>From:prato@imiucca.csi.unimi.it (Emanuela Prato Previde)
>Subject:Re: reinf definition
>
>Jon Bowen wrote
>
>>Aren't reinforcement and punishment just different ways of looking at the
>>same contingencies.
>>I am getting confused, and I thought that I understood this!
>>
>>For the cow:
>>1) non-shock and non-fence-touching are contingent.
>>and
>>2) shock and fence-touching are contingent.
>>
>>Negative reinforcement is an increase in a behaviour (in this case
>>non-fence-touching) caused by removal/avoidance of an aversive stimulus:
>>case 1.
>>
>>Positive punishment is the decrease in a behaviour by the delivery of an
>>aversive stimulus: Case 2.
>>
>>Is the difference that the cow cannot be aware of the
>>non-shock/non-fence-touching contingecy until the fence has been touched?
>>
>>Jon
>****************************************************************************
>Dear Jon,
>
>as far as I know in traditional learning theory, the term reinforcement is
>used to refer to any event (stimulus) that determine an increase in a
>given response (or behavior) that immediately follows it (contingency
>between two events, a stimulus and a response). According to Skinner,
>there are two different types of reinforcement: positive and negative
>reinforcement. Both positive and negative reinforcement do produce an
>increase in response: a positive reinforcement is, for instance, food
>presentation after bar pressing by a rat; the rat will increase responding
>in order to get food; negative reinforcement is shock presentation being
>interrupted after bar pressing: the rat will press the bar very
>efficiently in order to avoid the shock. In both cases there is a
>contingency between stimuli and responses.
>Punishment is a different thing from reinforcement and always decrease the
>emission of the behavior; that is, if a rat presses a lever it will
>receive a shock: this contingency will reduce bar pressing by the rat.
>Punishmen is generally considered a way of suppressing undesired behaviors
>(eventhough it can produce other interfering emotional responses like
>unconditioned fear responses)
>As far as I know the term Positive punishment does not exist: you might be
>confusing it with negative reinforcement.
>For the cow:
> shock and fence-touching are contingent: when the cow touch the fence she
>get a shock (punishment): the cows learns that if she avoids touching the
>fence she also avoid getting the shock
>
> It is true that non-shock and non-fence-touching are contingent; but it
>is also true that the cow cannot be aware of the
>non-shock/non-fence-touching contingecy until she has experienced that
>fence touching means getting a shock (punishment).
>These topics about reinforcement and punishment are considered and
>discussed in great detail in a book I love and use when teaching:
>Learning, behavior and cognition, second edition, 1993, by David
>Lieberman, Brooks/Cole Publishing Company.
>
>Hoping this might be of some help,
>
>Regards,
>
>Emanuela Prato Previde
>
>
From: IN%"ilsmith@utkux.utcc.utk.edu" "Ione Smith" 13-NOV-1998 08:10:34.94
To: IN%"cgaboury@total.net" "Chantal Gaboury"
CC: IN%"applied-ethology@sask.usask.ca"
Subj: RE: reinf definition
Woops, I thought I sent this yesterday but it's still here in my box.
Please excuse if this turns out to be a duplicate.
On Thu, 12 Nov 1998, Chantal Gaboury wrote:
>Consider this: A (non-masochistic :-) ) cow recieves an electic shock
>when it comes into contact with an electric fence.
>
>1)The electric shock is positive reinforcement for avoidance behaviour
>(avoiding the fence.)
No, it's negative reinforcement for avoiding the fence. The shock STOPS
when the avoiding behavior BEGINS.
