Function Of Boars Research Articles

Increasing the reproductive function of boars by introducing phosphatide concentrate into their diet

As a result of a number of experiments and studies, it was found that the introduction of phosphatide concentrate in addition to the main diet of boars in the amount of 1.0; 2.0; 3.0% allows to increase the manifestation of sexual reflexes. Also, the inclusion of this concentrate increases both quantitative and qualitative indicators of the sperm of experimental boars, which in the experimental groups allows increasing the number of piglets at birth by 7.9; 18.9; 19.7%, respectively, while the cost of obtaining them is reduced by 7.3; 16.0; 16.5%, respectively, compared with the control group.

RFamide-related peptide 3 and gonadotropin-releasing hormone-II are autocrine-paracrine regulators of testicular function in the boar.

Widespread use of artificial insemination in swine requires millions of doses of boar semen each year. Subfertility of boars remains a major constraint, which can impact the reproductive efficiency of thousands of sows, so a better understanding of testicular function is needed in order to develop methods to improve semen production. With this in mind, the effects of RFamide-related peptide 3 (RFRP3) and Gonadotropin-releasing hormone-II (GnRH-II) on gonadotropin secretion and testicular function of pigs are reviewed here. Receptors for RFRP3 are present in the pig hypothalamus, adenohypophysis, and testis. Evidence from in vitro studies indicates that RFRP3 could be a hypophysiotropic hormone in the pig by suppressing secretion of GnRH-I from the hypothalamus and luteinizing hormone (LH) from the pituitary gland; however, effects of RFRP3 on in vivo secretion of LH in pigs are minimal. Within the pig testis, RFRP3 suppresses testosterone secretion by inhibiting steroidogenic enzymes. GnRH-II and its receptor (GnRHR-II) are abundant in pig testes. Interstitial cells express GnRHR-II, and exogenous GnRH-II robustly stimulates secretion of testosterone in boars, despite minimal secretion of LH. Data illustrate that GnRH-II directly stimulates secretion of testosterone from the testes of mature boars. Thus, the primary function of RFRP3 and GnRH-II in the boar appears to be autocrine-paracrine inhibition and stimulation, respectively, of testosterone secretion within the testis. A better understanding of changes in the RFRP3 and GnRH-II systems within the testis during development will provide important clues about how to improve the testicular function of boars.

Effects of active immunization against GnRH versus surgical castration on hypothalamic-pituitary function in boars

The objective was to compare effects of anti-GnRH immunization (immunocastration) versus surgical castration on hypothalamic-pituitary function in boars. Thirty-six boars were randomly divided into three groups (n = 12/group): control, surgically castrated, or immunized against GnRH at 10 wk of age (boostered 8 wk later). Compared to intact boars, immunocastration reduced (P < 0.05) serum concentrations of LH, FSH, testosterone and inhibin B and caused severe testicular atrophy, whereas surgical castration increased (P < 0.05) serum concentrations of LH and FSH. Both immunocastration and surgical castration consistently reduced hypothalamic GnRH synthesis, with decreased (P < 0.05) mRNA expressions of GnRH, GnRH up-stream gatekeeper genes kiss1 and its receptor (GPR54), and androgen receptor in the hypothalamic arcuate nucleus (ARC) and anteroventral periventricular nucleus (AVPV), as well as GnRH content in the median eminence. Inconsistently, mRNA expressions of gonadotropin-inhibitory hormone (GnIH) in ARC and AVPV as well as its receptor (GPR147) in pituitary were selectively reduced (P < 0.05), but mRNA expressions of estrogen receptor alpha and aromatase (CPY17A1) in pituitary were selectively increased (P < 0.05) in surgical castrates. In response to selectively attenuated suppressive signaling from GnIH and testosterone, mRNA expressions of GnRH receptor (GnRHR), LH-β and FSH-β in pituitary were increased (P < 0.05) in surgical castrates, whereas these pituitary gene expressions were decreased (P < 0.05) in immunocastrates, due to loss of hypothalamic GnRH signaling. We concluded that immunocastration and surgical castration consistently reduced hypothalamic GnRH synthesis due to a testosterone deficiency disrupting testosterone-Kisspeptin-GPR54-GnRH signaling pathways. Furthermore, selectively attenuated GnIH and testosterone signaling in the pituitary increased gonadotropin production in surgical castrates.

