8,756 research outputs found
Effects of infrequent dried distillers grain supplementation on spring-calving cow performance
Feed and supplement costs and the expenses associated with delivery of winter supplements
account for a large proportion of the total operating expenditures for cow-calf
producers. Cattle grazing low-quality dormant native range (<6% crude protein) typically
are unable to consume sufficient protein from the forage base, which limits microbial
activity and forage digestion. Supplemental protein often is required to maintain
cow body weight and body condition score during the last trimester of pregnancy. Low
cow body condition scores at calving are common and may negatively affect lactation,
rebreeding rates, and calf weaning weight. Failure to maintain proper nutritional status
during this period severely affects short-term cow performance, reduces overall herd
productivity, and limits profit potential.
The most effective means of supplying supplemental protein to cows consuming
dormant native range is to provide a small amount of high-protein feedstuff (>30%
crude protein). Dried distillers grains with solubles (DDGS) are a by-product of the
ethanol refining process. Distillers grains supply the recommended 30% crude protein
level, are readily available, and often are favorably priced compared with more traditional
feedstuffs.
With the rising costs of inputs in today’s cow-calf sector, reducing cost is necessary to
maintain viability of the national cowherd. Reducing the frequency of supplementation
results in less labor and fuel use, effectively reducing input costs; however, this is viable
only as long as cow performance is maintained at acceptable levels. Therefore, the objective
of this study was to examine the effects of infrequent supplementation of dried
distillers grains with solubles on cow body weight and body condition score
Calf health and performance during receiving is not changed by fence-line preconditioning on flint hills range vs. drylot preconditioning
Ranch-of-origin preconditioning can improve the welfare and performance of beef
calves by decreasing the stress associated with weaning, transport, diet change, and
commingling with other calves. Preconditioning methods that involve pasture weaning
coupled with maternal contact (i.e., fence-line weaning) have been promoted as possible
best management practices for minimizing stress. Prior studies focused on performance
and behavior during preconditioning on the ranch of origin. Little information has
been published relating to carryover effects of fence-line preconditioning compared
with conventional drylot preconditioning on performance and behavior during feedlot
receiving.
Our objectives were to measure growth and health during a 28-day ranch-of-origin
preconditioning phase and during a 60-day feedlot receiving phase among beef calves
subjected to 1 of 3 ranch-of-origin preconditioning programs: (1) drylot preconditioning
+ dam separation, (2) pasture preconditioning + fence-line contact with dams, and
(3) pasture preconditioning + fence-line contact with dams + supplemental feed delivered
in a bunk. In addition, we recorded incidences of behavioral distress among these
treatments during first 7 days of feedlot receiving
Subdiffusion and cage effect in a sheared granular material
We investigate experimentally the diffusion properties of a bidimensional
bidisperse dry granular material under quasistatic cyclic shear.The comparison
of these properties with results obtained both in computer simulations of hard
spheres systems and Lenard-Jones liquids and experiments on colloidal systems
near the glass transition demonstrates a strong analogy between the behaviour
of granular matter and these systems. More specifically, we study in detail the
cage dynamics responsible for the subdiffusion in the slow relaxation regime,
and obtain the values of relevant time and length scales.Comment: 4 pages, 6 figures, submitted to PR
A Model for Force Fluctuations in Bead Packs
We study theoretically the complex network of forces that is responsible for
the static structure and properties of granular materials. We present detailed
calculations for a model in which the fluctuations in the force distribution
arise because of variations in the contact angles and the constraints imposed
by the force balance on each bead of the pile. We compare our results for force
distribution function for this model, including exact results for certain
contact angle probability distributions, with numerical simulations of force
distributions in random sphere packings. This model reproduces many aspects of
the force distribution observed both in experiment and in numerical simulations
of sphere packings
Metastability of a granular surface in a spinning bucket
The surface shape of a spinning bucket of granular material is studied using
a continuum model of surface flow developed by Bouchaud et al. and Mehta et al.
