Note: Descriptions are shown in the official language in which they were submitted.
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TITLE: Rapid and Automatic Determination of Metabolic Efficiency in Livestock
TECHNICAL FIELD
The use of non-invasive, rapid infrared thermography for the rapid
determination of metabolic efficiency of farmed animals is provided. More
specifically, the present apparatus and method relates to inducing animals
into a
non-steady biological states and utilizing infrared thermography information
about the animal to determine its metabolic efficiency.
BACKGROUND
Many animal management events experienced by livestock throughout the
animal's lifetime can influence its overall welfare, performance (e.g. the
quality of
food it produces), and the cost of agricultural resources required. For
instance,
exposure to handling and transport, co-mingling, auction and time off feed can
cause stress in animals, impeding their immune system and increasing the
incidence of disease. Left unmanaged, such events can have a considerable
economic impact on the agricultural industry. The use of agricultural
resources
for the production of animal products is increasingly being scrutinised as
human
populations expand, increasing the need to mitigate carbon footprints and
greenhouse gas emissions. Monitoring and controlling the impact animal
management events can lead to improved animal welfare and quality, and to
overall environmental benefits such as reduced carbon footprint and greenhouse
gas emissions.
Effective animal management can depend upon the ability to rapidly and
non-invasively determine when animals are in steady or non-steady states (e.g.
disease state, reproductive states, or growth phases). Monitoring these
biological
states is important to the agricultural industry, as well as to zoo and
wildlife
biology settings because they can influence a plethora of biometric
measurements and characteristics, such as an animal's metabolic efficiency.
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Metabolic efficiency has become an important attribute in animal
agriculture as competition for limited resources increases. Variation in
inherent or
normal growth efficiency among animals within a species can be large, at least
in
part due to genetic variation in feed conversion efficiency. Feed accounts for
a
large proportion of input costs required to raise livestock in all phases of
production, so it is vital that producers get the most value for their feed.
However,
measuring an animal's metabolic efficiency has always been a challenge as
many factors, including genetics, can dictate how feed affects the metabolic
efficiencies of livestock.
Feed or growth efficiency is the measure of energy or feed resources
required for a given gain in an identifiable animal product such as meat, milk
or
wool. Animals with poor feed efficiency not only grow less efficiently, but
also
produce more carbon dioxide and methane than higher feed efficiency animals,
making it desirable for producers to be able to sort and select animals based
on
their feed efficiency. For example, in some animals, it is estimated that 70%
of
the food energy requirements used by an animal are actually spent on
maintenance of the animal, not on growth or gain in an identifiable animal
product such as meat, milk or wool. Further, animals with poor feed efficiency
tend to produce more methane than the average animal because less of the
ingested biomass is converted to energy, instead being converted to waste by-
products such as methane. As such, the measurement of animal metabolic
efficiency is a prime directive in animal agriculture, as the selection of
only the
most efficient animals by producers improves efficiency in the use feed
resources.
Several techniques exist for classifying live animals into feed efficiency
categories without predicting or measuring actual feed efficiency. Ultrasound
can
be used to score animals based on their body conditioning and frame size,
however this approach merely selects larger body size, which is not a
consistent
indicator of feed efficiency. The "Kleiber ratio", which evaluates an animal's
metabolic rate based on its mass, can be used but again only provides for the
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selection larger body size. Known methods fail to account for variation in
growth
efficiency based on the overall health or the genetics of the animal.
One of the more accurate methods for monitoring feed efficiency is to use
indirect calorimetry which measures exactly the amount of oxygen and energy
used by an animal for a given increase in gain of a specific tissue while
noting
that the metabolism will also give off heat. This method requires the use of
expensive and complex indirect calorimetry equipment, the training of animals
and the necessity to conduct trials at a physiological steady state.
A more recent approach to monitoring feed or growth efficiency is to
monitor the residual feed intake (RFI) value, which partitions feed intake
into that
used for production and a residual portion reflecting efficiency.
Fundamentally,
this process compares the measured feed-to-gain against a known estimate for
feed-to-gain, based on scientifically accepted formulas. While reasonably
accurate, the RFI method requires a lengthy monitoring period of at least
seventy
days making it both expensive and impractical.
