Forage sources in total mixed rations for dairy calves: effects on performance, metabolism, behaviour, and development of the gastrointestinal tract

• Ano de defesa: 2024
• Autor(a) principal: Toledo, Ariany Faria de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Corn silage; Efetividade; Effectiveness; Enchimento intestinal; Gut fill; Ruminação; Rumination; Tract filling
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/11/11139/tde-02072024-105106/

This study aimed to investigate total mixed ration with increasing levels of whole-plant flint corn silage (WPFCS) in the diet of dairy calves and its effects on performance, metabolism, and behavior. In addition, evaluate effects of forage inclusion and sources on performance, metabolism, feeding behavior, and development of the gastrointestinal tract of dairy calves. For this study, two experiments were carried out. In both experiments, during the first 28 days of life, all calves received 3 L of whole milk twice daily, a commercial pelleted starter, and no forage ad libitum. After that, the solid diet was changed to the respective dietary treatments. Calves were blocked and randomly assigned to dietary treatments according to sex and body weight (BW) at 28 days of life. In the first experimental study, forty-five Holstein calves were assigned to 1 of 3 dietary treatments. Three TMR with increasing whole-plant flint corn silage content [0, 10, or 20% on a dry matter basis] were compared: 0CS, 10CS, or 20CS, respectively. Calves were gradually weaned from 52 to 56 days of age but were evaluated for an additional 14 days postweaning. Feed intake was measured daily, while body weight (BW) and metabolic indicators of intermediate metabolism were evaluated weekly. Rumen samples were taken to determine rumen pH and volatile fatty acid (VFA) concentrations. Behavioral analysis was carried out on weeks 7 (preweaning) and 10 (postweaning). In the second experimental study, forty-eight Holstein calves were assigned to 1 of 4 dietary treatments. Treatments consisted of a no-forage coarsely ground starter (CON); or total mixed ration containing 7.5% on DM basis of Tifton hay of either medium quality (MH) or low quality (LH); or 10% on DM basis of corn silage (CS). Feed intake, performance, BW, metabolic indicators of intermediate metabolism, ruminal fluid, and behavior were carried out as described in experiment 1. Two weeks after weaning, 5 per treatment, were harvested. The anatomical parts of the gastrointestinal tract were weighed with and without contents, and histological analysis was conducted. The inclusion of 10% corn silage in the TMR of dairy calves maximized feed intake and anticipated the rumination cycles pre- and post-weaning. In addition, the results suggest that 7.5% of hay, regardless of the quality, and 10% of corn silage in high-starch mixed diets increased solid feed intake, and benefit rumen health and promote greater gut fill without negative effects on final body weight. In conclusion, all forage sources included in the TMR showed feed intake and behavior benefits reinforcing the need for fiber from forage in pre- and post-weaning diets.