Document Type

Thesis - Open Access

Award Date

2017

Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

Johan Osorio

Abstract

The objective of this study was to evaluate the effects of SS a blend of commercially available essential oils (EO) on rumen microbial efficiency and kinetics, and consequently, effects on production parameters of dairy cows fed a low-starch diet and in vitro analysis of varying doses of SS on ruminal fermentation at different stages of lactation. The study consisted of two experiments, the in vivo Experiment 1, was conducted on a commercial robotic dairy in southwest Minnesota outfitted with two Lely Astronaut A4robotic milking units (Goter’s Clay & Dairy Equipment of MN, INC., Pipestone, MN). One hundred-seven Holstein cows were randomly assigned to either the control diet (CON) (25% starch) or the low-starch (LS) diet (22% starch) in a randomized complete block design (RCBD), where cows were blocked by body weight (BW) and body condition score (BCS). All cows were fed 28g/hd/d of SS throughout the trial. The experiment included 14 d of dietary adaptation and 28 d of data collection. A tendency for higher pellet intake was observed for the LS treatment. Milk production, fat, and protein yield were similar among treatments. Total volatile fatty acid concentrations were similar between treatments, with a tendency observed for an increase in acetate percentage for the LS treatment. BUN and MUN concentrations were similar between treatments, ammonia concentrations were significantly lower for LS (5.84 vs. 9.69mM), and pH values tended to be higher for LS treatment. In Experiment 2, an in vitro analysis was carried out as a 2 × 3 factorial arrangement of treatments with two doses (i.e., single and double) of SS and rumen fluid (RF) from Holstein cows at three stages of lactation (i.e., early, mid, and late). The latter was done with the aim to evaluate the effects of EO at different stages of lactation on ruminal fermentation characteristics and kinetics. Each treatment was replicated in 3 gas fermentation bottles plus a control treatment with RF only, and 3 batches containing all treatments were repeated 3 times on different days. RF was collected from 9 lactating multiparous cows (n = 3/group) at early [days in milk (DIM) 32-36], mid (DIM 144-157), and late (DIM 277-290) stages of lactation via esophageal tube at approximately 4 h after feeding. Gas production was significantly lower with the addition of the double dose of SS, but no treatment differences were observed. Total VFA concentrations were similar among treatments. Propionate percentage was significantly greater for the early lactation and single dose of SS treatment. Acetate: propionate ratio was significantly greater for the late lactation, and both single and double dose of SS. Ammonia concentrations were significantly lower in the early lactation and single dose of SS treatment, and early, mid and late lactation and double dose with mid lactation having the greatest concentration and early lactation having the lowest concentration. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were not affected by experimental treatment effects.

Library of Congress Subject Headings

Dairy cattle -- Feeding and feeds.
Essences and essential oils.
Rumen.
Lactation.

Description

Includes bibliographical references (pages 79-85)

Format

application/pdf

Number of Pages

98

Publisher

South Dakota State University

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Included in

Dairy Science Commons

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Rights Statement

In Copyright