Effect of plant oils and aspartate on rumen fermentation in vitro.

The effect of plant oils and aspartate (ASP) on rumen fermentation in vitro. The objective of this study was to determine the effect of plant oils (rapeseed - RO, sunflower - SO; linseed - LO; 10% wt/wt) and 8 mmol sodium aspartate on rumen fermentation of a diet (250 mg) consisting of hay, barley and sugar beet molasses (60 : 30 : 10). Rumen fluid was collected from two Slovak Merino sheep fed the same diet twice daily. Mixed ruminal micro-organisms were incubated in fermentation fluid (40 ml) containing rumen fluid and McDougall's buffer (1 : 4). Incubations were carried out in batch cultures for 72 h at 39 degrees C two times in a 3-week intervals. When compared to the control, all supplemented diets (RO, SO, LO, ASP) significantly increased the pH, the mol% of propionate (LO + 8.7%; SO + 10.12%; RO + 8.65%; ASP + 5.86%) and the acetate : propionate ratio and numerically decreased methane production (SO -32.8%; LO, RO -30.08%; ASP -21.56%). Lactate production was also significantly decreased. Addition of plant oils to aspartate-treated incubations partly inhibited the decrease of n-butyrate, lactate and the increase of pH and in vitro dry matter digestibility (IVDMD) caused by ASP treatment. The effect of combined additives (RO + ASP, SO + ASP, LO + ASP) on methane production SO + ASP (-19.23%) and mol% propionate SO + ASP (+2.66%), LO + ASP (+4.28%) was less effective. All combined additives caused a significant decrease in digestibility of the given feeds. No effect of plant oils and ASP could be observed on the parameters of rumen fermentation (mainly methane and propionate).