Influence of dietary fish oil on conjugated linoleic acid, omega-3 and other fatty acids in milk fat from grazing dairy cows

Feeding Polyunsaturated Supplements to Grazing Dairy Cows Improve the Healthy Value of Milk Fatty Acids

“…The EE content (7.64%) resulted high if compared to the values recorded in a previous experiment (1.15 to 4.52% DM) [6] and also than those observed in the experiments by [17] [18] but in the normal range (3% to 8%) for high quality pastures [19]. In this trial, pasture content of linolenic acid (56%) was also superior to the value (42%) observed by [17] [18] but near to the value informed by [20]. The milk CLA enriching effects of pastures are mainly explained by a high linolenic acid intake, its conversion to trans-11 C 18:1 at ruminal level and the subsequent conversion by mammary cells to cis-9, trans-11 CLA from the enzymatic delta-9 desaturation of rumen derived VA [21].…”

“…Compared with pre-trial records (Table 8) [18]. In our study, the sunflower seed-fish oil treatment was the most effective to reduce concentration of C 16:0 and C 14:0 and hence the AI of milk fat (Table 8).…”

“…Feeding fish oil (305 g/d) to dairy cows reduced milk fat content (−9.1 g/kg) and milk fat yield (−208 g/d) in the 27 trials revised by [28]. Milk fat content was reduced from 34.8 g/kg in control cows up to 29.9 g/kg and 23.4 g/kg in cows receiving 160 and 320 g/d of fish oil respectively and milk fat yield decreased from 0.92 kg/d to 0.78 and 0.58 kg/d in supplemented cows [18]. In our experiment further reductions in milk fat content or yield in treatments that included fish oil were not detected (Table 7).…”

“…Milk protein content was lower in grazing cows receiving 3 kg/d of rapeseed (33.9 g/100g) or soybean (33.8 g/100g) compared to control cows (34.9 g/100g) without effects on total milk protein secreted [27]. In grazing dairy cows, concentration or secretion of milk protein were not affected by a low dose (160 g/d) of fish oil but both parameters were decreased by feeding 320 g/d of fish oil [18].…”

“…trans-10, cis-12 CLA and trans-8, cis-10 CLA) reduce the activity and/or expression of genes that encode important enzymes involved in uptake, synthesis and desaturation of fatty acids in the mammary gland [29]. Negative correlations between milk fat percentage and milk fat content of trans-C 18:1 (−0.65), CLA (−0.63), EPA (−0.67) and DHA (−0.58) were reported by [18]. Duodenal infusion of the trans-10, cis-12 CLA, an isomer that was increased in milk fat after lipid supplementation (Table 8) whereas 503 g/d of sunflower oil packed in sunflower seed showed no effect (n = 8) in the experiments reviewed by [28].…”