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 5 Co-Synch program, at estrus detection and distribution

• Grant number: 12/01345-9
• Support Opportunities: Regular Research Grants
• Start date: May 01, 2012
• End date: April 30, 2014
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Production
• Principal Investigator: Alexandre Vaz Pires
• Grantee: Alexandre Vaz Pires
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Associated researchers: Roberto Sartori Filho

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)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

FERRAZ JUNIOR, MARCOS VINICIUS C.; PIRES, ALEXANDRE V.; BIEHL, MARCOS VINICIUS; SANTOS, MARCELO HENRIQUE; POLIZEL, DANIEL M.; NEPOMUCENO, DELCI D.; SARTORI, ROBERTO; BARRETO FILHO, JOAO BOSCO; GONCALVES, JOSE RENATO S.; DAY, MICHAEL L.. Luteolysis in Bos indicus cows on Days 5 and 7 of estrous cycle with varying doses of PGF(2 alpha). Theriogenology, v. 86, n. 5, p. 1268-1274, SEP 15 2016. (12/01345-9)

FERRAZ JUNIOR, MARCOS V. C.; PIRES, ALEXANDRE V.; BIEHL, MARCOS V.; SANTOS, MARCELO H.; BARROSO, JOSE P. R.; GONCALVES, JOSE R. S.; SARTORI, ROBERTO; DAY, MICHAEL L.. Comparison of two timed artificial insemination system schemes to synchronize estrus and ovulation in Nellore cattle. Theriogenology, v. 86, n. 8, p. 1939-1943, NOV 2016. (12/01345-9)