Evaluation of forage NDF content in the solid diet of preweaning dairy calves and strategies for its supply

• Grant number: 24/00326-8
• Support Opportunities: Regular Research Grants
• Start date: July 01, 2024
• End date: June 30, 2026
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Nutrition and Feeding
• Principal Investigator: Carla Maris Machado Bittar
• Grantee: Carla Maris Machado Bittar
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Associated researchers: Gercino Ferreira Virginio Júnior ; Joao Henrique Cardoso Costa ; João Ricardo Rebouças Dórea ; Márcia Saladini Vieira Salles

Abstract

Due to its effects on the rumen development process, fiber supply is typically low in dairy calf diets. For this reason, the fiber requirement of these animals is not well known, with great variation in recommendations and in some cases, non-recommendation. On the other hand, feeding diets with a high starch content and reduced particle size can result in a high rate of fermentation and acid production in the rumen. However, although these diets can benefit the fermentation profile of interest for rumen development, they carry a greater risk of acidosis, which reduces dry matter consumption, negatively affecting the development process and animal performance. Traditionally, hay has been fed to preweaning calves, with large discrepancies regarding the recommendations of its quality and particle size. Furthermore, corn silage has not been recommended for preweaning calves, although many producers do so considering its availability on the property. The objective of this research is to evaluate the best strategy for supplying forage NDF by comparing different forages combined with the starch content of the diets and different particle sizes depending on the quality of the forage. The responses of interest will be the performance, metabolism, ingestive and cognitive behavior, development of the gastrointestinal tract, fermentation profile and microbiome of calves from pre to post-weaning. For this, two experiments will be conducted with a 2 x 2 factorial experimental design with 60 animals each, 15 animals/treatment. In the first experiment, complete diets containing hay of two qualities (NDF < 70 or > 80%) in two particle sizes (4 or 19 mm) will be evaluated. In the second experiment, complete diets will be evaluated with different sources of NDF (Tifton hay or corn silage) and two starch levels (20 or 30%). Properly colosstrated animals will be individualized for daily measurement of dry matter intake, will be fed with 6L/d of milk replacer and will have concentrate and drinking water ad libitum. From the 22nd day of life, they will be fed complete diets. Weaning will be carried out gradually from day 57 to day 62, so that at 63 days (9 complete weeks) the animals will be weaned. Blood samples will be collected weekly to determine the biochemical profile and in weeks 6, 8 and 10 rumen fluid samples will be taken to analyze the fermentation profile and microbiome. On even-numbered weeks, the animals will be evaluated for their ingestive behavior, and the selection of particles from the diet consumed will also be evaluated, through evaluation with the Penn State sieve. In the 10th. week, 5 animals/treatment will be slaughtered to evaluate the development of the gastrointestinal tract, body composition and nutritional requirements. The data will be analyzed using PROC MIXED of the SAS statistical package (version 9.0, SAS Institute Inc., Cary, NC). (AU)