Control of oestrus and ovulation in peri-pubertal gilts with allyltrenbolone or a combination of natural gonadotrophins

One-hundred-and-twenty large white X landrace gilts were allocated at random to one of three treatment groups. Treatment A gilts were given an orally active progestogen, allyltrenbolone (Regumate; Hoechst UK) once daily for 18 days from 185 days of age. Treatment B gilts were given a subcutaneous injection of gonadotrophins (400 iu pregnant mare's serum gonadotrophin, 200 iu human chorionic gonadotrophin). (PG600; Intervet Laboratories) at 203 days of age. Treatment C gilts received no exogenous hormones. All the gilts were housed in groups of 10 from 153 days of age, and up to 203 days of age were isolated from boars. From 203 days each group of 10 gilts was subdivided into two groups of five, a boar was accommodated in a pen adjacent to each group of five and daily contact with it was allowed for one hour. Eight gilts in treatment A, five gilts in treatment B and seven gilts in treatment C failed to exhibit oestrus before 233 days of age (P greater than 0.05). The intervals from exposure to the boar to the onset of oestrus for treatments A, B and C were 8.5, 5.5 and 11.0 days respectively (P less than 0.001). Gonadotrophin treatment significantly reduced the time taken by gilts to show oestrus and the variability within the group was significantly less than that in the other two groups. There were no significant differences between the groups in the mean size of their litters.     

Possibilities of ovulation synchronization in puberty-induced gilts

Puberty was induced in 39 clinically prepuberal gilts (two groups of three sub-groups each) by parallel but locally separated application of 500 IU PMSG ("Maretropin") and 250 IU HCG ("Gonadex"), with the view to testing ways to synchronise ovulation. Seventy-two hours were allowed to elapse, before 24 animals received another application of 500 IU HCG and 15 animals 250 IU HCG. The animals were slaughtered in consecutive groups of study ovulation and histolotically examined to disclose endometrial processes. Ovulations were found to be well synchronised in the recipients of a second injection of 500 IU HCG. Only sub-threshold effects with no synchronised ovulation were recorded from the animals that had received a second dose of 250 IU HCG. A second injection of 500 IU HCG should be given not until something between 78 and 82 hours after puberty induction for optimum follicle maturation and adequate proliferation of the endometrium.     

Histological findings on the uterus of gilts following synchronized ovulation

Histological studies were undertaken with the view to testing uterus structure and function of gilts following synchronised ovulation by means of different PMSG doses. All proband groups received 500 I.U. HCG. All histomorphological, histochemical, and histometric checks revealed 500 I.U. PMSG to be too low a dosage, whereas the optimum amount was found to be between 750 and 1,000 I.U. PMSG. The uterine glands of all treated animals in all three groups were less favourably developed than those of the untreated controls. The best morphologico-histochemical pattern was observed following administration of 750 I.U. PMSG.     

Control of ovulation and fixed time insemination in heifers following cloprostenol.

The time of ovulation was determined in heifers following two injections 11 days apart of 500 microgram of cloprostenol by recovery of reproductive tracts at slaughter. Ovulation had not begun by 72 hours while 31%, 61% and 95% had ovulated by 78, 92 and 96 hours respectively after the second injection of cloprostenol. Injection of synthetic LH-releasing factor (GnRH) given 48 hours after cloprostenol significantly hastened the time of ovulation in animals slaughtered at 78 hours after the second cloprostenol injection. Insemination of heifers at 48, 60 or 72 hours resulted in lower fertility than two inseminations at 60 and 72 hours or at 48 and 72 hours after treatment. Controlling the time of ovulation with GnRH did not increase the fertility following a single insemination 71 hours after the treatment with cloprostenol.     

Changes in the serum concentrations of gonadotrophins and oestradiol in peripubertal Chinese Beijing Black gilts

Four gilts of the Chinese Beijing Black breed, all from the same litter, had their blood serum concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH) and oestrogens (E₂) measured by radioimmunoassay at intervals of 20 days between the ages of 5 and 185 days. The concentrations of LH declined sharply between days 5 to 25 and remained low until rising again from day 85 and reaching a peak at day 105 before declining again and remaining constant. The concentrations of FSH increased from day 85, peaking at day 105, followed by a slow decline to day 185. Serum E₂ concentrations were high at day 5 then decreased dramatically, but increased considerably at 185 days. These results are similar to those reported from European breeds.Abbreviations CV coefficient of variation - E₂ oestrogens - FSH follicle stimulating hormone - IU international unit - LH luteinizing hormone - RIA radioimmunoassay     

