RESUMO
The Vanishing Rainfrog (Craugastor evanesco) is an endemic and critically endangered frog species of Panama. It is suspected that 90% of the population has disappeared from the wild. Frogs were collected from the wild and brought to a Captive Breeding Program; however, accomplishing regular reproductive events for this species has been difficult. The objective of this study was to determine the effect of hormonal stimulation on the production and quality of C. evanesco spermatozoa, aiming to develop an efficient and safe sperm collection protocol as a tool to help reproduce this endangered species. Mature males received intra-peritoneal injections with one of six hormone treatments, including des-Gly10, D-Ala6, Pro-NHEt9-GnRH-A, Amphiplex or hCG. Urine samples were collected at 10 different time points post-injection. Quality assessments included sperm concentration, percentage motility, percentage forward progressive motility (FPM), osmolality, pH and morphology analysis. Our results indicate that the optimal treatment for the collection of highly concentrated sperm samples of C. evanesco is 4 µg/gbw GnRH, followed by Amphiplex and 2 µg/gbw GnRH as sub-optimal treatments and finally, 6 µg/gbw GnRH and 5 and 10 IU/gbw hCG as non-optimal treatments. GnRH-A at 4 µg/gbw and Amphiplex stimulated the production of samples with the highest sperm concentrations and quality, despite Amphiplex producing lower percentages of intact acrosome and tail. In contrast, hCG concentrations were not reliable inducers of sperm production, consistently showing lower concentrations, higher percentages of sperm abnormalities and more acidic spermic urine than that induced by Amphiplex and GnRH-A. Morphological assessments revealed that C. evanesco spermatozoa have a filiform shape with a large acrosome on the anterior part of an elongated head, a small midpiece and a long tail with two filaments joined together by an undulating membrane.
RESUMO
The aim of this review is to compare the performance of different reproductive programs using natural service, estrus synchronization treatment before natural service (timed natural breeding (TNB)), artificial insemination (AI) following estrus detection and timed artificial insemination (TAI) in beef herds. It is well known that after parturition the beef cow undergoes a period of anestrous, when they do not exhibit estrus, eliminating the opportunity to become pregnant in the early postpartum by natural mating or by AI after detection of estrus. Hormonal stimulation is already a consistent and well-proven strategy used to overcome postpartum anestrus in beef herds. Basically, hormones that normally are produced during the estrous cycle of the cow can be administered in physiological doses to induce cyclicity and to precisely synchronize follicular growth, estrus and ovulation. Furthermore, two options of mating may be used after hormonal stimulation: natural service (i.e. utilization of bull service after synchronization, referred to as TNB) and TAI. These strategies improve the reproductive efficiency of the herds compared with natural service without estrus induction or synchronization. After the first synchronized service, the most common strategy adopted to get non-pregnant cows pregnant soon is the introduction of clean-up bulls until the end of the breeding season. However, methods to resynchronize non-pregnant cows after the first service are already well established and offer a potential tool to reduce the time for subsequent inseminations. Thus, the use of these technologies enable to eliminate the use of bulls by using resynchronization programs (i.e. two, three or four sequential TAI procedures). The dissemination of efficient reproductive procedures, such as TNB, TAI and Resynch programs, either isolated or in combination, enables the production of a greater quantity (obtaining increased pregnancy rates early in the breeding season) and quality (maximization of the use of AI with superior genetic sires) of beef calves. These technologies can contribute to improve the production efficiency, and consequently, improve livestock profitability.