35 research outputs found
Enteric and manure-derived methane and nitrogen emissions as well as metabolic energy losses in cows fed balanced diets based on maize, barley or grass hay
Ruminant husbandry constitutes the most important source of anthropogenic methane (CH4). In addition to enteric (animal-derived) CH4, excreta are another source of CH4, especially when stored anaerobically. Increasing the proportion of dietary concentrate is often considered as the primary CH4 mitigation option. However, it is unclear whether this is still valid when diets to be compared are energy-balanced. In addition, non-structural carbohydrates and side effects on nitrogen (N) emissions may be important. In this experiment, diet types representing either forage-only or mixed diets were examined for their effects on CH4 and N emissions from animals and their slurries in 18 lactating cows. Apart from a hay-only diet, treatments included two mixed diets consisting of maize stover, pelleted whole maize plants and gluten or barley straw and grain and soy bean meal. The diets were balanced in crude protein and net energy for lactation. After adaptation, data and samples were collected for 8 days including a 2-day CH4 measurement in respiratory chambers. Faeces and urine, combined proportionately according to excretion, were used to determine slurry-derived CH4 and N emissions. Slurry was stored for 15 weeks at either 14°C or 27°C, and temperatures were classified as ‘cool' and ‘warm', respectively. The low-starch hay-only diet had high organic matter and fibre digestibility and proved to be equally effective on the cows' performance as mixed diets. The enteric CH4 formation remained unaffected by the diet except when related to digested fibre. In this case emission was lowest with the hay-only diet (61 v. 88 to 101 g CH4/kg digested NDF). Feeding the hay diet resulted in the highest slurry-CH4 production after 7 weeks of storage at 14°C and 27°C, and after 15 weeks at 14°C. CH4 emissions were, in general, about 10-fold higher at 27°C compared with 14°C but only after 15 weeks of storage. Urinary N losses were highest with the barley diet and lowest with the maize diet. There was a trend towards similar differences in N losses from the slurry of these cows (significant at 14°C). However, contrary to CH4, slurry-N emissions seemed to be temperature-independent. In conclusion, energetically balanced diets proved to be widely equivalent in their emission potential when combining animal and their slurry, this even at a clearly differing forage : concentrate ratio. The variation in CH4 emission from slurry stored shortly or at cold temperature for 15 weeks was of low importance as such conditions did not support methanogenesis in slurry anywa
Feeding barley grain-rich diets altered electrophysiological properties and permeability of the ruminal wall in a goat model
High-producing ruminants are commonly fed large amounts of concentrate to meet
their high energy demands for rapid growth or high milk production. However,
this feeding strategy can severely impair rumen functioning, leading to
subacute ruminal acidosis. Subacute ruminal acidosis might have consequences
for electrophysiological properties by changing the net ion transfer and
permeability of ruminal epithelia, which may increase the uptake of toxic
compounds generated in the rumen into the systemic circulation. The objective
of the present study was to investigate the effects of excessive barley
feeding on the electrophysiological and barrier functions of the ruminal
epithelium and serum inflammation and ketogenesis markers after a long-term
feeding challenge, using growing goats as a ruminant model. A feeding trial
was carried out with growing goats allocated to 1 of the 3 groups (n=5-6
animals/group), with diets consisting exclusively of hay (control diet) or hay
with 30 or 60% barley grain. Samples of the ventral ruminal epithelium were
taken after euthanasia and instantly subjected to Ussing chamber experiments,
where electrophysiological properties of the epithelium were measured in
parallel with the permeability of marker molecules of different sizes
[fluorescein 5(6)-isothiocyanate and horseradish peroxidase] from luminal to
apical side. Additionally, ruminal fluid and blood samples were taken at the
beginning of the experiment as well as shortly before euthanasia. Ruminal
fluid samples were analyzed for volatile fatty acids and pH, whereas blood
samples were analyzed for lipopolysaccharide, serum amyloid A, and
β-hydroxybutyrate. Electrophysiological data indicated that barley feeding
increased the epithelial short-circuit current compared with the control.
Tissue conductance also increased with dietary barley inclusion. As shown with
both marker molecules, permeability of ruminal epithelia increased with barley
inclusion in the diet. Despite a lowered ruminal pH associated with increased
volatile fatty acids (such as propionate and butyrate) concentrations as well
as altered epithelial properties in response to high-grain feeding, no signs
of inflammation became apparent, as blood serum amyloid A concentrations
remained unaffected by diet. However, greater amounts of grain in the diet
were associated with a quadratic increase in lipopolysaccharide concentration
in the serum. Also, increasing the amounts of barley grain in the diet
resulted in a tendency to quadratically augment serum concentrations of
β-hydroxybutyrate and, hence, the alimentary ketogenesis. Further studies are
needed to clarify the role of barley inclusion in the development of subacute
ruminal acidosis in relation to ruminal epithelial damage and the
translocation of toxic compounds in vivo. Copyright © 2013 American Dairy
Science Association. Published by Elsevier Inc. All rights reserved
Enteric and manure-derived methane and nitrogen emissions as well as metabolic energy losses in cows fed balanced diets based on maize, barley or grass hay
ISSN:1751-7311ISSN:1751-732
Stable carbon isotope Composition of c9,t11-conjugated linoleic acid in cow's milk as related to dietary fatty acids
This study explores the potential use of stable carbon isotope ratios
(delta C-13) of single fatty acids (FA) as tracers for the
transformation of FA from diet to milk, with focus on the metabolic
origin of c9,t11-18:2. For this purpose, dairy cows were fed diets based
exclusively on C-3 and C-4 plants. The FA in milk and feed were
fractionated by silver-ion thin-layer chromatography and analyzed for
their delta C-13 values. Mean delta C-13 values of FA from C-3 milk were
lower compared to those from C-4 milk (-30.1aEuro degrees vs. -24.9aEuro
degrees, respectively). In both groups the most negative delta C-13
values of all FA analyzed were measured for c9,t11-18:2 (C-3 milk =
-37.0 +/- A 2.7aEuro degrees; C-4 milk -31.4 +/- A 1.4aEuro degrees).
Compared to the dietary precursors 18:2n-6 and 18:3n-3, no significant
C-13-depletion was measured in t11-18:1. This suggests that the delta
C-13-change in c9,t11-18:2 did not originate from the microbial
biohydrogenation in the rumen, but most probably from endogenous
desaturation of t11-18:1. It appears that the natural delta C-13
differences in some dietary FA are at least partly preserved in milk FA.
Therefore, carbon isotope analyses of individual FA could be useful for
studying metabolic transformation processes in ruminants