Enhancing Fertility of Multiparous Dairy Cows

• Grant number: 24/04783-4
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: September 15, 2024
• End date: September 14, 2025
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Guilherme Pugliesi
• Grantee: Amanda Guimarães da Silva
• Supervisor: James Richard Pursley
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Michigan State University (MSU), United States
• Associated to the scholarship: 23/11777-8 - Pregnancy losses in precocious Nelore heifers and primiparous and impacts of the use of progesterone as a strategy to mitigate them, BP.DR

Abstract

The pregnancy loss had a negative impact on milk industry. Using average fertility sires, around 60% of multiparous cows have a conceptus attaching to the uterus after 1st TAI. However, these cows have a 40% chance to undergo pregnancy loss. The impact of bull fertility on embryonic development have a limited knowledge. Therefore, the aim of this study is to evaluate the effect of bull fertility on embryonic development and gestational loss. For this, 480 multiparous lactating dairy cows will be synchronized with Double Ovsynch and will be assigned into two treatment groups according to sire conception rate: High (HSCR) or Low (LSCR) fertility bulls. Cows will receive AI from their assigned high or low fertility sire 16 h after final GnRH of Double Ovsynch. Ovaries will be monitored with B-mode ultrasound four times during Double Ovsynch to ensure cows are synchronized to establish day 0 of the pregnancy. Blood samples will be collected daily from 15 to 26 days post-AI to assay for PSPB. Pregnancy diagnosis at days 35, 60, and 100 will be performed by the herd veterinarian with ultrasonography. On days 15, 17, 20 and 23 post-AI a subgroup of cows (n=40/treatment) will be subject to vaginal and cervical epithelial cells sampling with cytological brush to expression of ISG-15 mRNA. The model proposed here will enable to evaluate the impact of bull fertility on the development of the conceptus, as well as on PAGs concentrations and the maintenance of pregnancy in dairy cows.