It all started with a search for alter-native methods to assess animalwelfare, a growing concern all over

the world. Dr Késia Oliveira da Silva, aresearcher from the Nucleus ofResearch on Ambience (NUPEA) at theSuperior School of Agriculture ‘Luiz deQueiroz’ at the University of São Paulo,Brazil, explains that evaluation of well-being was mostly done through overtbehaviour and focused mainly on ther-mal stress.

For a couple of reasons, she wassearching for an alternative approach,both in methodology and also in focus.Direct visual observation is time-con-suming and demands specialised per-sonnel; moreover, the use of camerasdoes not solve any of these problemsand creates additional ones (insuffi-cient coverage for example).

Dr Irenilza de Alencar Nääs, aresearcher from the University ofCampinas stresses that sound is beingincreasingly studied all over the worldand it is becoming an important toolfor welfare evaluation, since it can indi-cate an internal state of the animal(hunger, pain, etc.) or the occurrenceof a stressing external event.

Then, in conversations with animalkeepers at Granja Querência, a farrow-to-finish unit located in Salto, Brazil,Silva found out that they claimed tointerpret some sow and piglet sounds.From that to the establishment of aresearch line attempting to analyse andinterpret the sounds it was a small stepaway.

“We started with two basic ideas.One, is the study of individual vocalisa-tions, possible only with sows and new-borns in the maternity. The other is tostudy the average animal noise in thenursery pens, and attempt to correlateit with environmental factors. In bothcases our aim was to get sound indica-tors of animal states and/or housingconditions,” Silva completes.

Lunch is servedBased on the initial hints given by thekeepers on the meaning of the calls,Silva selected six similar sows to studytheir and the piglets individual vocali-sations, in their nursing interactions.

The study started soon after thehomogenisation of the lots and beforethe contact with the sows. With a direc-tional microphone, like those used bybird-watchers, she recorded the soundsdirectly into a laptop while she record-ed the behaviour of the animals. Lateron, the calls were analysed with the aidof a special sound-analysis software,Cool Edit®, to describe their physicalparameters (frequency, amplitude, etc)and attempt to differentiate them.

Silva says that she was able to char-acterise four different sounds, two fromthe piglets and two from the sows.“The results were fascinating. Beforethe contact with the sows and duringmanipulation, the piglets produced afear call, and the sows showed signs ofanxiety. Then, when the pigletschanged to a ‘hunger call’, the sowsstarted to vocalise as well. Since thisresulted in an immediate approach ofthe piglets, this call was baptised the‘calling-to-nurse sound’. The sows didnot stop calling until the last piglet had

MMaannaaggeemmeenntt

As good as it sounds:understanding piggishBased initially on the knowledge of animal

keepers, a pioneer research in Brazil is starting

to unravel some of the secrets of pig

vocalisations. The study showed a complex

interplay between nursing and vocalisations

of piglets and sows, but found no relation

between temperature and the level of animal

noise at nurseries.

By Rogério G. T. da Cunha

www.PigProgress.net PIG PROGRESS Volume 22, No. 8 2006 13

Trial nursery pen showing a microphone, hanging from the ceiling, for detecting the sound level.

arrived at a nipple. Then, she changedto a ‘releasing milk sound’, which last-ed approximately 15 seconds. Milk wasreleased only while she was producingsuch sound,” Silva concludes.

After this initial study, NUPEA’s inten-tion is to expand the research in order

to analyse and characterise soundsemitted in other circumstances, suchas during pain, manipulation (castra-tion, vaccination, tail and teeth cut-ting), in the presence of unknown peo-ple and also different kinds of cough(to detect whooping cough for exam-ple). Their medium-term objective is todevelop a software that recognises thesounds (based on their different physi-cal properties) and interprets them tothe producer, a sort of ‘PiggishTranslating Machine’.

“It will be a module within an alreadyexistent traceability software, and it willhelp the producer to obtain a wealth ofinformation on the status and welfareof the animals in a simple and quickway, and also to check for deviations ofbehaviour,” Silva explains.

To show the utility of such results,Silva exemplifies with a situation inwhich a given piglet did not reach thenipple, for whatever reason. Even withonly one piglet missing, the sow willnot stop producing the ‘calling-to-nurse

sound’, and will not release the milk tothe others. “Animal keepers can betrained to recognise the sounds andquickly solve situations like this, bycorrectly positioning the missingpiglet,” Silva concludes.

The crowd is not so clear… yetThe other line of investigation is tostudy group noises in the collectivepens, since it is virtually impossible todistinguish individual sounds in suchsituations. The research approach hadto be different in this case. “We split a10 x 14 m nursery pen into 35 quad-rants of 4 m2 each. In the middle ofeach quadrant we measured tempera-ture, humidity and noise level,” DeAlencar Nääs explains. They measuredthe sound at feeding times, periods ofpeak noise production, but also aver-age and minimum noise. In order tofocus only on the sounds related to theanimals, they measured noise levelwithin the empty pen and subtractedthese values from the noise levels

Management

Screen of the sound-analysis software, Cool Edit®, showing thehunger call.The graph shows different frequencies (pitch)along time.The more intense the colour the more important isa given frequency to the final sound. Note that this sound,which has a grunting quality, accordingly situates in a low frequency (bass) range, up to 400 Hz. All illustrations are courtesy of Dr Késia Oliveira da Silva.

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Management

measured at feeding times. “Our intention was to verify if temper-

ature and humidity interfered in thenoise level, something that could be apowerful tool in evaluating environ-mental stress. Unfortunately we foundno correlation”, she completes.

However, Alencar Nääs did come upwith some interesting conclusions fromthe study. When they compared groupsof 33- and 38-day old piglets, theyounger group had higher averagenoise levels, but this was not statistical-ly relevant. The younger group alsohad more extreme noise values.

“We interpreted these results as anindication that the newly arrived piglets(33-day old group) were less habituat-ed to the new environment. We alsoobserved that the most extreme valuesoccurred at the edges of the pen,which might indicate an influence ofthe external environment,” AlencarNääs concludes.

Although the results were not as posi-tive as in the previous case, this

approach opened an interesting avenueof exploration. They are now attempt-ing to correlate the average noise inthe barn (an indicator of the stress lev-els of the animals) to the occurrence ofintermittent sounds, intentionally pro-duced by the researchers. In parallel,they are also studying the reaction ofindividual sows and piglets to thesesounds, which could allow a characteri-sation of specific sounds. The wholeidea is to check the reaction of the ani-mals to a potential and common stressfactor within producing units, whichcould lead to the suggestion of preven-tive measures.

Silva is also investigating sounds theother way round, that is, if the noiselevel at the barns and pens causes pre-mature deafness in sows. Her team andthe animal keepers noticed a higherloss of crushed piglets as the sows age.Therefore it seems likely that someolder sows do not answer appropriatelyto the fear and pain calls of the pigletswhen they sit or lie on them, simply

because they do not hear thecalls. “If we discover a correla-tion between noise level at theunit and deafness, measurescould be suggested to producersin order to avoid that, whichwould lead to a lower piglet mor-tality,” Silva concludes.

Promising studyGiven that other livestock ani-mals and many wild specieshave already been studied withrespect to their sounds, someintensively so, it is surprising tofind out how little we know aboutpig vocalisations. Equally aston-ishing is that it took so long torealise that the sounds could bea simple and powerful indicator of ani-mal condition, emotional state and wel-fare condition. But thanks to theresearch, this situation already startedto change.

Soon, we may be understanding pig-gish, to their and our benefit. PP

Decibel-level meter used in thegroup noise research

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