Pharmacological manipulation of the estrous cycle in Nellore cows: i - effect of doses of PGF2a for luteolysis on days 5 and 7 of the estrous cycle. II - effect of replacement of GnRH by EB, in the 5Co-Synch program, at estrus detection and distribution.

• Grant number: 11/16328-0
• Support Opportunities: Scholarships in Brazil - Master
• Start date: March 01, 2012
• End date: July 31, 2013
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Alexandre Vaz Pires
• Grantee: Marcos Vinicius de Castro Ferraz Junior
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The TAI is a tool that allows the AI to a large scale of production in beef cattle. Therefore, the physiology of the processes involved in the protocols has been the subject of numerous studies in an attempt to improve the reproductive rates of this technique. The increase of proestrus, through the removal of sources of progesterone (P4) 5 days after synchronization of follicular development, can increase the time of action of gonadotropin in the physiological processes involved in the follicular maturation, ovulation and subsequent production of P4, thus enabling a higher rate of conception. However, the withdrawal of P4 source in 5Co-Synch program, results in luteolysis of CL in the early luteal phase and there is a consensus of what would be the best way of use PGF2a in the program. In Brazil it is common to use replacement for GnRH by EB in TAI protocols, mainly because of costs. However, the literature is scarce in the replacement of GnRH by EB in protocols with 5 days of P4 source. The aim of experiment I is to evaluate three different treatments of PGF2a in the luteolysis (A: 2,5 mg Dinoprost thometanine; B: 25mg of Dinoprost thometanine, C: 50mg Dinoprost thometanine) in the 5th and 7th days after estrus for determine its applicability in 5CIDR+EB program. The aim of Experiment II is to evaluate the replacement of the applications of GnRH by EB in 5 days protocols. In the experiment III, we intend to perform the analysis of the results of experiment II, especially with regard to the distribution of estrus, this data will be used to determine the correct time for the realization of TAI in 5CIDR+EB program (experiment III). For this, we intend to compare the onset and distribution of estrus in the protocols, the rate of ovulation and pregnancy. (AU)

Academic Publications

(References retrieved automatically from State of São Paulo Research Institutions)

FERRAZ JUNIOR, Marcos Vinicius de Castro. Pharmacological manipulation of the estrous cycle in Nellore cows: I - Effect of doses of PGF2α for luteolysis on days 5 and 7 of the estrous cycle. II - Effect of replacement of GNRH by EB, in the 5Co-Synch program, at estrus detection and distribution, at ovulation rate and pregnancy rate. 2013. Master's Dissertation - Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) Pirassununga.