エンリッチド・養豚
Improved Pig-Keeping
小針大助 茨城大学農学部附属フィールドサイエンス教育研究センター 講師
Daisuke KOHARI Lecturer at the Field Science Center, College of Agriculture, Ibaraki University
Thank you very much. I am Daisuke

the gist of the animal welfare concept.

Kohari, and I work as a lecturer atIbaraki University. President Toyoshita

Actually, in order for pigs to make use of their adaptiveof Porkland has just talked about theabilities to the full, we need to know what kind of

actual practice of rearing pigs at thebehavior they carry out. So in order to do this, I made aproduction site. I myself have actuallylist of the pigsʼ behavioral repertoire, [slide 4]. I took thisworked at Porkland, where I

from a well-known textbook Kachiku Kodo Zuzetsu

conducted research into welfare-oriented pig keeping(Illustrated Livestock Activity), and the full repertoire

systems and how much effect they have on pigs

consists of between 70 and 100 behaviors. In here, I

compared with conventional piggery systems, [slide 1].

have listed approximately 70 of these behaviors that

And today I would like to tell you about this research.

pigs naturally perform when they can. Accordingly,
allowing them to perform these behaviors helps bringBut before that, let me talk first about the methods ofout their adaptive behavior. However, as a practicalrearing pigs, [slide 2]. There are a great many methods

matter, pigs are not required to express all of theseof rearing pigs. Some of these photos show pigs being

behaviors, and under modern pig keeping methods,

kept in pasturage and others show them being kept at athere is a considerable variation in the possibility oflivestock farm. When it comes to keeping pigs in barns,

expressing these behaviors depending on how the pigs

there are a number of forms. Also, there are a great

are kept.

many pig-raising methods. For example, depending on
the brand, there are all sorts of rules and standards toStill, when pigs have an opportunity to carry out a wide-

be observed, such as that pigs must be kept in this or

ranging activity repertoire, they actually adjustthat way, etc. Even for the same variety of pigs, there arethemselves to the environment by carrying out

diﬀerent rearing methods.

appropriate activities such as lying around, eating grass
whenever they choose, or, when they feel hot,Now, when we think about comfortable pig farming,

wallowing in mud to cool down. By contrast, however,what sort of factors should we consider? [Slide 3]. I haveas this next picture of pigs kept in conﬁned conditions

listed five things on this slide. But actually, these areshows, [slide 5] when pigs are unable to satisfy theirmerely some more concrete expressions for the fivedesire for activities, or when they cannot adapt to theirfreedoms that have been mentioned many times

living environment, a variety of behavioral problems

already. They are: ʻprovide pigs with feed and water inoccur, such as biting other pigs or people, which canthe proper wayʼ, ʻkeep them under conditions that are

result in injuries, etc.

neither too cold nor too hotʼ, ʻprevent them frombecoming injured or developing diseasesʼ, ʻdonʼt scareNow, by how much can the behavior and the lives ofthem unnecessarilyʼ, and ʻallow them to behave in line

pigs be improved by switching to keeping methods

with their natural habits and environmentʼ.

that pay consideration to the pigsʼ amenities? On thisoccasion, I studied the diﬀerences between the biobed

By practicing these things, pigs can live healthily, and at

system operated by Porkland (as introduced earlier),

the same time, they are able to use their original abilities

and ordinary conﬁned production systems, with special

to the full. This in turn ensures their comfort, which isreference to the following three points, [slide 6].

Workshop Ⅲ Welfare and Management of Farmed Animals

29

Firstly, by how much can the pigsʼ ﬁghting or abnormal

biobed system, this piggery has a concrete draining-behavior be ameliorated? Secondly, how muchboard floor. Now letʼs see the comparison, [slide 9].

tolerance do pigs have for the stresses placed on them?

