PSXII-8 Effects of fat matrix and particle size of coated methionine on by-pass fraction of dry matter and nitrogen

Abstract

Abstract The aim of this study was to evaluate the By-Pass fraction (BPF) of the dry matter (DM) and nitrogen (N) of coated methionine with different fat matrix (FM) and particle size (PS). Two FM (Hydrogenated Stearin, HS, and Hydrogenated Palm Fatty Acid Distillate, HPFAD) and four PS (< 500, 500–750, 750–1400, and >1400 µm) were evaluated in an in situ trial with three rumen-cannulated sheep. Intact samples (1 g) were weighed into nylon bags and incubated in the rumen for 2, 4, 8, 12 and 24 h; process repeated twice in each sheep. After extraction from the rumen, the bags were washed with cold water, frozen and lyophilized, before determining N content in the incubation residue. Effective degradability of DM and N was calculated for a rumen passage rate of 0.08/h-1 according to Ørskov and McDonald (1979), and the BPF was calculated as 100 minus the effective degradability. Data were analyzed using a mixed-effect model, with FM, PS and FMxPS interaction as fixed effects and sheep as random; means were compared with LSD test (P ≤ 0.05). HS-coated methionine had higher values of BPF of DM and N (78.2 and 49.6%, respectively; values averaged for all PS; P < 0.001) than HPFAD-coated methionine (64.4 and 17.7%, respectively). There was an interaction between FM and PS (P < 0.001) for BPF of DM and N. Increasing PS of HS-methionine augmented the BPF from 68.9 to 90.3% for DM and from 22.9 to 79.8% for N, whereas the increases for PFAD-methionine were lower (from 66.3 to 66.3% for DM, and from 7.5 to 28.6% for N). It is concluded that the use of HS as FM and the increase of PS are valid strategies to improve methionine protection from ruminal degradation, reaching BPF values of 90.3 and 79.8 % for DM and N, respectively.