Milk removal

Sammanfattning: Milk from dairy cows is a staple dietary component for humans all over the world. Regardless of whether milk is consumed in its purest, unaltered form or as high-end products such as fine cheese or ice cream, it needs to be of high quality when taken from the cow, produced at a low price and produced in a system that consider aspects such as animal health, animal welfare and sustainability. This thesis investigated the role of milk removal and the importance of residual milk on milk yield, milk composition and milking efficiency in dairy cows. The specific aspects examined were whether residual milk retained in the udder, specifically its fat component, is involved in regulation of milk synthesis and secretion and whether removal of this residual milk influences milk yield, composition and quality, measured as milk fatty acid composition and free fatty acid content. The results showed that milking efficiency could be increased by increasing the pulsation ratio or using a higher cluster or teat cup take-off threshold, without negative effects on milk yield or milk composition. Milking time in automatic milking systems could thereby be decreased by one minute per cow and milking or more. Milk fatty acid composition was affected by several treatments tested, but the content of free fatty acids and the size distribution of milk fat globules were unaffected. Residual milk yield increased both due to repeated residual milk removal and to use of a higher cluster take-off level. Residual milk removal also increased the relative proportion of short-chain fatty acids in milk. The overall conclusion of this thesis is that residual milk removal in mid-lactation dairy cows does not affect milk yield and that milking efficiency in an automatic milking system can be increased with higher takeoff levels without affecting milk yield or composition. No evidence of a regulatory mechanism in residual milk was found, but residual milk removal increased milk fat synthesis.