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Abstract
Milk fat is the most variable component of milk, it is easily changed by nutritional and environmental factors rendering it a central point of interest for the daily market and scientists. Dietary manipulation can have a profound influence on milk fat synthesis and its fatty acid profile. However, our basic understanding of how dietary manipulations regulates mammary lipogenesis is limited by the use of mammary biopsy to obtain representative tissue sample for gene expression analysis, as repeated biopsies over short time interval from the same animal is not possible. Therefore, the general objective of this dissertation was to measure the sequential changes in milk fat concentration, milk fatty acid profile and mammary lipogenic gene expression that occur during the transition from normal to dietary induced either elevated or depressed milk fat concentration, using new non-invasive alternative technique by extracting RNA from cytosolic crest trapped in large fat globules. Two experiments were conducted: 1) feed restriction that induce negative energy balance, body fat mobilization, and elevated milk fat concentration, 2) dietary induced milk fat depression by the use of dietary CLA that resulted in depression in milk fat concentration.