Ruminant Nutrition: Carbohydrates and Lipids

摘要

The aim of this study was to analyze ruminal degradability and bypassfraction of a C18:3 source (linseed oil), either free or coated with palmstearin. Two samples (free linseed oil with palm stearin (LSS) and coatedlinseed oil, commercialized as HiFlax (HFX) by NOREL) were evaluatedin an in vitro trial. Ruminal content was obtained from 3 cannulated sheepfed a 50:50 concentrate:forage ration, and filtered through gauze to get thefluid. Intact samples (80 mg of HFX or a mixture of 25 mg linseed oil and55 mg palm estearin) were weighed in vials containing 1 g of the diet fedto animals. Vials were filled up with 80 mL of a 1:4 ruminal fluid:incubationmedium 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 3replicates. After incubation, vials contents were placed in weighed sterileplastic containers that were immediately frozen at −80°C to stop fatty acids(FA) biohydrogenation, and lyophilized. The fat content and FA profileof the samples and incubation residues were analyzed. The disappearanceof each C:18 FA was calculated as the difference between the amount addedin the vials with the ruminal inoculum, basal substrate and sample, andthe amount in the incubation residue. The bypass fraction of each FA wascalculated as 100 minus the measured disappearance. Data were analyzedusing the PROC MIXED of SAS, where the fixed factor was the sampleand the random factor was the inoculum. The C18:3 in LSS was extensivelybiohydrogenated (90.7%), but the C18:3 in HFX showed lowerdisappearance (P = 0.093; 61.3%) and therefore a greater bypass fraction(38.7%). There was no difference (P > 0.05) in the disappearance of C18:2and C18:1 between the 2 samples (53.2 and 62.9% for C18:2, and 10.0and −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 inHFX is a valid strategy to protect C18:3 from ruminal biohydrogenation.