J.E. Wheaton

CIDR: A new progesterone-releasing intravaginal device for induction of estrus and cycle control in sheep and goats

Abstract The controlled internal drug release dispenser (CIDR) is an intravaginal device constructed of a progesterone-impregnated medical silicone elastomer molded over a nylon core. The CIDR-G is suitable for treatment of parous ewes, lambs and goats. Plasma progesterone levels increase rapidly after insertion of CIDR, reach highest concentrations on Day 3 and then gradually decrease. In an on-farm trial conducted during the breeding season, CIDR were used to synchronize estrus. The bulk of ewes lambed within 6 days of each other. A second group of ewes lambed 16 days after the first in which 20% of ewes lambed. Sponges and CIDR were compared for out-of-season breeding using pregnant mares serum gonadotropin (PMSG). Both types of pessaries were effective when used with PMSG. Percentages of ewes bred, ewes lambing and lambs born were similar for sponge and CIDR-treated ewes. Out-of-season breeding also was stimulated without PMSG. For this purpose, CIDR were applied in conjunction with the ram effect. A month before the onset of the normal breeding period, ewes were treated with CIDR and then exposed to rams. Estrus, conception and lambing were advanced in ewes that had received CIDR compared with those that had not. In a subsequent experiment, breeding was advanced, and after lambing and lactation, ewes were retreated with CIDR/ram effect in late winter/early spring. Most ewes (94%) lambed the following summer. In goats, CIDR have been substituted successfully for sponges for estrous synchronization, superovulation, artificial insemination and embryo transfer. The CIDR-G provides a convenient means to deliver exogenous progesterone to sheep and goats and offers an alternative to the progestogen sponge for reproductive management.

Comparison of progesterone sponges, cronolone sponges and controlled internal drug release dispensers on fertility in anestrous ewes

Abstract Three farm trials involving 581 mature ewes were conducted during April and May of 1984, 1985 and 1986. All ewes had lambed and lactated prior to treatment. In the first trial, polyurethane sponges containing 400 mg progesterone or 30 mg Cronolone were compared. On each of six farms, ewes were assigned randomly in approximately equal numbers to treatment groups. Sponges were left in place for 14 days and upon withdrawal ewes were injected with 750 IU pregnant mare serum gonadotropin (PMSG). Another PMSG injection was given 16 days later. Rams ( 1 10 ewes) were joined 2 days later. Responses to treatments were similar (P > 0.05). Of ewes treated with progesterone and Cronolone sponges, respectively, 86 and 87% were bred, 56 and 60% lambed and 83 and 105% lambs were born. The second trial was conducted like the first except that 366 mg progesterone type S controlled internal drug release dispensers (CIDR-S) and Cronolone sponges were compared in ewes on each of 10 farms. Similar results were obtained with CIDR-S and sponges in numbers of ewes bred (92 and 93%), ewes lambing (64 and 73%) and lambs born (100 and 108%). In both trials significant differences in response rates were noted among farms. A third trial was conducted to determine whether CIDR-S without PMSG would induce fertility in anestrous Suffolk ewes. One of 25 animals was bred following dispenser removal and no ewes subsequently lambed. In conclusion, natural progesterone delivered via intravaginal sponges or CIDR-S can replace Cronolone for progestogenic priming of anestrous ewes.

PLASMA PROGESTERONE LEVELS IN EWES TREATED WITH PROGESTERONE-CONTROLLED INTERNAL DRUG-RELEASE DISPENSERS, IMPLANTS AND SPONGES

Abstract Replicate experiments were conducted using ovariectomized ewes to evaluate four progesterone-releasing devices. Treatments were: (1) controlled internal drug-release (CIDR) dispensers containing 12% (w/w) progesterone, (2) CIDR dispensers containing 9% progesterone, (3) solid silastic implants containing 0.9 g progesterone, and (4) polyurethane sponges containing 0.4 g progesterone. Progesterone CIDR dispensers had an outer surface of silicone elastomer impregnated with progesterone and weighed 5.2 g. Implants and pessaries were inserted 9 days after ovariectomy and left in place for 13 days (Exp. 1). Nine days later, ewes were rerandomized and progesterone treatments reimposed for another 13 days (Exp. 2). Blood samples were taken daily beginning 1 day pretreatment. Progesterone levels were similar in replicate experiments but differed significantly between treatments and days. Pretreatment progesterone levels were generally

