Effect of replacing wheat straw with alfalfa hay and corn silage in the diets ‎containing similar concentrations of physically effective NDF on performance of‏ ‏lactating dairy cows

This study aimed to investigate the effects of partial replacement of wheat straw for corn silage and alfalfa hay at 7% diet dry matter (DM) on feed intake, nutrient digestibility, and milk production of late-lactation Holstein cows. Eight multiparous Holstein cows (averaging 2.9±0.35 parity; 43.6±2.6 kg/d milk yield; 214±18 d in milk) were used in a replicated 4×4 Latin Square design. During each of four 21-d periods, cows were fed  total mixed rations varying in forage source: 1) control (13.5% alfalfa hay, 20% corn silage and 66.5% concentrate), 2) wheat straw replaced for corn silage, 3) wheat straw replaced for alfalfa hay 4) wheat straw equally replaced for corn silage and alfalfa hay. Diets were formulated to contain similar values of NDF, forage NDF and physically effective NDF. The DM intake, milk production and compositions as well as total tract digestibility of DM, organic matter, NDF, and crude protein were unaffected by treatments. Likewise, ruminal and blood parameters were not affected by experimental treatments. Body weight gain tended to be lower (P=0.06) for cows fed the wheat straw-included diets. These results indicated that, at 7% of diet DM, chopped wheat straw could be used as an alternative for major forage sources high concentrate diets for lactation cows yielding over 40 kg/d milk.