necropsy on day 3 of the cycle was without effect on the concentrations of biogenic amines in the stalk median eminence (SME) or hypothalamus proper (HP). In both treated and control ewes, however, norepinephrine (NE) concentrations were higher (P < .01) in the HP than in the SME. Conversely, dopamine and serotonin concentrations were found to be higher (P < .01) in the SME than in the HP. Treatment of ovariectomized ewes with 750 /~g of estradiol 3 hr prior to necropsy elevated NE concentrations in the SME (P .07) but failed to alter NE concentrations in the HP. Although not significant statistically, serotonin concentrations in both the SME and HP tended to increase after treatment of these ewes with estradiol. One hour after iv injection of ovariectomized ewes with L-dopa (12 mg/kg) biogenic amine concentrations in the SME and HP qualitatively resembled those detected in ewes following injection of estradiol.

The gonadal hormone inhibin regulates daily sperm production (DSP) indirectly through negative feedback control of FSH secretion and may also affect DSP via direct actions within the testis. Studies attempting to increase DSP through the immunization against inhibin have yielded equivocal results. The current study compared 2 inhibin antigens for effects on DSP and hormone secretion. Hampshire ram lambs (BW = 42 +/- 2 kg; age = 113 +/- 3 d) were assigned randomly to 3 groups: 1) control (n = 4); 2) alpha-peptide conjugate (PTC, n = 6); and 3) alpha-subunit (SUB, n = 6). Antigen PTC consisted of an alpha-inhibin, N-terminal, 25-amino acid peptide conjugated to ovalbumin. Antigen SUB was the complete inhibin alpha-subunit. Lambs were immunized on d 0 (June 19, 2006), 18, 38, and 63. Body weight was recorded on immunization days and scrotal circumference on d 63. Blood samples were collected on d 0, 7, 14, 18, 28, 35, 38, 49, 56, 63, and 70. Rams were slaughtered on d 71. Testes were weighed, and parenchyma was obtained for DSP determination. Plasma alpha-inhibin antibody titer and LH, FSH, and testosterone concentrations were measured. alpha-Inhibin antibody titer was first detectable on d 14 in both PTC- and SUB-immunized ram lambs and generally increased thereafter. Mean DSP per gram of testis (DSP/g) was increased (P < 0.01) 26% in PTC- and SUB-immunized ram lambs over that in control ram lambs. Total DSP per ram lamb and testes weight did not differ among the 3 treatment groups. Variation in DSP per ram lamb and testes weight were greater (P = 0.05) in PTC- and SUB-immunized ram lambs than in control ram lambs. Plasma FSH concentrations were similar in PTC- and SUB-immunized ram lambs. Immunization against either alpha-inhibin antigen did not alter LH, testosterone, BW, or scrotal circumference. Findings indicate that 1) the 2 alpha-inhibin antigens increase DSP/g to similar extents; 2) alpha-inhibin antibody may act at least in part through an intratesticular mechanism because DSP/g was increased in some animals without concomitant increases in FSH; and 3) immunization against alpha-inhibin may affect testes weight by actions independent of those that regulate DSP/g.

