10,831 research outputs found
Relationship between hatchling length and weight on later productive performance in broilers
Hatchling length and weight are used as tools to measure hatchling quality. However, the relationship between these parameters and later performance are not well known. This review evaluates the relationship between hatchling length or weight and slaughter weight, breast meat yield and feed conversion ratio (FCR) in both male and female broilers. Datasets from two trials were compared. In the first, hatchling length and weight of 100 male and 100 female broilers were measured and body weight and breast meat yield were determined at 38 days of age. In experiment 2, hatchling length of 187 female and 230 male broilers was measured and body weight was determined at 21 and 42 days of age. Feed intake was determined between 21 and 42 days of age. In both experiments, male broilers showed a positive relationship between hatchling length and slaughter weight or breast meat yield, but no relationship was found with hatchling weight. The relationship between hatchling length and performance in female broilers differed between the two experiments. In female broilers, a negative relationship between hatchling weight and breast meat yield was found. No relationship between hatchling length and FCR in both male and female broilers was found. From this limited dataset, it can be concluded that hatchling length seems to be a better parameter to predict subsequent chick performance, excluding FCR, than hatchling weight, but gender needs to be taken into accoun
Meeting embryonic requirements of broilers throughout incubation: a review
During incubation of chicken embryos, environmental conditions, such as temperature, relative humidity, and CO2 concentration, must be controlled to meet embryonic requirements that change during the different phases of embryonic development. In the current review, the effects of embryo temperature, egg weight loss, and CO2 concentration on hatchability, hatchling quality, and subsequent performance are discussed from an embryonic point of view. In addition, new insights related to the incubation process are described. Several studies have shown that a constant eggshell temperature (EST) of 37.5 to 38.0 degrees C throughout incubation results in the highest hatchability, hatchling quality, and subsequent performance. Egg weight loss must be between 6.5 and 14.0% of the initial egg weight, to obtain an adequate air cell size before the embryo internally pips. An increased CO2 concentration during the developmental phase of incubation (first 10 days) can accelerate embryonic development and hatchability, but the physiological mechanisms of this acceleration are not completely understood. Effects of ar increased CO2 concentration during late incubation also need further investigation. The preincubation warming profile, thermal manipulation, and in ovo feeding are new insights related to the incubation process and show that the optimal situation for the embryo during incubation highly depends on the conditions of the eggs before (storage duration) and during incubation (environmental conditions) and on the conditions of the chickens after hatching (environmental temperature)
The chicken embryo and its micro environment during egg storage and early incubation
When egg storage periods are prolonged (>7 days), hatchability and chick quality declines. The reason for this decline has been investigated, but is still not completely understood. At oviposition the developmental stage of the chicken embryo varies and so do the total number of viable cells. During storage, changes can occur in the embryo. Embryo viability at the end of storage seems to be dependent on the number of viable cells and the developmental stage of the embryo at oviposition. When the hypoblast is completely formed (during the quiescent developmental stage), the embryo seems to be more able to endure prolonged storage periods than embryos that are less or more advanced. During storage, changes also occur in egg characteristics such as albumen viscosity, albumen pH and yolk pH. There appears to be an interaction between albumen pH and embryo viability during early incubation and perhaps also during storage. An albumen pH of 8.2 seems to be optimal for embryo development. Albumen pH may influence embryo viability, but embryo viability may in turn, affect albumen pH. It has been hypothesised that an embryo in which the hypoblast is completely formed is better able to provide an effective barrier between the internal embryo and the exterior (yolk and albumen) and/or is better able to produce sufficient amount of carbon dioxide, which will reduce the pH level in the micro environment of the embryo to the optimal pH of 8.2. It appears that, to maintain hatchability and chick quality after prolonged storage periods, embryonic development should be advanced to the stage in which the hypoblast is completely formed or the atmosphere during storage and early incubation should be altered in such a way that albumen pH is maintained at the optimal level of 8.2
Parametric Forcing of Waves with Non-Monotonic Dispersion Relation: Domain Structures in Ferrofluids?
