Barley protein meal for lactating dairy cows: Effects on production, intake, and nutrient excretion1

The objectives of this study were to quantify production performance and nutrient excretion of lactating dairy cows fed barley protein meal (BPM) and to assess its potential as a source of ruminal bypass protein and ruminally protected lysine. Forty-two lactating cows were fed diets formulated to meet NRC nutrient requirements, containing either BPM at 15% of diet DM, corn distillers grains (CDG), or soybean meal (SBM) to supply equal dietary N. Dietary treatment had no effect on milk production or BW. Milk fat content and yield were greater for cows fed BPM compared with cows fed SBM. Dry matter intake was less in cows fed CDG compared with cows fed BPM and SBM. Apparent digestibility of N and P were less (and fecal P excretion was greater) in cows fed BPM than in cows fed SBM. Ruminal degradation rates of CP and DM were similar for BPM and SBM and greater than CDG. Loss of BPM DM and CP from the Dacron bags at zero-time was much greater than for SBM or CDG, resulting in much lower estimates of ruminal escape. However, half of the zero-time loss was apparently due to small particle loss, which would bias estimates of ruminal escape. Degradation rates of the insoluble DM and CP were similar for BPM and SBM and lower for CDG. Undegraded barley protein was a better source of arginine, leucine, and methionine than was SBM and a better source of arginine, lysine, methionine, threonine, and valine than was CDG.