Effects of wheat straw chop length in high-straw dry cow diets on intake, health, and performance of dairy cows across the transition period

摘要

The study investigated the effect of chop length ofwheat straw in a high-straw dry cow diet on the feedingbehavior, health, and performance of Holstein dairycows across the transition period. Forty cows were enrolledat dry off, approximately 45 d before expectedcalving, and assigned to 1 of 2 dietary treatments containing(on a dry matter basis) 36% corn silage, 35%dry cow pellet, and 29% wheat straw. Diets were formulatedto target an energy consumption of 19 Mcal/d ofnet energy for lactation per cow. The diets differed inthe chop length of wheat straw: (1) long straw choppedwith a 10.16-cm screen (LDD; n = 20), or (2) shortstraw chopped with a 2.54-cm screen (SDD; n = 20).Dietary treatments were fed throughout the dry period.Feeding behavior, rumination time, and reticulorumenpH were monitored electronically, and feed sampleswere collected to determine feed sorting. Blood sampleswere taken weekly, and body condition scores and bodyweights were taken every 2 wk. Postcalving, all cowswere fed the same lactating cow total mixed rationfor 28 d; the same measurements were recorded withthe addition of daily milk yield and twice weekly milkcomponents. During the dry period, cows fed the SDDtreatment consumed more dry matter (15.6 vs. 15.0kg/d), had more consistent dry matter intake in theweek leading up to calving, had a faster feeding rate,consumed 0.4 kg/meal more, and had 0.6 fewer mealsper day. No differences were observed in ruminationtime or mean reticulorumen pH between treatmentsin both the dry and lactating period. Regardless oftreatment during the dry period, cows sorted againstthe long particles (>19 mm) and in favor of the shortparticles (<8, >4 mm), but cows fed the LDD treatmentsorted to a greater extent than cows fed the SDDtreatment. Dietary treatment in the dry period did notinfluence feed sorting behavior postcalving. Cows fedthe LDD treatment had a greater daily change (decline)in rumen pH in the first week postcalving andhad a greater blood β-hydroxybutyrate concentrationin the third week postcalving. Overall, the results fromthis study indicate that feeding shorter chopped wheatstraw in a high-straw dry cow diet improved intake,reduced sorting during the dry period, and resulted ingreater metabolic health and rumen stability in earlylactation.