Surface waves on ferrofluids exposed to a dc-magnetic field exhibit a
non-monotonic dispersion relation. The effect of a parametric driving on such
waves is studied within suitable coupled Ginzburg-Landau equations. Due to the
non-monotonicity the neutral curve for the excitation of standing waves can
have up to three minima. The stability of the waves with respect to long-wave
perturbations is determined a phase-diffusion equation. It shows that the
band of stable wave numbers can split up into two or three sub-bands. The
resulting competition between the wave numbers corresponding to the respective
sub-bands leads quite naturally to patterns consisting of multiple domains of
standing waves which differ in their wave number. The coarsening dynamics of
such domain structures is addressed.Comment: 23 pages, 6 postscript figures, composed using RevTeX. Submitted to
PR
Renormalization Group Method and Reductive Perturbation Method
It is shown that the renormalization group method does not necessarily
eliminate all secular terms in perturbation series to partial differential
equations and a functional subspace of renormalizable secular solutions
corresponds to a choice of scales of independent variables in the reductive
perturbation method.Comment: 5 pages, late
1420 MHz Continuum Absorption Towards Extragalactic Sources in the Galactic Plane
We present a 21-cm emission-absorption study towards extragalactic sources in
the Canadian Galactic Plane Survey (CGPS). We have analyzed HI spectra towards
437 sources with S > 150 mJy, giving us a source density of 0.6 sources per
square degree at arcminute resolution. We present the results of a first
analysis of the HI temperatures, densities, and feature statistics. Particular
emphasis is placed on 5 features with observed spin temperatures below 40 K. We
find most spin temperatures in the range from 40 K to 300 K. A simple HI
two-component model constrains the bulk of the cold component to temperatures
(T_c) between 40 K and 100 K. T_c peaks in the Perseus arm region and clearly
drops off with Galactocentric radius, R, beyond that. The HI density follows
this trend, ranging from a local value of 0.4 cm^{-3} to less than 0.1 cm^{-3}
at R = 20 kpc. We find that HI emission alone on average traces about 75% of
the total HI column density, as compared to the total inferred by the emission
and absorption. Comparing the neutral hydrogen absorption to CO emission no
correlation is found in general, but all strong CO emission is accompanied by a
visible HI spectral feature. Finally, the number of spectral HI absorption
features per kpc drop off exponentially with increasing R.Comment: 13 pages, 13 figures, Accepted for March 2004 Ap
The Equilibrium State of Molecular Regions in the Outer Galaxy
A summary of global properties and an evaluation of the equilibrium state of
molecular regions in the outer Galaxy are presented from the decomposition of
the FCRAO Outer Galaxy Survey and targeted 12CO and 13CO observations of four
giant molecular cloud complexes. The ensemble of identified objects includes
both small, isolated clouds and clumps within larger cloud complexes. 12CO
velocity dispersions show little variation with cloud sizes for radii less than
10 pc. It is demonstrated that the internal motions of regions with molecular
masses greater than 10**4 msuns are bound by self gravity, yet, the constituent
clumps of cloud complexes and isolated molecular clouds with M < 10**3 msuns
are not in self gravitational equilibrium. The required external pressures to
maintain the equilibrium of this population are (1-2)x10**4 cm-3-K.Comment: To appear in ApJ, 32 pages, 13 figures, 2 table
Vibrational instability, two-level systems and Boson peak in glasses
We show that the same physical mechanism is fundamental for two seemingly
different phenomena such as the formation of two-level systems in glasses and
the Boson peak in the reduced density of low-frequency vibrational states
g(w)/w^2. This mechanism is the vibrational instability of weakly interacting
harmonic modes. Below some frequency w_c << w_0 (where w_0 is of the order of
Debye frequency) the instability, controlled by the anharmonicity, creates a
new stable universal spectrum of harmonic vibrations with a Boson peak feature
as well as double-well potentials with a wide distribution of barrier heights.
Both are determined by the strength of the interaction I ~ w_c between the
oscillators. Our theory predicts in a natural way a small value for the
important dimensionless parameter C ~ 10^{-4} for two-level systems in glasses.
We show that C ~ I^{-3} and decreases with increasing of the interaction
strength I. We show that the number of active two-level systems is very small,
less than one per ten million of oscillators, in a good agreement with
experiment. Within the unified approach developed in the present paper the
density of the tunneling states and the density of vibrational states at the
Boson peak frequency are interrelated.Comment: 28 pages, 3 figure
A study of the neglected Galactic HII region NGC 2579 and its companion ESO 370-9
The Galactic HII region NGC 2579 has stayed undeservedly unexplored due to
identification problems which persisted until recently. Both NGC 2579 and its
companion ESO 370-9 have been misclassified as planetary or reflection nebula,
confused with each other and with other objects. Due to its high surface
brightness, high excitation, angular size of few arcminutes and relatively low
interstellar extinction, NGC 2579 is an ideal object for investigations in the
optical range. Located in the outer Galaxy, NGC 2579 is an excellent object for
studying the Galactic chemical abundance gradients. In this paper we present
the first comprehensive observational study on the nebular and stellar
properties of NGC 2579 and ESO 370-9, including the determination of electron
temperature, density structure, chemical composition, kinematics, distance, and
the identification and spectral classification of the ionizing stars, and
discuss the nature of ESO 370-9. Long slit spectrophotometric data in the
optical range were used to derive the nebular electron temperature, density and
chemical abundances and for the spectral classification of the ionizing star
candidates. Halpha and UBV CCD photometry was carried out to derive stellar
distances from spectroscopic parallax and to measure the ionizing photon flux.Comment: To be published in Astronomy & Astrophysic
Convective Nonlinearity in Non-Newtonian Fluids
In the limit of infinite yield time for stresses, the hydrodynamic equations
for viscoelastic, Non-Newtonian liquids such as polymer melts must reduce to
that for solids. This piece of information suffices to uniquely determine the
nonlinear convective derivative, an ongoing point of contention in the rheology
literature.Comment: 4 page
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