Ione
-- Ione L. Smith, DVM -- Department of Comparative Medicine --
-- University of Tennessee, College of Veterinary Medicine --
==================================================
http://funnelweb.utcc.utk.edu/~ilsmith/SVME.html
The Society for Veterinary Medical Ethics
http://funnelweb.utcc.utk.edu/~ilsmith/ethics.html
for all sides of the AR/AW/anti-AR debate
==================================================
I play, therefore I am. -- Renee DeCat
From: IN%"poli@imiucca.csi.unimi.it" "Marco Poli" 13-NOV-1998 08:29:56.78
To: IN%"applied-ethology@sask.usask.ca"
CC:
Subj: RE: reinf definition
Going back to the origins, the following quotations may be useful to the
solution of the question:
"A ... better ... way is .. to define _positive_ reinforcers as those
stimuli which strengthen responses when _presented_ (e.g. food strengthens
bar-pressing ...), and _negative_ reinforcers as those which strengthen
when they are _removed_"
F.S. Keller & W.N. Schoenfeld, 1950. Principles of Psychology, Appleton
Century Crofts, New York
"It seems reasonable to distinguish between those reinforcers whose effect
is to increase the probability of instrumental responses, and those whose
effect is to decrease the probability of such responses. Thorndike (19011)
referred to the former as satisfiers and to the latter as annoyers. Here
they will be referred to as appetitive reinforcers or rewards, and aversive
reinforcers or punishing stimuli".
N.J. Mackintosh, 1974. The Psychology of Animal Learning, Academic Press,
London
"In order to insure the occurrence of learning, it is necessary to employ
.... the operation of reinforcement. To paraphrase Skinner (1938),
reinforcement refers to the occurrence of one of a certain class of events
called reinforcers, in the proper relation to the to-be-learned response;
the proper relation being that which tends to increase the probability that
the response so reinforced will recur with representation of the situation.
The failure to reinforce a response decreases the probability of occurrence
of the response. Some events possess reinforcing power; others do not. The
question of which events do have it is an empirical one, to be answered by
a series of defining experiments designed to identify the conditions which
are effective in producing learning. The usage of the term reinforcement in
the preceding treatment is an empirical one. The statement that such
events, placed appropriately with respect to some response, lead to an
increase in the probability that the response will recur in the situation
is a statement of the empirical law of reinforcement (effect), sometimes
called the "weak" law of effect. Its acceptance does not commit the user to
any stronger version of the law of effect such as Hull's drive-reduction
hypothesis".
G.A. Kimble, 1968. Hilgard and Marquis' Conditioning and Learning. Appleton
Century Crofts, New York
best wishes,
Marco
*************************
Marco D. Poli
Istituto di Psicologia
Facolta' di Medicina
Universita' di Milano
via T. Pini 1
20134 Milano, ITALY
phone: + 39 02 21210200
fax: + 39 02 26413376
e.mail: poli@imiucca.csi.unimi.it
*************************
From: IN%"scrowell@calc.vet.uga.edu" "Sharon Crowell-Davis" 13-NOV-1998 08:38:18.95
To: IN%"ilsmith@utkux.utcc.utk.edu"
CC: IN%"applied-ethology@sask.usask.ca"
Subj: RE: reinf definition
> >Consider this: A (non-masochistic :-) ) cow recieves an electic shock
> >when it comes into contact with an electric fence.
> >
> >1)The electric shock is positive reinforcement for avoidance behaviour
> >(avoiding the fence.)
>
> No, it's negative reinforcement for avoiding the fence. The shock STOPS
> when the avoiding behavior BEGINS.
To be picky, the cow probably makes a transition through the two
major categories of negative reinforcement. The first time it is
shocked, moves away, and "escapes" the shock. Subsequently it
"avoids" the shock by staying away. Moving away and staying away are
both negatively reinforced. The behavior increases. The stimulus is
escaped or avoided.
Often positive punishment and negative reinforcement are two sides of
the same coin. The cow has been positively punished for walking up
to the fence and touching it (the presence of the stimulus causes
the behavior to decrease), and negatively reinforced for walking away
and staying away (the removal/absence of the stimulus causes the
behavior to increase).
Sharon Crowell-Davis
**********************************************
Sharon L. Crowell-Davis DVM, PhD
Diplomate, American College of Veterinary Behaviorists
College of Veterinary Medicine
University of Georgia
Athens, Georgia 30602
scrowell@calc.vet.uga.edu
If a little knowledge is dangerous,
where is the man who has so much
as to be out of danger?
