Carbohydrates and protein digestive traits in beef cattle grazing fertilised or mixed tropical pasture

ABSTRACT

This study was performed to investigate the nitrogen (N) and carbohydrate digestive traits of grazing heifers. The experiment was carried out at the Federal University of Lavras. The treatments were a Marandu palisadegrass (Urochloa brizantha [Syn, Brachiaria brizantha] Stapf. A. Rich. cv. Marandu) monoculture fertilised with 150 kg N/[ha ∙ year] (FP) or Marandu palisadegrass mixed pasture with forage peanut (MP). The pastures were grazed by six rumen-cannulated zebu heifers. A double cross-over design was used in four periods. Nutritive value, intake and apparent digestibility of forage, ruminal traits and kinetics and N balance were evaluated. Apparent total-tract digestibility of dry matter (DM) and neutral detergent fibre (NDF) were greater for FP than for MP. There was no effect in apparent total-tract digestibility of N. The estimated intestinal digestibility of nutrients was greater on MP than FP. Even though N intake and faecal N output were greater on MP than FP, there was no effect in urine N output. The N balance tended to be greater on MP than FP. The forage peanut, which contains condensed tannins, decreased ruminal fibre degradation, apparent digestibility and ruminal protein degradation, increased N flow from the rumen. Inclusion of forage peanut in the mixed pasture decreased the ruminal fibre degradability but increased N retention by the animals.

KEYWORDS:

• Digestibility
• digestion in rumen
• legumes
• nitrogen balance
• tannins

Acknowledgments

This work was funded by the Minas Gerais Research Foundation (FAPEMIG), National Council for Scientific and Technological Development (CNPq), National Institute of Science and Technology in Animal Science (INCT‐CA), and Coordination for the Improvement of Higher Education Personnel (CAPES). The authors thank the members of NEFOR (Brazilian Forage Team) for their contributions during the field trial setup. RMB and BJRA gratefully acknowledge “Productivity in Research” fellowships from CNPq and research grants under the program “Cientista de Nosso Estado” from the Rio State Research Foundation (FAPERJ).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Additional information

Funding

The work was supported by the Conselho Nacional de Desenvolvimento Científico e Tecnológico, Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Fundação de Amparo à Pesquisa do Estado de Minas Gerais, Instituto Nacional de Ciência e Tecnologia de Ciência Animal.