An experimentally observed central subcritical region is reproduced by the
model. The subcritical region occurs when a metastable surface becomes unstable
via a nonlinear instability mechanism. The nonlinear instability mechanism
destabilizes the surface in large systems while a linear instability mechanism
is relevant for smaller systems. The range of angles in which the granular
surface is metastable vanishes with increasing system size.Comment: 8 pages with postscript figures, RevTex, to appear in Phys. Rev.
Percolating through networks of random thresholds: Finite temperature electron tunneling in metal nanocrystal arrays
We investigate how temperature affects transport through large networks of
nonlinear conductances with distributed thresholds. In monolayers of
weakly-coupled gold nanocrystals, quenched charge disorder produces a range of
local thresholds for the onset of electron tunneling. Our measurements
delineate two regimes separated by a cross-over temperature . Up to
the nonlinear zero-temperature shape of the current-voltage curves survives,
but with a threshold voltage for conduction that decreases linearly with
temperature. Above the threshold vanishes and the low-bias conductance
increases rapidly with temperature. We develop a model that accounts for these
findings and predicts .Comment: 5 pages including 3 figures; replaced 3/30/04: minor changes; final
versio
Clustering and Non-Gaussian Behavior in Granular Matter
We investigate the properties of a model of granular matter consisting of
Brownian particles on a line subject to inelastic mutual collisions. This model
displays a genuine thermodynamic limit for the mean values of the energy and
the energy dissipation. When the typical relaxation time associated with
the Brownian process is small compared with the mean collision time
the spatial density is nearly homogeneous and the velocity probability
distribution is gaussian. In the opposite limit one has
strong spatial clustering, with a fractal distribution of particles, and the
velocity probability distribution strongly deviates from the gaussian one.Comment: 4 pages including 3 eps figures, LaTex, added references, corrected
typos, minimally changed contents and abstract, to published in
Phys.Rev.Lett. (tentatively on 28th of October, 1998
Presynchronizing PGF2α and GnRH injections before timed artificial insemination CO-Synch + CIDR program
Fixed-time artificial insemination is an effective management tool that reduces the
labor associated with more conventional artificial insemination programs requiring
detection of estrus. The 7-day CO-Synch + controlled internal drug release (CIDR)
insert protocol has been shown to effectively initiate estrus and ovulation in cycling
and non-cycling suckled beef cows, producing pregnancy rates at or greater than 50%
in beef cows. The gonadotropin-releasing hormone (GnRH) injection that begins the
CO-Synch + CIDR program initiates ovulation in a large proportion of cows, particularly
anestrous cows. The CIDR, which releases progesterone intravaginally, prevents
short estrous cycles that usually follow the first postpartum ovulation in beef cows. Our
hypothesis was that inducing estrus with a prostaglandin injection followed 3 days later
with a GnRH injection, 7 days before applying the 7-day CO-Synch + CIDR protocol,
might increase the percentage of cycling cows that would exhibit synchronous follicular
waves after the onset of the CO-Synch + CIDR protocol. We also hypothesized that
the additional GnRH injection would increase the percentage of anestrous cows that
would ovulate, thereby increasing pregnancy outcomes
Relationship of hypoxia to metastatic ability in rodent tumours
The relationship between tumour oxygenation in vivo and metastatic potential was investigated in 2 rodent tumour models, KHT-C fibrosarcoma and SCC-VII squamous cell carcinoma. The oxygen status in these rodent tumours transplanted intramuscularly in syngeneic mice was measured using the Eppendorf pO 2 Histograph. The results indicate a considerable heterogeneity in oxygenation between individual tumours within each tumour cell line. At different tumour sizes, animals were killed and lung lobes were examined for macroscopic and microscopic lung metastases. In the KHT-C tumours, a significant increase in early pulmonary metastasis formation was observed in mice with hypoxic primary tumours. Hypoxic SCC-VII tumours did not give rise to enhanced lung metastasis formation despite oxygenation in a range similar to the KHT-C tumours. However, the overall metastasis incidence in the SCC-VII model was very low. The results obtained in the KHT-C model, which show that hypoxic tumours are more likely to metastasize, are in agreement with recent clinical data suggesting that a hypoxic environment might be implicated in metastatic ability of human tumours. © 2001 Cancer Research Campaign http://www.bjcancer.co
- …