Milk Fatty Acid Dynamics in Cows Grazing Standard and Multispecies Pastures Under Two Management Systems

This study evaluated the influence of three pasture‐management systems on milk fatty acid (FA) profiles in New Zealand dairy cows: standard–contemporary (STD–CON), diverse–contemporary (DIV–CON), and diverse–regenerative (DIV–REG). The STD–CON pastures consisted of ryegrass–clover, whereas diverse pastures included up to 16 species of grasses, legumes, and herbs. Monthly herd test records ( n = 790) from the 2023 to 2024 lactation season were used to assess milk yield and composition. Composite milk samples were collected and analyzed for fat, protein, and mid‐infrared spectral data. FA concentrations (g/100 g milk) were predicted using partial least squares regression models calibrated with 120 reference samples with FA determined by gas chromatography. Lactation curves for FA were fitted using random regression with orthogonal polynomials. FAs differed across systems: C16:0 was lowest in DIV–REG (−6%) and intermediate in DIV–CON (−1%) vs. STD–CON; C18:2 n‐6 was highest in DIV–REG (+13%), while STD–CON and DIV–CON were similar. Polyunsaturated FAs were higher in diverse pastures (+15% DIV–REG; +7% DIV–CON) than in STD–CON. These findings show that pasture diversity can enhance milk fat composition while maintaining production in pasture‐based systems.