Establishing histidine requirements for lactating Holstein cows

• Grant number: 16/21253-2
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: April 01, 2017
• End date: October 27, 2017
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Nutrition and Feeding
• Principal Investigator: Marcos Veiga dos Santos
• Grantee: Cristian Marlon de Magalhães Rodrigues Martins
• Supervisor: Alexander Nikolov Hristov
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Institution abroad: Pennsylvania State University, United States
• Associated to the scholarship: 15/03942-2 - Milk stability during thermal processing of pasteurization and UHT (Ultra High Temperature), BP.DR

Abstract

The goal of present study is to establish histidine (His) requirements for lactating Holstein dairy cows. To fulfill the objectives of this proposal we shall conduct experiments in order to establish His requirements in lactating dairy cows fed metabolizable protein (MP)-deficient diets or diets supplying MP at or above NRC (2001). These experiments will be Latin square design with 28-d periods, 21 d of which will be for adaptation and 7 d for sample and data collections. The present scholarship candidate will conduct the first trial. The first trial will establish His requirements in cows fed a diet supplying adequate MP. Diets will be supplemented with rumen-protected Met and Lys to meet or exceed the requirements for digestible Lys and Met, i.e. 6.6 and 2.2% of MP, respectively (NRC, 2001). Rumen-protected His will be top-dressed to provide digestible His at 1.80 (control, unsupplemented diet), 2.30, 2.80, and 3.30% of MP (estimated using NRC, 2001 and based on actual AA analysis of the feeds). The main response variable in these experiments will be milk protein yield. In addition, we will evaluate the following outcomes: dry matter intake, milk yield and composition, blood plasma His (and total AA profile), carnosine, anserine, and whole blood hemoglobin concentrations. Blood samples for these analyses will be collected 4 times in 2 consecutive days (at 1100 and 1600 h on d 1 and 1400 and 2000 h on d 2), twice during each experimental period (wk 2 and 4).