T.H. Huxley
On Elementary Instruction in Physiology
From: IN%"wattsjon@duke.usask.ca" "Jon Watts" 13-NOV-1998 09:19:14.94
To: IN%"chris.sherwin@bristol.ac.uk" "Chris Sherwin"
CC: IN%"Kattykorn2@aol.com", IN%"applied-ethology@sask.usask.ca"
Subj: RE: No Messages
On Mon, 17 Feb 2003, Chris Sherwin wrote:
>
> Yeah, and we scientists were 'told off' for spoiling debate and
> appearing pompous by giving references to pertinent work. So, who
> does that leave to further discussions?
>
> Chris
>
Hey, not by me either! I'm all for it. I've done it and I've been pleased
when other people have done it. A couple of times though I've seen
discussion stalled when someone just throws out a reference, almost as a
rebuke, as though to say, "If you people knew anything at all you'd know
this is the first and last word on the subject and further discussion is
beside the point". That's a little different from offering pertinent
references as PART of the discussion. Besides, to my way of thinking,
research literature taken as dogma is not unlike faith in the literal
truth of religious scriptures. More soothing to the soul than stimulating
to the mind.
Jon
-----------------------------------------------------------------------------
Jon Watts (___) ) )
University of Saskatchewan |o o|___________/ (
Dept of Herd Medicine O \#/ | )
and Theriogenology |bser| | Statistical | (
Western College of Vet. Med. |vati| | analysis | )
52 Campus Drive |ons.| \___________/| *&
Saskatoon ------ || || %$#@
S7N 1B4 / \ || || ^*@*~
Canada &^%%#$@
wattsjon@duke.usask.ca "The Holy Cow"
-----------------------------------------------------------------------------
From: IN%"rondog@btinternet.com" "Jon Bowen" 13-NOV-1998 09:35:04.79
To: IN%"applied-ethology@sask.usask.ca"
CC:
Subj: RE: reinf definition
This is a multi-part message in MIME format.
--Boundary_(ID_KeyFMShtN9enDMFBExlb5g)
Content-type: text/plain; charset="iso-8859-1"
Content-transfer-encoding: quoted-printable
Thanks to Emanuela for her comments,
I think the term 'positive punishment' is a proper term, but I am not =
sure where I heard it!!!
Forgive me for rattling on about this again, but I have read Liebermann =
and plenty of primary references and i still see things this =
way......perhaps if I explain myself better then someone can understand =
waht i am going on about and then correct me if I am wrong.
First the punishment thing:
The distinction between positive and negative punishment is the same as =
between positive and negative reinforcement.
all punishment reduces the emission of the behaviour.
Positive punishment is delivery of an aversive stimulus and negative =
punishment is that which occurs when a 'desirable' stimulus is witheld.
Positive and negative punishment plus positive and negative =
reinforcement are sides of the same coin.
Next the cows:
The most subtle contingencies must be the everyday non-event =
contingencies where patterns of behaviour are selected and reinforced =
by, for example, the absence of aversive consequences. I think Lieberman =
mentions this in his book.
The danger must be to consider that associative learning only occurs =
when an extraordinary event, such as being shocked, happens.
True, non-shock/non-fence-touching(but standing close to it) contingency =
exists only after the shock; but so does the shock/fence-touch =
contingency for the same reason; neither can be learned until the shock =
is experienced.
Perhaps evidence of this comes from watching cattle when they experience =
shocks from a fence for the first time.
After the shock they withdraw rapidly and then only gradually begin to =
approach the fence. Initially all proximity to the fence is avoided =
because the exact contingency learned is not specific. After several =
hours of trying to graze closer and closer to the fence the =
non-shock/non-fence-touching(but standing close to it) contingency is =
consecutively repeated and the animal learns graze normally without =
touching the fence. This is presumably the mechanism of extinction =
working for all contingencies that are not quite the same as the one =
that actually resulted in shock.
Is the best way to consider operant conditioning to simply think of a =
creature wandering through life comparing two sets of information all =
the time; one is what is happening in the perceptual 'now' and the other =
is the record of what has happened in the 1-2 seconds of preceding time. =
This comparison is continuous and also includes information about the =
significance of previous learned stimuli and events.=20
Is this right, or complete cobblers?!
Jon
--Boundary_(ID_KeyFMShtN9enDMFBExlb5g)
Content-type: text/html; charset="iso-8859-1"
Content-transfer-encoding: quoted-printable
Thanks to Emanuela for her =
comments,
I think the term 'positive =
punishment'=20
is a proper term, but I am not sure where I heard =
it!!!
