Fermentative and histological parameters of the cecum of Holstein calves supplemented with a partially rumen-metabolizable methionine analogue

• Grant number: 25/04436-5
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: May 01, 2025
• End date: April 30, 2026
• Field of knowledge: Agronomical Sciences - Animal Husbandry - Animal Nutrition and Feeding
• Principal Investigator: Danilo Domingues Millen
• Grantee: Analú Frigerio Bonatti
• Host Institution: Faculdade de Ciências Agrárias e Veterinárias (FCAV). Universidade Estadual Paulista (UNESP). Campus de Jaboticabal. Jaboticabal , SP, Brazil

Abstract

Methionine is a limiting amino acid in suckling calves and can compromise body development. A partially metabolizable methionine analogue in the rumen may enhance post-weaning solid intake as a response to digestive tract development. The cecum ferments particles that escape the rumen, and its health and fermentation can serve as parameters for evaluating the efficiency of rumen development in growing calves. This study aims to evaluate the fermentation parameters and histology of the cecum in Holstein calves supplemented with different doses of a partially metabolizable methionine analogue in the rumen. Thirty-six male Holstein calves, starting at seven days of age, will be allocated into blocks and distributed into three dietary treatments: (1) 0 g/day, (2) 8 g/day, and (3) 16 g/day of the methionine analogue. During the lactation phase, the animals will receive 8 L/day of milk replacer, along with concentrate and Tifton 85 hay (Cynodon dactylon). After weaning, at 56 days of age, they will be fed concentrate and hay. At 57 days of age, 18 animals will be removed from the study, while the remaining 18 will be slaughtered upon reaching an average body weight of 126 kg. After slaughter, the cecum will be removed for full and empty weight measurements. The cecal content will be analyzed for fermentation products, and approximately 1 cm² of the epithelium will be collected for histological analyses, including crypt depth and the number of goblet cells in all crypts. Data will be subjected to analysis of variance (ANOVA) using the F-test, with significance set at P ¿ 0.05, and regression analysis will be performed to assess linear and quadratic effects of the methionine analogue doses in the diets.