Kalvutdragaren
The calf extrator's function has been studied, through measuring traction and how this varies in different situations, in comparison with corresponding manual traction situations. This was done against the background that excessive force at assisted calvings at dystocia can mean life threatening...
| Autor principal: | |
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| Formato: | Otro |
| Lenguaje: | sueco sueco |
| Publicado: |
2009
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| Materias: | |
| Acceso en línea: | https://stud.epsilon.slu.se/11804/ |
| _version_ | 1855571942826835968 |
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| author | Nilsson, Maja |
| author_browse | Nilsson, Maja |
| author_facet | Nilsson, Maja |
| author_sort | Nilsson, Maja |
| collection | Epsilon Archive for Student Projects |
| description | The calf extrator's function has been studied, through measuring traction and how
this varies in different situations, in comparison with corresponding manual
traction situations. This was done against the background that excessive force at
assisted calvings at dystocia can mean life threatening damages on the calf such as
grave acidosis, vertebral fractures, femur fractures and rib fractures. The calf
extractor has earlier been measured to pull with greater force than the established
maximum force of "two strong men". The general instruction is that it should be
used "with caution". The hope is to raise a discussion that can lead to better
animal welfare for the calves.
The experiment was lined up on the basis of the hypothesis that the traction from the calf extractor exceeds the traction of two
men, where the calf extractor's force is not influenced of how it is maneuvered.
Measurements were done of the traction on one front leg at forced extraction of a
dead calf from an artificial cow. The experiment was performed in five parts with
mechanical traction and two parts with manual traction. Numbers of pullingperiods
and numbers of handle movements per pulling-period were registered.
The extractions were applied according to a fictitious contraction scheme. The
maximum manual force generated by one respectively two persons, standing and
sitting and by the calf extractor, was examined in a laboratory environment.
Measurements of the force generated by the calf extractor at varied handle
movements were done also. The pulling power in kilograms was registered
electronically and computer-logged with one value per second. The load dosage
over time was calculated by the area under the curve. The total load on the calf
was actually twice as big, since the measured force only represented what was
applied on one front leg. The persons who pulled weighed 60-73 kg and were
considered "normally strong".
The descriptive experiments showed that the hypothesis could to its first part be
verified and to its other part be rejected. One person standing on the floor pulls 42
kg and sitting on floor with support for the feet pulls 114 kg. Two persons
standing on the floor pull 87 kg. Two persons sitting on the floor with support for
their feet pull 184 kg. With the calf extractor one person pulls 300+ kg. A half
range pull on the calf extractors handle achieve maximum force slower than a full
range pull. Applying additional lubrication was shown to be of great importance
in order to decrease the friction and force development. The load increases when
the extraction angle is changed from 45° downward to 45° upward, which can
arise in a lying cow. The calf extractor can moreover by its placement near the
vagina cause a pressure from the outside on the soft tissues that counteracts
pulling. The load increases on the calf when using a calf extractor compared with
manual extraction.
A big difference between mechanical and manual extraction is
clearly seen when the passage of delivery is obstructed. When pulling with the
calf extractor a 3.35 times greater total load is achieved compared with
corresponding manual extraction. This is because of the higher maximum forces
achieved and the long duration of remaining tension in the pulling ropes, in
between "contractions". Through loosening the brake and pushing the handle of
the calf extractor forward between contractions the load would decrease
markedly.
After difficult deliveries careful survey of the calf is required regarding
damages and acidosis. Knowledge of the normal birth is a basic requirement in order to do a correct evaluation. Through awareness, farmers and field
veterinarians can make decisions that better protects the animal welfare. |
| format | Otro |
| id | RepoSLU11804 |
| institution | Swedish University of Agricultural Sciences |
| language | Swedish swe |
| publishDate | 2009 |
| publishDateSort | 2009 |
| record_format | eprints |
| spelling | RepoSLU118042017-10-17T06:41:24Z https://stud.epsilon.slu.se/11804/ Kalvutdragaren Nilsson, Maja Veterinary science and hygiene - General aspects The calf extrator's function has been studied, through measuring traction and how this varies in different situations, in comparison with corresponding manual traction situations. This was done against the background that excessive force at assisted calvings at dystocia can mean life threatening damages on the calf such as grave acidosis, vertebral fractures, femur fractures and rib fractures. The calf extractor has earlier been measured to pull with greater force than the established maximum force of "two strong men". The general instruction is that it should be used "with caution". The hope is to raise a discussion that can lead to better animal welfare for the calves. The experiment was lined up on the basis of the hypothesis that the traction from the calf extractor exceeds the traction of two men, where the calf extractor's force is not influenced of how it is maneuvered. Measurements were done of the traction on one front leg at forced extraction of a dead calf from an artificial cow. The experiment was performed in five parts with mechanical traction and two parts with manual traction. Numbers of pullingperiods and numbers of handle movements per pulling-period were registered. The extractions were applied according to a fictitious contraction scheme. The maximum manual force generated by one respectively two persons, standing and sitting and by the calf extractor, was examined in a laboratory