Regulation of Translation by Essential Amino Acids and Glucose in Mammary Glands and Skeletal Muscle of Lactating Dairy Cows

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Nichols, Kelly
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University of Guelph

The effect of glucose on protein synthesis in mammary and muscle when supplied with 884 g/d or 1126 g/d of essential amino acid (EAA) was tested on 5 early lactation Holstein cows fed a 12% CP diet and abomasally infused for 5 d in a Latin square design. EAA infusion increased mammary uptake of EAA from plasma and led to higher milk protein yield. Addition of glucose decreased arterial Ile, Leu, and Val, and did not affect mammary uptake or milk protein yield. Mammary mRNA translation was activated by EAA infusion, and was depressed when glucose was added to EAA infusates. In skeletal muscle, mRNA translation was activated by EAA infusion, and stimulated further by the addition of glucose. Data presented in this thesis support amino acid partitioning towards skeletal muscle when glucose is infused into cows, stimulating protein synthesis in muscle rather than in the mammary glands.

dairy cow, amino acid, glucose, protein synthesis, mammary, muscle, mRNA translation