The Effect of Sustainable Feeding Systems, Combining Total Mixed Rations and Pasture, on Milk Fatty Acid Composition and Antioxidant Capacity in Jersey Dairy Cows

Abstract

This study was carried out to assess the effect of using pasture combined with total mixed ration (TMR) on milk production and composition, fatty acid (FA) profiles, fat-soluble antioxidant content, and total milk antioxidant capacity (TAC). In addition, the effect of milk pasteurization and storage at 2 °C for 4 days, lipophilic antioxidants and TAC were assessed. Two homogeneous groups of Jersey cows (n = 8) were constituted, which were randomly assigned to one of the two treatments: TMR (without access to pasture), or partial mixed diet (pTMR: grazing 8 h/day + TMR indoors). To establish FA profiles and lipophilic antioxidants’ changes in milk during the grazing period, in case of the pTMR group the experimental period was spilt in three grazing periods: P1 (May), P2 (June), and P3 (June/July). Milk yielded from cows having limited access on pasture (pTMR diet) showed an improved FA profile, with higher concentrations of FAs considered benefic for human health (vaccenic acid (VA), conjugated linoleic acid (CLA), omega-3 FA (n-3 FA)) (p < 0.01) and a lower concentration of FAs with hypercholesterolemiant potential (C12:0, C14:0, and C16:0) (p < 0.05), compared to that of the TMR diet. This change in FA profile was correlated with improved sanogenous lipid indices of milk fat (n-6/n-3 FA atherogenic index and thrombogenic index). Milk yielded during the P1 grazing period had higher concentrations of VA, CLA, and n-3 FA (p < 0.05) and lower concentrations of C14:0 and C16:0 (p < 0.01); it exhibited the best values for the main sanogenous fat lipid indices of fat. Moreover, pTMR milk showed a higher α-tocopherol, retinol, and β-carotene content (p < 0.05), positively correlated with TAC values in milk (P1 ˃ P2 ˃ P3). By comparison, cows fed using the TMR diet yielded a higher quantity of milk (p < 0.05), but a lower fat and protein content (p < 0.01), and also a higher saturated FAs and n-6 FA content (p < 0.05) together with a lower concentration of lipophilic antioxidants in milk. Thermal treatment showed no effect on α-tocopherol and retinol content in milk, but their concentrations decreased during the storage, at the same time a TAC decrease. The results of this study prove the positive effect of using pasture combined with TMR on FA profiles, milk antioxidant content, and antioxidant capacity, with beneficial effects on nutrition and health in humans.

The Effects of Feeding Milled Rapeseed Seeds with Different Forage:Concentrate Ratios in Jersey Dairy Cows on Milk Production, Milk Fatty Acid Composition, and Milk Antioxidant Capacity

“…FA analysis of milk samples was performed as reported by Santa et al [ 2 ], in two stages: transesterification/methylation of FAs and quantification of FA methyl esters (FAME) by gas chromatography (GC). The extraction of fat from milk was done according to the method described by Folch et al [ 35 ] and the preparation of methyl esters of FAs was conducted by transmethylation of methyl alcohol.…”

“…The column was washed with MTBE:MeOH (50:50) after each determination. Chromatograms were monitored at 450 nm for β-carotene, 340 nm for retinol and 290 nm for α-tocopherol [ 2 ]. The quantification of the bioactive compounds was carried out using the regression equations of the calibration curves of the standards with a degree of purity >90% (β-carotene: C4582; trans -retinol: R7632, and α-tocopherol: T3251) (Sigma Aldrich, Madrid, Spain).…”

“…Nowadays, many consumers are aware of the relation between diet and health. A major interest in modifying milk fatty acids (FAs) composition, aiming to enhance the health status of consumers, was noticed in the last two decades [ 1 , 2 , 3 ]. Such changes are intended to decrease the proportion of saturated FAs (SFAs) in milk fat composition, and to increase the proportion of healthy FAs, such omega-3 FAs (n-3 FAs), conjugated linoleic acid (CLA, cis -9, trans -11 C18:2), oleic acid (OA, C18:1 cis -9), and vaccenic acid (VA, C18:1 trans -11) [ 4 ].…”

“…Increasing the concentration of nutritionally beneficial FAs in milk also increases the risk of milk fat oxidation, leading to changes in the nutritional and dietary properties of milk [ 1 ]. To maintain high milk quality, the concentration of antioxidants should therefore be increased [ 23 ], for them to ensure an increased antioxidant capacity of milk [ 2 , 24 ]. Higher concentrations of milk antioxidants (α-tocopherol, β-carotene, and retinol) have been reported in cows fed diets based on grass silage compared to diets rich in concentrates [ 25 ], but also by supplementing the diet with oilseeds [ 26 ].…”

Milk Yield and Milk Fatty Acids from Crossbred F1 Dairy Cows Fed on Tropical Grasses and Supplemented with Different Levels of Concentrate

“…Today, consumers are aware of saturated FA in milk and they prefer to avoid its intake [ 3 ]. However, in milk from grazing cows, the presence of unsaturated FA could be higher compared to cows fed under total mixed rations [ 4 ].…”