Effects of Calcium Hydroxide Treated Corn Stover Inclusion as a Partial Forage Replacement in Diets for Lactating Dairy Cows

Brittany Casperson, Purdue University

Abstract

The central hypothesis of this dissertation is that calcium hydroxide treatment would improve the feeding value of corn stover and treated corn stover could replace a portion of the traditional forages fed to lactating dairy cattle. There are four main objectives addressed in this dissertation to test the central hypothesis. First, evaluate the effects of pretreatment of corn stover with calcium hydroxide. Second, determine the effects of replacing alfalfa haylage in the diet of dairy cows with calcium hydroxide-treated corn stover and the effect of further replacement of corn silage on dry matter intake, milk production, and milk composition. Third, determine the effects of maximal replacement of either alfalfa haylage or corn silage with treated corn stover on feed intake, total tract digestibility, rumen fermentation parameters, rumen digestibility, and milk production in order to assess the origins of increased feed efficiency of mid-lactation dairy cows fed alkaline treated corn stover, and lastly, to evaluate the effects of feeding a fortified corn stover pellet, pelleted treated corn stover (PTCS), on dry matter intake, milk production, milk composition, total tract digestibility, rumen fermentation parameters, and rumen digestibility. Furthermore, the effect of physical form of the PTCS ingredients were evaluated by comparing PTCS ingredients fed in pellet or non-pellet form. Calcium hydroxide treated corn stover was first evaluated in a lactation performance trial where treated corn stover was fed in a TMR at 0% of the diet DM or replaced either alfalfa haylage or alfalfa haylage and a portion of the corn silage at 15 or 30% of the diet DM, respectively. After 10 weeks of feeding, cows fed treated corn stover to replace alfalfa haylage resulted in reduction (P < 0.05) of DMI. Subsequently, milk production, milk composition, and energy corrected milk production were not different (P > 0.05) between the treatments. However, energy corrected milk per unit of DMI (kg/kg), a measure of feed efficiency, tended ( P < 0.10) to be improved. Cows fed treated corn stover had consistent DMI over the 10-week feeding period compared to cows fed no treated corn stover which had slight increases in feed intake, over time. To determine the overall impact on feed efficiency with the inclusion of treated corn stover, we evaluated inclusion of treated corn stover to maximally replace either alfalfa haylage at 15% of the diet DM or corn silage at 19% of the diet DM. When treated corn stover was included in the diet to replace either traditional forage, we saw a reduction (P < 0.05) of DMI but no differences (P > 0.05) in milk production, confirming the results of the previous study. Furthermore, percentage of milk fat was reduced (P < 0.05) with the inclusion of treated corn stover but there was no difference in yield of milk fat (P > 0.05). Energy corrected milk production per unit of DMI (kg/kg) was greater for cows fed diets containing treated corn stover. Inclusion of treated corn stover resulted in decreased (P < 0.05) apparent total tract digestibility of DM, OM, and CP when replacing corn silage. There was no difference (P > 0.05) in NDF digestibility, suggesting NDF digestibility was successfully improved with calcium hydroxide pretreatment. There was no difference (P > 0.05) on rumen pH or VFA concentrations. Improved feed efficiency is supported by changes in diet digestibility and the potential for changes in post-ruminal digestion. Improvements in feed efficiency using treated corn stover are promising but implementation of such feeding strategies may be limited to certain regions near site of harvest as the bulk density of corn stover is low. Therefore, to overcome this limitation for implementation into diets for lactating cows, we evaluated feeding treated corn stover as part of a fortified pellet- pelleted treated corn stover (PTCS). The PTCS pellet was included at 21 or 40% of the diet DM. The ingredients of PTCS were fed individually in a third treatment to match the 40% PTCS and evaluate if physical form had an impact. Dry matter intake was reduced (P < 0.05) with higher inclusion levels (40%) but physical form had no impact on DMI. Milk production and 4% energy corrected milk did not differ (P > 0.05) among the dietary treatments. Milk fat percentage was reduced (P < 0.05) with the inclusion of PTCS. Digestibility of DM and OM were reduced ( P < 0.05) with inclusion of treated corn stover. The inclusion of PTCS resulted in decreased (P < 0.05) acetate and increased (P < 0.05) propionate concentration, yielding a reduced (P < 0.05) acetate:propionate ratio. Rumen digestibility of diet ingredients were not different (P > 0.05) between dietary treatments. (Abstract shortened by ProQuest.)

Degree

Ph.D.

Advisors

Donkin, Purdue University.

Subject Area

Animal sciences

COinS