Influence of boar breeds or hybrid genetic composition on semen quality and seminal plasma biochemical variables

The enzyme concentrations of seminal plasma are important for spermatozoa metabolism and function in boars. The need has arisen for introducing a biochemical evaluation of semen, along with the usual standard semen analyses. There are no data on the influence of boar breeds on the seminal plasma biochemical variables investigated in this study. Therefore, the objective was to determine the influence of breed and hybrid genetic composition of boars on semen quality and seminal plasma biochemical variables. Semen samples of 27 boars (Swedish Landrace, German Landrace, Large White, Pietrain and Pig Improvement Company hybrid—PIC-hybrid), aged between 1.5 and 3 years, were collected. After evaluation of semen quality, the seminal plasma was separated from the spermatozoa by centrifugation of semen. The seminal plasma was subjected to spectrophotometric analysis to determine alkaline phosphatase (ALP), acid phosphatase (ACP), γ-glutamyltransferase (GGT), creatine kinase (CK) and lactate dehydrogenase (LDH) and to atomic absorption spectrophotometric analysis to measure the concentration of calcium and magnesium. Conventional semen quality variables differed depending on breed and PIC-hybrid genetic composition, though these differences were typically insignificant. In the seminal plasma, significant differences were determined in enzyme activity (ALP, GGT, CK and LDH) and in calcium concentration among boars of differnt breeds. There are, therefore, differences in semen quality and significant differences in the seminal plasma biochemical variables among boars of different breeds and PIC-hybrid genetic composition. The data and differences in semen variables detected in the present study provide knowledge for enhancing evaluation and monitoring of boar reproductive potential, semen quality and explain the potential causes of boar infertility.

Effects of Improvac and Bopriva on the testicular function of boars ten weeks after immunization

This study investigated the effects of Improvac and Bopriva, two anti-GnRF immunization products, on testicular function in boars. We predicted that both products would diminish testicular function; however, we specifically tested the hypothesis that the duration of efficacy for Bopriva would be longer than that of Improvac. Animals were immunized with either Improvac or Bopriva and then observed ten weeks after the second injection. Serum GnRF antibody titers rose after the second injection and peaked approximately two weeks later. At the same time testosterone concentrations decreased to undetectable levels and remained below assay detection for at least six weeks. At approximately eight weeks, testosterone began to increase in animals treated with Improvac though levels remained decreased in Bopriva treated animals throughout the ten weeks. Daily sperm production at 10 weeks was significantly reduced in both treatment groups; however, the reduction was greater in Bopriva treated boars. Examination of testes of both treatments revealed incomplete spermatogenesis with impaired spermatid production and reduced seminiferous tubule diameter. These findings were universal in Bopriva treated animals, but Improvac treated animals exhibited morphologies intermediate between Bopriva treated animals and control boars. Overall testicular function in Bopriva boars remained suppressed ten weeks post-immunization while Improvac boars appeared to be recovering.

Effect of Immunological Castration on the Testicular Function of Boars Given Two Different Anti-GnRF Vaccines.

Effect of Immunological Castration on the Testicular Function of Boars Given Two Different Anti-GnRF Vaccines.

Effects of long-term treatment with the GnrH agonist deslorelin (Suprelorin®) on sexual function in boars

Immunization against GnRH has been proven effective for boar taint removal, and long-term treatment with GnRH analogues has been shown to suppress GnRH dependent reproductive processes in several species. This study was conducted to treat boars (n = 5) with Suprelorin®, i.e., an implant that contains 4.7 mg of the long-acting GnRH analogue deslorelin, and to test the effects on sexual function. Insertion of the implant occurred at the age of 5 weeks and animals were observed until market age at 26–27 weeks. Surgically castrated (n = 4) and intact boars (n = 3) served as controls. Testes growth was markedly reduced and steroidogenesis (testosterone, estrone, estrone sulphate, estradiol 17β) as well as spermatogenesis suppressed in 4 of 5 GnRH treated boars, respectively. The remaining fifth boar resumed testes growth after week 17 of age and had high hormone concentrations when tested at weeks 26 and 27. Restoration of spermatogenesis was observed at 34 weeks of age. There were no effects of treatment on general health, nor were there local inflammatory reactions. Results indicate that suppression of sexual functions in boars due to long-term treatment with the GnRH agonist deslorelin through an implant such as Suprelorin® is possible and can last for several months up to market age; thus it has potential as an alternative to other methods used for boar taint removal. Because the maximum duration of suppression seems to vary between boars, further studies are necessary to refine the treatment.

