Protein nutrition of growing cattle: Food intake and growth responses to rumen degradable protein and undegradable protein

J. R. Newbold*, P. C. Garnsworthy, P. J. Buttery, D. J.A. Cole, W. Haresign

*Corresponding author for this work

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Groups of eight Friesian steers were given one of eight diets from 114 to 300 kg live weight. The iso-energetic diets were formulated to supply four levels of protein degradability within two concentrations of crude protein (CP), giving a range of rumen-degradable protein (RDP) and undegradable dietary protein (UDP) concentrations both above and below Agricultural Research Council (1980) recommendations. There were significant (P < 0·05), positive, linear responses of mean daily dry-matter (DM) intake (DMI) (g/kg M°75) to RDP concentration (g/kg DM) for both the low CP diets (DMI = -98·0 + 1·76 (RDP); P = 0·013) and the high CP diets (DMI = -157·5 + 218 (RDP; P = 0017). For the high CP diets, there was a significant (P = 0·045) positive, linear response of live-weight gain (LWG) (kg/day) to UDP concentration (LWG = 0·47 + 0·017 (UDP); P = 0·045). No such response was observed for the low CP diets, where the range of UDP concentrations supplied was smaller than expected. For both the low and high CP diets, LWG decreased as metabolizable energy, UDP and RDP intake increased. These negative responses to nutrient intake were reflected in a wide discrepancy between observed rates of gain and those predicted by current energy and protein nutrition systems. Interactions between food intake and digestive processes, which obstruct effective interpretation of these results, should form an explicit part of any revised protein nutrition scheme.

Original languageEnglish
Pages (from-to)383-394
Number of pages12
JournalAnimal production
Volume45
Issue number3
DOIs
Publication statusPrint publication - Dec 1987
Externally publishedYes

Bibliographical note

© British Society of Animal Science 1987

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