environment. Measurements of the force generated by the calf extractor at varied handle movements were done also. The pulling power in kilograms was registered electronically and computer-logged with one value per second. The load dosage over time was calculated by the area under the curve. The total load on the calf was actually twice as big, since the measured force only represented what was applied on one front leg. The persons who pulled weighed 60-73 kg and were considered "normally strong". The descriptive experiments showed that the hypothesis could to its first part be verified and to its other part be rejected. One person standing on the floor pulls 42 kg and sitting on floor with support for the feet pulls 114 kg. Two persons standing on the floor pull 87 kg. Two persons sitting on the floor with support for their feet pull 184 kg. With the calf extractor one person pulls 300+ kg. A half range pull on the calf extractors handle achieve maximum force slower than a full range pull. Applying additional lubrication was shown to be of great importance in order to decrease the friction and force development. The load increases when the extraction angle is changed from 45° downward to 45° upward, which can arise in a lying cow. The calf extractor can moreover by its placement near the vagina cause a pressure from the outside on the soft tissues that counteracts pulling. The load increases on the calf when using a calf extractor compared with manual extraction. A big difference between mechanical and manual extraction is clearly seen when the passage of delivery is obstructed. When pulling with the calf extractor a 3.35 times greater total load is achieved compared with corresponding manual extraction. This is because of the higher maximum forces achieved and the long duration of remaining tension in the pulling ropes, in between "contractions". Through loosening the brake and pushing the handle of the calf extractor forward between contractions the load would decrease markedly. After difficult deliveries careful survey of the calf is required regarding damages and acidosis. Knowledge of the normal birth is a basic requirement in order to do a correct evaluation. Through awareness, farmers and field veterinarians can make decisions that better protects the animal welfare. Kalvutdragarens funktion har studerats, genom att mäta dragkrafter och hur dessa varierar i olika situationer och jämförts med motsvarande manuella situationer. Detta gjordes mot bakgrunden att överdriven kraft vid assisterade förlossningar vid dystoki, kan innebära livshotande skador på kalven i form av grav acidos, ryggradsfrakturer, lårbensfrakturer och revbensfrakturer. Kalvutdragare har tidigare konstaterats dra med mer kraft än den vedertagna maximala från ”två starka karlar”. Instruktionen är att den skall användas ”med försiktighet”. Förhoppningen är att väcka diskussion som kan leda till bättre djurskydd för kalvarna. Försöket ställdes upp utifrån hypotesen att dragkraften från kalvutdragaren överskrider dragkraften hos två personer, där kalvutdragarens dragkraft inte påverkas av hur den manövreras. Mätningar gjordes av belastningen på ena frambenet vid forcerad framdragning av en död kalv från en konstgjord ko. Fem delförsök med mekanisk utdragning och två manuella delförsök genomfördes. Antal dragperioder och handtagsrörelser per dragperiod registrerades. Utdragningarna skedde enligt ett fiktivt krystningsschema. Den maximala kraften vid en respektive två personer, stående respektive sittande och hos kalvutdragaren undersöktes i laboratoriemiljö. Mätning av kraftutvecklingen hos kalvutdragaren vid varierad handtagsrörelse gjordes också. Belastningen i kg, registrerades elektroniskt och data-loggades med ett mätvärde per sekund. Belastningsdosen, arean under kurvan, beräknades. Den totala belastningen på kalven var egentligen dubbelt så stor, då kraftgivaren applicerades bara på ena benet. Personerna som drog vägde 60-73 kg och ansågs vara ”normalstarka”. De deskriptiva delförsöken visade att hypotesen kunde till sin första del verifieras och till sin andra del förkastas. En person stående på golvet drar 42 kg och sittande med stöd för fötterna 114 kg. Två personer stående på golvet drar 87 kg och sittande på golvet med stöd för fötterna 184 kg. Med kalvutdragaren drar en person 300+ kg. Ett halvt utslag på kalvutdragarens handtag uppnår maximal kraft långsammare än vid fullt utslag. Tillförande av extra involvens visade sig ha stor betydelse för att minska kraftutvecklingen. Belastningsdosen ökar om utdragsvinkeln ändras från 45° nedåt till 45° uppåt, så som kan uppstå på en liggande ko. Belastningsdosen ökar på kalven vid användning av kalvutdragare jämfört med manuell utdragning. Kalvutdragaren kan dessutom vid placering för nära vagina pressa utifrån mot de mjuka förlossningsvägarna och motverka utdragning. Stor skillnad mellan mekanisk och manuell utdragning ses tydligt framförallt vid stort motstånd i förlossningsvägarna, då man med kalvutdragaren uppnådde 3,35 gånger större belastningsdos jämfört med motsvarande manuella mätning. Det på grund av högre maxbelastning och spänning som ligger kvar i draglinorna mellan ”krystningarna”. Genom att lossa spärren och föra fram handtaget på kalvutdragaren mellan krystvärkarna skulle belastningsdosen minska avsevärt. Efter svåra kalvningar krävs noggrann undersökning av kalven med avseende på skador och acidos. Kunskap om den normala förlossningen är en grundförutsättning för att göra en korrekt bedömning. Genom medvetenhet kan lantbrukare och veterinärer i fält ta beslut som bättre värnar om djurskyddet. 2009-03-05 Other NonPeerReviewed application/pdf sv https://stud.epsilon.slu.se/11804/1/nilsson_m_171017.pdf Nilsson, Maja, 2009. Kalvutdragaren : en hjälpande hand?. UNSPECIFIED, Uppsala. Uppsala: (VH) > Dept. of Clinical Sciences (until 231231) <https://stud.epsilon.slu.se/view/divisions/OID-715.html> urn:nbn:se:slu:epsilon-s-7885 swe |
| spellingShingle | Veterinary science and hygiene - General aspects Nilsson, Maja Kalvutdragaren |
| title | Kalvutdragaren |
| title_full | Kalvutdragaren |
| title_fullStr | Kalvutdragaren |
| title_full_unstemmed | Kalvutdragaren |
| title_short | Kalvutdragaren |
| title_sort | kalvutdragaren |
| topic | Veterinary science and hygiene - General aspects |
| url | https://stud.epsilon.slu.se/11804/ https://stud.epsilon.slu.se/11804/ |