Evaluation of progesterone controlled internal drug release dispensers for synchronization of estrus in sheep

Three experiments were conducted to evaluate 366 mg progesterone, type S, controlled internal drug release dispensers (CIDR-S) for estrous synchronization. In Experiment 1, synchronization of estrus was investigated in early fall. Of 129 ewes treated for 12 days, 117 (91%) were bred within 5 days of dispenser removal. A total of 118 (91%) ewes lambed with 74% of lambings occurring within 6 days of each other. In Experiment 2, duration of progesterone release from CIDR-S was examined over a 45-day period. In ovariectomized ewes, plasma progesterone levels were 2.8 ng/ml 3 days after insertion and then decreased gradually to 0.3 ng/ml by day 30. In cycling ewes, Day 3 levels were 4.5 ng/ml due to contribution of luteal progesterone. Exogenous progesterone blocked estrus and ovulation for 27 to 31 days, after which ovulation occurred without estrus. Estrus with ovulation occurred by Day 38 to 45. In Experiment 3, cycling ewes were treated for 0, 4 or 12 days and progesterone residue in adipose, liver, kidney and muscle tissues was measured. Residues differed (P < 0.05) among treatment groups and tissue types with no interaction. Tissue progesterone levels of ewes treated for 4 days were greater than those in ewes treated for 0 and 12 days. Adipose tissue contained over 10 times as much progesterone as other tissues. Progesterone residues were related (r = 0.5, P < 0.05) to circulating progesterone levels at time of death but with neither total nor peak levels reached during the treatment period. CIDR-S had a 92% retention rate and provided a simple and effective delivery of natural progesterone.

Induction of ovarian cystic follicles in sheep

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.

Neonatal hemiorchidectomy of bulls alters plasma growth hormone levels and advances onset of pubertal testosterone secretion.

Bovine GH and testosterone profiles were determined in plasma collected at 20 min intervals during 3 hr bleeding periods on day 25 of life and every 15 days thereafter in six intact (I) Holstein bull calves and in six others which had been hemiorchidectomized (HO) at 10 days of age. In I bulls average plasma GH concentrations varied between 7.9 and 14.5 ng/ml (P greater than 0.05) until 130 days of age, after which the GH level gradually rose (P = 0.007) to a maximum of 19.4 ng/ml on day 205 of life. Episodic release of GH was apparent in 55 day-old and older I bulls and in HO bulls of all ages. Plasma GH concentrations in HO bulls were higher than in I bulls 15 and 30 days after surgery (P = 0.07), at which times the levels in HO bulls averaged 19.6 and 22.5 ng/ml and in I bulls 10.3 and 10.2 ng/ml, respectively. Plasma GH in HO bulls again exceeded that of I bulls at ages of 130-190 days (P = 0.04). Plasma testosterone was virtually nondetectable before 130 days of age in I bulls but thereafter exhibited the typical episodic pattern. In HO bulls, plasma testosterone concentrations began to rise 15 to 30 days before those in I bulls, resulting in an age X treatment interaction (P less than 0.0001). Furthermore, average testosterone levels were higher (P = 0.07) in HO than I bulls at 235 and 250 days of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of human pancreatic and rat hypothalamic growth hormone-releasing factors on growth hormone secretion in steers

