Influence of urea–calcium mixtures as rumen slow-release feed on in vitro fermentation using a gas production technique

Abstract

In this experiment the effects of different urea products (urea [U] and urea–calcium mixtures [UCM]) on rumen fermentation were investigated in dependence of different energy sources by using in vitro techniques. The 7 × 2 factorial arrangement followed a completely randomised design using seven urea products (U100, U40CaCl₂, U50CaCl₂, U60CaCl₂, U40CaSO₄, U50CaSO₄ and U60CaSO₄) in combination with cassava chips (CC) or corn meal (CM). Compared with other treatments, the cumulative gas production (96 h) was significantly increased for U60CaCl₂ + CC and U60CaSO₄ + CC (p < 0.01), which was combined with a higher in vitro true digestibility (p < 0.01). In addition, the concentration of volatile fatty acids in the fluid of U60CaCl₂ + CC and U60CaSO₄ + CC was significantly higher than in other treatments. Urea treatments (U100 + CC and U100 + CM) caused the highest concentration of ruminal ammonia nitrogen (p < 0.01), which was significantly decreased by all UCM products in combination with CC, but not with CM. The highest levels of total bacteria, Fibrobacter succinogenes and anaerobic fungi were found for treatment U60CaCl₂ + CC and U60CaSO₄ + CC (p < 0.05). The findings revealed that the utilisation of U60CaCl₂ and U60CaSO₄ in combination with cassava chips improved the ruminal fluid fermentation in terms of NH₃-N and volatile fatty acid concentration, digestibility of energy and increased the fibrobacter concentrations.

Keywords:

• calcium chloride
• calcium sulphate
• energy sources
• in vitro digestibility
• rumen microorganisms
• urea

Acknowledgements

The authors would like to express sincere thanks to the Tropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Thailand and the Thailand Research Fund (TRF) through the Royal Golden Jubilee Ph.D. Program for providing financial support for the research and the use of the research facilities.