Gonzalo Fitz-Rodríguez

Importance of intense male sexual behavior for inducing the preovulatory LH surge and ovulation in seasonally anovulatory female goats

The present study was carried out to determine whether the presence of photostimulated sedated male goats could stimulate the LH preovulatory surge and ovulation in seasonal anestrous goats. Sexually experienced male goats were treated with artificial long days (16 hours light per day) from 1 November to 15 January to stimulate their sexual activity in March and April, corresponding to the natural sexual rest. A female group of goats (n=20) was exposed to non-sedated males who displayed an intense sexual behavior and provided strong odor (non-sedated group). Another female group of goats (n=20) was exposed to the photo-stimulated male goats, but these males were sedated with Xylazine 2% to prevent the expression of sexual behavior (sedated group). The sedated males also provided a strong odor. Females of both groups had full physical and visual contact with non-sedated or sedated males. In both groups, the males remained with females during 4 days. The LH preovulatory surge of 10 female goats per group was measured by determination of LH plasma concentrations in samples taken every 3 hours. In addition, in all goats, (n=20 by group), ovulation was determined by measuring plasma concentrations of progesterone. The proportion of female goats showing a preovulatory LH surge was higher in goats exposed to non-sedated (10/10) than in those exposed to sedated bucks (0/10; P<0.0001). Similarly, most of does in contact with non-sedated males ovulated (19/20), but none of those in contact with sedated males did so (0/20; P<0.0001). We conclude that the expression of an intense sexual behavior by male goats is necessary to induce LH preovulatory surge and ovulation in seasonally anovulatory goats.

The ovulatory response of anoestrous goats exposed to the male effect in the subtropics is unrelated to their follicular diameter at male exposure.

This study was designed to determine whether the follicular diameter at the introduction of the bucks influences the ovarian response in does exposed to males during the anoestrous season in the subtropics. Bucks (n = 4) were subjected to 2.5 months of long days from November 1st to stimulate their sexual activity. On 29th March, one of the four treated males was joined with the females (n = 13), being exchanged with other males every 12 h, during 10 days. Oestrous behaviour was recorded twice daily. Ultrasound examinations of the ovaries were performed once daily from Day -7 to -1 and twice daily from Day 0 to 6. Follicles that ovulate were categorized according to the diameter at the moment when females were joined with males, as Small (<3.9 mm), Medium (4.0-5.9 mm) or Large (>6.0 mm). All females ovulated (13/13) and 12 came into oestrus during the first 5 days after exposure to males. The growth rate of the follicles increased after the introduction of the bucks from 1.1 ± 0.1 mm per day to 1.5 ± 0.1 mm per day (p < 0.05). The percentage of follicles from each category that ovulated did not differ (p > 0.05; Small 47.8%; Medium 34.8% and Large 17.4%). From follicles that ovulated, the growth rate of those that were Small at the moment of the introduction of the bucks was greater (2.1 ± 0.1 mm per day; p < 0.05) than that observed in those that were Medium (1.3 ± 0.1 mm per day) and Large follicles (1.1 ± 0.1 mm per day). In 12 does, the largest follicle present in the ovaries was growing when bucks were introduced. From these follicles, five finally ovulated and seven finally regressed. In conclusion, the follicular diameter at the introduction of the bucks is not related to the oestrous behaviour and ovulatory responding patterns in female goats exposed to sexually active bucks in the subtropics.

Sexually active bucks are able to stimulate three successive groups of females per day with a 4-hour period of contact

Bucks rendered sexually active by a photoperiod treatment of long days can induce fertile ovulation in a group of goats with only 4 h of contact daily with a male:female ratio of 1:10. Here we tested whether such bucks could induce fertile ovulations when stimulating successively three different groups of anovulatory goats when interacting 4 h per day during 15 consecutive days. Control males (n=3) were introduced in the control group (n=25) of does at 8:00 h and were removed at 12:00 h. Experimental males (n=3) were in contact with the experimental groups of does: from 8:00 h to 12:00 h with a first group (n=27), from 12:00 h to 16:00 h with a second group (n=26) and with a third one (n=27) from 16:00 h to 20:00 h. Bucks were then placed until next day in another pen. Both in the control and the experimental groups, more than 85% of females ovulated, and the proportions did not differ between the control and experimental groups (P≥0.67) or between the three experimental groups (P≥0.67). Moreover, the ovulation rate did not differ significantly between the control and the experimental females nor between the three experimental groups. Bucks were able to fertilize more than 72% of does independently of the number of females they were exposed to (P≥0.17). Finally, more than 58% of females kidded and fertility did not differ between the control and experimental groups (P=1) nor among experimental groups (P≥0.77). We conclude that sexually active bucks are able to induce fertile ovulation in three successive groups of anovulatory goats even when the period of contact between sexes is reduced to 4 h per day.

Absence of previous sexual experience did not modify the response of anoestrous goats to photo-stimulated bucks in Spring

Abstract Sexually inexperienced rams display lower frequency of nudging, ano-genital sniffing, mounting attempts, and mounts with intromission than experienced ones. Experienced photo-stimulated males display high level of sexual behaviour. The aim of this study was to determine: i) whether sexually inexperienced photo-stimulated males display similar sexual behaviour as the experienced ones, and ii) whether these inexperienced bucks can stimulate sexual response in anoestrous goats, as the experienced ones. Sexually inexperienced and experienced photo-stimulated males (n = 5 each) were used. In April, two groups of anovulatory females (n = 50 each) were exposed to these males for 15 d. Male sexual behaviour was registered for three days, upon their introduction into female groups. On day 1, the inexperienced males displayed higher nudging than the experienced ones (p < .001), whereas on days 2 and 3, the experienced males displayed higher nudging than the inexperienced ones (p < .001). The ano-genital sniffing, mounting attempts, and mounts with intromission did not differ between the inexperienced and experienced groups (p > .05). The proportion of females ovulating did not differ between the two groups (≥82 %; p = 1.0). Pregnancy rate (≥68 %; p = .829) did not differ between the females exposed to inexperienced or experienced males. It is concluded that sexually inexperienced photo-stimulated males show similar sexual behaviour as the experienced ones, and they are able to induce sexual response in seasonally anoestrous goats through the male effect.