Abstract
Dairy cows mobilize large amounts of body fat during early lactation to overcome negative energy balance which typically arises in this period. As an adaptation process, adipose tissues of cows undergo extensive remodeling during late pregnancy and early lactation. The objective of the present study was to characterize this remodeling to get a better understanding of adaptation processes in adipose tissues, affected by changing metabolic conditions including lipid mobilization and refilling as a function of energy status. This was done by determining adipocyte size in histological sections of subcutaneous and retroperitoneal adipose tissue biopsy samples collected from German Holstein cows at 42 days prepartum, and 1, 21, and 100 days postpartum. Characterization of cell size changes was extended by the analysis of DNA, triacylglycerol, and protein content per gram tissue, and β-actin protein expression in the same samples. In both adipose tissue depots cell size was becoming smaller during the course of the study, suggesting a decrease in cellular triacylglycerol content. Results of DNA, triacylglycerol, and protein content, and β-actin protein expression could only partially explain the observed differences in cell size. The retroperitoneal adipose tissue exhibited a greater extent of time-related differences in cell size, DNA, and protein content, suggesting greater dynamics and metabolic flexibility for this abdominal depot compared to the investigated subcutaneous depot.
Highlights
Energy metabolism of dairy cows is continuously subjected to adjustments driven by the varying energy status of the lactation cycle
This adaptation process substantially affects the metabolism of adipose tissue as the main organ for energy storage [1,2,3]
Results of the present study provide a deeper insight to the structural aspects of adipose tissue plasticity in response to the dynamic changes of energy homeostasis throughout the periparturient period in dairy cows
Summary
Energy metabolism of dairy cows is continuously subjected to adjustments driven by the varying energy status of the lactation cycle. Early lactation is a period of catabolism associated with an intensive lipid mobilization The reason for this is a negative energy balance which arises in high-yielding dairy cows due to the mismatch between high energy demand for lactation and decreased feed intake. This results in well-defined physiological and metabolic processes to maintain sufficient energy flow towards life sustaining processes and milk synthesis [4,5]. This cycle of lipid storage and lipid mobilization, which is a typical metabolic phenomenon in dairy cows, necessarily induces extensive adipose tissue remodeling [6,7]
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