Association of allelic variants of thyroid-binding globulin with puberty in boars and responses to hemicastration.

Hemicastration of males increases weight of remaining testis when conducted before Sertoli cells cease to proliferate. The current studies re-examined responses to hemicastration in one-quarter Meishan crossbred boars that differed for two alleles of thyroid-binding globulin (TBG). In the first experiment, boars at 25 days of age with either allele did not differ in degree of testicular development; however, at 56 days, boars with the C allele had more advanced testicular development than littermates with the A allele as evidenced by testes with seminiferous tubules of larger diameter (P<0.

Alteration of fertility endpoints in adult male F-344 rats by subchronic exposure to inhaled benzo(a)pyrene.

The objective of this study was to evaluate the reproductive risk associated with exposure of adult male Fisher-344 rats to inhaled benzo(a)pyrene (BaP). Rats were assigned randomly to a treatment or control group. Treatment consisted of sub-chronic exposure of rats via inhalation to 75microgBaP/m(3), 4h daily for 60 days, while control animals were unexposed (UNC).

Effects of benzo(a)pyrene on intra-testicular function in F-344 rats.

The objective of this study was to evaluate the reproductive risk associated with exposure of adult male Fisher-344 (F-344) rats to inhaled benzo(a)pyrene (BaP), a ubiquitous environmental toxicant present in cigarette smoke, automobile exhaust fumes and industrial emissions. Rats were assigned randomly to a treatment or control group. Treatment consisted of exposure of rats via nose-only inhalation to 75 microg BaP/m3, 4 hours daily for 60 days, while control animals were unexposed (UNC).

Growth and pubertal development of F1 bulls from Hereford, Angus, Norwegian Red, Swedish Red and White, Friesian, and Wagyu sires.

The objective of the study was to characterize body growth, testicular development, and puberty from 8 to 14 mo of age in bulls (n = 120) produced by mating sires from Hereford, Angus, Norwegian Red, Swedish Red and White, Friesian, and Wagyu breeds to MARC III ((1/4) Hereford, (1/4) Angus, (1/4) Red Poll, and (1/4) Pinzgauer) cows. Traits evaluated were birth weight, weaning weight (at 215 d), yearling weight, ADG from 8 to 14 mo of age, paired testicular volume growth from 8 to 14 mo of age, age at puberty (determined by production of 50 x 10(6) sperm with 10% motility), age at freezable semen (determined by production of 500 x 10(6) sperm with 50% motility), and, at 15 mo of age, paired testicular weight and daily sperm production per testis pair. There was an effect of sire breed (P = 0.

Genetic variation in sperm production.

In boars, the primary determinant of daily sperm production is the number of Sertoli cells, which establishes testicular weight. The only breed comparison of foetal testicular development in boars contrasted two diverse breeds, White composite (WC, Landrace-Yorkshire) with Meishan, a Chinese breed that undergoes pubertal development at a young age and has small testicular size. During the prenatal period, the pattern of change in testicular development is similar in these two breeds with both having their greatest proportion of proliferating Sertoli cells at 90 days of gestation, and with WC boars possessing more Sertoli cells and greater mass of seminiferous tubules during the latter half of gestation.

Comparative response of rams and bulls to long-term treatment with gonadotropin-releasing hormone analogs.

The objective was to compare the relative response between rams and bulls in characteristics of LH, FSH and testosterone (T) secretion, during and after long-term treatment with GnRH analogs. Animals were treated with GnRH agonist, GnRH antagonist, or vehicle (Control) for 28 days. Serial blood samples were collected on day 21 of treatment, and at several intervals after treatment.

Testicular development of Zebu bulls after chronic treatment with a gonadotropin-releasing hormone agonist.

The objective was to compare testis characteristics of Zebu bulls treated with the GnRH agonist, deslorelin, at different times and for different durations during their development. An additional objective was to determine the usefulness of a stain for the transcription factor GATA-binding protein 4 (GATA-4) as a specific marker for Sertoli cell nuclei in cattle. Bulls (54) were allocated to nine groups (n = 6) and received s.

Fertility of yearling beef bulls during mating.

Crossbred (Bos taurus) yearling beef bulls were assessed for breeding soundness and physical traits prior to multi-sire natural mating at pasture. Bulls (n = 60) were assigned to six groups of nine or 10 bulls and two bull-groups were rotated on 14-day intervals during a 63-day mating season in each breeding herd (n = 3) of 191-196 cows. The remaining bulls (n = 14) were maintained under similar environmental conditions without mating exposure.