Firstly, look at this table I produced comparing hostile

Or, in other words, how strong does their resistancebehavior and abnormal behavior (Kohari, unpublished).

against stress become? And thirdly, how do pigs

The upper “conv.” figures refer to conventional

respond when their keepers change?

conﬁnement rearing data, while the lower “bio” ﬁguresrefer to biobed rearing data. You can see that hostile

Now I will introduce the rearing system in question. Thisbehavior is much less common under biobed thanis the biobed system that I mentioned earlier, [slide 7].

confinement conditions and the frequency of fights is

In this system, rice husks are laid on the ﬂoor to form aalso much lower. Also, regarding abnormal behavior,

layer approx. 30~40cm thick and perhaps 50cm thick inthe survey checked three things: Firstly, sham chewing,

the deepest places. This material is then allowed towhich is a typical form of abnormal behavior among

ferment by installing a fermenter. Of course, pigpigs (they chew even though they donʼt have anything

excrement falls onto the layer, but the generation ofin their mouth because they feel the need to chew

ammonia from the excrement is moderated due to thesomething); secondly, biting other individuals, as I

effects of the fermentation. The keeping area is alsomentioned earlier; and thirdly, roughly biting fences

made slightly wider than is the case under aand other facilities. As the ﬁgures show clearly, all three

conventional rearing system. As the floor is covered

forms of abnormal behavior were frequently observedwith rice husks, it doesnʼt matter if the pigs dig into it

in the conﬁnement piggery but hardly ever observed inwith their snouts whenever they like. The pigs can also

the biobed piggery.

play and jump about while ranging freely within abroad area. Moreover, the outside air moves throughHere are the results of a second survey, [slide 10], thisthe keeping area, and the animals are exposed totime on the subject of resistance to stress. The subjects

natural light, while the temperature differs from place

were placed under some stress and then their stressto place depending on the degree to which the pile ofresistance was measured. The method used was ahusks is fermenting. This means that the pigs have therestraint and blood stress test. As you can see from theopportunity to gather where the floor temperature ispicture, when collecting blood from pigs, if the nose islower on hot days and where it is higher on cold days.

tied and pressure is applied (nose retention) while
restraining the individual, they are unable to move. TheFor a comparison with the biobed system, letʼs look at

ﬁrst blood sample is collected shortly after the restraint

this windowless conﬁnement piggery, [slide 8]. Actually,

begins, and a second sample is collected after thethis example is quite a lot wider than an ordinary

individual has been restrained for ﬁve minutes. Because

piggery. I think there are probably about 400 pigs there,

the pigs are restrained throughout this time, they are

and the keeping area is larger than that of an ordinary

placed under stress. Then the difference in the stresspiggery. It is very rare to see confinement pig rearing

indicators for the two tests is measured.

carried out on this large scale, but because this time we30

were interested in making a comparison with theThe indicator of stress selected was the blood cortisol

biobed situation, we chose a large-group rearing facility

level. The first blood sample was taken within one

rather than an ordinary piggery where the animals areminute of the start of the restraint, and this length of

divided into smaller groups. As you can see, there are

restraint had little eﬀect on the blood cortisol level andno windows letting in light from the outside at all.

produced no signiﬁcant diﬀerence between biobed andAlthough there are some small windows along one side

windowless confinement-raised pigs. However, fivethat has a corridor for operator use, these are merely tominutes later, the blood cortisol level had risen steeply

allow people to observe the interior of the piggery, notamong the windowless confinement-reared pigs. By

to let in daylight. As for the floor, quite unlike thecontrast, while the cortisol level also rose in the case of

ワークショップⅢ

産業動物の福祉と経営biobed-reared pigs, the rise was considerably lessof confined rearing, where the animals get lesspronounced. This result (Kohari, unpublished) shows

stimulation.

that the biobed-reared pigs had greater resistance thanconfinement-raised pigs did to the same degree of

As I explained earlier, by rearing pigs in a way thatstress.