United States Patent Application No. 10/558,854 (Publication No.
U52007/0093965 Al) filed by Harry Harrison et al. ("Harrison") teaches the use
of infrared thermography (IRT) to determine or predict growth efficiency in
animals. Infrared thermography is a known method of detecting the dissipation
of
heat from animals and operates on the principle that infrared radiation can be
utilized to observe radiated heat loss and to provide an early indicator of
fever
because up to 60% of the heat loss from an animal occurs in infrared ranges.
While IRT can be an effective in non-invasive identification of transport and
other
environmental stressors, the Harrison method requires that sufficient animals
be
sampled to over long periods of time (several weeks or months) to provide
enough data to predict animal growth. As such, the method is not suitable for
rapidly determining the metabolic efficiency of one animal at a time.
Further, the Harrison method requires that the animals be in a steady-
state condition, meaning that the animal's endocrine, physiological and
metabolic
value are all within a normal range and the animal is not stressed. It is well
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known, however, that animals often do not display overt signs of illness or a
non-
steady state (that would be detectable by a caregiver) until later in the
progression of the disease. As such, despite the Harrison method expressly
attempting to exclude animals in a non-steady state, it is entirely possible
that the
collected values from many animals could be skewed as a result of
inadvertently
including animals having an abnormal thermal expression.
There is a need for a non-invasive means for identifying metabolic
efficiency in livestock without requiring the animal to be in a steady-state
condition, enabling producers to rapidly determine each animal's overall
health
and performance, and to predict its response to various animal management
events (e.g. disease, stress, growth, reproduction). The method could provide
for
the ranking, selection, breeding and/or culling of animals based upon their
efficiency, adding value to the herd and decreasing production and
environmental costs.
SUMMARY
The use of infrared thermography (IRT) to predict metabolic efficiency in
steady-state animals is known, but it was not until infrared thermography
images
were used in combination with behavioural "fidgeting" information about an
animal that a correlation between an animal's metabolic efficiency in a non-
steady state was observed, and that such information could be used to identify
animals having a positive or negative residual feed intake. Due to the
requirement that IRT information be taken from animal's having a normal range,
non-steady state animals skew data and are expressly excluded from known IRT
methods.
Using embodiments herein, the present apparatus and method may be
used to determine an animal's metabolic efficiency when the animal is in a non-
steady state. Animals are counterintuitively inducted into non-steady states
before IRT information is collected and used to determine the animal's
metabolic
efficiency. The present apparatus and method enables a fast (e.g. less than 24
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hours), effective and automatic way to rank, breed and/or cull animals,
improving
product quality, reducing operation costs, and minimizing greenhouse gas
emissions.
In one embodiment, a method of determining metabolic efficiency of an
5 animal is provided, the method comprising inducing the animal into a non-
steady
state, collecting infrared thermography information about the animal, and
utilizing
the information to determine the metabolic efficiency of the animal. Non-
steady
states may be induced via various means such as, for example, merely removing
feed from the animal (e.g. instituting a postprandial period), introducing a
disease
(e.g. viral infection, bacterial infection, fungus, micoplasmid or mold),
causing an
increase in heat production (e.g. providing the animal with an energy bolus),
or
hormonally inducing a reproductive or estrus state. Using a predictive model,
IRT
images can be collected and rapidly analysed within 24 ¨ 72 hours, and
preferably in less than 24 hours, following the induction of the non-steady
state.
In another embodiment, an apparatus for determining the metabolic
efficiency of an animal induced into a non-steady biological state is
provided, the
apparatus comprising at least one infrared thermography camera for obtaining
infrared information about the animal, and a processor in wired or wireless
communication with the camera for receiving and processing information to
determine the animal's metabolic efficiency using a predictive model. The
apparatus further comprises animal identification means.
FIGURES
Figure 1 depicts an embodiment of an apparatus for collecting infrared images
about an animal according to embodiments described herein,
Figure 2 shows a top view schematic of an example embodiment of Figure 1,
Figure 3 shows a graphical representation of infrared thermography information
correlated against residual feed intake information, and
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Figure 4 is a table showing the comparison of infrared thermography
information
and residual feed intake information for animals induced into a non-steady
state
via feed withdrawal.
