Lactation responses to sulfur-containing amino acids from feather meal or rumen-protected methionine.

The objectives of this experiment were to determine: 1) if Cys in hydrolyzed feather meal (HFM) can contribute to the supply of sulfur amino acids for meeting requirements of dairy cows; 2) if the feeding value of meat and bone meal (MBM) can be enhanced by HFM or ruminally protected Met (rpMet); and 3) the value of HFM sulfur amino acids relative to rpMet. Fifteen multiparous Holstein cows were used in a replicated 5 x 5 Latin square design with 21-d periods. The control (CTRL) diet was designed to contain feeds that were low in RUP and Met and consisted of 50% alfalfa silage and 50% corn-based concentrate. Additional treatments were modifications of CTRL in which MBM (4% of DM), MBM + rpMet (Smartamine M) (4 and 0.08% of DM), MBM + HFM (4 and 2% of DM), and MBM + rpMet + HFM (4, 0.04, and 1% of DM) replaced corn grain. Feeding MBM depressed milk and 3.5% fat-corrected milk (FCM) yields. Adding rpMet to MBM enhanced dry matter intake, milk and 3.5% FCM yields, and milk crude protein percentage. Milk fat percentage and 3.5% FCM yield were increased when HFM and rpMet were added to MBM. Supplementing HFM to a diet containing MBM could not duplicate the response of adding rpMet to MBM. Results of this study indicate that feeding HFM may not alleviate Met deficiency in lactating dairy cows.