Chemical composition, intake, ruminal fermentation, plasma metabolites and hormones in range steers

Abstract

The objective of this study was to determine and compare, seasonally, across two consecutive years the chemical composition, intake, ruminal fermentation and plasma concentrations of glucose (G), urea-N (UN), non-esterified fatty acids (NEFA) and insulin in grazing steers. Data were analysed as repeated measures within a split plot design. The crude protein (CP), metabolisable protein (MP), neutral detergent fibre (NDF) and metabolisable energy (ME) were different within years and seasons (P<0.05). The values for organic matter intake (OMI), CP intake (CPI) and metabolisable protein intake (MPI) were greater in wet season (P<0.01). The pH values were not affected by years and seasons (P > 0.05). Ruminal ammonia (NH3–N) and volatile fatty acid (VFA) concentrations were lower during dry season than during wet season (P < 0.05). The plasma concentrations of G, UN, and insulin were higher in the wet season (P<0.05); however, the NEFA concentrations were higher in the dry season (P<0.05). The variables corresponding to chemical composition, intake, ruminal fermentation and concentrations of metabolites and hormones were affected over time by the years and seasons.