DESCRIPTION OF EMBODIMENTS
Using embodiments described herein, an apparatus and method for the
rapid detection of metabolic efficiency in animals is provided. It was
discovered
that the infrared thermography (IRT) information about an animal in a non-
steady
biological state correlated with the metabolic efficiency of that animal and
could
be used to identify animals having a positive or negative residual feed
intake.
Herein, animals are induced into non-steady biological states (e.g.
postprandial,
disease, increased heat production, reproduction or estrus), and non-invasive,
real-time infrared thermography (IRT) images about the animal are collected
and
utilized to rapidly determine the animal's metabolic efficiency.
Non-steady states in animals can include conditions in which an animal's
endocrine, physiological or metabolic values are in a state of flux (e.g. due
to
stress or growth phases), rather than a "steady" state where such values are
in
normal ranges. Non-steady states may be induced via any means such as, for
example, withdrawing the animal's feed to institute a postprandial period,
infecting the animal with a disease or illness, or causing the animal to
increase its
heat production (e.g. via an energy bolus). Using a predictive model, the
animal's
metabolic efficiency can be determined, enabling producers to rapidly rank,
breed and/or cull animals, improving animal product quality and quantity, and
reducing greenhouse gas emissions.
While the present disclosure generally relates to cattle, it is understood
that other livestock animals, including farmed domestic ruminant and
monogastric animals such as swine, horses, bison, sheep, deer, llama, elk,
goats, ostrich, and poultry (e.g. chickens, turkeys, ducks, and geese can be
used.
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For the purposes of this specification, the terms "metabolic efficiency",
feed efficiency", "feed conversion efficiency", "growth efficiency" and
grammatical
variations thereof refer interchangeably to the efficiency of feed utilisation
of an
animal. In other words, these terms refer to the growth of the animal or unit
of
exported protein production, such as milk, per unit of resource or feed input.
These terms can also refer to a unit of measuring the amount of feed (or
energy)
consumed per unit of growth of an animal, such as body weight, muscle mass or
fat mass gain. The measurement of resource inputs are further defined to
include
or be represented by feed input such as grain or hay, feed component inputs
such as carbon, nitrogen, calcium, phosphorus or other sources of energy.
Infrared thermography may be utilized to measure energy loss in joules,
providing a direct measure of energy use of an animal, rather than a
calculated
value such as reed required per gain.
Having regard to Figure 1, according to embodiments herein, the present
apparatus and method may comprise a receiving area 10 equipped with a multi-
animal scanning apparatus comprising a processor 12, at least one camera 14
(shown in camera housing) and an enclosure 16 for receiving animals, the
enclosure 16 being optionally equipped with animal identification means.
Receiving area 10 may be any configuration designed for the receipt of one or
more animals from one or more direction, provided that the at least one camera
14 is positioned to collect accurate infrared thermography images about the
animals without having to restrain or reduce the animal's movement. For
example, receiving area 10 may any pen or pasture with enclosure 16 being a
water or food station, or any other such design that accomplishes the
functions
described herein. A water station may be preferred given that animal's in non-
steady states, such as illness, cease eating due to loss of appetite before
they
cease drinking.
Having regard to Figure 2, a top down view of an exemplary receiving
area 10, having enclosure 16 positioned between two side panels 1, is shown. A
two-water bowl float system 2 (e.g. Ritchie Cattle Fountains, Conrad IA, USA),
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positioned between optional panels 3 for centering/positioning the animal's
head,
can be accessed by the animal entering the enclosure 16. Optionally, viewing
windows 4 may be provided for observing the animal.
Enclosure 16 may be equipped with animal identification means such that
images taken from each unique animals can be distinguished (e.g. ear tags,
RFID tags, pain or other markings, implanted tags, or the like). For example,
Figure 2 provides at least two in-phase loop antennae 5 mounted at or near the
receiving area 10 for receiving digitally transmitted information from unique
RFID
tags on each animal. The antennae 5 may be connected to an RFID control
module or reader 6 (e.g. Allfex PNL-OEM-MODLE-3) capable of transmitting
radio frequency signals and reading said signals. Optional electromagnetic
shielding means 7 may be provided to prevent the improper reading of RFID tags
on animals that are not within the enclosure.
