The effect of partial replacement of corn silage on rumen degradability, milk production and composition in lactating primiparous dairy cows

Abstract

The objective of this experiment was to evaluate the effects of partial replacement of corn silage with long alfalfa hay and/or coarse chopped wheat straw on neutral detergent fibre (NDF) rumen degradability, milk yield and composition in late lactating dairy cows fed diets with 50% forage on dry matter basis. Twelve late lactating Holstein primiparous cows including four cows equipped with a rumen cannula, averaging 210 +/- 20 d in milk and weighing 575 +/- 50 kg were randomly assigned in a 4x4 Latin square design. During each of four 21-d periods, cows were fed 4 total mixed diets that were varied in the forage sources: 1) 50% corn silage (CS), 2) 35% corn silage + 15% wheat straw (CSW), 3) 35% corn silage + 15% alfalfa hay (CSA), 4) 25% corn silage + 10% wheat straw + 15% alfalfa hay (CSWA). The production of milk averaged 18.55, 20.41 and 20.06 kg/d for unadjusted milk production, 4% fat corrected milk and solid corrected milk, respectively, and was not affected by treatments. Likewise, milk composition or production of milk components was not affected by diets and averaged 4.69% fat, 3.66% protein, 4.51% lactose, 866 g/d fat, 665 g/d protein, 824 g/d lactose. Treatments had no effect on in situ NDF soluble, degradable and potential degradability of all diets, whereas the effective degradability (ED) of NDF was greater for cows fed CS diet than for cows fed CSW, CSA and CSWA diets (P<0.05). These values suggested that the partial replacement of corn silage with alfalfa hay and/or wheat straw has no unfavourable effect on the productive parameters.