POPULATION OF PROTOZOA AND RUMINAL FERMENTATION PRODUCTS OF DUTCH CALVES SUPPLEMENTED WITH METHIONINE ANALOG PARTIALLY METABOLIZABLE IN THE RUMEN

• Grant number: 24/22344-8
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: March 01, 2025
• End date: February 28, 2026
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Nutrition and Feeding
• Principal Investigator: Danilo Domingues Millen
• Grantee: Matheus Lima Pereira
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

Methionine is considered a limiting amino acid in the protein properties of ruminants, due to its low content in conventional diets. Methionine analogues with partial metabolism in the rumen favoring fibrolytic bacteria and the properties of short-chain fatty acids in the rumen of adult ruminants, but the effects on animals in the rumen development phase have not been described. The objective of this study was to evaluate the effects of partially metabolizable methionine in the rumen on fermentation products, counting and identification of rumen protozoa. Thirty-six male Holstein calves at seven days of age will be used, allocated in blocks and distributed in three experimental diets: 1) without supplementation 2) supplementation with 8 g/d or 3) 16 g/d of partially metabolizable methionine analogue in the rumen. The study will be divided into two phases. During lactation, the animals will be fed 8 L/day of replacer, concentrate and Tifton 85 hay (Cynodon dactylon). The animals will be weaned at 56 days of age, by gradual weaning. At 57 days of age, 18 animals will be slaughtered for collection of ruminal content, while the remaining animals will be slaughtered when they reach an average body weight of the block equivalent to 126 kg. The ruminal content will be filtered to separate the solid and liquid portions. Aliquots of each portion will be conditioned together and kept in formalin for differential counting of specific protozoa. The liquid portion will be used to determine the fermentation products: short-chain fatty acids, ammonia nitrogen and lactate, to be analyzed by gas chromatography and colorimetry. Statistical analysis will be performed using SAS PROC MIXED, adopting a randomized block model, followed by ANOVA using the F test and PROC REG to evaluate the linear and quadratic effects of the methionine analogue doses.