Examinando por Autor "Adams, Gregg P."

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Biotecnologías reproductivas en camélidos sudamericanos domésticos: avances y perspectivas
(Asociación Latinoamericana de Producción Animal, 2007-10-31) Huanca, Wilfredo; Cordero, Aida; Huanca Mamani, Teodosio; Adams, Gregg P.
La crianza de camélidos domésticos, alpacas y llamas, es una de las actividades de mayor importancia e impacto en el desarrollo socioeconómico de la población altoandina del Perú, debido a su capacidad de adaptación a condiciones ambientales difíciles, por encima de los 4,000 msnm, y a su utilización como fuente de proteína de origen animal y de transporte y en el caso de la alpaca, para la producción de fibra de buena calidad. El Perú cuenta con más de 3 millones de alpacas (87% de la población mundial) y la segunda población mundial de llamas (+1 millón); sin embargo, las deficiencias en los esquemas tradicionales de crianza, como la crianza conjunta de alpacas y llamas, con los consecuentes cruces no programados, han contribuido a reducir la calidad genética de los animales, ocasionando una pérdida en la cantidad y calidad de fibra, reportándose que el 45% de la producción de fibra tiene una finura de 26.0 micras y el 46% una de 33.0 micras y sólo el 8% tiene una fibra de 22.0 micras. La aplicación de biotecnologías reproductivas como la Inseminación Artificial (IA) ha contribuido al progreso genético obtenido en especies domésticas como el ganado lechero. En camélidos, la posibilidad de mejora genética de los rebaños productores mediante pruebas de progenie, con la formación de núcleos reproductores, requiere años de trabajo y está limitada, entre otros factores, por el largo intervalo generacional y la capacidad fisiológica de una hembra que sólo puede tener hasta 4 crías, a lo largo de su vida reproductiva. El objetivo de este trabajo es mostrar el estado actual del conocimiento, especialmente en Inseminación Artificial, Transferencia Embrionaria y Fertilización In Vitro; con el propósito de contar con alternativas tecnológicas que puedan servir como herramientas para el mejoramiento genético de camélidos domésticos, alpacas y llamas; así como la posibilidad de su uso potencial en camélidos no domésticos.
Induction of superovulation in South American camelids
(Elsevier B.V., 2013-01-10) Ratto, Marcelo H.; Silva, Mauricio E.; Huanca López, Wilfredo; Huanca Mamani, Teodosio; Adams, Gregg P.
The development of assisted reproductive technologies such as embryo transfer (ET), artificial insemination (AI) and in vitro fertilization (IVF) in South American camelids is considerably behind that of other livestock species. Poor success of the embryo transfer technique has been related to a lack of an effective superstimulatory treatment, low embryo recovery rate, and the recovery of hatched blastocysts that are not conducive to the cryopreservation process. Superstimulation has been attempted using equine chorionic gonadotropin (eCG) and follicle stimulating hormone (FSH) during the luteal, or the sexually receptive phase, sometimes given at follicular wave emergence. The rationale for inducing a luteal phase prior to or during superstimulation in camelids is not clearly understood, but it may simply reflect an empirical bias to conventional methods used in other ruminants. The number of ovulations or CL varies widely among studies, ranging from 2 to more than 15 per animal, with the number of transferable embryos ranging from 0 to 4 per animal. The control of follicular growth combined with superstimulatory protocols has resulted in a more consistent ovarian response and a greater number of follicles available for aspiration and oocyte collection. Recent studies in llamas have demonstrated that the use of ovulation inducing treatments or follicle ablation can synchronize follicular wave emergence allowing the initiation of gonadotropin treatment in the absence of a dominant follicle resulting in a more consistent ovulatory response. Few studies in alpacas have been reported, but it appears from recent field studies that the ovarian response is more variable and that there is a greater number of poor responders than in llamas. A review of superstimulation protocols that have been used in llamas and alpacas in the last 15 years is provided, including a discussion of the potential of protocols designed to initiate treatment at specific stages of follicular growth.
Ovarian response and embryo production in llamas treated with equine chorionic gonadotropin alone or with a progestin-releasing vaginal sponge at the time of follicular wave emergence
(Elsevier Inc., 2009-07-18) Huanca López, Wilfredo; Cordero, Aida; Huanca Mamani, Teodosio; Cárdenas Minaya, Oscar Efraín; Adams, Gregg P.; Ratto, Marcelo
The objective of the study was to compare the ovulatory response and embryo production in llamas (Lama glama) treated with a single dose of equine chorionic gonadotropin (eCG) alone or combined with intravaginal medroxyprogesterone acetate (MPA) at the time of follicular wave emergence. Llamas with a growing follicle ≥7 mm in diameter were assigned to one of the following groups: (1) Control (n = 28): Nonstimulated llamas were mated and embryos were collected 7 d after mating. (2) eCG (n = 32): Llamas were given 5 mg luteinizing hormone (LH) (Day 0) to induce ovulation, 1000 IU eCG on Day 2, a luteolytic dose of prostaglandin F2α on Day 6, mating on Day 7, and embryo collection on Day 14. (3) eCG+MPA (n = 34): Llamas were treated as those in the eCG group, but a sponge containing 60 mg MPA was placed intravaginally from Days 2 to 6. Llamas that did not respond to synchronization or superstimulation were excluded, leaving data from n = 26, 26, and 27 in the control, eCG, and eCG+MPA groups, respectively, for statistical analysis. The mean (±SD) number of follicles > 7 mm at the time of mating was greatest in the eCG group, intermediate in the eCG+MPA group, and lowest in the control group (16.6 ± 5.3, 12.9 ± 3.7, and 1.0 ± 0.0, respectively, P < 0.001). The number of corpora lutea was similar between eCG and eCG+MPA groups (10.1 ± 2.9 and 8.6 ± 3.7, respectively); both were higher (P < 0.001) than in controls (0.9 ± 0.3). The number of embryos did not differ significantly between the eCG and eCG+MPA groups (4.8 ± 2.8 and 3.5 ± 3.0, respectively), but both were higher (P < 0.001) than in the controls (0.7 ± 0.4). In conclusion, eCG, with or without MPA effectively induced a superovulatory response and multiple embryo production in llamas.