The objective of the present study was to determine whether treatment of postpartum multiparous and primiparous anestrous beef cows with an intravaginal progesterone-releasing insert (CIDR) and PGF2α, with and without the addition of GnRH or estradiol cypionate (ECP) at the time of CIDR insertion, is effective in stimulating onset of estrous cycles. Postpartum lactating Angus primiparous (n = 47, 2 years of age, 495 ± 6 kg) and multiparous (n = 76, ≥3 years of age, 553 ± 9 kg) cows were assigned by calving date to four blocks spaced 21-day apart. Cows were assigned sequentially by calving date to four treatment groups: (1) PGF2α (n = 30), (2) CIDR–PGF2α (n = 30), (3) GnRH–CIDR–PGF2α (n = 33), and (4) ECP–CIDR–PGF2α (n = 27). Intravaginal CIDR inserts were in place from days −7 to 0. A single 100 μg injection of GnRH or 2 mg ECP were administered on day −7, and 25 mg PGF2α was administered on day 0. Day 0 averaged 38 ± 1 day postpartum. Blood samples were collected on days −19, −9, 0, 5, 9, 12, 16, 19, 23, 26, and 30 for determination of plasma progesterone concentrations. Pre-treatment luteal activity (progesterone ≥ 1 ng/ml) was detected in 19% of primiparous and 8% of multiparous cows. Progesterone concentrations on day 0 were greater (P < 0.001) in primiparous (3.2 ± 0.3 ng/ml) than multiparous (2.0 ± 0.2 ng/ml) cows. Following CIDR withdrawal, progesterone concentrations from days 5 to 30 were used to categorize response profiles as either: (1) treatment-induced onset of estrous cycles, (2) continued anestrus, or (3) spontaneous ovulation and subsequent formation of a CL. Incidence of treatment-induced onset of estrous cycles, which was defined as progesterone concentrations ≥1 ng/ml in three or more consecutive samples from days 9 to 19, was influenced by treatment and parity. Percentages of cows initiating estrous cycles were greater (P < 0.001) in the three CIDR-treated groups than in the PGF2α group (55 and 8%, respectively). Percentages of cows initiating estrous cycles in the CIDR–PGF2α, GnRH–CIDR–PGF2α, and ECP–CIDR–PGF2α groups were 55, 58, and 52%, respectively. Incidence of treatment-induced estrous cycles in the three CIDR-treated groups of cows was greater (P = 0.008) in primiparous (76%) than multiparous (43%) cows. Treatment of postpartum anestrous primiparous and multiparous beef cows with CIDR–PGF2α approximately 40-day postpartum provides an approach to increase the percentage of cows that have reinitiated estrous cycles by the start of the breeding season.

Spermatogonial stem cell transplantation is a technique that has potential in livestock to enhance genetic gain and generate transgenic offspring through the male germ line. A means for depletion of endogenous germ cells in a recipient's seminiferous tubules is necessary for this technology to be applied. The objectives of this study were to evaluate several methods for depletion of endogenous germ cells in the testes of adult rams and to evaluate ultrasound-guided injections into the rete testes as a means for infusing a suspension into the seminiferous tubules. Sixteen adult rams were randomly divided into 4 treatment groups (n = 4 per group). Treatments consisted of active immunization against LHRH (IMM), localized testicular irradiation (IR), LHRH immunization + irradiation (IMM+IR), and untreated control. Serial bleedings were conducted pretreatment and monthly after treatment for 4 mo, at which time all rams were castrated. Both IMM and IMM+IR rams received exogenous gonadotropin in the form of Perganol weekly for 8 wk before castration to bypass the immunization. All rams also received an ultrasound-guided injection of PBS containing 0.4% trypan blue into the rete testis of one testicle before castration. Rams receiving IMM and IMM+IR treatments had higher (P < 0.05) average percentages of seminiferous tubule cross sections with depleted germ cells compared with controls. Serum testosterone was decreased (P < 0.05) in IMM and IMM+IR rams 1 mo after treatment and throughout the remainder of the study compared with controls and IR rams, which were not different from each other. Serum inhibin concentration was unchanged in all rams following treatment indicating that Sertoli cell function was unaltered. A greater (P < 0.05) average percentage of the total testicular area could be filled with the trypan blue solution by rete testis injection in IMM and IMM+IR rams. These data demonstrate the depletion of endogenous germ cells in adult ram testes without alteration of Sertoli cell viability and function that have potential as methods for preparing recipient animals for germ cell transplantation.

