Fatty acids profile of cow’s milk produced from alpine grazing.

Milk from alpine grazing shows a different fatty acids profile (FA) from that produced in lowlands farms. In particular, it seems to have an increased content in Mono- and Polyunsaturated Fatty Acids (MUFA and PUFA) and a better n-6 to n-3 ratio. Conjugated linoleic acid compounds (CLA) content also seems to be enriched. The present study aimed at evaluating the effect of alpine grazing (AG), in comparison to a Total Mixed Ration (TMR) feeding system, on fatty acids profile of milk. The study took place from May to September 2006 and involved a farm which during summer move to alpine grazing (Novegno Mountain - Vicenza, North Italy). During the lowland period (P1, May, 25) animals were fed a TMR diet, whereas during the alpine periods (P2, July, 18; P3, September, 5) animals were kept at pasture and received a concentrate supplement based on maize and barley. Bulked milk samples (mix of evening and morning milking) were collected 3 times throughout one week of each experimental periods (n=9). FA profile was assessed by gas-chromatography and the obtained data (% of the total detected FAME) were submitted to a one-way ANOVA; the 3 levels of fixed effect Period/Feeding system were used to calculate two orthogonal contrasts (P1 vs P2+P3 and P2 vs P3). Results showed a significant decrease of Saturated Fatty Acids (from P1: 62.9 to P3: 56.6%; P<0.001) and an increase of MUFA (from P1: 25.3 to P3: 31.1; P<0.001) and PUFA (from P1: 4.2 to P3: 5.5; P<0.01), determining also a better n-6 to n-3 ratio (from P1: 3.6 to P3: 2.6; P<0.01), Thrombogenic (from P1: 3.1 to P3: 2.3; P<0.001) and Atherogenic (from P1: 2.6 to P3: 1.9; P<0.001) indexes and CLA content (from P1: 0.8 to P3: 2.2; P<0.001). For all of these variables contrast analysis showed a significant difference (P<0,01) between TMR (P1) and Alpine grazing (P2+P3). These results could be explained by the higher intake of unsaturated FA when cows grazed on alpine pasture. Moreover, the increase of Unsaturated Fatty Acids during P2 and P3 periods was probably due to the high mobilization of body fat, as a result of the deficiency in energy intake and/or of the advanced stage of lactation. In conclusion, alpine grazing seems to enhance fatty acid profile of milk, with particular regard to those fractions of interest in human nutrition.