Abomasally infused amino acid imbalance alters milk fatty acid profile and desaturase percentage during milk fat depression
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Ten rumen-fistulated, second-lactation Holstein cows housed at the Dairy Research and Innovation Center (Elora, ON) were randomly assigned to one of six abomasal infusion treatments in a replicated 6 X 6 Latin square. Treatments consisted of three infusions: water as control, glucose at 1 kg/d, and conjugated linoleic acid (CLA) at 50 g/d. Each infusion was delivered with 0 or 600 g/d of an essential amino acid imbalance (AAI) solution lacking histidine. Cows were infused continuously for 7 d followed by a 7 d washout. AAI did not affect total milk fat yield but yield of fatty acids < 16 carbons in length and desaturase percentages increased. Mammary extraction from plasma of the milk fat precursor acetate was also increased by AAI. AAI effects were additive to that of infusate. These findings open up the floor for further research on amino acid nutrition as a means to alter milk composition.