Improving the Quality of Milk Fatty Acid in Dairy Cows Supplemented with Soybean Oil and DHA-Micro Algae in a Confined Production System

Abstract

The objective was to reduce saturated fatty acids (SFA) and increase conjugated linoleic acid (CLA, cis- 9, trans -11 C18:2), α-linolenic (cis- 9, cis- 12, cis- 15 C18:3) and docosahexaenoic (DHA, C22:6) contents in milk from confined dairy cows in order to promote a healthier option. The work was carried out in a commercial farm (Talar) located in Laguna del Sauce, Maldonado (Uruguay). Twenty four cows were assigned to one of two treatments (12 cows per treatment) over a 6 weeks experimental period. Treatments consisted in a control total mixed ration (C-TMR) without supplementary lipids (L) or the same TMR with the addition of 0.144 kg/cow∙day of algae and 0.72 kg/cow∙day of soybean oil (L-TMR). Chemical composition of the TMR (44.27% DM) averaged 15.94% for crude protein (CP), 38.20% neutral detergent fiber (NDF), 20.36% acid detergent fiber (ADF), 5.56% fat, 5.30% ash and 28.6% nonstructural carbohydrate (NSCH) with 1.81 Mcal/kg of net energy for lactation (NEL). After 39 days of feeding, individual milk samples were collected during three consecutive days. From the total milk collected, 20 ml were immediately used for chemical composition (Milko Scan) and 80 ml for analysis for milk FA profile. From week 3 onwards, milk production (kg/cow∙day) resulted higher (P < 0.001) in L-TMR (36.9) compared to C-TMR (35.2). At week 6 of trial, the difference in milk production averaged 5.14% for L-TMR. Supplementary lipids reduced (P < 0.002) milk fat concentration (g/100g) from 3.36 in C-TMR to 2.40 in L-TMR without effect (P = 0.43) on milk protein content (C-TMR = 3.20; L-TMR = 3.07 g/100g). Milk lactose (C-TMR = 4.86, L-TMR = 4.69 g/100g) and urea nitrogen contents (C-TMR = 21.18, L-TMR = 17.33 g/100g) tended (P < 0.056) to decrease in L-TMR as well as fat corrected milk output (C-TMR = 30.89, L-TMR = 29.49 kg/cow∙day, P < 0.098). Lipid supplementation reduced (−23%) milk content of C12:0 to C16:0 FA averaging 45.19 in C-TMR and 34.74 g/100g in L-TMR (P < 0.001). The atherogenic index (AI) of milk decreased (P < 0.001) from 2.69 in C-TMR to 1.50 in L-TMR (−44.2%). Concentration (g/100g) of elaidic (C18:1 trans -9) (0.23) and C18:1 trans -10 (0.44) FA increased (P < 0.001) in L-TMR milk. Milk vaccenic acid (trans- 11 C18:1, VA) increased from 1.08 in C-TMR to 2.56 g/100g of FA in L-TMR (P < 0.001). Milk CLA content (cis- 9, trans- 11 C18:2) increased (127%) from 0.62 in C-TMR to 1.41 g/100g FA in L-TMR milk. Content of α-linolenic acid resulted 20% higher (P < 0.001) in L-TMR milk (0.35 g/100g FA) compared to C-TMR (0.30 g/100g FA). Milk DHA increased from 0 in C-TMR to 0.14 g/100g FA in L-TMR. The omega-6/-3 ratio in C-TMR milk (9.61) was reduced (P < 0.001) to 6.78 in L-TMR milk. Milk oleic acid (cis -9 C18:1) resulted higher (P < 0.001) in L-TMR (23.65) than in C-TMR (19.75 g/100g FA). The nutritional value of milk fat from confined cows was naturally improved by feeding polyunsaturated FA in the ration, obtaining a reduction of saturated FA and increased levels of healthy FA (CLA, DHA and α-linolenic).