Active immunization against inhibin has been shown to advance puberty and increase ovulation rate in ewe lambs; but in ram lambs, effects on puberty and sperm production are equivocal. The objective of the present study was to determine whether active immunization against an inhibin α-subunit peptide advances the onset of puberty in ram lambs. St. Croix hair sheep ram lambs were assigned to inhibin-immunized (n=7) and control (n=8) treatment groups. Lambs in the inhibin-immunized group were immunized against a synthetic peptide-carrier protein conjugate, α-(1–25)-human α-globulin (hα-G), and control lambs were immunized against hα-G. Lambs were immunized at 3, 7, 13, 19, 25, 31, and 37 weeks of age. On the day of immunization a blood sample was collected and lambs were weighed. Another blood sample was collected 1 week following each immunization. At 20 weeks of age additional blood samples were collected at 20min intervals for 8h. Beginning at 20 weeks of age and at weekly intervals thereafter, scrotal circumference (SC) was measured and semen was collected using electroejaculation. A subsequent ejaculate was collected 1 week following onset of puberty, which was defined as the week of age when an ejaculate first contained ≥50×106 sperm cells. In control lambs, plasma α-(1–25)-antibody (Ab) was nondetectable. In inhibin-immunized lambs, α-(1–25)-Ab titer increased from 7 to 25 weeks of age and then plateaued at a level that varied (P<0.001) among animals. Body weight and SC of control and inhibin-immunized lambs were similar at the onset of puberty. At pubertal onset inhibin-immunized lambs were older than control lambs (31.9±0.5 vs. 29.5±0.7 weeks of age, P<0.05). Plasma FSH concentrations were similar in control and inhibin-immunized lambs from 3 to 38 weeks of age. Plasma LH levels were lower (P<0.01) in inhibin-immunized than control lambs. During the 8-h blood sampling period at 20 weeks of age, LH and testosterone concentrations were lower (P<0.05) in inhibin-immunized than control ram lambs, and the LH pulse frequency was similar in the two groups of animals. The decreased LH secretion is consistent with the immunoneutralization of a putative inhibin α-subunit-related peptide that stimulates LH secretion in ram lambs. Present findings show that active immunization against an inhibin α-peptide delays rather than advances puberty in ram lambs.

The hormone-producing equine granulosa cell tumor (GCT) may secrete high levels of inhibin. Measurement of inhibin concentrations may be useful in the diagnosis and conformation of mares with GCT. Inhibin may be measured using RIA, which recognizes dimeric αβA-inhibin as well as the monomeric (free) inhibin α-subunit, or using a two-site immunoradiometric assay (IRMA) specific for αβA-inhibin. The objective of this study was to examine concurrent relationships among α-inhibin (as measured using RIA), αβA-inhibin (as measured using IRMA), and other hormones (testosterone, estradiol, LH, FSH) in mares with GCT. Hormone concentrations were measured in single serum or plasma samples obtained from 22 mares with GCT and from 31 normal cycling mares. One GCT mare had blood samples collected at 12-h intervals for 21 days, and at 15-min intervals for two 6-h periods during that time. Results showed that in GCT mares α-inhibin was increased to a greater extent, was more uniformly elevated, and had a less variable secretory pattern than did αβA-inhibin. Concentrations of α-inhibin and tumor mass were positively correlated (P<0.01). Concentrations of LH were higher (P<0.02) in GCT mares than control mares and were positively associated with testosterone concentrations (P=0.05). Concentrations of FSH tended to be lower in GCT than control mares and were inversely related with αβA-inhibin in GCT mares. Testosterone and estradiol concentrations were variable. It was concluded that immunoreactive α-inhibin reflected detection of both αβA-inhibin and free α-subunit. Free α-subunit was evidently secreted at a relatively steady rate dependent upon mass of the GCT, whereas secretion of αβA-inhibin was more responsive to FSH regulation. Determination of α-inhibin using RIA appeared to be a more reliable indicator of the presence of a GCT than specific measurement of αβA-inhibin using IRMA.

The aim of this study was to examine inhibin production in granulosa-theca cell tumours (GTCT). The experimental aims were: (i) to determine GTCT cell types that produce inhibin alpha- and betaA-subunits; (ii) to determine whether alpha- and betaA-subunit forms differ in GTCT fluid and normal equine follicular fluid (eFF); and (iii) to determine whether dimeric inhibin (alpha betaA) is present in GTCT plasma and tumour fluid. Plasma, tumour fluid and tumour tissue were collected from mares (n=6) with GTCT. Plasma and eFF were collected during the follicular phase from mares (n=4) undergoing normal cycles. Immunohistochemical examination of GTCT tumour sections showed strong inhibin alpha- and betaA-Subunit immunostaining in granulosa cells and polyhedral-shaped cells in the thecal-stromal layer. The presence of polyhedral-shaped cells was related to testosterone concentration in tumour fluid. Low molecular weight alpha-subunit forms were less abundant in tumour fluid than in eFF, whereas the amounts of betaA-subunit forms were similar in tumour fluid and eFF. Concentrations of betaA were increased in plasma from mares with GTCT and similar in tumour fluid and eFF. In summary, lower molecular weight alpha-subunit forms were less prominent in GTCT fluid than in eFF and concentrations of betaA were higher in GTCT plasma than in control plasma.