The course of ovulation in gilts after the use of two GnRH injections for ovulation stimulation

The status of ovulation and amount of ovulated follicles in 410 gilts which had received differentiated pretreatment produced evidence to the feasibility of substitution of HCG by Gn-RH vet. "Berlin-Chemie" to stimulate ovulation. Yet, 2 injections are necessary with an adequate interval between them and with appropriate dosage. The highest synchronisation effect in all experimental variants was obtained from 350 and 750 micrograms of Gn-RH with 50 minutes in between or 750 plus 750 micrograms of Gn-RH with an interval of 40 minutes. Ovulation was most reliably stimulated by 500 I.U. of HCG.     

The course of ovulation in gilts after the partial replacement of HCG by GnRH for ovulation stimulation

The ovulation status and the amount of ovulated follicles were determined in 3 experiments from 197 gilts which had been given differentiated treatment and which were subsequently slaughtered. Ovulation stimulation produced high synchronisation effects, as compared to untreated animals. Partial substitution proved possible of Gn-RH vet. "Berlin-Chemie" for 500 I.U. of HCG which were generally used to stimulate ovulation, since the amount of ovulated follicles 169 hours from the last application of Suisynchron premix was in all 3 cases above the specified value of 85.0 per cent even after injection of 300 I.U. HCG/300 micrograms Gn-RH.     

Effect of the gonadotrophins treatment on morphological alterations in ovary and peripheral plasma concentrations of steroid hormones in gilts

The present study was designed to examine the influence of gonadotrophins treatment on the ovarian morphology changes and plasma concentrations of steroid hormones in peripheral blood. The experiment was performed on sexually pubertal gilts (Large White x Landrace) of similar age (7-8 months) and body mass (100-110 kg) with two controlled subsequent estrous cycles. The animals were randomly divided into four groups: two control consisting of pigs with the luteal phase (n = 9, the 10th day of the estrous cycle) and the follicular phase (n = 6, the 20th day of the estrous cycle) and two experimental ones consisting of animals with both mentioned periods (n = 7 and n = 9) treated with gonadotrophins (PMSG and hCG). The gilts in the luteal phase were injected (s.c.) with gonadotrophins at a daily dose of PMSG 400 and hCG 200 IU from the 16th to the 27th day (the 6th day of the next estrous cycle). The gilts in the follicular phase, were injected with the same dose of gonadotrophins but from the 8th to the 19th day of the estrous cycle. Plasma concentrations of P4, A4, T, E1, E2 and metabolite of PGF2 alpha-PGFM were determined by radioimmunoassay (RIA) method. Injections of PMSG and hCG in both experimental groups produced several times enlarged: weight, size and volume of ovaries and alterations in a number of structural elements as compared with those found in the control animals. The morphological elements presented in ovaries: corpora haemorrhagica, corpora lutea, regular and atretic follicles and first of all cysts by distinctly differentiation thickness of the walls are characteristic for cystic ovarian degeneration. Plasma concentrations all determined hormones after gonadotrophins treatment in experimental groups were increased except E1 (insignificant decrease) in luteal phase as compared with those found in the control groups. Statistically significant increase (p < 0.001) in plasma concentrations of P4, A4, and T in both experimental groups and E2 (p < 0.001) in luteal phase were noted. In peripheral plasma concentrations increase of E1 and E2 in follicular phase of the estrous cycle were insignificant.     

Ovarian influence on uterine growth in prepubertal gilts

A determination of age of the prepubertal gilt at which ovaries affect uterine growth is necessary before establishing the extent to which length of uterus is influenced by inherent differences, as opposed to those due to ovarian secretions. In Exp. 1 and 2, the effect of presence of ovaries on uterine growth was determined following ovariectomy in 186 crossbred gilts. The uterus was examined 40 or 80 d after ovariectomy for length, weight and diameter. Growth of uterine horns in gilts from 20 to 60 d of age was equal with or without ovaries. Uterine horns in ovariectomized gilts continued to grow slowly from 60 to 140 d of age and then remained static to 180 d of age. Uterine horns in gilts with ovaries increased rapidly in length, weight and diameter, with concomitant increase in ovarian weight between 100 and 180 d of age. In Exp. 3, uterine growth and ovarian compensation after unilateral ovariectomy and hysterectomy at 60 d of age were determined in 85 crossbred gilts from 60 to 180 d of age to evaluate the unilateral ovariohysterectomy model for studying association of uterine length before puberty and subsequent uterine capacity. In response to removal of an ovary and a uterine horn, the remaining ovary compensated, but the remaining uterine horn did not. This study demonstrated that the ovaries did not influence uterine growth until after 60 d of age and that unilateral ovariohysterectomy could be performed as early as 60 d of age without altering consequent normal uterine growth.     