Forgive me for rattling on about this =
again, but I=20
have read Liebermann and plenty of primary references and i still see =
things=20
this way......perhaps if I explain myself better then someone can =
understand=20
waht i am going on about and then correct me if I am wrong.
First the =
punishment=20
thing:
The distinction between positive and =
negative=20
punishment is the same as between positive and negative=20
reinforcement.
all punishment reduces the emission of =
the=20
behaviour.
Positive punishment is delivery of an =
aversive=20
stimulus and negative punishment is that which occurs when a 'desirable' =
stimulus is witheld.
Positive and negative punishment plus =
positive and=20
negative reinforcement are sides of the same coin.
Next the cows:
The most subtle contingencies must be =
the everyday=20
non-event contingencies where patterns of behaviour are selected and =
reinforced=20
by, for example, the absence of aversive consequences. I think Lieberman =
mentions this in his book.
The danger must be to consider that =
associative=20
learning only occurs when an extraordinary event, such as being shocked, =
happens.
True, non-shock/non-fence-touching(but =
standing=20
close to it) contingency exists only after the shock; but so =
does the=20
shock/fence-touch contingency for the same reason; neither can be =
learned until=20
the shock is experienced.
Perhaps evidence of this comes from =
watching cattle=20
when they experience shocks from a fence for the first =
time.
After the shock they withdraw rapidly =
and then only=20
gradually begin to approach the fence. Initially all proximity to the =
fence is=20
avoided because the exact contingency learned is not specific. After =
several=20
hours of trying to graze closer and closer to the fence the=20
non-shock/non-fence-touching(but standing close to it) contingency is=20
consecutively repeated and the animal learns graze normally without =
touching the=20
fence. This is presumably the mechanism of extinction working for all=20
contingencies that are not quite the same as the one that actually =
resulted in=20
shock.
Is the best way to consider operant =
conditioning to=20
simply think of a creature wandering through life comparing two sets of=20
information all the time; one is what is happening in the perceptual =
'now' and=20
the other is the record of what has happened in the 1-2 seconds of =
preceding=20
time.
This comparison is continuous and also =
includes=20
information about the significance of previous learned stimuli and =
events.=20
Is this right, or complete =
cobblers?!
Jon
--Boundary_(ID_KeyFMShtN9enDMFBExlb5g)--
From: IN%"ilsmith@utkux.utcc.utk.edu" "Ione Smith" 13-NOV-1998 10:05:12.53
To: IN%"scrowell@calc.vet.uga.edu" "Sharon Crowell-Davis"
CC: IN%"applied-ethology@sask.usask.ca"
Subj: RE: reinf definition
On Fri, 13 Nov 1998, Sharon Crowell-Davis wrote:
>Often positive punishment and negative reinforcement are two sides of
>the same coin. The cow has been positively punished for walking up
>to the fence and touching it (the presence of the stimulus causes
>the behavior to decrease), and negatively reinforced for walking away
>and staying away (the removal/absence of the stimulus causes the
>behavior to increase).
Right. And the shock can't be a reinforcer for anything until after the
first time the cow experiences it. So it all depends on which behavior
you're talking about, AND which point in time is being referenced.
Ione
-- Ione L. Smith, DVM -- Department of Comparative Medicine --
-- University of Tennessee, College of Veterinary Medicine --
==================================================
http://funnelweb.utcc.utk.edu/~ilsmith/SVME.html
The Society for Veterinary Medical Ethics
http://funnelweb.utcc.utk.edu/~ilsmith/ethics.html
for all sides of the AR/AW/anti-AR debate
==================================================
I play, therefore I am. -- Renee DeCat
From: IN%"abrereton@tinet.ie" 13-NOV-1998 11:56:29.96
To: IN%"applied-ethology@sask.usask.ca" "applied-ethology"
CC:
Subj: feeding patterns in bovines
Robin Walker's reply is interesting but he tells how the instinctive
behaviour of oxen has influenced human behaviour. Our interest is in the
other direction - what is controlling the instinctive behaviour of the
animal?
