In vitro and in vivo analyses of the nutritive value of native and ensiled partial crop field peas

Abstract

This study was conducted to determine the effect of ensiling on the nutritive value of partial crop field peas. The field peas were harvested with approximately 500 g dry matter (DM) at a cutting height of 25 cm and ensiled without previous wilting or use of inoculants. In vitro gas production kinetics were determined in ruminal fluid batch cultures. The apparent total tract digestibility of crude nutrients, detergent fibers and gross energy and the content of metabolizable energy and net energy lactation of native and ensiled peas was determined in a digestibility trial with wethers. Microbial nitrogen efficiency was calculated on the basis of allantoin excreted via the urine. The pea silage was characterized by a low pH (4.1) and contained relevant quantities of lactic acid (56.3 g/kg DM) and acetic acid (16.8 g/kg DM). The proportions of crude protein, starch and nitrogen-free extracts were slightly increased in the silage, while the concentrations of fiber fractions decreased. Soluble protein was increased in the silage from 56% to 66% of crude protein due to increasing non-protein nitrogen concentrations. Gas production was higher in ensiled than in native peas (P < 0.001). Apparent digestibility of crude protein and acid ether extract increased in the silage by 3% and 10% points, respectively. Digestibility of crude fiber, neutral detergent fiber and acid detergent fiber decreased by 9%, 6% and 5% points, respectively (P < 0.05). The contents of metabolizable energy and net energy lactation increased by 0.5 and 0.3 MJ/kg DM, respectively (P < 0.05). The microbial nitrogen efficiency tended to be higher in animals that received ensiled partial crop peas (P > 0.05), but strongly depended on individual excretion quantities. In conclusion, ensiling of partial crop field peas with approximately 500 g DM/kg at harvest led to well conserved feed with increased concentrations of nutrients and content of energy.