Enclosure 16 may further be equipped with at least one infrared
thermography camera 8 for acquiring thermal images or videos about the
animals. In embodiments contemplated herein, the cameras 8 may be capable
of detecting radiation in the infrared range of the electromagnetic spectrum
(roughly 5,000-15,000 nanometers or 5 ¨ 15 pm) and producing images related
thereto, called thermograms. Cameras 8 may be capable of obtaining at least 1
¨
60 images/second (e.g. FLIR S60 broadband camera; FLIR Comp., Boston, MA).
Cameras 8 may be capable of transmitting IRT information about the animal to
processor 12 via wired or wireless. It is understood that multiple cameras 8
may
be used to achieve greater accuracy (e.g. by collating more information to
give a
clearer result), and to provide sufficient information to minimize having to
move
or reposition the animal for accurate measurements. Cameras 8 may be
manually or automatically operated (e.g. via motion sensor triggered by the
animal). Cameras 8 may be hand held or mounted to the receiving area 10.
Where mounted, any known mounting means for positioning and rotating
(manually or automatically) the cameras 8 may be used. Rotating means may be
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automatic and comprise a geared-head motor connected to the camera 8 for
powering rotation thereof.
Cameras 8 may be positioned to capture at least one IRT image about the
animal from at least one view. Radiated temperature is known to be heat lost
by
an animal due to radiation as electromagnetic radiation (e.g. in most mammals,
about 40 ¨ 60% of the heat lost is due to radiated heat lost and much is in
the
infrared range). Any area providing an accurate thermal reading of radiated
heat
from an animal for use in determining non-steady states may be used. For
example, images may be obtained from animals at or near a location providing
an accurate radiated peripheral temperature reading about the animal such as a
dorsal, lateral, distal, ventral, frontal, facial region, or combination
thereof. In one
embodiment, IRT images may be captured from the animal's orbital area (e.g. at
the eye 1 cm surrounding the eye). Images taken from each region may or may
not cover the entire animal surface from that view and an image may only
include
a portion of a given view. The images and thermal information derived
therefrom
may be stored after capture via any known electronic memory means.
Processor 12 may be operative to control camera positioning, the
frequency and timing of infrared images taken for each animal, and for
receiving,
storing and processing the infrared images received from the camera 8.
Instrument integration and the hardware and software used in embodiments
herein was designed and developed, in part, at the Lacombe Research Centre,
Lacombe, Alberta, Canada. Processor 12 may allow for the present system to be
automatically monitored and controlled remotely, and may be capable of
producing a final data report about each animal.
Processor 12 may further be operative to receive animal identification
information corresponding to each image, to calculate a value of statistical
measurement of temperature about the animal, and to utilize a predictive model
to determine the metabolic efficiency about the animal. Image data may be
analysed used known means, and the statistical measurement of temperature
data for each IRT image may be a measure of central tendency such as the
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mean or average, mode or median. Statistical measures of dispersion may also
have utility and would include, without limitation, the variance, range,
standard
deviation, coefficient of variation and standard error. Measurement may also
be
made of the calculation of nonparametric or rank scale values. Reference to
the
5 predictive model may be defined as any mathematical model that has high
accuracy in predicting feed efficiency as units of tissue accumulation per
unit of
feed resource. Statistical measurements of temperature data for each image may
be included as input variables. The animal metabolic or feed efficiency may be
determined by the predictive model:
ADG LT
GE = _____________ x __
10 EFC:
where GE represents the metabolic or growth efficiency, ADG represents
the average daily grain intake of the animal, EFC represents the estimated
feed
consumption, IRT represents the infrared thermographic value and W represents
the body weight of the animal. The predictive model may be developed from a
sample population of animals of the same species and of sufficient numbers
that
enable statistically significant comparison. Such a sample size may contain as
few as three but preferably greater than 100 animals. Any one or more of the
following factors may be used in the predictive model: body weight,
compositional data, or feed consumption. Use of the image data in the
predictive
model may be through any known statistical techniques to determine the
relationship between the input and output variable including multiple linear
regression, cluster analysis, discriminate analysis, curve fitting, ranking,
and
artificial neural network learning.
