Impaired milk quality and cheese making properties is not a concern for managing cows for 15 or 18 months calving intervals

The effect of extended lactation on milk quality was investigated. Of special focus were changes in composition, cheese making qualities and sensory properties as affected by calving interval (CInt), or gestation stage, expressed as days before calving (DBC). Late lactation milk from cross-breed cows managed for 15 or 18 months CInt was sampled at 180, 90 and 60 DBC, and investigated in relation to overall composition, indicators of udder integrity, sensory quality, cheese making properties and detailed protein composition by liquid chromatography-electrospray ionisation-mass spectrometry, including posttranslational modifications. Protein-related traits, including casein:protein ratio, the relative amount of κ-casein and the level of glycosylated relative to total κ-casein were affected by DBC, indicating enhanced cheese making properties with decreasing DBC. In contrast, CInt did not exert any major impact on late lactation milk composition and cheese making properties. Moreover, milk sensory quality was not affected by either DBC or CInt.