Nora Lewis's reply raises another question. What is the survival value of
the behaviour we described? If we assume that grazing in the dark is not a
good idea because individuals are exposed to predation and/or because the
individual lying down and the herd forming a close group can conserve
energy during cold nights then a mechanism that initiates grazing at first
light is a good idea. Even if total grazing time is 10 hours and daylight
is only 7 hours it still means that the daylight perod is used fully. I
would add that if the stimulus to begin grazing at dawn is related to the
spectral quality of light than the same stimulus would operate at dusk. The
second stimulus would reinforce the effect of the dawn by bringing grazing
to an earlier close each day. Our preoccupation with the spectral quality
of light arises from the observation that the association with sunrise and
sunset is very close. A mechanism depending on some aspect of light
intensity would not give rise to this close association here because
day-to-day variations in cloud cover are very great.
It is commonly asserted that bovines are day-grazers. Our data suggests to
us that this is not so inthe sense that grazing is restricted exclusively
to daylight hours but the controls that operate tend to favour day-light
grazing.
Anthony
Dr. A. J. Brereton
23 Richmond Hill, Cork, Ireland
Phone +353 21 551866
From: IN%"DMCWILLIAMS@APS.UoGuelph.CA" "Deborah McWilliams" 13-NOV-1998 12:46:32.74
To: IN%"applied-ethology@sask.usask.ca"
CC:
Subj: RE: refs
Hi Jon!
People in "science" use references as a tool - not as a rebuke
(although I can understand how it may be perceived that way). We
work with, and build our work upon, that of other researchers.
Replication is very important in the research process.
Because we use other's work, often as pivotal, we speak in that
manner also. It is also a professional courtesy (ethical and legal
as well) to make others aware that you are quoting someone's work.
Referencing also enables someone who is interested to look up the
work for more information. This is available to anyone - you can go
to your local university and ask for someone to show you how to look
uo a reference.
DebMcW
> Date sent: Fri, 13 Nov 1998 09:02:42 -0600 (CST)
> From: Jon Watts
> Subject: Re: No Messages
> To: Chris Sherwin
> Copies to: Kattykorn2@aol.com, applied-ethology@skyway.usask.ca
>
> On Mon, 17 Feb 2003, Chris Sherwin wrote:
>
> >
> > Yeah, and we scientists were 'told off' for spoiling debate and
> > appearing pompous by giving references to pertinent work. So, who
> > does that leave to further discussions?
> >
> > Chris
> >
>
> Hey, not by me either! I'm all for it. I've done it and I've been pleased
> when other people have done it. A couple of times though I've seen
> discussion stalled when someone just throws out a reference, almost as a
> rebuke, as though to say, "If you people knew anything at all you'd know
> this is the first and last word on the subject and further discussion is
> beside the point". That's a little different from offering pertinent
> references as PART of the discussion. Besides, to my way of thinking,
> research literature taken as dogma is not unlike faith in the literal
> truth of religious scriptures. More soothing to the soul than stimulating
> to the mind.
>
> Jon
>
> -----------------------------------------------------------------------------
> Jon Watts (___) ) )
> University of Saskatchewan |o o|___________/ (
> Dept of Herd Medicine O \#/ | )
> and Theriogenology |bser| | Statistical | (
> Western College of Vet. Med. |vati| | analysis | )
> 52 Campus Drive |ons.| \___________/| *&
> Saskatoon ------ || || %$#@
> S7N 1B4 / \ || || ^*@*~
> Canada &^%%#$@
> wattsjon@duke.usask.ca "The Holy Cow"
> -----------------------------------------------------------------------------
dmcwilliams@aps.uoguelph.ca
Deborah A. McWilliams
Room 043, Animal and Poultry Science
University of Guelph
Guelph, ON, Canada, N1G 2X7
From: IN%"wattsjon@duke.usask.ca" "Jon Watts" 13-NOV-1998 15:30:35.08
To: IN%"DMCWILLIAMS@APS.UoGuelph.CA" "Deborah McWilliams"
CC: IN%"applied-ethology@sask.usask.ca"
Subj: RE: refs
On Fri, 13 Nov 1998, Deborah McWilliams wrote:
> Hi Jon!
