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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.

Simple SummaryConsumers demand healthier dairy products. Supplementing plant lipids, rich in poliunsaturated fatty acids, results in improved milk fatty acid profile, but these oils could enter into competition with human food needs and compromise animal performance. The aim of this study was to test the feasibility of formulating cold-pressed sunflower cake (CPSC, high-fat by-product) in a dairy cows’ concentrate to improve milk fatty acid profile. Cold-pressed sunflower cake increased total trans-mono unsaturated fatty acids (21%), total conjugated linoleic acid (31%), and polyunsaturated fatty acids to saturated fatty acids ratio (18%), but did not affect milk production, digestibility, intake, and milk composition. However, reduced fat yield (9%) and fat corrected milk (7%) were observed. Feeding CPSC improved overall acceptability of milk by improving flavor. In conclusion, CPSC could modify milk FA profile without observing a detrimental effect on digestibility, production performance, or milk acceptance. Adopting feeding systems based on the use of cheaper and local alternative feedstuffs rich in polyunsaturated fatty acids would represent a good strategy to change milk fatty acid profile and contribute the promotion of low-input production systems.AbstractCold-pressed sunflower cake (CPSC) is a cheap by-product of oil-manufacturing. Supplementing diets with CPSC, rich in fat and linoleic acid, could be an effective tool for increasing healthy fatty acids (FA) in milk. To test this hypothesis, 10 cows were used in a crossover design with two experimental diets fed during two 63-day periods. Cows’ milk production was recorded and samples were taken for fat, protein, lactose, and for FA composition analysis. Dry matter intake (DMI) and dry matter apparent digestibility (DMD) were estimated using two markers. Milk acceptance test was carried out. CPSC decreased milk C12:0 (10%, p = 0.023) and C16:0 (5%, p = 0.035) and increased C18:1 cis-12 (37%, p = 0.006), C18:1 trans-11 (32%, p = 0.005), C18:2 cis-9 cis-12 (13%, p = 0.004), and cis-9 trans-11 CLA (35%, p = 0.004). CPSC increased total trans-monounsaturated FA (21%, p = 0.003), total CLA (31%, p = 0.007), and PUFA:SFA ratio (18%, p = 0.006). CPSC did not affect milk production, DMD, DMI and milk composition, but reduced fat yield (9%, p = 0.013) and FCM (7%, p = 0.013). CPSC improved milk overall acceptability. In conclusion, CPSC could modify milk FA profile without a detrimental effect on digestibility, production performance, or milk acceptance.