The GE may be measured indirectly by reference to the residual feed
intake or "RFI". The RFI for a group of animals may range from -2.0 to +2.0
depending on the animal feed efficiency where 0.0 represents a predicted feed
efficiency. RFI numbers greater than this (+) represent poor efficiency
animals
requiring more food than predicted and/or converting that food to waste energy
such as heat. RFI numbers lower than this (-) represent higher feed
efficiencies
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where less food may be required or where the animal is better able to convert
the
feed to energy. The RFI may range from -1.5 to +1.5.
It is an advantage of the present non-invasive method that measurements
taken from animals in induced non-steady biological states can be done with
minimal confounding factors such as human touching, movement or startling of
the animal. Each of these factors are known to cause an elevation in
temperature, impacting the animal's feed efficiency, measurements taken about
the animal, and accuracy of results. It is understood that the present method
may
be used alone or in combination with other measurement methods such as body
weight, compositional data or feed consumption.
It should be understood that animals having a higher metabolic feed
efficiency tend to produce fewer by-products, and instead produce more energy
than is captured for growth and therefore tend to be fitter, stronger and
healthier
animals. This in turn leads to better quality meat, milk, and/or fibre product
from
the higher efficiency animals.
It is contemplated that the present apparatus and method may be used in
the genetic selection of animals, which can be useful for animal producers
breeding stock animals, dairy cattle and show animals. For instance, animals
determined to have a negative metabolic efficiency (negative residual feed
intake) may be culled, removed from breeding pens, or combinations thereof,
whereas animal found to have a positive metabolic efficiency can be selected
for
future breeding, having genetic material removed and used to produce
transgenic animals with increased RFI, selected for and used for producing
wool
or other animal derived fibre, for racing, for breeding stock and show, to
reduce
greenhouse gas emissions, or combinations thereof.
It is contemplated that one advantage of the present apparatus and
method may be the ability to increase the feed efficiency of an animal group
by
first determining the metabolic efficiency of animals in the group and
selectively
breeding animals having a high metabolic efficiency with each other and/or
culling animals in the group with a low feed efficiency. Animals having
similar
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feeding efficiencies can also be grouped together with growth finishing diets
tailored to the measured growth efficiency of the animal group. Further, the
feed
efficiency information may be used to develop or test diet efficiency for a
given
group of metabolically similar animals, that is ¨ to determine which specific
types
of resource inputs (diet types) result in the greatest efficiency of growth.
It is contemplated that another advantage of the present apparatus and
method may be the ability to increase the quality and/or quantity of animal
derived products in an animal group by the first determining the metabolic
efficiency of animals in the group and selectively breeding animals having a
high
metabolic efficiency with each other and/or culling animals in the group with
a low
feed efficiency.
It is known that animals with poor metabolic efficiency convert more feed
into waste products than energy. It is contemplated that another advantage of
the
present apparatus and method may be the ability to decrease the greenhouse
gas emitted from animals in a non-steady state in a group by first determining
the
metabolic efficiency of the animals in the group and selectively breeding
animals
having a high metabolic efficiency with each other and/or culling animals in
the
group with a low feed efficiency, increasing the group efficiency and
decreasing
greenhouse gas emissions from the animal group.
It is contemplated that another advantage of the present apparatus and
method may be the ability to utilize radiated temperature information to
evaluate
causes of heat loss not necessarily related to animal growth (e.g. non-steady
state heat production arising from physiological stress and the catabolism of
tissue, shivering thermogenesis, disease and infection, and the presence of
tumours)
It is contemplated that another advantage of the present apparatus and
method may be the ability to group or pen animals having similar metabolic
efficiencies together, producing animals having similar growth patterns, which
can be expressed by a lower degree of variation in animal traits (e.g. carcass
yield, efficiency of diet utilization). Grouping and selecting animals could
result in
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the production of animal product having more consistent quality, production
volumes (milk), fibre growth and fibre characteristics (wool) and other
characteristics.
Generally, the present apparatus and method aim to provide means for
determining the metabolic efficiency of an animal via a non-invasive, time-
efficient and comparatively inexpensive method, which enables the selection
and
grouping of the most efficient animals for optimizing resource usage and
reducing greenhouse gas production.
