Ruminal phosphorus release from selected forages determined by the in sacco technique

Abstract

This study was focused on measuring the NDF degradability and phosphorus release from forages – lucerne hay from the 1st and 2nd cut (LH1 and LH2 ), orchard grass hybrid Rela (GR) and hybrid Niva (GN), grass silage (GS), red clover silage treated with Feed Tech (RCSFT) or with Kofasil (RCSKO). The forages were different in NDF content (from 325.50 to 597.70 g.kg-1DM) and in NDF disappearance (P≤0.01). The effective NDF degradability ranged from 26% to 39.40% at an outflow rate of 0.06·h-1. There were also differences (P ≤ 0.01) in phosphorus disappearance in the rumen. The release of phosphorus through incubation time has been adequatelly expressed by cubic polynomials regression. A greater percentage of phosphorus was solubilized by washing from GS (92.6 %) followed by RCSFT (84.8 %) and RCSKO (76.5 %). With incubation time the concentration of phosphorus in tested legumes increased in comparison with its concentration after washing (in LH1 from 1.10 to 4.39 g.kg-1 DM, in RCSFT from 0.4 to 2.32 g.kg-1 DM for 72 h incubation). This study shows that the in sacco method is not an objective one for determination of the kinetics of phosphorus release in the rumen from forages due to re–binding of phosphorus with the nylon-bag residues from the rumen environment.