Fat Profiles of Milk and Butter Obtained from Different Dairy Systems (High and Low Pasture) and Seasons (Spring and Fall): Focus on Healthy Fatty Acids and Technological Properties of Butter

This study aimed to evaluate the fatty acid (FA) profile in milk from commercial farms with varying pasture levels in the diet during spring and fall, and to investigate the physical and chemical properties of butter to assess the impact of FAs on technological and nutritional properties. Milk sampling was conducted biweekly from six farms, categorized into high (HP) and low (LP) pasture treatments based on pasture intake: >60% and <35%, respectively. Butter was made from a pasture-based system (GRZ) and a confined system (C). No differences were observed in milk fat percentage between HP and LP in either season. High pasture had 85–66% more conjugated linoleic acid (CLA, p = 0.01), 74–48% more trans-vaccenic acid (TVA, p = 0.01), and 21–15% more branched-chain FAs (BCFAs, p = 0.006) than LP in spring and fall, respectively. In fall, butter from C had lower saturated FAs (SFAs, p = 0.005), higher unsaturated FAs (UFA, p = 0.008), and a lower spreadability index (SI, p = 0.005) than GRZ, resulting in softer butter. In conclusion, HP in both seasons had higher contents of FAs considered healthy for consumers compared to LP. Contrary to expectations, in fall, C showed higher UFAs and lower SFAs in butter, leading to better technological characteristics than GRZ.