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Ruminal degradability and bypass fraction of a coated omega-3 source.

L. R. Royo



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Ruminal degradability and bypass fraction of a coated omega-3 source.
L. R. Royo*1, T. de Evans2, M. Puyalto1, J. J. Mallo1, M. D. Carro2. 1Norel SA Madrid, Spain, 2Dpto. Producci�n Agraria, ETSIAAB, Universidad Polit�cnica de Madrid Madrid, Spain.

The aim of this study was to analyze ruminal degradability and bypass fraction of a C18:3 source (linseed oil), either free or coated with palm stearin. Two samples (free linseed oil with palm stearin (LSS) and coated linseed oil, commercialized as HiFlax (HFX) by NOREL) were evaluated in an in vitro trial. Ruminal content was obtained from 3 cannulated sheep fed a 50:50 concentrate:forage ration, and filtered through gauze to get the fluid. Intact samples (80 mg of HFX or a mixture of 25 mg linseed oil and 55 mg palm estearin) were weighed in vials containing 1 g of the diet fed to animals. Vials were filled up with 80 mL of a 1:4 ruminal fluid:incubation medium mixture, and incubated at 39�C for 12 h (passage rate 8%/h). Each sample was incubated with the rumen liquid of each sheep to obtain 3 replicates. After incubation, vials contents were placed in weighed sterile plastic containers that were immediately frozen at −80�C to stop fatty acids (FA) biohydrogenation, and lyophilized. The fat content and FA profile of the samples and incubation residues were analyzed. The disappearance of each C:18 FA was calculated as the difference between the amount added in the vials with the ruminal inoculum, basal substrate and sample, and the amount in the incubation residue. The bypass fraction of each FA was calculated as 100 minus the measured disappearance. Data were analyzed using the PROC MIXED of SAS, where the fixed factor was the sample and the random factor was the inoculum. The C18:3 in LSS was extensively biohydrogenated (90.7%), but the C18:3 in HFX showed lower disappearance (P = 0.093; 61.3%) and therefore a greater bypass fraction (38.7%). There was no difference (P > 0.05) in the disappearance of C18:2 and C18:1 between the 2 samples (53.2 and 62.9% for C18:2, and 10.0 and −34.8% for C18:1; values for HFX and LSS, respectively). For LSS, the amount of C18.1 in the incubation residue was greater than that incubated, as a result of more extensive ruminal biohydrogenation of C18:3. It is concluded that the use of palm stearin to coated linseed oil utilized in HFX is a valid strategy to protect C18:3 from ruminal biohydrogenation.

Keywords: C18:3, rumen, biohydrogenation.