Hormone‐free Protocols for the Control of Reproduction and Artificial Insemination in Goats

Abstract

Contents The dairy goat industry is of great economic importance to certain rural areas of the European Union (EU), especially the Mediterranean region. Its sustainability, however, is severely affected by the seasonality of goat reproduction, which leads to fluctuations in the availability of final products. Classical hormone treatments based on progestagens and eCG are the main tools employed in the effort to achieve fertility outside of the normal breeding season. They are also used to induce and synchronize oestrus and ovulation in artificial insemination programs. The food safety policy of the EU is becoming ever stricter with regard to the use of hormonal treatments for reproductive purposes, pushing livestock‐raising towards ever cleaner and greener production systems. Recent advances in the use of natural methods able to generate endocrine signals that induce the ovulatory process have improved our capacity to foster reproduction in the non‐breeding season. When used in a fashion appropriate for the latitude at which animals live, their breed, and the management system under which they are raised, environmental (photoperiod), nutritional and sociosexual (the male effect) signals offer alternatives to classic hormonal techniques. This affords the fragile and heterogeneous goat production sector with new opportunities. This article describes the most representative advances made in the use of the male effect as a natural method of inducing ovulation during seasonal anoestrus. Its association with other methods for optimizing responses and synchronizing induced ovulation is also discussed; such associations allow it to be used as an alternative to hormonal treatment in artificial insemination programs.

Male effect associated with suckling interruption on the reproductive performance of Santa Inês ewes

“…This result may have been found because the females were between 45 and 60 days postpartum, and as reported by gEytEnbEEK et al (1984), the male effect becomes more effective in sheep when females are exposed to a male 43 days after lambing. Several reports have described that the male effect induces a preovulatory LH peak that further stimulates follicular development, leading to ovulation (CHEMinEau, 1987;Martin et al, 1986;pEarCE and oLdHaM, 1988;CoHEn-tannoudJi et al, 1989;dELgadiLLo, 2011;LopEz-sEbastián et al, 2014;CaLdas et al, 2015).…”

Alternative methods for control of reproduction in small ruminants: A focus on the needs of grazing industries

“…This "male effect" offers control at two levels: i) the timing of births is no longer determined by the natural breeding season of the females; and ii) the induced ovulations are synchronized among the females in the flock or herd. The synchrony can be sufficient for artificial insemination (Martin and Scaramuzzi, 1983;Lopez-Sebastián et al, 2014) and is certainly sufficient for implementation of CGE management tools such as an ultrasound, focus feeding during pregnancy, and the management of birth. Equally as important is the simplicity and practicality-putting males in the field with the females and then knowing with confidence when the females will ovulate, conceive, and give birth.…”

Reproduction in Goats

“…Luteolysis begins around day 16-17 of the estrus cycle, releasing uterine prostaglandins, influenced by oxytocin. With the above, the concentration of progesterone decreases, causing a strong increase in the frequency of pulses of LH and its amplitude, which causes ovulation [10].…”

“…Short-term protocols typically combine the use of progesterone with multiple follicle-controlling hormones, such as follicle stimulating/ovulation inducing, a combination of equine chorionic gonadotropin (eCG), human chorionic gonadotropin (hCG), and PGF2α [26]. Using multiple hormonal controls in short-term synchronization protocols gives an increased ability to control luteal and follicular dynamics (see Figure 4) [10]. Previous research indicates that serum progesterone concentrations are maintained at an increased level when compared with a long-term progesterone insert protocol [27].…”

“…Within this context, the male effect on dairy goats has also been evaluated, where the presence of estrus occurs later compared to the breeds of meat, where the period of breeding is extended by 31 days more [31]. The presence of bucks creates olfactory, behavioral, and visual stimuli which in an increase in the secretion of luteinizing hormone which stimulates folliculogenesis and ovulation [10]. Although it was initially believed that pheromones played a pivotal role in the male effect, subsequent work has proved that visual and behavioral stimuli are equally as important as the smell [31].…”