Daily excretion of indigestible dry matter and fiber on lactating cows

• Grant number: 18/03640-4
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: June 01, 2018
• End date: May 31, 2019
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Nutrition and Feeding
• Principal Investigator: Francisco Palma Rennó
• Grantee: Lucas Yudi Sakamoto
• Host Institution: Faculdade de Medicina Veterinária e Zootecnia (FMVZ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

The evaluation of the digestibility is fundamental for the evaluation of feed nutritional value and indispensable component of researches in animal nutrition. The conventional method, which is the total collection of feces, is a laborious, expensive method and can incur stress for the animal. Methods with internal markers use have been widely used for estimating total tract apparent digestibility in performance trials or partial digestibility in metabolism assays. However, the indicator to be used as well as the sampling protocol still raises doubts of many researchers. Since the circadian rhythm of markers excretion in conventional diets of lactating cows under Brazilian conditions is unknown. This study will evaluate faecal recovery of indigestible dry matter, indigestible neutral detergent fiber and indigestible acid detergent fiber; when the animals receive diets supplemented with lipids and protein sources with different ruminal degradabilities. In addition, we will study the behavior of the concentration of such indicators in spot fecal samples obtained at different times throughout the day: 0:00; 3:00; 6:00; 9:00; 12:00; 15:00; 18:00 and 21:00. Eight Holstein cows (approximately 100 days in milk, 580 kg BW and 35 kg / day milk production) will be distributed in a 4 × 4 Latino square design, to receive one of four experimental, composited by a 2 × 2 factorial. The studied factors will be the RDP content of the diet (9.8 or 11.0%) and lipid supplementation (0 or 3.3% of calcium salts of soybean oil fatty acids). Cows will be submitted to total fecal sampling and spot samples will be collected at the previously mentioned times.