Peripheral action of kisspeptin at reproductive tissues-role in ovarian function and embryo implantation and relevance to assisted reproductive technology in livestock: A review

Kisspeptin (KISS1) is encoded by the KISS1 gene and was initially found to be a repressor of metastasis. Natural mutations in the KISS1 receptor gene (KISS1R) were subsequently shown to be associated with idiopathic hypothalamic hypogonadism and impaired puberty. This led to interest in the role of KISS1 in reproduction. It was established that KISS1 had a fundamental role in the control of gonadotropin releasing hormone (GnRH) secretion. KISS1 neurons have receptors for leptin and estrogen receptor α (ERα), which places KISS1 at the gateway of metabolic (leptin) and gonadal (ERα) regulation of GnRH secretion. More recently, KISS1 has been shown to act at peripheral reproductive tissues. KISS1 and KISS1R genes are expressed in follicles (granulosa, theca, oocyte), trophoblast, and uterus. KISS1 and KISS1R proteins are found in the same tissues. KISS1 appears to have autocrine and paracrine actions in follicle and oocyte maturation, trophoblast development, and implantation and placentation. In some studies, KISS1 was beneficial to in vitro oocyte maturation and blastocyst development. The next phase of KISS1 research will explore potential benefits on embryo survival and pregnancy. This will likely involve longer-term KISS1 treatments during proestrus, early embryo development, trophoblast attachment, and implantation and pregnancy. A deeper understanding of the direct action of KISS1 at reproductive tissues could help to achieve the next step change in embryo survival and improvement in the efficiency of assisted reproductive technology

Adhesion molecules in gamete transport, fertilization, early embryonic development, and implantation—role in establishing a pregnancy in cattle: A review

Cell–cell adhesion molecules have critically important roles in the early events of reproduction including gamete transport, sperm–oocyte interaction, embryonic development, and implantation. Major adhesion molecules involved in reproduction include cadherins, integrins, and disintegrin and metalloprotease domain-containing (ADAM) proteins. ADAMs on the surface of sperm adhere to integrins on the oocyte in the initial stages of sperm–oocyte interaction and fusion. Cadherins act in early embryos to organize the inner cell mass and trophectoderm. The trophoblast and uterine endometrial epithelium variously express cadherins, integrins, trophinin, and selectin, which achieve apposition and attachment between the elongating conceptus and uterine epithelium before implantation. An overview of the major cell–cell adhesion molecules is presented and this is followed by examples of how adhesion molecules help shape early reproductive events. The argument is made that a deeper understanding of adhesion molecules and reproduction will inform new strategies that improve embryo survival and increase the efficiency of natural mating and assisted breeding in cattle

Synchronization techniques to increase the utilization of artificial insemination in beef and dairy cattle

Abstract The main objective of the implementation of Artificial Insemination (AI) in cattle is to produce a sustained genetic progress in the herd. Although AI is an old reproductive biotechnology, its widespread implementation is very recent and is mainly due to the use of protocols that allows the AI without heat detection, commonly called fixed-time artificial insemination (FTAI). The development of FTAI protocols also allowed the application of AI in larger, extensively managed, herds and especially in suckled cows instead of just reducing the breeding programs to the heifers. FTAI treatments are widely used in South America, with about 2,500,000 cows inseminated in the last season in Argentina and about 6,500,000 in Brazil. This manuscript aims to present and describe several treatments available and some of the factors that may affect pregnancy rates

Effects of equine chrionic gonadotrophin (eCG) on corpus luteum development and progesterone concentrations in Nelore cows.

This trial aimed to test eCG as an enhancer of the luteal function, as well as to evaluate the ability of eCG to delay or prevent luteolysis mechanism. A group of 32 mature, synchronized (CRESTAR@), lactating Nelore (Bos taurus indicus) cows were randomly allotted to receive either 400 lU of eCG at implant withdrawal (GeCG; n=16) or remain as contrais (GC; n=16). Ultrasound per rectum evaluation of avaries was conducted daily, from implant rem oval up to the following ovulation (a complete estrous cycle). Simultaneously, blood samples were taken to determine plasmatic concentration of progesterone ([P4]). Data were analyzed by GLM of the SAS program. GeCG showed non-significant (P>.05) higher volume of corpus luteum (CL) from day 3 after synchronized ovulation up to lhe rest of lhe luteal phase. In addition, eCG promoted a longer lasting growing period of lhe CL without changing its growing rale (P>.05) as compared to GC. As a result, CI maximum volume was reached later (9.2:t .47 days) and achieved a larger dimension (6927.5:t 405.86 mm3) for GeCG than occurred for GC (respectively, 7.7:t .47 days and 5437.8:t 405.86 mm3). The peak of [P4] was observed at lhe same time for both groups (11.3 t .59 and 11.4 t .59 days for GeCG and GC, respectively). However, maximum [P4] was higher (P.O5) for both groups (17.3 t .45 to GeCG and 17.1 t .45 days of lhe estrous cycle to GC). As a consequence, estrous cycle length did not differ (P>.O5) between treated (21.8 t .57 days) and non-treated cows (21.4 t .57 days). In summary, eCG not only increased CL dimension but also optimized [P4] over the luteal phase ofthe estrous cycle. Therefore, eCG given at implant removal provided a luteotrophic effect, but it was not capable to delay luteolysis

Aplicación de biotecnologías para una mayor producción de terneros

Baruselli, P.S.; Marques, M.O.; Vieira, L.M.; Konrad, J.L.; Crudeli, G.A.: Aplicación de biotecnologías para una mayor producción de terneros. Rev. vet. 26: 2, 154-159, 2015