USING A DYNAMIC METABOLIC MODEL TO INVESTIGATE DIFFERENCES IN METABOLIC PATTERNS AMONG LACTATING ANIMALS

Abstract Text:

In dairy cattle, the metabolic flux in body tissues, primarily in visceral, muscle, and adipose tissues make up a large contribution to variations in efficiency among animals housed and fed alike.  Metabolic processes are affected by genotype, phenotype, and intake; genotypic differences eventually result in variation in patterns of metabolism which have different metabolic efficiencies. In continued work with the objective of identifying the patterns of metabolic flux in the most efficient dairy cattle, an existing mechanistic metabolic model (Molly, UC Davis) was used to describe differences in energetic and nitrogen efficiency among cows fed and housed alike. Data were from 42 high producing cows fed an alfalfa/corn/SBM based TMR. Data on genetic merit and DMI were input into the model, and milk component output, changes in adipose tissue lipid metabolism; visceral and body protein and lipid, nitrogen were output.  Each cow was simulated separately.  There was a range in metabolic processes from  27 % (maintenance costs) to 93 % (MUN) (Table 1). Tissue metabolism rates (lipogenesis, lipolysis) varied by 48 to 74 %; indicating a wide range in potential to metabolize nutrients.  The intricate range of patterns of nutrient metabolism underlay the 21 % range in net energy efficiency (milk energy/ ME intake).   A systems approach and model can be used, eventually, toimprove selection of cows to reduce the variation in energy efficiency.  Integrating all the biological processes with data on genomics and transcriptomics using systems models will help reduce variation in energy efficiency.

Item                     Min         Max         SD           % range

DMI                     19.8         31.5         3.2           159%

MILK, kg/d           28.7         49.8         5.1           174%

Lipolysis, M/d        8.1           12            1.3          148%

Lipogenesis, M/d    5.4          9.4           0.87        174%

MES, Mc/d          17.8         30.1         3.07          169%

Maint, Mc/d        25.4         32.4         3.5            127%

HI Main, kg/d       7.4         11.0         1.16          148%

Prot Intake, kg/d  1.3           2.0           0.21         159%

Aa to Milk, M/d   7.8           13.5         1.4           174%

MUN, mg/dl        5.5           10.6         1.3           193%

MES/MEI, %      34.0          41.0         1.7           121%

Keywords: efficiency,  systems biology, metabolic model