Chronic use of a GnRH agonist (deslorelin) or immunization against GnRH: effects on testicular function and sperm quality of bucks.

Chronic use of GnRH agonists and immunization against GnRH have been used as reversible contraceptive methods. The aim of this study was to compare the effectiveness of both treatments to inhibit reproductive function of adult bucks, in terms of strength and duration of the effects. We used 9 control untreated bucks (CON), 7 bucks treated chronically with a GnRH agonist (subcutaneous implants with 7.4 mg of deslorelin, Suprelorin, Virbac) (AGO), and another 7 bucks were immunized against GnRH (dose of 2 mL of Improvac-Zoetis with 300 µg of a synthetic incomplete analog of natural GnRH; 300 mg of diethylaminoethyl-dextran; and 2.0 mg of chlorocresol) (IMM). Testicular and sperm evaluations, testosterone concentrations, and male odor were determined from 4 wk before applying the treatments until 17 mo of their application. Scrotal circumference of CON (21.0 ± 0.1 cm) and IMM (21.2 ± 0.2 cm) was greater than that of AGO bucks (19.9 ± 0.2 cm) (P < 0.05 for each), without difference between CON and IMM bucks. Pixels' color intensity of testicular ultrasound images was not affected by treatment (general mean ± SEM: 116.0 ± 1.8). Testosterone concentration was greater in CON than AGO and IMM in months 3 and 4, greater in CON and IMM than AGO bucks in months 15 and 16, and greater in IMM than CON and AGO bucks in month 17 (P < 0.05 for all comparisons). Male odor was greater in CON (1.5 ± 0.0) than IMM bucks (1.3 ± 0.0) and greater in IMM than AGO (1.1 ± 0.0) bucks (P < 0.05 for each). Treatment negatively affected all the sperm variables: the total number of sperm in the ejaculate, sperm motility, sperm with normal morphology and sperm with integral membrane function. It was concluded that both treatments were effective in inhibiting the reproductive axis; however, neither of them produced azoospermia or decreased testosterone concentrations to undetectable levels. With both treatments, there were individual males exhibiting characteristics of fertility in all periods of the study. However, chronic use of a GnRH agonist seemed to be the most effective treatment in terms of duration and strength.

Asymmetrical size and functionality of the pampas deer (Ozotoceros bezoarticus) testes: Right testis is bigger but left testis is more efficient in spermatogenesis.

Information about gonadal asymmetries in ruminants is very scarce. In this work, we performed three complementary studies to compare characteristics of both testes: (i) weight and size of offspring and adult dead males; (ii) the tissue:fluid relationship determined by ultrasound scanning; and (iii) the spermatogenic status using fine needle aspiration cytology. The right testis was heavier than the left one in both offspring and adult animals and had greater width and volume in adult males than the left one. The ultrasound pixel intensity was similar in both testes. The right testis tended to have more spermatogonia (p = .06) and had a greater percentage of early spermatids (p = .004) than the left testis. On the other hand, the left testis had a greater percentage of spermatozoa (p = .05). The left testis had a greater spermatozoa/spermatogonia ratio (p = .02) and tended to have more spermatozoa/Sertoli cells ratio (p = .07). The spermatogenic index tended to be greater in the left than in the right testis (p = .06). Overall, we concluded that the right testis of pampas deer males is bigger but according to the cytology, it seems to be less spermatogenically effective than the left one, but these differences are not explained by different tissue:fluid ratio in each testis. Although differences were greater in adults than in offspring, asymmetry was observed even in just born offspring.

Competition Between Different Social Ranked Rams has Similar Effects on Testosterone and Sexual Behaviour Throughout the Year.

Dominant rams have preferential access to females, as they frequently interrupt sexual behaviour from subordinated. Testosterone concentrations are directly linked to sexual and aggressive behaviour and have important variations along the year. Therefore, it may be expected that the effects of dominance relationships on reproductive behaviour differ according to testosterone concentrations, and thus to the period of the year. The aim of this study was to compare the effects of dominance relationships on testosterone and sexual behaviour in different moments of the year in rams. Twelve rams were maintained in a single group. Social rank was determined in January (maximum reproductive development), May (regression of the reproductive status) and August (lowest reproductive activity), and the four rams with higher (HR) and the four with lower (LR) success index were used. Testosterone serum concentration was weekly measured four times during each experimental period. Sexual behaviour was evaluated in each period with an oestrous ewe, and with the oestrous ewe and another ram from the other social rank (each HR with each LR ram). Testosterone concentration was greater in HR than LR rams in January (p = 0.03), and all the behaviours were displayed more frequently in non-competitive than in competitive tests (p < 0.05). Rams modified their sexual strategy in competitive environments decreasing the display of sexual behaviour independently of their social status. This effect was observed consistently throughout the year: high-ranked rams have greater testosterone concentrations than LR rams only during the pre-rut, when they naturally compete to join the groups of ewes.

Reproductive development of male goat kids reared with or without permanent contact with adult females until 10 months of age.