Testis Morphometry, Duration of Spermatogenesis, and Spermatogenic Efficiency in the Wild Boar (Sus scrofa scrofa)1

The wild boar is a natural inhabitant of Europe, Asia, and North Africa and is phylogenetically the ancestor of the domestic pig. Because of its phylogenetic and economic importance, this species is an interesting model for studying testis function in boars. Therefore, the present study was performed to investigate the testis structure, spermatogenic cycle length, and Sertoli cell (SC) and spermatogenic efficiencies in eight adult wild boars. Each spermatogenic cycle lasted 9.05 days, and the total duration of spermatogenesis was estimated as lasting approximately 41 days. The percentages of testis volume occupied by seminiferous tubules and by Leydig cells were 87% and 6%, respectively. The mean number of SCs per gram of testis was 42 million. The SC (round spermatids per SC) and spermatogenic (daily sperm production per gram of testis) efficiencies were 6.6 cells and 28.6 million, respectively. In general, the testis structure, overall germ cell associations at the different stages of the seminiferous epithelium cycle, and duration of spermatogenesis in the wild boar were similar to those in domestic pigs. Probably because of the small size of Leydig cells (400 microm3), their number per gram of testis (157 million) was the highest among investigated mammalian species. Although the SC efficiency in wild boars was low, their spermatogenic efficiency was comparable to that observed in domestic pigs, mainly because of the higher number of SCs per gram of testis in wild boars. These data suggest that SCs became more efficient during evolution, genetic selection, and domestication in pigs.

The effects of mutated skeletal ryanodine receptors on hypothalamic-pituitary-adrenal axis function in boars.

The objectives of the current experiment were to determine whether boars heterozygous for the mutation in skeletal ryanodine receptors (sRyR), known to cause porcine stress syndrome, differed from wild-type boars in hypothalamic-pituitary-adrenal axis (HPA) function. We have examined basal plasma ACTH, cortisol, and corticosteroid-binding globulin (CBG) concentrations; plasma ACTH and cortisol responses to a nose-snare stressor and at slaughter; dexamethasone suppression of plasma ACTH and cortisol concentrations; and glucocorticoid receptor (GR) density in the pituitary gland, hippocampus, hypothalamus, and frontal cortex. We have also examined carcass yields, composition, and meat quality to determine whether differences in HPA activity were accompanied by an increased incidence of meat quality characteristics associated with pale, soft, exudative (PSE) meat. Thirty boars either heterozygous or wild-type (n = 15 per genotype) for mutated sRyR were tested for HPA function at 7 mo of age. Heterozygous boars had lower basal plasma ACTH (P < .05) and cortisol (P < .04) concentrations. Integrated basal plasma ACTH and cortisol levels were also lower (P < .05 and P < .005, respectively). Genotype had no significant effect on basal CBG, stressor-induced (nose snare or slaughter) or dexamethasone suppression of plasma ACTH or cortisol concentrations. No differences in immunoreactive GR levels were found in the pituitary gland or any brain region examined. We did find a significant, negative correlation (r = -.62, P < .02) between peak (0800) basal plasma ACTH concentrations and hippocampal GR levels. The alterations in basal HPA function in heterozygous boars were accompanied by lighter body weights (P < .03), decreased carcass fat depth (P < .04), and increased carcass lean yields (P < .02). There was a higher incidence of meat quality characteristics associated with PSE meat in heterozygous boars indicated by higher carcass temperatures (P < .04) and meat brightness (P < .0001) with lower carcass pH at slaughter (P < .03) and after chilling (P < .003). In conclusion, we have found differences in basal and not stressor-induced HPA function between boars heterozygous and wild-type for mutated sRyR. This altered basal HPA activity was accompanied by an increased incidence of meat quality aspects associated with PSE meat in heterozygous boars.

