Data/hora: 18/05/2024 17:27:13

Provedor de dados: 	56	
País: 	Brazil	
Título: 	Synchronization of ovulation in crossbred dairy heifers using gonadotrophin-releasing hormone agonist, prostaglandin F2a and human chorionic gonadotrophin or estradiol benzoate	
Autores: 	Castilho,C.; Gambini,A.L.G.; Fernandes,P.; Trinca,L.A.; Teixeira,A.B.; Barros,C.M.	
Data: 	2000-01-01	
Ano: 	2000	
Palavras-chave: 	Follicle; Corpus luteum; Ovulation; HCG; GnRH; Artificial insemination.	
Resumo: 	Girolando (Gir x Holstein) is a very common dairy breed in Brazil because it combines the rusticity of Gir (Bos indicus) with the high milk yield of Holstein (Bos taurus). The ovarian follicular dynamics and hormonal treatments for synchronization of ovulation and timed artificial insemination were studied in Girolando heifers. The injection of a gonadotrophin-releasing hormone (GnRH) agonist was followed 6 or 7 days (d) later by prostaglandin F2&lt;FONT FACE="Symbol"&gt;a&lt;/FONT&gt; (PGF2&lt;FONT FACE="Symbol"&gt;a&lt;/FONT&gt;). Twenty-four hours after PGF2&lt;FONT FACE="Symbol"&gt;a&lt;/FONT&gt; injection either human chorionic gonadotropin (hCG, GPh-d6 and GPh-d7 groups) or estradiol benzoate (EB, GPE-d6 and GPE-d7 groups) was administered to synchronize ovulation and consequently allow timed artificial insemination (AI) 24 and 30 h after hCG and EB injection, respectively. Follicular dynamics in Girolando heifers was characterized by the predominance of three follicular waves (71.4%) with sizes of dominant follicles (10-13 mm) and corpus luteum (approximately 20 mm) similar to those for Bos indicus cattle. In the GnRH-PGF-hCG protocol, hCG administration induced earlier ovulation (67.4 h, P&amp;lt;0.01) compared to the control group (GnRH-PGF) and a better synchronization of ovulation, since most of it occurred within a period of 12 to 17 h. Pregnancy rate after timed AI was 42.8 (3/7, GPh-d6) to 50% (7/14, GPh-d7). In contrast, estradiol benzoate (GnRH-PGF-EB protocol) synchronized ovulation of only 5 of 11 heifers from the GPE-d7 group and of none (0/7) from the GPE-d6 group, which led to low pregnancy rates after timed AI (27.3 and 0%, respectively). However, since a small number of Girolando heifers was used to determine pregnancy rates in the present study, pregnancy rates should be confirmed with a larger number of animals.	
Tipo: 	Info:eu-repo/semantics/article	
Idioma: 	Inglês	
Identificador: 	http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2000000100013	
Editor: 	Associação Brasileira de Divulgação Científica	
Relação: 	10.1590/S0100-879X2000000100013	
Formato: 	text/html	
Fonte: 	Brazilian Journal of Medical and Biological Research  v.33 n.1 2000	
Fonte: 	info:eu-repo/semantics/openAccess