Cystic follicles are a significant cause of infertility in women, dairy cattle and sheep. Sheep were used as a model to identify factors that may elicit formation of cystic follicles. Insulin resistance and elevated LH activity were tested in overweight ewes because of associations among these factors and the formation of cystic follicles. Sheep were synchronized using a progesterone-releasing pessary and insulin resistance was induced during the synchronization period through administration of bovine somatotropin. Following removal of pessaries follicular growth was stimulated by treatment with eCG or eCG and hCG (PG-600). Follicular growth was monitored via daily transrectal ultrasonography and blood samples were collected for hormonal analyses. Six of 18 ewes had a subnormal or absent preovulatory gonadotropin surge and developed cystic follicles. Neither insulin resistance nor elevated LH activity were associated with formation of cystic follicles. Ewes that developed cystic follicles were heavier (93 +/- 4 kg) than ewes that ovulated (81 +/- 3 kg; P = 0.02). Furthermore, following pessary removal and initiation of daily ultrasonography, ewes that developed cystic follicles lost body weight (-3 +/- 1%), while ovulatory ewes continued to gain body weight (1 +/- 1%; P = 0.005). It is speculated that in heavy ewes metabolic factors associated with acute body weight loss inhibit the positive feedback of estradiol and thereby suppress the preovulatory gonadotropin surge leading to formation of cystic follicles.

Hair sheep ewes (St. Croix White and Barbados Blackbelly) were used to evaluate 3 methods of estrus synchronization for use with transcervical artificial insemination (TAI). To synchronize estrus, ewes (n = 18) were treated with PGF2alpha (15 mg, im) 10 d apart, with controlled internal drug release (CIDR) devices containing 300 mg progesterone for 12 d (n = 18), or with intravaginal sponges containing 500 mg progesterone for 12 d (n = 18). On the day of the second PGF2alpha injection or at CIDR or sponge removal, sterile rams were placed with the ewes. Jugular blood samples were collected from the ewes at 6-h intervals until the time of ovulation, and daily for 16 d after estrus (Day 0). Plasma was harvested and stored at -20 degrees C until LH, and progesterone concentrations were determined by RIA. There was no difference (P>0.10) in time to estrus among the CIDR-, PGF2alpha- or sponge-treated ewes. All of the ewes in the CIDR group and 94.4% of the sponge treated ewes exhibited estrus by 36 h after ram introduction, while only 72.2% of PGF2alpha-treated ewes showed signs of estrus by this time (P<0.06). The time from ram introduction to ovulation was not different (P>0.10) among the CIDR-, PGF2alpha- or sponge-treated ewes. The time to the preovulatory LH surge was similar (P>0.10) among CIDR, PGF2alpha and sponge treated ewes. Progesterone levels through Day 16 after the synchronized estrus were not different (P>0.10) among treatment groups. Hair sheep ewes (n = 23) were synchronized using PGF2alpha and bred by TAI using frozen-thawed semen 48 h after the second injection. The conception rate to TAI was 2/23 (8.7%) and produced 3 ram lambs. In a subsequent trial, 17 ewes were synchronized with CIDR devices and bred by TAI using frozen-thawed semen 48 h after CIDR removal, resulting in a conception rate of 52.9% (9/17). It is possible to synchronize estrus in hair sheep using either CIDRs, sponges or PGF2alpha. Even though there were no significant differences in the timing of ovulation or the LH surge among the treatment groups, a higher conception rate was achieved in ewes synchronized with CIDR devices during the second trial. This may reflect an increase in the skill level of the TAI technician.