Quantitative trait loci for male reproductive traits in beef cattle.

The objective of the present study was to detect quantitative trait loci (QTL) for male reproductive traits in a half-sib family from a Bos indicus (Brahman) x Bos taurus (Hereford) sire. The sire was mated with MARC III (1/4 Hereford, 1/4 Angus, 1/4 Red Poll and 1/4 Pinzgauer) cows. Testicular traits were measured from 126 male offspring born in 1996 and castrated at 8.

A variant of porcine thyroxine-binding globulin has reduced affinity for thyroxine and is associated with testis size.

The field of genomics applies the dissection of genetic differences toward an understanding of the biology of complex traits. Quantitative trait loci (QTL) for testis size, plasma FSH in boars, and body composition (backfat) have been identified near the centromere on the X chromosome in a Meishan-White Composite resource population. Since thyroid function affects Sertoli cell development and adult testis size in rodents, and thyroxine-binding globulin (TBG) maps to this region on the porcine X chromosome, TBG was a positional candidate gene for testis size.

Ovarian follicular development in cattle selected for twin ovulations and births.

Comparisons of numbers of antral ovarian follicles and corpora lutea (CL), of blood hormone concentrations, and of follicular fluid steroid concentrations and IGFBP activity were conducted between cows selected (twinner) and unselected (control) for twin births to elucidate genetic differences in the regulation of ovarian follicular development. Ovarian follicular development was synchronized among cows by a single i.m.

Stereological evaluation of Sertoli cell ontogeny during fetal and neonatal life in two diverse breeds of swine.

Chinese Meishan (MS) boars have smaller testes due to fewer Sertoli cells compared with White Composite (WC) boars. The objective was to describe Sertoli cell development relative to circulating FSH concentrations in fetal and neonatal MS and WC boars. Testes and blood samples were collected on days 60, 75, 90 and 105 postcoitum (dpc) and 1, 7, 14 and 25 postpartum (dpp).

Growth and pubertal development in Brahman-, Boran-, Tuli-, Belgian Blue-, Hereford- and Angus-sired F1 bulls.

Growth and testicular development between 7 and 15 mo of age were evaluated in bulls produced by mating sires of six breeds (Hereford, Angus, Belgian Blue, Brahman, Boran, and Tuli) to Angus, Hereford, and MARC III (four-breed composite) cows. At 12 mo of age, Angus- and Hereford-sired bulls had the heaviest body weight (P < 0.08 to 0.

Relationships of testicular iron and ferritin concentrations with testicular weight and sperm production in boars.

The inverse relationship of testicular size and circulating follicle-stimulating hormone (FSH) concentrations has been documented, and accompanying this relationship is the change in color of the parenchymal tissue of the testes. Large testes (300 to 400 g) are pink to light red and small testes (100 g) are dark maroon with color gradations for weights in between. It was hypothesized that this color most likely represented an iron protein.

Effect of chronic treatment with the gonadotrophin-releasing hormone agonist azagly-nafarelin on basal concentrations of LH in prepubertal bulls.

Administration of GnRH agonist for an extended period inhibits pulsatile LH release but enhances testicular function of bulls. The mechanism whereby long-term administration of GnRH agonist enhances testosterone concentration in the blood of bulls has not been determined. The aim of this study was to determine whether chronic treatment with the GnRH agonist, azagly-nafarelin, increases blood concentrations of LH and FSH in prepubertal bulls.

Sertoli cells in the boar testis: changes during development and compensatory hypertrophy after hemicastration at different ages.

Changes in Sertoli cell numbers and testicular structure during normal development and compensatory hypertrophy were assessed in crossbred Meishan x White Composite males. Boars were assigned at birth to unilateral castration at 1, 10, 56, or 112 days or to remain as intact controls through 220 days. The first testes removed were compared to assess testicular development.

Identification of genomic regions controlling plasma FSH concentrations in Meishan-White Composite boars.

The Chinese Meishan (ME) breed of pig is unique for many reproductive traits. Compared with Western breeds of swine, ME females reach puberty earlier, ovulate more ova per estrus, and have greater uterine capacity, while intact males (boars) have smaller testes and extremely elevated plasma levels of pituitary-derived glycoprotein hormones. In an effort to identify the genetic mechanisms controlling the elevated plasma levels of pituitary-derived glycoprotein hormones [in particular, follicle-stimulating hormone (FSH)] and to determine whether some of these genetic factors are also responsible for differences in other phenotypes, we scanned the entire genome for regions that affected plasma FSH in boars from a Meishan-White Composite (equal contributions of Chester White, Landrace, Large White, and Yorkshire) resource population.