The following examples are provided to aid the understanding of the
present disclosure, the true scope of which is set forth in the claims. It is
understood that modifications can be made in the system and methods set forth
without departing from the spirit or scope of the same, as defined herein.
EXAMPLES
Example 1 ¨ METABOLIC EFFICIENCY RANKING UNDER NON-STEADY
STATE CONDITIONS INDUCED BY FEED WITHDRAWAL
Sixty yearling bulls averaging 500 kg body weight of British or Continental
breeding and fed ad libitum a cereal grain silage diet which met NRC feeding
recommendations (NRC 1996) were used. Bulls were monitored for feed intake
for the previous one hundred days using an automated feed weight measuring
system (Growsafe , Airdrie, Alberta). Using the feed intake data and knowledge
of weight gain, the residual feed intake values (RFI) representing the actual
feed
required per unit of weight gain displayed by an animal compared to the
predicted amount of feed required per gain was calculated using known methods.
Animals displaying a greater growth efficiency will have lower RFI values
compared to animals with lower growth efficiency. For example, an RFI value of
-1 represents an animal consuming 1 kg of feed less per day for the same body
weight gain than would be predicted. Likewise, an animal displaying an RFI
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value of 1 represents a heifer consuming 1 kg of feed per day more for the
same
body weight gain than would be predicted.
Following the feeding trial used to evaluate the RFI values, the bulls were
removed and held off feed for approximately 18h (i.e. postprandial period of
18
hours) with free access to water and a wood shavings area to lay on. This
process and period of feed restriction constituted a moderate nutritional
challenge to the animals.
After the postprandial period of feed restriction, infrared thermographs
were taken of the bulls using a hand held FLIR S60 broad range camera. Care
was taken to fix the focal distances and angles for the images. Radiated
temperatures were calculated using known procedures, and values were
collected for many anatomical views (including the cheek) representing
approximately a 5 cm X 5 cm area over the mandible.
RFI values between -1.4 to +0.9 were observed, representing a typical
variation in metabolic efficiency in cattle of this type. Animals displaying
greatest
efficiency also displayed the lowest baseline radiated temperature, while
animals
with the highest RFI values displayed the highest radiated temperatures.
Having
regard to Figure 4, when the initial or baseline values for radiated
temperature
were ranked using all animals with the RFI values there was a significant
(P<0.05) relationship between RFI and radiated temperature.
There are many factors that determine or influence growth efficiency in an
animal. Of these factors, thermoregulation and protein synthesis, and heat
production are known to have a significant influence. Figure 4 demonstrates
that
managing heat production, as evident by the reduced radiated energy loss in
the
infrared spectrum in more efficient animals, is one biological strategy that
can be
used to control or retain growth efficiency advantages under periods of
adversity
such as nutritional insufficiency.
By monitoring the radiated heat loss in animals under a moderate dietary
challenge or non-steady state it appears that this relationship or variation
in
growth efficiency can be revealed. The results may be used to stratify the
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grouping of animals into greater and lesser efficient groups to more
effectively
take advantage of these traits through culling inefficient animals and/or
breeding
more efficient animals. For example, animals can be stratified into quartile
groups
whereby the third top most efficient animals (low RFI and low IRT) could be
5 separated from the lowest third most efficient animals (high RFI and high
IRT).
The most efficient animals could be used for herd selection and the least
efficient
animals culled. This stratification could also be used to direct animals to
different
feeding regimes.
10 Example 2 - GROWTH EFFICIENCY RANKING UNDER NON-STEADY STATE
CONDITIONS INDUCED BY A DISEASE STATE
Fifteen Hereford X Angus crossbred seven month old heifers having an
average 189 kg live weight were maintained on a balanced cubed alfalfa hay
based diet which provided 1.5 times the calculated maintenance diet level for
15 these animals. The heifers were housed in groups of five animals in three
separate rooms within a bio-containment facility kept at thermo-neutral
temperature and humidity. Ad libitum fresh water and rubber mats for bedding
were provided for all animals.
