Abstract This study aimed to evaluate the effect of synchronization with prostaglandin F2α in Baixadeiro mares during the rainy and dry seasons. Fourteen mares were synchronized by administering two doses of 1 mL prostaglandin PGF 2α and monitored by rectal palpation and ultrasound for the assessment of follicular development and uterine echotexture. Of this total, nine mares allowed the collection of blood, in which the blood was collected by venipuncture of the jugular vein to determine progesterone (P4) by ELISA. Mares showed no differences (P > 0.05) in weight, body score condition (BSC), tone, uterine edema, frequency of ovulation, synchronization interval, estrus, and the total number of follicles between periods. However, there was a difference in large increased follicle diameter (P < 0.05) during the dry season. The average concentrations of P4 in mares differed (P < 0.05) between the pre- and post-ovulatory phases for both seasons and after ovulation, with higher concentrations in the rainy season. Furthermore, statistical differences in daily light (P < 0.05) were observed between the dry and rainy periods. Thus, we conclude that mares from the genetic grouping Baixadeiro showed no reproductive seasonality, though there was a difference in luminosity between the rainy and dry seasons. The treatment with two doses of PGF 2α was effective in synchronizing the mares, promoting the return of estrus in the dry and rainy periods. The mares remaining cyclically active throughout the year provided there were appropriate forage availability and quality levels to allow for normal values of body weight and condition.

In order to determine the profile of leptin and insulin values in seminal plasma and their correlations with sperm patterns during the peripuberty, a total of 16 crossbred Gyr dairy bulls were monitored from 60 days before to 60 days after puberty, separated into two groups, early and regular, according to the onset of puberty. Hormone values were determined by radioimmunoassay after gel filtration in fast performance liquid chromatography and semen patterns, according to the Brazilian College of Animal Reproduction. Insulin concentrations in seminal plasma did not differ between groups, nor between the ages, with the pooling of the data showing average of 35.15±16.93, 36.60±26.21, 26.82±09.81, and 43.56±31.71 32.24±16.71 U/mL for the pubertal period of -60, -30, 0, +30 and +60 days, respectively. These values were not correlated with sperm parameters, but differed in the group of animals with the highest percentage of major defects (31.08±18.58 U/mL) compared with those with lower percentage of these sperm defects (40.01±25.37 U/mL). Leptin was not correlated with sperm parameters and did not differ between groups or stage of sexual development, with concentrations of 23.10±10.43, 24.35±9.42, 22.41±9.90, 23.76±9.69 and 24.99±11.42 ng/mL for the periods of puberty aforementioned, respectively, after being grouped. These results demonstrated the binding of insulin to the structural quality of the sperm cell, and this hormone is indicated in andrologycal evaluation of future breeding soundness.

For decades, the development and use of the artificial insemination in the equine, especially with frozen semen, was restricted due to impositions of equine breeders associations that opposed the use of the technique. Recently, these legislations have become more flexible in several countries, allowing the registration of products originating from frozen semen. In Brazil, based on these changes, the main donkey breed association (Brazilian Breeders Association of the Pêga Donkeys) revised their concepts and started to allow the use of this biotechnology. The current interest in many countries for the donkey sire is the production of mules, because their acceptability as these animals inherits suitable characteristics of both donkeys and horses. The first reports on donkey frozen semen used extenders based on egg yolk and glycerol, packed in glass ampoules, and followed the existing methodology for freezing bull semen. However, despite of the elapsed time, few research works have been carried out on this species, especially on semen. This literature review discussed the main techniques of freezing equine semen and describes studies on freezing of sperm of asinine species.

Por muchas décadas, el desarrollo y utilización de la inseminación artificial en los équidos, especialmente con semen congelado, estuvo restringido, principalmente, por imposiciones de las asociaciones de criadores. Recientemente, las legislaciones de criadores de équidos en varios países se han tornado más flexibles, permitiendo el registro de productos oriundos de semen congelado. En el Brasil, frente a ese nuevo cambio, la principal asociación de criadores de burros (Associação Brasileira de Criadores de Jumento Pêga) revisó sus conceptos y comenzó a permitir la utilización de esta biotecnología. Asimismo, en muchos países, el mayor interés en el asno o burro como semental está relacionado a la producción de mulares, pues estos animales son deseables en el medio rural, debido a que reúnen las mejores características del burro y del caballo. Los primeros trabajos en congelamiento de semen de asnos utilizaron dilutores a base de yema de huevo y glicerol, y ampolletas de vidrio como sistema de envase, basados en la metodología de congelamiento de toros. Sin embargo, pese al tiempo transcurrido, pocas investigaciones han sido dirigidas a esta especie, en especial a biotecnologías del semen. En esta revisión de literatura se discuten las principales técnicas de congelamiento de semen de équidos y se describen estudios referentes al congelamiento de semen de la especie asnal.

Por muitas décadas, o desenvolvimento e utilização da inseminação artificial nos eqüídeos, principalmente com sêmen congelado, esteve restrito devido a imposições por muitas associações de criadores que não permitiam a utilização da técnica. Recentemente, as legislações das associações de criadores de eqüídeos em diversos países do mundo se tornaram mais flexíveis, permitindo o registro de produtos oriundos de sêmen congelado. No Brasil, frente a essa nova mudança, a principal associação criadores de jumentos (Associação Brasileira de Criadores de Jumento Pêga), revisou seus conceitos e passou a permitir a utilização desta biotecnologia. Atualmente em muitos países, o maior interesse no reprodutor jumento é para a produção de muares, pois esses animais são produtos bastante desejáveis no meio rural, devido reunirem as melhores características destas duas espécies. O primeiro trabalho envolvendo o congelamento de sêmen de jumentos utilizaram diluidor a base de gema de ovo, glicerol e ampolas de vidro como sistema de envase baseados na metodologia de congelamento de touros. Contudo, apesar da longa data de início dos estudos, poucas pesquisas têm sido direcionadas à espécie, em especial a biotecnologias do sêmen. Nesta revisão de literatura discute se as principais técnicas de congelamento de sêmen de eqüídeos bem como descrição detalhada dos estudos envolvendo o congelamento de sêmen da espécie asinina.