The value of in vivo real time ultrasonography in assessing loin muscularity and carcass composition of rabbits S.R. Silva * , C.M. Guedes, J.L. Mourão, A. Pio, V.M. Pinheiro CECAV-Universidade de Trás-os-Montes e Alto Douro, Department of Animal Science, Apartado 1013, P.O. Box 1013, 5000-801 Vila Real, Portugal article info Article history: Received 11 November 2007 Received in revised form 27 July 2008 Accepted 31 August 2008 Keywords: Real time ultrasound Muscularity Carcass composition Rabbits abstract Sixty nine growing rabbits were scanned over the lumbar region using a real time ultrasonography (RTU) machine to estimate loin muscularity and carcass composition. Longissimus thoracis et lumborum muscle (LM) depth, width and area were taken. Animals were weighed (LW), slaughtered and carcass composi- tion was determined. Equivalent measurements to those taken by RTU in vivo were taken on the carcass and muscularity indices were calculated on carcass and in vivo. Simple correlations between the two types of measurements were determined and carcass composition was estimated by simple and multiple regressions. The LW varied from 1200 to 3410 g. The simple correlations between carcass and in vivo RTU LM mea- surements were high (P < 0.001) and the LM area was the trait with the highest correlation (r = 0.92). Simple correlations between muscularity indices measured by RTU and in carcass were significant (P < 0.001). In vivo RTU measurements explained a large amount of the variation of the carcass meat weight (MW) and bone weight (r 2 range from 0.49 to 0.77; P < 0.001). Using multiple regression equations to estimate carcass composition, the best fit was obtained with the LW and one or more in vivo RTU measurement. The LW explained 90.6% of the variation of MW in the carcass. In vivo RTU is able to estimate loin muscularity and carcass composition of rabbits with accuracy. The usefulness of in vivo RTU and LW to predict carcass composition of rabbits using multiple regressions was also shown. Ó 2008 Elsevier Ltd. All rights reserved. 1. Introduction Rabbit meat is an important product in Mediterranean coun- tries of EU. Several studies (Hernández, Aliaga, Pla, & Blasco, 2004; Larzul, Gondret, Combes, & Rochambeau, 2005; Metzger et al., 2006) on the selection of rabbits have shown the effect of growth rate and live weight on carcass characteristics and meat quality. An effective tool for in vivo evaluation of carcass traits and quality is required for breeding programs. Although several non-invasive techniques using image analysis have been success- fully used to evaluate carcass composition in animals (Stanford, Jones, & Price, 1998; Szabo et al., 1999) but only few studies have been conducted on rabbits (Kövér, Szendrö, Romvári, Jensen, & Mil- isits, 1998; Pascual, Castella, Cervera, Blas, & Fernández-Carmona, 2000; Szendrö et al., 1992). Most of these studies are related to the estimation of fat deposits (Kövér et al., 1998; Pascual et al., 2000). Pascual et al. (2000) used real time ultrasonography (RTU) for estimating the body condition of young rabbit does and con- cluded that this technique was an accurate method for estimating carcass perirenal fat weight (r 2 = 0.95; n = 42) and total fat weight (r 2 = 0.93; n = 42). In most domestic species variation in carcass fatness is one of the main factors influencing carcass and meat quality. However, rabbit carcasses have a small dissectible fat content (Pascual & Pla, 2007; Pla, Hernández, & Blasco, 1996) and it is not normally used as a quality factor for carcass evaluation. Therefore, the main criteria used to define rabbit carcass quality have been meat per- centage in the carcass and the muscularity defined as the ratio be- tween meat and bone (Blasco, Estany, & Baselga, 1984; Lambertini, Bergoglio, Masoero, & Gramenzi, 1996; Lukefahr & Ozimba, 1991; Varewyck & Bouquet, 1982). Studies have shown that apparent body muscularity or cutability attributes may be improved by selection (Lukefahr, Hohenboken, Cheeke, & Patton, 1983; Luke- fahr, Hohenboken, Cheeke, Patton, & Kennick, 1982). The develop- ments of in vivo measures that are closely associated with measures considered most important in describing the muscularity of a rabbit carcass will be required for application in genetic improvement programs or simply in economic carcass evaluation. This subject has been investigated on other species (cattle: Pur- chas, Fisher, Price, & Berg, 2002; sheep: Wolf, Jones, & Owen, 2006). In rabbits, studies have also been conducted to predict 0309-1740/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2008.08.013 * Corresponding author. Tel.: +351 259350417. E-mail address: ssilva@utad.pt (S.R. Silva). Meat Science 81 (2009) 357–363 Contents lists available at ScienceDirect Meat Science journal homepage: www.elsevier.com/locate/meatsci