La variabilità del profilo acidico del grasso del latte bovino: influenza di fattori genetici e non genetici

Almost 1,000 individual milk samples of Italian Simmental cows were collected and analyzed by gas chromatography to obtain the fatty acid profile. For each sample, the relative content of almost 80 fatty acids was obtained. Of them, the most important were investigated to identify non‐genetic and genetic effects affecting their variability. Herd played a fundamental role in milk fat composition. Content of saturated fatty acids (SFA) and of C16:0 was lower at the beginning (< 90 d) and at the end of lactation. Content of PUFA was roughly constant in the first half of lactation and slightly increased at the end of lactation. Conversely, MUFA showed the opposite trend compared to SFA. C:14 and C14:1 exhibited a very similar trend across lactation periods, whereas C16:1 showed an opposite trend in comparison with that observed for C16:0. A general increase in short‐chain SFA (C4:0‐C14:0) was observed in the group containing the 10% most productive animals compared to the group containing the 10% less productive cows. Conversely, the content of C18:0 showed a 10%‐decrease. With the increasing of milk fat content, a significant reduction of all PUFA, especially CLA (‐11%), was observed, whereas an increase of C4:0, C6:0 and C18:0 was obtained. Medium‐chain fatty acids (C14:0, C14:1, C16:0 and C16:1) decreased with the increase of total milk fat content. The heritability values estimated for the short‐chain SFA ranged from 0.03 to 0.20. Low values of heritability were observed for C14: 0 and C16:0 (0.21 and 0.08, respectively). In contrast, moderate values of heritability were estimated for C14:1 (0.31) and for C16:1 (0.40), which were the most heritable fatty acids. Even the long‐chain unsaturated fatty acids and PUFA showed heritability values comparable with those obtained for the short‐chain fatty acids and variable between 0.00 and 0.16. Based on observed estimated values of heritability, the genetic progress obtainable by breeding programs for improving the composition of milk fat would be very slow.