The influence of exogenous pituitary growth hormone on the ovulatory response to PMSG and hCG and the LH response to estradiol benzoate in prepubertal gilts

Two experiments were performed to examine the influence of exogenous growth hormone on the reproductive axis in gilts. Experiment one employed 26 Yorkshire × Landrace prepubertal gilts, which were selected at 150 d and 86.5 ± 1.5 kg bodyweight (BW) and assigned equally to two treatments. Gilts received injections of either porcine growth hormone at 90 μg/kg BW, or vehicle buffer, from 150 to 159 d. At 154 d gilts received 500 IU PMSG, followed 96 hr later by 250 IU hCG. Gilts were slaughtered at 163 days and their ovaries recovered to determine ovulatory status. In each treatment, gilts failed to show any ovarian response to PMSG/hCG. All remaining control gilts ovulated and their ovaries appeared morphologically normal. In gilts receiving exogenous growth hormone, fewer ovaries (4/11, P<.01) appeared morphologically normal. The ovaries of all other growth hormone injected gilts had very large (12–25 mm) non-luteinized follicles. In experiment two, 20 prepubertal Yorkshire × Landrace gilts were selected at 138 days and 85 kg BW. These gilts received injections of growth hormone at 90 μg/kg BW (n=9) or vehicle (n=11) from 138 to 147 days. At 143 days, all gilts were given an injection of estradiol benzoate (EB) at 15 μg/kg BW. Blood samples were taken at the time of EB injection, at 24 and 36 hr and then at 6 hr intervals until 78 hr. All samples were assayed for serum LH concentrations. The EB induced LH peak height was lower (P<.04) in gilts receiving exogenous growth hormone than in controls. The results presented indicate that the daily injection of growth hormone at 90 μg/kg BW reduced the estradiol-induced release of LH in addition to reducing the number of corpora lutea in gonadotrophin stimulated gilts.     

The effect of a bacterial endotoxin or cloprostenol on the clinical status and hormonal levels in 80-100 days pregnant gilts

An experiment was conducted to examine the effect of a lipopoly-saccharide (LPS) of Salmonella typhimurium on the luteal function in 80 days pregnant gilts. Four animals were i.v. injected with 2 μg LPS/kg body weight and 3 animals were i.m. injected with 500 μg cloprostenol (CP). Gilts which maintained pregnancy after the initial injection were reinjected with GP around day 100. Clinical observations were made and plasma levels of 15-keto-13,14-dihydro-PGF₂α, progesterone, oestradiol-17β and oestrone sulphate were analysed by radioimmunoassay.The LPS induced a characteristic clinical endotoxemia. All LPS treated gilts maintained pregnancy until day 100 when 1 gilt aborted, 1 was emergency slaughtered and 2 reinjected. The comparative injections of CP induced abortion! within 48 h in 2 of 3 gilts at 80 days and in all reinjected animals at 100 days of pregnancy. Progesterone decreased immediately after both LPS and CP injections. In non-aborting gilts, the progesterone decrease had a transient character. The PGF_2α metabolite levels responded to LPS by a dramatic surge of approximately 4 h duration. All abortions were accompanied by a massive release of PGF_2α reaching peak levels during expulsion of the foetuses. Oestradiol-17ß and oestrone sulphate followed an ascendent pattern between days 80 and 100. Occasional transient decreases in oestradiol-17ß or increases in oestrone sulphate levels after LPS and CP injections were observed in several animals. Abortions were followed by a sharp decrease of both oestrogens. Post-abortum reproductive disorders occurred frequently. Endocrine changes associated with post-abortum ovarian activity were relevant to the clinical and morphological observations. The relationship between the stage of pregnancy in the pig and its endocrine response to abortifacient agents as well as some foetopathic effects of the endotoxin are discussed.     

Appearance of the uterine specific proteins following induction of ovulation in prepubertal gilts.

