Fecha/hora: 06/06/2024 10:16:29

Biblioteca(s): 	INIA Treinta y Tres.	
Fecha corriente: 	14/01/2022	
Fecha de la última actualización: 	14/01/2022	
Autoria: 	NÚÑEZ OLIVERA, R.; BÓ, G.A.; MENCHACA, A.	
Afiliación: 	R. NÚÑEZ OLIVERA, Instituto de Reproducción Animal Uruguay, Fundación IRAUy, Montevideo.; G.A. BÓ, Instituto de Reproducción Animal Córdoba (IRAC), Córdoba, Argentina. // Instituto A.P. de Ciencias Básicas y Aplicadas, Medicina Veterinaria, Universidad Nacional de Villa María. Córdoba, Argentina.; JOSE ALEJO MENCHACA BARBEITO, INIA (Instituto Nacional de Investigación Agropecuaria), Uruguay.	
Título: 	Association between length of proestrus, follicular size, estrus behavior, and pregnancy rate in beef heifers subjected to fixedetime artificial insemination.	
Año de publicación: 	2022	
Fuente/Imprenta: 	Theriogenology, 15 March 2022, volume 181, pages 1-7. doi: https://doi.org/10.1016/j.theriogenology.2021.12.028	
DOI: 	10.1016/j.theriogenology.2021.12.028	
Idioma: 	Inglés	
Notas: 	Article history: Received 9 June 2021 / Received in revised form 22 December 2021 / Accepted 25 December 2021 / Available online 31 December 2021.	
Contenido: 	This study evaluated the relationship between proestrus length and follicular size, estrous behavior, and pregnancy rate in Bos taurus beef heifers subjected to ixedetime artificial insemination (FTAI). A total of 911 heifers received a synchronization treatment protocol for FTAI (JeSynch) consisting of an intravaginal
progesterone device for 6 d, estradiol benzoate at the time of device insertion cloprostenol sodium and eCG at device removal and GnRH at the time of FTAI. The presence or absence of a corpus luteum (CL) was determined by ultrasonography at device insertion and all heifers were tail painted at device removal for estrus detection at the time of FTAI. For the establishment of different periods of proestrus length (i.e., interval from device removal to FTAI), GnRH was administered i.m. at 48 h (n ¼ 308), 60 h (n ¼ 290) or 72 h (n ¼ 313) after device removal. The diameter of the largest follicle at the time of GnRH administrationwas determined by ultrasonography, expression of estrous was determined by percentage of tail paint removal, and FTAI was performed at the time of GnRH administration in all heifers. The diameter of the largest follicle was greater when GnRH/FTAI was performed at 72 or 60 h (12.9 ± 0.2 mm and 12.8 ± 0.1 mm, respectively) than at 48 h (12.2 ± 0.1 mm, P < 0.05). The proportion of heifers in estrus tended to be greater when GnRH/FTAI was performed at 72 h (77.0%, 137/178) than at 48 h (68.2%,
122/179; P ¼ 0.06), and intermediate at 60 h (71.4%, 120/168). Pregnancy rate tended to be greater in heifers with the longest (72 h: 70.0%, 219/313) than the shortest (48 h: 63.6%, 196/308; P < 0.1) proestrus length, while 60 h proestrus length was intermediate (63.1%, 183/290; P¼ NS). Pregnancy rate was
affected by the presence of a CL at device insertion (71.3%, 352/494 in heifers with a CL, vs. 59.0%, 246/417 for those without a CL; P < 0.01). For those heifers bearing a CL, pregnancy rate was greater in heifers with a 72 h proestrus length (77.0%, 134/174) than with 48 or 60 h proestrus length (67.7%, 107/158 and
68.5%, 111/162; respectively; P < 0.05). In heifers without a CL, proestrus length did not affect pregnancy rate. In summary, extending proestrus length by delaying the interval from device removal to GnRH/FTAI from 48 to 72 h, was associated with a greater diameter of the preovulatory follicle, greater proportion of heifers expressing estrus at the time of FTAI, and greater pregnancy rate in cycling beef heifers.	
Palabras-Clave: 	FOLÍCULO; FOLLICLE; OVULATION; TIMED ARTIFICAL INSEMINATION; ULTRASONOGRAFIA; ULTRASONOGRAPHY.	
Categoría del tema: 	L53 Fisiología Animal - Reproducción	
Registro original: 	INIA Treinta y Tres (TT)	
Ejemplares: 	TT - (103463-1) - PXI - AP - DD - PP/Theriogenology/2022/Nuñez -  -  - DIS