Masters of Science
Date
2016-09-22
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0000-0001-9192-7642
Type
Thesis
Degree Level
Masters
Abstract
This project was targeted at identifying if it is possible to select a barley cultivar that has a higher NDF digestibility (NDFD) which can be ensiled in following years for livestock feed in order to increase digestibility and animal performance. Three barley cultivars, CDC Cowboy (H-NDFD), CDC Copeland (I-NDFD), and Xena (L-NDFD) were selected based on respective high, intermediate, and low NDFD following 30 h in vitro digestion of silage collected from commercial farms. The objective of the first study was to determine if a higher NDFD of a barley cultivar would alter the fermentation pattern of the silage compared to cultivars with lower NDFD. This was accomplished by ensiling the three barley cultivars in mini-silos to be opened at 3, 7, 14, 21, and 60 d after ensiling to measure fermentation parameters and microbial enumeration. Barley cultivars were also ensiled in bunker-silos for the feeding trial. Following 60 d ensiling, the silage was exposed to air to measure aerobic stability with temperature change measured continually, and fermentation parameters and microbial enumeration measured after 3, 7, 14, and 21 d of exposure. Chemical analysis compared fresh forage to 60 d silage, and silage from the bunker-silos used in the feeding trial, as well 60 d mini-silos and bunker-silo samples underwent in vitro NDFD analysis to compare to the selection criteria. There was no difference in in vitro NDFD of the three cultivars grown for this study. The H-NDFD cultivar had lower pH and higher lactate levels. Starch was higher in L-NDFD, and I-NDFD had higher ADF and NDF than the other cultivars. Bunker-silos had higher VFA concentrations than the mini-silos, and pH of I-NDFD and L-NDFD was lower in bunker-silos than mini-silos. Aerobic spoilage was only apparent in H-NDFD which saw silage temperature increase, lactate decrease and pH increase compared to the other cultivars.
The objective of the second trial was to determine whether increased in vitro NDFD would increase digestibility and animal performance through improved intake, weight gain, or carcass traits. A replicated 3x3 Latin square used rumen cannulated wethers to measure total tract digestibility of the three barley cultivars as part of a 50:50 barley silage to concentrate diet (DM basis). Rumen pH was measured using in dwelling pH probes to record pH over 48 h. Total collections were conducted over four days with rumen fluid collection on the fourth day at 0, 3, 6, 12 h after feeding for VFA, ammonia, and protozoa enumeration. A lamb performance trial was conducted feeding 42 lambs equally divided ram and ewe lambs between the three barley cultivars with diets comprised of 40:60 silage to concentrate (DM basis). Intake was recorded daily, and lamb weight weekly, for ADG and F:G calculations. Following 72 d on feed, ram lambs were slaughtered and carcass characteristics recorded. The L-NDFD digestibility trial diet had lower ADF and NDF, and higher starch than the H-NDFD diet, but there was no difference in total tract digestibility, consistent with lack of in vitro NDFD differences. Average rumen pH was lower for lambs fed L-NDFD. The 40% silage diets in the performance trial saw no difference between cultivars. Lambs fed I-NDFD had lower DMI than the other two cultivars, but no difference was observed in terms of weight gain. Carcass characteristics were similar between cultivars, with dressing percentage of L-NDFD lambs being higher than I-NDFD lambs.
The results of this thesis suggest that selecting a barley cultivar with improved NDFD is more difficult than selecting the cultivar with the highest in vitro NDFD. Differences in fermentation patterns and lamb performances when fed different cultivars suggest that selection for barley cultivar to improve NDFD might have some merit though plant maturity has a strong effect.
Description
Keywords
barley silage, neutral detergent fiber digestibility, fermentation, aerobic stability, lamb performance
Citation
Degree
Master of Science (M.Sc.)
Department
Animal and Poultry Science
Program
Animal Science