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

Abstract

The study investigated the effect of chop length of wheat straw in a high-straw dry cow diet on the feeding behavior, health, and performance of Holstein dairy cows across the transition period. Forty cows were enrolled at dry off, approximately 45 d before expected calving, 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 formulated to target an energy consumption of 19 Mcal/d of net energy for lactation per cow. The diets differed in the chop length of wheat straw: (1) long straw chopped with a 10.16-cm screen (LDD; n = 20), or (2) short straw chopped with a 2.54-cm screen (SDD; n = 20). Dietary treatments were fed throughout the dry period. Feeding behavior, rumination time, and reticulorumen pH were monitored electronically, and feed samples were collected to determine feed sorting. Blood samples were taken weekly, and body condition scores and body weights were taken every 2 wk. Postcalving, all cows were fed the same lactating cow total mixed ration for 28 d; the same measurements were recorded with the addition of daily milk yield and twice weekly milk components. During the dry period, cows fed the SDD treatment consumed more dry matter (15.6 vs. 15.0 kg/d), had more consistent dry matter intake in the week leading up to calving, had a faster feeding rate, consumed 0.4 kg/meal more, and had 0.6 fewer meals per day. No differences were observed in rumination time or mean reticulorumen pH between treatments in both the dry and lactating period. Regardless of treatment during the dry period, cows sorted against the long particles (>19 mm) and in favor of the short particles (<8, >4 mm), but cows fed the LDD treatment sorted to a greater extent than cows fed the SDD treatment. Dietary treatment in the dry period did not influence feed sorting behavior postcalving. Cows fed the LDD treatment had a greater daily change (decline) in rumen pH in the first week postcalving and had a greater blood β-hydroxybutyrate concentration in the third week postcalving. Overall, the results from this study indicate that feeding shorter chopped wheat straw in a high-straw dry cow diet improved intake, reduced sorting during the dry period, and resulted in greater metabolic health and rumen stability in early lactation.

Moisture content of high-straw dry cow diets affects intake, health, and performance of transition dairy cows

“…Contrary to our hypothesis, and in agreement with Havekes et al (2020), dietary treatment in the dry period did not influence how cows sorted their diet postcalving. Sorting during early lactation, when energy demands are high, is likely more related to energy balance (DeVries et al, 2011;Moore and DeVries, 2018) than it is related to a carry-over effect from the dry period.…”

“…Interestingly, cows sorted against the fine fraction, which was surprising as these are usually sought-after particles (Miller-Cushon and DeVries, 2017). Similar sorting results were seen when dairy cows were fed finely chopped straw in both a lactating ration (Coon et al, 2018) and a dry cow ration (Havekes et al, 2020), suggesting that cows may prefer not to consume straw fines, which would have made up a large proportion of the fine particle fraction.…”

“…Sample size and power analyses were used to calculate (as per Morris, 1999) the minimum number of replicates needed per treatment (n = 20) to detect a 10% level of observed mean difference for the primary outcome variables, including DMI, feeding behavior, and feed sorting. Estimates of variation for these variables were based on previously reported values (Coon et al, 2018;Dancy et al, 2019;Havekes et al, 2020).…”

“…As such, it could be hypothesized that minimizing the severity of the change by manipulating characteristics, such as particle size and moisture content, of the dry cow ration to make it more similar to the lactating ration may ease that transition. Reducing straw particle size in highstraw dry cow diets has recently been demonstrated to improve DMI in the dry period and promote greater rumen and metabolic health postcalving (Havekes et al, 2020). In that work the shorter chop length of straw reduced sorting; however, it did not eliminate sorting completely (Havekes et al, 2020), suggesting that other dietary and management factors associated with these diets need to be implemented to minimize the risk of that behavior.…”

Metabolic Stress in the Transition Period of Dairy Cows: Focusing on the Prepartum Period

“…Havekes et al [32][33][34] very recently proposed a variety of strategies to reduce the sorting behavior in low energy diets in the dry period. In a first experiment [32], they demonstrated that prepartum cows being fed a short chop length (2.54 cm screen) of wheat straw is preferable since it was associated with lower serum BHB concentration in the third week postpartum compared to that in cows fed a long chop length (10.16 cm screen) of wheat straw. Although a shorter chop length of straw reduced sorting, it did not (completely) eliminate this behavior.…”