Adult male ruminants that were reared in contact with females display greater sexual behavior than those reared in single male groups. The aim of the experiment was to compare the reproductive development of prepubertal male kids reared with or without direct permanent contact with adult females until they were 10 months old. Seventeen Saanen male kids were maintained in two groups until 44 weeks of age: kids reared in permanent direct contact with four adult goats (group FEM, N = 8) and kids that remained isolated from females (group ISO, N = 9). All goats in the FEM group became pregnant approximately when bucks attained 28 weeks of age. Scrotal circumference and testosterone concentration were measured, and semen was obtained by electroejaculation to avoid female contact in the ISO group. Scrotal circumference was greater in FEM kids at 12 and 14 weeks of age (P < 0.0001) and testosterone when they were 20 and 22 weeks old (P < 0.0001). Testosterone concentration was greater in ISO kids from 28 to 44 weeks of age. All semen characteristics increased with age (P < 0.0001). Individual motility was greater in FEM kids than that in ISO kids at 15 and 17 weeks (P < 0.005); mass motility was greater in ISO than that in FEM kids at 32 weeks (P < 0.05); total number of spermatozoa/ejaculate was greater in ISO kids at 30, 32, and 40 weeks and in FEM kids at 43 weeks (P < 0.005); total number of motile spermatozoa was greater in ISO kids at 32 and 40 weeks, whereas at 43 weeks, it was greater in FEM kids (P < 0.005). It was concluded that permanent contact with adult goats had transient and short-time positive effects in male kids' reproductive traits during prepubertal development. However, positive effects stopped after goats used as stimulus became pregnant.

Sexual performance and stress response of previously unknown rams after grouping them in dyads.

The establishment and maintenance of individual social status is a stressor that affects negatively the reproductive function. Therefore, the aims of this study were to determine if after grouping two unknown rams there is a stress response, and their sexual behavior is affected, and if those responses differ between the rams that resulted dominants and those that resulted subordinates. Twelve adult rams were maintained in individual pens for one month, and on Day 0, hour 0 two rams of similar body weight were grouped in a neutral pen. Social rank was determined using the food competition test, in which each pair of rams was allowed to compete for feed in a bucket only large enough for one of them; the ram that was able to eat from the bucket for more than 1 min, was considered to be the dominant individual. Cortisol concentrations were measured on Day 0 during the first 12h after grouping. Testosterone concentrations were measured from Day -9 to Day 16. Sexual behavior of rams toward estrus ewes was determined before and after grouping in individual pen tests. There was no difference between dominant and subordinated rams in none of the studied variables. Cortisol concentration had a peak 30 min after grouping the rams (P<0.0001). There was a significant decrease in testosterone concentration on Day 5 and Days 8-14 compared to concentration before grouping (P=0.02). The frequency of ano-genital sniffing and flehmen of estrus ewes decreased after grouping, with no differences between dominant and subordinated rams (P=0.009 and 0.03 ano-genital sniffing and flehmen, respectively). However, the frequency of lateral approaches (P=0.005), and all mating behaviors towards ewes increased after grouping the rams (mount attempts: P=0.02; mounts: P=0.008; mounts with ejaculation: P=0.05; total mounts: P=0.003; ejaculation/total mounts: P=0.0004). It was concluded that grouping unknown rams modified their sexual strategy resulting in an increase in the number of mating behaviors when rams were tested alone with estrus ewes. However, grouping two unfamiliar rams was a stressful event that negatively affected testosterone concentrations but the stress and behavior responses did not differ according to rams' social rank.

Social rank during pre-pubertal development and reproductive performance of adult rams.

Reproductive performance of rams when they were 1.5 and 2.5 years old during two breeding seasons was investigated. The objective was to compare the reproductive performance of the rams on the basis of their social ranks, which had been scored for each subject during the lamb development stage. The subjects were aged matched Corriedale x Milchschaf rams (n=12: all singles born during the same week from multiparous ewes) were used. Data were collected from the five rams with greater (GR) and lesser (LR) social rank scores when lambs. These data included body weight, scrotal circumference, sexual behavior toward estrual ewes (e.g. incidence of ano-genital sniffing, lateral approaches, Flehmen, mount attempts, actual mounts, and mounts with ejaculations, and ejaculation/total mount ratio) during a 30-min period, and semen variables (semen volume, mass motility, individual sperm motility and total number of spermatozoa in the ejaculate). During the first breeding season, GR rams were heavier (62.9+/-2.7 kg) than LR rams (69.4+/-3.0 kg; P<0.0001). There were no differences in scrotal circumference or testosterone concentration measures. Semen volume was greater in GR rams (0.5+/-0.1 mL compared to 0.7+/-0.1 mL for GR and LR rams; P<0.004), but it tended to have a greater percentage of abnormal spermatozoa. Although some courtship behaviors were more frequent in LR rams (lateral approaches and Flehmen) and ejaculation/total mount ratio of LR rams also tended to be greater, mounting activity (mount attempts and mounts) was more frequent in GR rams. During the second year, GR rams still tended to be heavier (83.3+/-2.0 kg compared to 85.9+/-2.4 kg; P=0.09) but had smaller scrotal circumference than LR rams (37.5+/-0.2 cm compared to 36.5+/-0.6 cm; P<0.045). Semen characteristics were not different for the rams, but mass motility tended to be greater for LR rams. Generally, LR rams displayed more lateral approaches, showed Flehmen more often, mounted with ejaculation more often, and tended to have a greater mount with ejaculation/total mounts ratio. Conclusions were courtship of rams may differ in line with the social status they had as lambs although there are not clear effects on other sexual behaviors or semen characteristics.