The appearance of the uterine specific proteins following induction of ovulation in prepubertal gilts is described. 12 gilts each at 3, 4, and 5 months of age were allotted randomly to 1 of 2 treatment groups prior to induction of ovulation: 1) saline treated and 2) human chorionic gonadotropin (HCG) treated (400 IU daily from Days 12 through 16 of the induced cycle). Ovulation was induced with HCG following treatment with pregnant mare serum gonadotropin and the day of ovulation was designated as Day 1. All the gilts were laparotomized and uteri infused with phosphate-buffered saline on Day 16 to obtain uterine protein secretions. Plasma progesterone levels on Day 11 and observations made at laparotomy indicated that only 1 gilt 3 months of age failed to ovulate. The number of corpora lutea, plasma progesterone, total recoverable uterine protein, and uterine specific protein on Day 16 were markedly affected by the age of the gilt. These same characteristics, except uterine specific protein, were additionally affected by HCG treatment. Total recoverable uterine protein and uterine specific protein in saline and HCG-treated gilts at 3, 4, and 5 months of age were 6.3 and 1.5, 10.4 and 2.8; 38.8 and 15.2, 51.6 and 15.9; 20.4 and 7.7, 47.8 and 14.6 mg, respectively. Polyacrylamide slab gel electrophoresis showed that HCG-treated gilts at 3 months of age and both saline- and HCG-treated gilts at 4 and 5 months of age generally produced the purple basic protein and the complete profile of the low molecular weight acidic proteins during the induced cycle.     

不同定时输精程序处理对有无初情期后备母猪发情及妊娠的影响

为探讨有无初情期和不同定时输精程序处理对后备母猪发情及妊娠的影响,随机选择182头有初情期和193头无初情期的后备母猪,其中将182头有初情期后备母猪分为3组,对照组(C1组,62头)、烯丙孕素组(A1组,60头)、烯丙孕素+孕马血清促性腺激素(PMSG)+促性腺激素释放激素(GnRH)组(APG1组,60头);193头无初情期后备母猪分为对照组(C2组,63头)、烯丙孕素组(A2组,65头)、烯丙孕素+PMSG+GnRH组(APG2组,65头),并且比较不同组间后备母猪的发情集中度、发情率、妊娠率等。结果显示:无初情期A2、APG2组经程序处理后分别于停药后第5～9天、第6天集中发情,有初情期A1组、APG1组母猪于停药后第6～9天、5～6天集中发情;烯丙孕素可显著提高有初情期后备母猪A1组发情率与妊娠率(P0.05),APG1与APG2组的发情率与妊娠率极显著高于C1组、C2组(P0.01),且APG1、APG2组间差异极显著(P0.01);隐性发情后备母猪妊娠率APG1、APG2组间无显著差异(P0.05)。结果表明:有无初情期显著影响后备母猪定时输精处理的效果,利用定时输精程序处理后可使母猪发情集中度、发情率、妊娠率均显著提高。     

The effect of systemic administration of cloprostenol on ovulation in mares treated with a prostaglandin synthetase inhibitor

Prostaglandins (PGs) are essential to trigger the cascade of events that degrade the extracellular matrix of follicles leading to follicular rupture and ovulation. In mares, systemic administration of flunixin meglumine (FM), a PG synthetase inhibitor, blocks ovulation by inducing luteinized unruptured follicles (LUF). In the rat, the administration of PGF(2α) (PGF) and PGE restored ovulation in indomethacin treated animals. The mares were treated with FM 0, 12, 24 and 36 h after human chorionic gonadotrophin (hCG) administration to induce experimentally LUF (n = 15) or were left untreated (controls, n = 5). In addition, 250 μg of cloprostenol were administered intravenously to the mares 33, 35 and 36 h (CLO 33, n = 5) or 48, 49 and 50 h (CLO 48, n = 5) after hCG. One group was treated with FM but not with cloprostenol (FM-control, n = 5). The ovulation rate, follicular diameter and progesterone concentration were compared amongst groups. The ovulation rate at 48 h was higher (p < 0.05) in the controls (100%) than in the FM-control (0%), CLO 33 (0%) or CLO 48 (20%) mares. All but one FM treated mares developed LUF by 48 h after hCG administration. Two LUF collapsed between 48 and 60 h and 72 and 84 h in one mare from FM-control and from the CLO 33 group each, respectively. Progesterone concentration was significantly higher (p < 0.05) in the control mares than in any of the FM treated mares 5, 9 and 13 days after hCG. In conclusion, FM administered during the periovulatory period blocked ovulation in the mares. In contrast, the administration of cloprostenol, a PGF analogue, in the previously FM treated mares failed to restore ovulation.