Potencies of human pancreatic growth hormone-releasing factor [hpGRF(1–40)-OH] and of a peptide corresponding to the N-terminal 29 residues of rat hypothalamic GRF, [rGRF(1–29)-NH2] were compared in two experiments. Eight Angus steers averaging 297 days of age and 290 kg in February 1984 were used in Exp. 1. Five months later six of the steers, weighing 391 kg, were used in Exp. 2. In Exp. 1, hpGRF(1–40)-OH and rGRF(1–29)-NH2 were infused for 5 min at rates of 0, 1.3, 2.6, 5.2, 7.8 and 13.3 pmol/min/kg. Two steers were infused simultaneously, one received hpGRF(1–40)-OH and the other the equivalent dose of rGRF(1–29)-NH2. Four pairs of steers received each dose. Both peptides elicited rapid GH release. Plasma GH concentrations peaked 15 to 20 min following onset of GRF administration, and returned to baseline levels 60 to 90 min later. Minimum effective doses, the lowest dose tested that resulted in a statistically significant GH reponse, were 5.2 pmol/min/kg hpGRF(1–40)-OH and 13.3 pmol/min/kg rGRF(1–29)-NH2. Magnitudes of GH responses to 5.2, 7.8 and 13.3 pmol/min/kg hpGRF(1–40)-OH and 13.3 pmol/min/kg rGRF(1–29)-NH2 were similar; corresponding to respective peak concentrations of 79, 66, 57 and 56 ng/ml. Growth hormone levels before GRF administration averaged 16 ng/ml. Experiment two was designed like the first except steers were infused for 6 hr with hpGRF(1–40)-OH and rGRF(1–29)-NH2 at rates of 0, .5 and 1 pmol/min/kg. Both peptides at both rates raised (P<.05) GH concentrations during the 6 hr infusion period. Mean GH levels were 7 ng/ml during saline infusion, 30 and 23 ng/ml during infusion of .5 pmol/min/kg hpGRF(1–40)-OH and rGRF(1–29)-NH2, and 41 and 27 ng/ml during infusion of 1 pmol/min/kg of the respective peptides. The initial GH response was biphasic, after which GH levels decreased temporarily and then one or two more GH surges occurred during the latter portion of the infusion period. Results demonstrate that hpGRF(1–40)-OH and rGRF(1–29)-NH2 are potent GH secretagogues in steers. Potency of rGRF(1–29)-NH2 is about 40% of hpGRF(1–40)-OH. Intrinsic activities, their ability to stimulate maximum GH secretion, appear to be similar. Both peptides are effective in raising GH levels over a 6 hr constant infusion period.

Measurement of dimeric inhibin in porcine serum: evidence for low concentrations and existence of binding proteins.

An immunoradiometric assay and serum extraction procedure were developed to measure dimeric inhibin in porcine serum with minimal interference by putative inhibin-binding proteins. Assay sensitivity was 50 pg/tube, and it incorporated antibodies against the N-terminal region of inhibins alpha-subunit, alpha-(1-25)-Ab, and against the C-terminal region of inhibins beta A-subunit. To determine whether inhibin-binding proteins were present in porcine serum, serum was incubated with [125I]-recombinant human (rh)-inhibin and then chromatographed by gel filtration. Radioiodinated rh-inhibin was associated with protein(s) > 600 kDa. Radioiodinated rh-inhibin also was incubated with alpha 2-macroglobulin, an inhibin-binding protein in human and rat serum. Elution profiles were similar for serum and alpha 2-macroglobulin. Serum- and alpha 2-macroglobulin-[125I]rh-inhibin complexes dissociated upon exposure to 8 M urea. Porcine serum was treated with urea, after which inhibin was isolated and concentrated. The recovery of rh-inhibin added to starting serum was 28%. Concentrations of endogenous dimeric inhibin were < 28 pg/ml in serum collected from sows at random stages of the estrous cycle and were < 21 pg/ml in serum collected from sows 2 d postweaning. Results demonstrate that 1) concentrations of dimeric inhibin are low in porcine serum, and 2) an inhibin-binding protein(s), consistent with alpha 2-macroglobulin, is present in porcine serum.

Effects of immunization against α-inhibin using two adjuvants on daily sperm production and hormone concentrations in ram lambs

Twenty-five ram lambs were immunized against alpha-inhibin peptide emulsified in Freunds 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.