OBJECTIVE:To determine whether concentrations of dimeric inhibin (CaCA) are greater in plasma and tumor fluid from mares with granulosa-theca cell tumors (GTCT), compared with concentrations in plasma and equine follicular fluid (eFF) from control mares.ANIMALS:6 mares with GTCT and 12 clinically normal mares.PROCEDURE:The alphabetaA immunoradiometric assay used 2 antibodies, one against each subunit of inhibin (alpha and betaA subunits). Tumor tissue, tumor fluid, and a single blood sample were collected at the time of surgical removal of the GTCT. A single blood sample was collected from 7 control mares during various stages of the estrous cycle. Five other control mares were ovariectomized when their ovaries contained growing follicles of 25 to 35 mm in diameter. A blood sample and eFF from the largest follicle were collected at the time of ovariectomy.RESULTS:Mares with GTCT had significantly greater plasma concentrations of betabetaA (mean +/- SEM, 0.86 +/- 0.53 ng of recombinant human-alphabetaA/ml), compared with control mares (0.14+/-0.02 ng/ml). Concentrations of alphabetaA in tumor fluid and eFF were similar. Concentrations of alphabetaA were significantly lower after ovariectomy.CONCLUSIONS AND CLINICAL RELEVANCE:Dimeric inhibin concentration was higher in plasma from mares with GTCT than in plasma from control mares. Increased granulosa cell mass and loss of mechanisms regulating alphabetaA release in mares with GTCT likely accounted for the increase in plasma concentrations. Measurement of alphabetaA concentrations may be useful for identifying mares with GTCT.

The objective of the experiment was to determine whether passive immunization against inhibin at weaning would increase FSH secretion and thereby influence postweaning reproductive performance in sows. Commercial Yorkshire sows (n = 173) were assigned within parity to 5 alpha-inhibin fragment antibody (alpha-IF-Ab) dosage groups: 0 (control), 3.25, 6.5, 13 and 26 RP-2 kU/kg alpha-IF-Ab. Antibody had been semipurified from ovine antisera raised against alpha-IF, a peptide that mimicked the N-terminal region of inhibin's alpha-subunit. A RP-2 U refers to a laboratory reference preparation. Sows were administered a single intramuscular injection of control solution or alpha-IF-Ab just before 21-d-old piglets were weaned. Blood samples were taken immediately before immunization and 24 h later. Sows were bred upon expression of estrus. Serum alpha-IF-Ab titers in sows 24 h following passive immunization increased (P < 0.001) with dosage. In control sows serum FSH concentrations decreased 24% by 24 h postweaning (P < 0.001). The decrease was diminished or prevented by alpha-IF-Ab treatment in a dose-responsive manner (P < 0.001). Most (167/173) sows were bred within 10 d postweaning, and wean-to-service intervals tended (P < 0.1) to be shorter in the 13 and 26 RP-2 kU/kg alpha-IF-Ab dosage groups. Farrowing rate was 72% (124/173) and was similar among sows in the alpha-IF-Ab dosage groups. Litter size, expressed as total or live piglets born per sow or per sow farrowed, was unchanged by alpha-IF-Ab treatment. Results demonstrate that 1) inhibin plays a key role in regulating FSH secretion at weaning, and 2) blocking the acute postweaning drop in FSH secretion has little if any effect on subsequent reproductive performance.

An experiment was conducted to determine whether factors affecting pregnancy rate out-of-season are associated more with transcervical artificial insemination (T-AI) procedures or with the reproductive state of the ewe. Twenty Finncross ewes were treated with progesterone sponges, and at sponge removal (0 h) 10 ewes were treated with eCG. Blood samples were collected for LH and progesterone analyses, and follicular development was monitored using ultrasonography. Ewes were inseminated from 48 to 52 h with 200 million motile frozen-thawed spermatozoa. The incidence of estrus, LH surges and ovulation was greater (P < 0.01) and intervals to these responses were shorter (P < 0.01) in the eCG-treated ewes. The number of follicles > 5 mm was higher (P < 0.05) in eCG-treated than control ewes. Progesterone concentrations increased and remained elevated through Day 19 in 7 eCG-treated and in 1 control ewe, and these ewes were pregnant based upon ultrasonographic examination. The results demonstrate that the T-AI technique using frozen-thawed semen produces a relatively high (70%) pregnancy rate out-of-season. The pregnancy rate was found to reflect primarily the reproductive condition of the ewe.