>
> People in "science" use references as a tool - not as a rebuke
> (although I can understand how it may be perceived that way). We
> work with, and build our work upon, that of other researchers.
> Replication is very important in the research process.
> Because we use other's work, often as pivotal, we speak in that
> manner also. It is also a professional courtesy (ethical and legal
> as well) to make others aware that you are quoting someone's work.
> Referencing also enables someone who is interested to look up the
> work for more information. This is available to anyone - you can go
> to your local university and ask for someone to show you how to look
> uo a reference.
>
> DebMcW
Thanks for the explanation. I wondered what references were for... Any day
now I'll be sure to go to the library and ask someone how to look one up.
Jon
-----------------------------------------------------------------------------
Jon Watts (___) ) )
University of Saskatchewan |o o|___________/ (
Dept of Herd Medicine O \#/ | )
and Theriogenology |bser| | Statistical | (
Western College of Vet. Med. |vati| | analysis | )
52 Campus Drive |ons.| \___________/| *&
Saskatoon ------ || || %$#@
S7N 1B4 / \ || || ^*@*~
Canada &^%%#$@
wattsjon@duke.usask.ca "The Holy Cow"
-----------------------------------------------------------------------------
From: IN%"MouseNY22@aol.com" 15-NOV-1998 10:37:09.37
To: IN%"applied-ethology@sask.usask.ca"
CC:
Subj: RE: raptors
My prof. has asked me to look at the effect that a predator's presence has on
the amount of time squirrels will spend feeding in a certain area. The answer
seems clear to me already, but I'm sure he wouldn't ask me to do this if I
wasn't going to learn something!
I think I'm going to try using a model and playing back a call, and see which
method works best.
From: IN%"dreyn@sirius.com" 15-NOV-1998 13:03:42.40
To: IN%"applied-ethology@sask.usask.ca" "Applied-Ethology"
CC:
Subj: RE: raptors
MouseNY22@aol.com wrote:
> My prof. has asked me to look at the effect that a predator's presence has on> the amount of time squirrels will spend feeding in a certain area. The answer> seems clear to me already, but I'm sure he wouldn't ask me to do this if I> wasn't going to learn something!
> I think I'm going to try using a model and playing back call, and see which > method works best.
Mouse-
I'm curious...Do you know for sure that the RTH's in your area prey on
squirrels? (I'm quessing you mean red fox tree squirrels?)
I ask because I know the RTH's in my local area tend to avoid the tree
squirrels (nasty bite potential and difficulties in chasing them down
) in favor of jacks, ground squirrels, gophers, etc.
If this were the case, maybe your squirrels would not have the fear
response of the RTH that you would expect?
If there is any question of this, see if you can locate a local
falconer who will be able to fill you in on the favorite dinners of
RT's in your area. (And let me know how it goes...I'd like to know)
Good luck and have fun
Donna Reynolds
(Note to Deb - "Our" non-releasable RTH's are not imprinted...so are
actually sounding in the spring in hopes of calling in an interested
mate. This has actually worked! Besides the spring calling...I
interpret the off-season calls to be aggressive warnings. In the wild,
they will cry out if you get to close to one that is on a kill or in
the nest. Otherwise, the males do seem to warn other RTH's of
"territory infringements". Cheers, Donna)
From: IN%"abrereton@tinet.ie" 15-NOV-1998 18:56:09.91
To: IN%"applied-ethology@sask.usask.ca" "applied-ethology"
CC:
Subj: Fw: cows, grazing
Dr. A. J. Brereton
23 Richmond Hill, Cork, Ireland
Phone +353 21 551866
----------
> From: brereton
> To: joseph.stookey@usask.ca
> Subject: Re: cows, grazing
> Date: 14 November 1998 02:40
>
>
>
> ----------
> > From: joseph.stookey@usask.ca
> > On Wed, 11 Nov 1998, brereton wrote:
> > > So what?:
> > > These patterns are commonly reported. However, we are attempting to
> > > assemble a conceptual explanatory framework for the observed
patterns.
> We
> > > are trying to assemble a mechanistic concept and we make the
> > > assumption that cows don't think.