Pituitary and Leydig cell function in boars actively immunized against gonadotrophin-releasing hormone.

Crossbred boars were (a) immunized against GnRH conjugated to human serum globulin (200 micrograms GnRH-hSG) in Freund's adjuvant at 12 weeks of age and boosted at weeks 18 and 20 (N = 10), (b) served as controls and received hSG only in adjuvant (N = 10), or castrated at weaning (N = 10). At 24 weeks of age (immediately before slaughter), the boars were challenged with saline or pig LH (1 microgram/10 kg body weight). After slaughter, fresh testicular fragments were incubated with pig LH (0.05 and 0.2 ng/2 ml medium) to assess the effects of immunization on Leydig cell function. Pituitary contents of LH and FSH, and testicular LH receptor content were also measured. The results indicated that plasma LH and testosterone concentrations, pituitary LH content, testicular LH receptor content, testis and sex accessory organ weights were significantly reduced in GnRH-immunized boars compared to hSG-adjuvant controls. However, plasma and pituitary FSH content were not affected by high antibody titres generated against GnRH. The testicular testosterone response to exogenous LH in vivo and in vitro was significantly reduced (P less than 0.05) in GnRH-immunized boars. These results indicate that active immunization against GnRH impairs pituitary and Leydig cell functions in boars.

Relationships among Measures of Testicular Development and Endocrine Function in Boars

Nine blood samples were taken at 30-min intervals from 36 Landrace X Large White boars at each of eight ages (42, 56, 70, 84, 98, 112, 126 and 140 d). Serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone (T) and estradiol-17 beta (E2) were quantified by radioimmunoassay procedures. The maximum concentration of LH and the age at maximum concentration were predicted for each boar. Variability of LH samples was described for each boar by the pooled within age variance among LH samples and by the number of LH peaks. Measurements of testicular development taken at 140 d of age included: in situ testis width and length, excised testis weights and histological traits of excised testes (seminiferous tubule diameter, percentage of tubules with a lumen and percentage of tubules with active spermatogenesis). Pooled within line correlations were calculated with data from boars selected for either high or low testis weight. Correlations among the testicular traits ranged from .45 to .88. Luteinizing hormone concentration (mean over all ages) was related to measures of testicular development (r = .24 to .49). Concentrations of LH from 42 to 84 d of age were more highly correlated with testicular traits than were the concentrations from 98 to 140 d.(ABSTRACT TRUNCATED AT 250 WORDS)

Testicular Function in Boars Exposed to Elevated Ambient Temperature1

Pituitary-testicular function was examined in yearling boars exposed to 23 ± 1#{176}C (control) or 34.5 ± 1#{176}C for 8 h and 31 ± 1#{176}C for 16 h during each 24 h period (heat stressed). Plasma testosterone and immunoreactive LI concentrations were monitored throughout treatment and testes were removed after 13 weeks to quantify spermatogenesis and assess steroidogenesis by measuring the incorporation of E1�l 4C1 acetate into selected L� 4C1 androgens by slices of testicular tissue incubated in vitro. Plasma testosterone and LI concentrations were similar when control and heat stressed boars were bled infrequently during treatment. However, heat stress significantly altered androgen biosynthesis in vitro as evidenced by decreased amounts of II Cl associated with androstenedione, testosterone and dihydrotestosterone and increases in androsterone and androstanediol. Addition of LH and FSH to testicular incubates markedly enhanced the amount of (1-’ 4CI acetate incorporated into 1l 4C1 androgens but further differences between control and heat stressed boars were not apparent. In another experiment, plasma testosterone was quantified in the serum of boars every 30 mm for 12 h on Days 0, 7 and 14 during exposure to 23 ± 1#{176}C (control) or 34.5 ± 1#{176}C (heat stressed). Serum testosterone was reduced (P(0.10) after 7 days of heat stress. Elevated ambient temperature for 90 days significantly reduced the number of young spermatids in round cross sections of seminiferous tubules at stage 1 of the cycle of the seminiferous epithelium but failed to affect the number of type A spermatogonia or preleptotene and pachytene spermatocytes. The results demonstrate that heat stress can exert a transitory decline in plasma