enhances their degree of freedom and pays due
consideration to their amenities, as in the case ofMoving on to the third test, [slide 11]. This time, Ibiobed rearing, it is possible to reduce the amount ofchecked the animalsʼ reactions to people. (This table

abnormal behavior such as fighting displayed by thealso includes the results of a novelty object introduction

animals. In addition, their stress resistance is enhanced

test as well.) Since people also represent a newand their reactions to people become milder. Thesestimulation, what I did was to let people stand in thewere the results I obtained. However, although it is very

piggery and then check how long it took for pigs toencouraging from an animal welfare standpoint thatapproach the people and how the animals behaved

this kind of rearing is being carried out at Porkland,

towards the people. As Prof. Sato mentioned during his

there are difficulties to be overcome in practicing thislecture, when people go into a piggery, the pigs tend toform of pig rearing commercially. Much of the problem

rally around them en masse, so people may kick thestems from the common consumer sentiment that, “allanimals unintentionally. And as we saw earlier,in all, as far as animal products go (including pork), itʼs

conﬁnement-style rearing environments tend to have a

OK as long as itʼs cheap.” Moreover, consumer

rather uniform and simple structure. Of course, they areconsciousness about how pig rearing is carried out ordesigned in that way to simplify hygiene management.

how animal products are made is very low. Indeed, myBut under such environments, the pigs get very little

actual feeling is that almost all consumers know little or

stimulation so, when some new stimulation appears,

nothing of the subject. Accordingly, in order to actually

the pigs move towards it and gather around it. The

carry out rearing that is comfortable for pigs and, whatʼsamount of time people stood in the pig-rearing area

more, to popularize and promote it, it is vital to have

was only about 30 seconds. This is because they couldnʼ

highly aware producers (of course) but also consumers.

t stand to remain there any longer than that. The way

It is necessary for the consumers, those who actually

this test was performed was that people would enter

beneﬁt from eating pork, to develop an interest in how

the piggery and be asked to stand at the center of apigs are reared and feel that they ʻwishʼ to consume

circle with a radius of one meter for 30 seconds. During

pork reared in the more comfortable way, and that they

this time, the degree to which pigs came close to theunderstand what animal welfare entails. I think thesepeople and sniffed or bit them was measured. Thethings are essential if we are to realize pig farming that

results are as shown in the lower part of the table.

is comfortable for the pigs at pig farms throughout

Compared with biobed rearing, in the conﬁned rearing

Japan.

environment the animals came close to the people
much more rapidly, commonly within 2 seconds or so,and they bit the visitors regardless of whether they
were men or women. After the pigs sank their teeth into
the people they would not release their grip for around
25 seconds on average (Kohari, unpublished). In thebiobed case too, there were pigs that came close topeople, sniﬀed them and bit them. But in this case, theywould approach the new arrivals in a more guarded
fashion, and only when they had assured themselves itwas OK would they bite. The results show that both thelength and the degree of biting were greater in the case

Workshop Ⅲ Welfare and Management of Farmed Animals

31

32

ワークショップⅢ䇼㪪㫃㫀㪻㪼 䋱䇽䇼㪪㫃㫀㪻㪼㩷㪌䇽䇼㪪㫃㫀㪻㪼 䋲䇽䇼㪪㫃㫀㪻㪼㩷㪍䇽䇼㪪㫃㫀㪻㪼 䋳䇽䇼㪪㫃㫀㪻㪼㩷㪎䇽䇼㪪㫃㫀㪻㪼㪋䇽䇼㪪㫃㫀㪻㪼㩷㪏䇽

産業動物の福祉と経営䇼㪪㫃㫀㪻㪼㩷㪐䇽䇼㪪㫃㫀㪻㪼㪈㪊䇽䇼㪪㫃㫀㪻㪼㩷㪈㪇䇽䇼㪪㫃㫀㪻㪼㩷㪈㪈䇽䇼㪪㫃㫀㪻㪼㩷㪈㪉䇽Workshop Ⅲ Welfare and Management of Farmed Animals

33