Interrelationships of porcine X and Y chromosomes with pituitary gonadotropins and testicular size.

Endocrine and testicular responses to unilateral castration on 1, 10, 56, or 112 days of age were characterized in 132 Chinese Meishan (MS) x White composite (WC) crossbred boars in which testicular size associates with a quantitative trait locus (QTL) on X chromosome. At 220 days of age, testicles of boars unilaterally castrated on Day 1 or 10 weighed more and had greater total daily sperm production (DSP) than one testicle of bilaterally intact boars (P < 0.05); compensation did not double these two responses.

Specific staining of Sertoli cell nuclei and evaluation of Sertoli cell number and proliferative activity in Meishan and White Composite boars during the neonatal period.

The positive relationship between Sertoli cell number and testicular size emphasizes the importance of determining factors involved in the regulation of the Sertoli cell population. Based on data from other species and indirect evidence in the boar, it is generally accepted that porcine Sertoli cells proliferate rapidly throughout the early postnatal period. However, direct evaluation of Sertoli cell number and the proliferative activity of Sertoli cells during the early postnatal period in boars have not been reported.

GnRH antagonist inhibition of gonadotropin and steroid secretion in boars in vivo and steroid production in vitro.

The hormone GnRH has a stimulatory effect on gonadotropin synthesis and secretion. The objective of the first study was to evaluate concentrations of FSH and LH in plasma of boars after successive treatment with SB75, a GnRH antagonist. Thirteen boars greater than 1 yr of age (eight White Composite [WC] and five Meishan [MS]) were injected once daily with SB75 (10 microg/kg of body weight) for 4 d.

Relationships of gonadotropins, testosterone, and cortisol in response to GnRH and GnRH antagonist in boars selected for high and low follicle-stimulating hormone levels.

Considerable variation exists in the serum levels of gonadotropins in boars; this results in differential testicular function. Boars (Chinese Meishan, European White composite, and crosses of the two breeds) selected for high and low circulating FSH concentrations were used to define possible differences in pituitary sensitivity to GnRH and GnRH antagonist and gonadal and adrenal responses. After a 2-h pretreatment sampling period, boars were injected with GnRH or GnRH antagonist and repetitively sampled via jugular cannula for changes in serum concentrations of FSH, LH, testosterone, and cortisol.

Testicular morphology and function in boars differing in concentrations of plasma follicle-stimulating hormone.

The objective of this study was to evaluate morphological characteristics and testicular function of boars with different endogenous concentrations of FSH. Boars were selected at 6 mo of age on the basis of mean FSH concentrations in plasma collected at 4, 5, and 6 mo of age. Boars were classified within half-sibling families based on whether they had high concentrations of FSH (HiFSH, > 500 ng/ml, n = 9) or low concentrations (LoFSH, < 500 ng/ml, n = 7).

Prevalence of morphologic defects in spermatozoa from beef bulls.

Objective: To determine the overall prevalence of morphologic defects in spermatozoa from beef bulls and to determine whether prevalence varies with the age of the bull.

Design: Cross-sectional observational study.

Animals: 2,497 beef bulls that were evaluated for breeding soundness in 1994 by 29 practicing veterinarians in a 5-state geographic region.

Negative relationship between blood concentrations of follicle-stimulating hormone and testicular size in mature boars.

Relationships between blood concentration of FSH and testicular size and daily sperm production were evaluated with data obtained from five studies originally designed to investigate regulation of FSH secretion in Meishan (MS), White composite (WC), and crossbreds of these. A minimum of three blood samples/boar were obtained at greater than 4-d intervals for determination of FSH, and testes were obtained at castration or slaughter. In a random sample of boars, FSH was fivefold greater (P < .

Relationship between scrotal infrared temperature patterns and natural-mating fertility in beef bulls.

The infrared temperature pattern (IRT) of the scrotal surface was recorded for 73 yearling beef bulls and a color video thermogram of the pattern of each bull was recorded. The average scortal surface temperature, temperature at the top and bottom of the scrotum, scortal temperature gradient, and thermal class (normal, questionable, or abnormal scortal surface thermal pattern) were recorded for each thermogram. Thirty-seven bulls had a normal temperature pattern (51%), 20 had a questionable pattern (27%), and 16 had an abnormal temperature pattern (22%).