Nutrigenomics: effects of rumen-protected methionine in the mammary gland during heat stress

• Grant number: 25/16018-3
• Support Opportunities: Scholarships abroad - Research Internship - Post-doctor
• Start date: October 30, 2025
• End date: October 29, 2026
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Nutrition and Feeding
• Principal Investigator: Arlindo Saran Netto
• Grantee: Danielle de Cássia Martins da Fonseca
• Supervisor: Juan J Loor
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil
• Institution abroad: University of Illinois at Urbana-Champaign, United States
• Associated to the scholarship: 23/05352-4 - Biofortification of milk from lactating cows with different sources of selenium and comparison of composition and quality of biofortified milk, BP.PD

Abstract

This study aims to evaluate the potential benefit of methionine on mammary gland function during heat stress. Samples of mammary tissue will be collected from 11 multiparous Holstein cows in lactation, with an average of 252 ± 15 days in milk (DIM), a body weight of 711 ± 28 kg, parity of 2.3 ± 0.7 (number of calvings), milk production of 34.8 ± 1.9 kg/day, and dry matter intake of 23.1 ± 2.0 kg/day. The experimental design is a randomized block design, in which 6 cows will be fed a basal diet without protected methionine from the rumen (MPR), based on corn silage, alfalfa silage, and corn grains (AMTS Cattle Pro), and 5 cows will receive a diet with protected methionine from the rumen (MPR), supplied at a rate of 0.10% of the diet's dry matter and administered once daily over the total mixed ration (TMR). The cows will be fed once daily after the morning milking and milked twice daily at 4:00 a.m. and 3:30 p.m. The experimental period will last 31 days, with 21 days under thermoneutral conditions and 10 days under heat stress conditions using electric thermal blankets. Milk samples will be collected weekly during the thermoneutral period and on days 3, 6, and 9 of heat stress. Vaginal temperature will be measured every 10 minutes (Thermochron iButton) throughout the heat stress period. Blood will be collected from the coccygeal vein on the last day before the start of heat stress and on the 10th day of stress to obtain plasma. The cows will be anesthetized and slaughtered at the University of Illinois College of Veterinary Medicine, Urbana-Champaign. Approximately 10 minutes after bleeding, the cows' body cavities will be sectioned, and samples of various tissues, including the mammary gland, will be immediately collected and frozen in liquid nitrogen before being stored at -80°C in the Mammalian Nutrifisiogenomics Laboratory. The mammary tissue and milk samples will be sent to the Metabolomics Unit at the W. M. Keck Biotechnology Center at the University of Illinois, Urbana-Champaign, for metabolomic analysis. An untargeted metabolite profiling will be performed using UHPLC-Orbitrap-MS. Discriminant analysis by partial least squares (PLS-DA) and figures for the metabolomics data will be generated using MetaboAnalyst 6.0 software, following the methodology described by Jiang et al. (2024). (AU)