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Pregnancy losses in precocious Nelore heifers and primiparous and impacts of the use of progesterone as a strategy to mitigate them

Grant number: 23/11777-8
Support Opportunities:Scholarships in Brazil - Doctorate
Start date: December 01, 2023
Status:Discontinued
Field of knowledge:Agronomical Sciences - Veterinary Medicine - Animal Reproduction
Principal Investigator:Guilherme Pugliesi
Grantee:Amanda Guimarães da Silva
Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated scholarship(s):24/04783-4 - Enhancing Fertility of Multiparous Dairy Cows, BE.EP.DR

Abstract

The objective is to study the factors involved in gestational losses of precocious Nelore heifers and primiparous. In addition, injectable P4 (P4i) will be used in different strategies in order to mitigate pregnancy losses in both categories. In Exp. 1, carried out in the 2022/2023 breeding season, the effect of two ovulation induction protocols using P4i prior to the TAI protocol on pregnancy rates and pregnancy loss in heifers aged 10-17 months was tested. Day zero (D0) was considered the beginning of TAI protocol. The experimental groups (n=600 animals/group) were: Control (no treatment); 1P4i, who received 150 mg of P4i on D12; and 2P4i, received 150 mg P4i D24 and 150 mg P4i D12. In Exp. 2, the effect of pre-exposure to P4i seven days before (D-7) the beginning of the TAI protocol on the reproductive performance of primiparous cows with 2 years old will be studied. Also, the effect of P4i administration in cows with an active corpus luteum (CL) in the Doppler diagnosis (22 days post-TAI) on gestational losses. Initially, two experimental groups will be formed (n=500 animals/group): Control: no treatment; and P4i: receiving 150 mg of P4i on D7. At the time of Doppler diagnosis, half of the cows with active CL will be treated with 150 mg of P4i. Thus, we have a 2x2 factorial arrangement and 4 experimental groups will be formed (n= approx. 150 animals/group): Control: no treatment; P4i-Pre: 150 mg P4i on D7; P4i-Post: 150 mg P4i on D33; and P4i-Pre/Post: 150 mg of P4i on D7 and D33. In both experiments, sequential pregnancy diagnoses will be performed to detect pregnancy losses. With the study, it will be possible to identify the factors involved in pregnancy loss in precocious heifers and primiparous cows, enabling strategies to mitigate them, such as studying the effect of administering injectable P4 at different times.

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