Effect of replacing palm fat with high-linoleic cold-pressed rapeseed or sunflower cakes on fatty acid biohydrogenation in an artificial rumen (Rusitec)

The present study aimed to evaluate the effect of substituting high-linoleic cold-pressed rapeseed or sunflower cakes for palm fat on fatty acids biohydrogenation in an artificial rumen. Three isoproteic and isolipidic diets (forage : concentrate ratio 10 : 90) were evaluated. The three diets consisted of barley straw plus a concentrate mixture supplemented with (1) prilled palm fat (CTR, Control), (2) cold-pressed rapeseed cake (CPRC treatment) or (3) cold-pressed sunflower cake (CPSC treatment) as a lipid source. The assay was conducted using a Rusitec unit consisting of six vessels (two vessels per treatment). After 7-day adaptation period, nutrients disappearance, rumen fermentation parameters and fatty acid profile of rumen digesta were determined for 3 days. CPRC treatment had no effect on nutrients disappearances and rumen fermentation. In contrast, CPSC reduced neutral detergent fibre (P = 0.04), acid detergent fibre (P = 0.01), protein (P = 0.01), organic matter (P< 0.01) and dry matter (P = 0.01) disappearances, compared with CTR and CPRC. CPSC also decreased total volatile fatty acids (P = 0.01) production and shifted rumen fermentation pattern towards lower acetate (P = 0.03) and higher propionate proportion (P = 0.01), in comparison to CTR and CPRC. Both CPRC and CPSC altered the fatty acids composition of ruminal digesta by decreasing the total saturated fatty acids (P < 0.01) and increasing the accumulation of C18:0 (P < 0.01), total C18:1 cis (P < 0.01) and total C18:1 trans (P < 0.01). Vaccenic acid was increased (P < 0.01) 2.18-fold by CPRC and 4.09-fold by CPSC. C18:1 trans-10 :trans-11 ratio remained constant among treatments (P = 0.31). Rumenic acid was not affected by CPRC but was increased (P = 0.04) 4.25-and 2.83-fold by CPSC compared with CTR and CPRC, respectively. Overall, feeding CPRC or CPSC to ruminants might improve the ruminal fatty acid profile mainly by reducing saturated fatty acids and promoting cis-monounsaturated fatty acids and vaccenic acid accumulation without altering the trans-10 :trans-11 ratio. These changes in rumen fatty acid composition could occur without detrimental effects on ruminal fermentation for CPRC but they might be associated with impaired rumen function for CPSC.