Non-invasive methods for the determination of body and carcass composition in livestock: dual-energy X-ray absorptiometry, computed tomography, magnetic resonance imaging and ultrasound: invited review.
The ability to accurately measure body or carcass composition is important for performance testing, grading and finally selection or payment of meat-producing animals. Advances especially in non-invasive techniques are mainly based on the development of electronic and computer-driven methods in order to provide objective phenotypic data. The preference for a specific technique depends on the target animal species or carcass, combined with technical and practical aspects such as accuracy, reliability, cost, portability, speed, ease of use, safety and for in vivo measurements the need for fixation or sedation. The techniques rely on specific device-driven signals, which interact with tissues in the body or carcass at the atomic or molecular level, resulting in secondary or attenuated signals detected by the instruments and analyzed quantitatively. The electromagnetic signal produced by the instrument may originate from mechanical energy such as sound waves (ultrasound - US), 'photon' radiation (X-ray-computed tomography - CT, dual-energy X-ray absorptiometry - DXA) or radio frequency waves (magnetic resonance imaging - MRI). The signals detected by the corresponding instruments are processed to measure, for example, tissue depths, areas, volumes or distributions of fat, muscle (water, protein) and partly bone or bone mineral. Among the above techniques, CT is the most accurate one followed by MRI and DXA, whereas US can be used for all sizes of farm animal species even under field conditions. CT, MRI and US can provide volume data, whereas only DXA delivers immediate whole-body composition results without (2D) image manipulation. A combination of simple US and more expensive CT, MRI or DXA might be applied for farm animal selection programs in a stepwise approach.
1Livestock Center Oberschleißheim,Ludwig-Maximilians-University Munich,Sankt-Hubertusstrasse 12,85764 Oberschleißheim,Germany.
A M
AM
Scholz
2SRUC,Animal and Veterinary Sciences,Roslin Institute Building,Easter Bush,Midlothian,Scotland EH25 9RG,UK.
L
L
Bünger
3Norsvin,Department of Animal and Aquacultural Sciences,c/o Norwegian University of Life Sciences,PO Box 5003,N-1432 Ås,Norway.
J
J
Kongsro
4Institute of Farm Animal Genetics,Friedrich-Loeffler-Institut,Hoeltystr.10,31535 Neustadt,Germany.
U
U
Baulain
5Agricultural Research Service (Retired),US Department of Agriculture, 10300 Baltimore Avenue, BARC-West,Beltsville,MD 20705,USA.
A D
AD
Mitchell
D015502:Absorptiometry, Photon / Q000379:methods / Q000662:veterinary*; D000818:Animals; D001823:Body Composition / Q000502:physiology*; D058751:Livestock / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods / Q000662:veterinary*; D008460:Meat / Q000592:standards*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods / Q000662:veterinary*; D014465:Ultrasonics / Q000379:methods*
X-ray attenuation; animal; body composition; magnetic resonance imaging; ultrasound