Methionine Hydroxy Analog: Varying Levels for Lactating Cows

Beginning two weeks before anticipated parturition and for 90 days post-partum, 24 Holstein cows received a concentrate (14.5% crude protein) containing either 0, 0.2, 0.4, or 0.8% methionine hydroxy analog. Concentrate was limited to 11 to 12 kg/day and corn silage-urea (0.5%) was offered free choice. A milk production response curve indicated peak production at approximately 25 g analog/day. Fat content of milk increased with analog intake. Reduced silage and concentrate consumption was common with the highest analog level. Free fatty acid and triglyceride content of serum a-lipoproteius and triglycerides of the fllipoproteins were reduced in cows fed analog from those with no analog.