In this case, differences in growth efficiency were determined by inducing
into a non-steady disease state. For example, the non-steady disease state
comprised introducing the animals to a viral disease or more specifically,
Bovine
Viral Diarrhea or "BVD". The animals were thus placed into a condition of non-
steady state via a disease induction model. Briefly, the present disease
induction
model involved the introduction of live virus particles to the treatment
animals
(n=10) via a nasal gavage. Control heifers received a sham gavage with saline.
Body weight was monitored on all animals before and after. Radiated
temperatures were monitored on the animals using an Inframetrics broad band
740 camera (Inframetrics Comp.). Infrared images from multiple views of the
calves were taken with focal distances and angles standardized.
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During the infective stage of the trial the orbital (eye plus surrounding 1 cm
of skin) maximum radiated temperatures for the BVD infected calves displayed
an increased change in temperature or delta T of 2.43 C. Changes were
apparent within 24 ¨ 78 hours, and preferably within 24 hours of the infective
stage. Control or non-infected calves did not display a change in orbital
temperatures. Infected calves displayed a lower weight change average of 0.3
kg/day increase in body weight compared to an average of 0.54 kg/d weight gain
for the control calves (P=0.046 one tail unequal variance least squares
analysis).
Calves displaying the lowest weight gain had the highest radiated orbital
temperature. The calves were all provided the same quality and quantity of
diet
and with the exception of the peak days of infection, consumed similar amounts
of feed. As such, the growth efficiency was lower in the animals displaying a
higher temperature or conversely, greater growth efficiency was seen in
animals
with a lower radiated temperature under the conditions of non-steady state
induced by viral model.
Example 3- GROWTH EFFICIENCY RANKING UNDER NON-STEADY STATE
CONDITIONS INDUCED BY INCREASING HEAT PRODUCTION
In this example, an increase in heat production (non-steady state) was
induced via providing an energy bolus or providing the animal with feed. It is
well
established that the consumption of food will result in what is referred to as
a
heat increment of feeding. This is due to a host of factors and when an animal
is
experiencing this heat increment they are considered to be in a non-steady
physiological state. An animal that is more efficient will retain more of the
gross
energy from a meal loosing less of that energy to the environment. That
difference should display itself as a lower post meal radiated temperature in
more
efficient animals. It is understood that other means for increasing heat
production
in animals could be used.
Following the measurement of base line radiated measurements, heifers
were offered 2.5 kg of rolled barley while contained in their individual pens.
It
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was anticipated that the animals would consume their meal quite quickly since
they had been off feed or in a postprandial period for some time
(approximately
18h). The animals were then followed for some 6h collecting infrared radiated
images at scheduled times. It was observed that two of the heifers consumed
96-100% of their diet. These animals also were known to have some significant
difference in their growth efficiency with difference in RFI as measured in
Example 1. These two heifers were followed and measured via IRT for another
four hours collecting infrared images every 20-30 minutes.
Consistent with the results of Example 1, the efficient animal (RFI -0.7)
was seen to display firstly a lower baseline cheek temperature (24.7 C)
compared to the lesser efficient animal (RFI 0.83) showing a baseline cheek
temperature of 26.5 C. Also, for these two animals, the more efficient animal
(RFI -0.07) displayed a change in temperature (delta T) over the four hours of
2.3 C on the cheek image compared to a higher delta T of 2.8 C for the less
efficient animal.
More efficient animals appear to display a lower post meal radiated
temperature reflecting a greater retention of energy, enabling the present
method
to be used for measuring metabolic efficiency in non-steady state animals.
These examples aim to illustrate several types of non-steady state models
whereby animals displaying greater growth efficiency also display a lower
baseline radiated thermal value and a lower delta T value when exposed to a
stressful situation. It is understood that the present models may be utilized
in any
farmed livestock animals, and that any means for effectively inducing animals
into a non-steady state may be considered.
Aspects of IRT measurement and use of this technique in respect of
evaluating animal feed efficiency have been described by way of example only
and it should be appreciated that modifications and additions may be made
thereto without departing from the scope of the claims herein. The scope of
the
claims should not be limited by the preferred embodiments set forth in the
CA 02854345 2014-06-16
18
examples, but should be given the broadest interpretation consistent with the
description as a whole.