> > > 1. The primary feature of the pattern is the bout. The bout implies
> that
> > > there is a control that determines when grazing commences and ends.
> Rumen
> > > capacity plays a part but does not explain why snacks are only one
hour
> and
> > > dinner is more than 4 hours.
> > > 2. The rigid association of breakfast and dinner bouts with dawn and
> dusk
> > > implies that light also plays a part.Shorter wavelengths are more
> absorbed
> > > by the atmosphere than longer wavelengths. When the sun is near the
> horizon
> > > the ratio of shorter and longer wavelengths is quite different
compared
> to
> > > mid-day. In plant science it is well known that the ratio of red and
> > > far-red light is detected by plants and is involved in the control of
> > > flowering.(There were some comments recently on Turkeys squabbling in
> > > relation to light that I thought might help but didn't)
> > > 3. That the total grazing time is constant suggests that yet another
> > > control is operating that is related to the state of the animal
> relative to
> > > a target state. And this control relates to a 24-hour period.
> > >
> > Dear Dr. Brereton,
> >
> > I thought you might be interested in some of the work currently being
> > conducted by researchers D. S. Fisher, J.C. Burns and H.F. Mayland from
> > the USDA-ARS stations at Watkinsville, GA, North Carolina State
> > Univeristy, Raleigh and the USDA-ARS, Kimberly, ID. These researcher
> > presented one of the more interesting abstracts at the recent joint
> > meeting of the American Society of Animal Science and the American
Dairy
> > Science Association in Denver. They too are well aware of the diurnal
> > pattern of grazing you observed, with a bout in the morning but more
> > importantly always the longest bout of grazing occurring before and
> around
> > dusk. This grazing pattern seems to be closely associated with the
peak
> > nutritional characteristics of plants. The plant is alway higher in
> > digestible components in the evening, following a day of
photosynthesis,
> > compared to the plant in the morning. By grazing more at the end of
the
> > day, compared to any other times, the animal makes better use of the
> > plant's biology. It makes sense from an evolutionary view for the
animal
> > to graze later in the day. The fascinating research being conducted at
> > the USDA involves the animal's ability to select and prefer forages
> > harvested in the afternoon! They have convincing evidence that cattle,
> > sheep and goats can all select and prefer alfalfa hay or fescue hay
> > harvested in the PM compared to hay from the same field harvested the
> same
> > day, but in the AM. In the trials with alfalfa, three different
harvest
> > of hay were made. "In all three harvests in the three experiments,
> > perference for the PM hays was greater than the AM hays (P<0.01)."
> >
> Joe
>
> We considered the possibility that evening quality might play a part. We
> haven't rejected that possibility but we have set it aside for several
> reasons. 1. In grass swards in this climate of limited sun and heavy
> overcast the quality changes probably occur intermittently so that they
> would not explain the daily persistence of the big evening meal. 2.We try
> to keep the concept as simple as possible. When we take the light quality
> factor as the stimulus to begin grazing at dawn then, because the same
> conditions of light are repeated at dusk, we have to take the light
> stimulus on board as an evening factor. In that way we use one factor to
> explain two features of the pattern. If we try to take on the quality
> factor then we have two factors and also one of the effects has two
causes.
>
> In recent years research at the Institute for Grassland and Environmental
> Research(IGER) at Devon in the UK revealed that sheep exhibit no
> preference between grass monoculture and clover in monoculture during the
> morning but in the evening they exhibit a significant preference for the
> clover. We think it possible that this may be a response to the problem
of
> packing more into a full rumen under circumstances where there is a
strong
> drive to feed. In the same way we feel that the evening quality that you
> refer to may be seen as facilitating the extended evening bout rather
than
> causing it.
>
> At the outset of the project we were asked to determine if it was
possible
> to increase the intake of cows grazing in the rotational paddock system
> that is standard practice here. We set up two streams in the project. One
> has explored the limitations arising from sward structure(architecture)
and
> the other has looked at feeding behaviour of the animal. We have
assembled
> a working hypothesis- a conceptual model. The model is relatively simple
> but too much for posting here. Nevertheless I am hoping to pick up
> alternative ideas or discover weaknesses in our thinking from the
comments
> made.
>
> Thank you
>
> Anthony