Carcass and meat properties of six genotypes of young bulls finished under feedlot tropical conditions of Mexico O. V. Vazquez-Mendoza A , G. Aranda-Osorio A , M. Huerta-Bravo A , A. E. Kholif B , M. M. Y. Elghandour C , A. Z. M. Salem C,D and E. Maldonado-Simán A A Departamento de Zootecnia, Universidad Autónoma Chapingo, Mexcio. B Dairy Science Department, National Research Centre, 33 Bohouth Street, Dokki, Giza, Egypt. C Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma del Estado de México, México. D Corresponding author. Email: asalem70@yahoo.com Abstract. The effect of six genotypes (Zebu = Z, European Brown Swiss = EBS, Holstein = H, Z · EBS, Zebu · American Brown Swiss = ABS, Z · ABS, Z · H) on carcass and meat characteristics of young bullocks finished under feedlot conditions was tested. The Z · ABS bullocks had the highest (P = 0.001) average daily gain. The highest (P = 0.017) final liveweight was observed with Z · ABS > EBS > H genotypes. The ribeye area was larger (P = 0.012) for EBS bullocks. Both H and EBS bullocks had lowest (P = 0.001) physiological maturity; although the H bullocks had higher (P = 0.006) pelvis and heart fat values. The best (P = 0.014) conformation was obtained with the Z · ABS and Z · EBS genotypes. The greatest amount of marbling (P = 0.001) was obtained with the H genotype. In general, the crossbred genotypes showed better feedlot performance and carcass characteristics, and it seems that Holstein breed could have a an advantage from the marbling score point of view. Additional keywords: beef cattle, carcass characteristics. Received 31 December 2014, accepted 17 March 2016, published online 6 July 2016 Introduction In Mexico, there are three main identified climatic zones, located in the north, centre and south of the country. Climatic conditions of each region have great influences on agriculture practices and also determine the type of cattle breeds and production systems which can be exploited. In this context, the production of beef cattle is distributed into 20.0% in the north, 35.4% in the centre and 44.6% in the south of Mexico. A significant portion of the agriculture practices in the northern region is exported to the USA, whereas those of the central and southern regions are intended to meet domestic demands (Gallardo et al. 2006). The meat quality can defined in many ways and vary according to the end user, packer, retailer and consumer requirements. Recently, meat quality can be considered as the sum of all factors of quality, in terms of hygienic nutritious sensory properties (the most important one), toxicological, technological and social factors (Hocquette et al. 2007). However, existing world markets have different quality requirements. Well-formed carcass, high lean meat percentage and degree of fatness are the most important factors (Albertí et al. 2005), whereas the physiological maturity of the carcass, and marbling score are used in other markets to estimate the degree of meat quality due to its close relation with the meat (Polkinghorne and Thompson 2010). Production factors and management such as breed, age, sex, feed and practices before slaughtering may determine the potential carcass and meat quality (Sañudo et al. 2004). In the case of genotype, Albertí et al.(2008), Prado et al.(2008), Maggioni et al.(2010) reported differences characteristics of carcasses (e.g. conformation, back fat, marbling score) and meat (e.g. protein and fat contents) among breed groups and their crosses. In the case of Mexico, some researchers (Méndez et al. 2009; Torrescano et al. 2010) described the characteristics of carcasses and meat from cattle slaughtered in different geographical areas of the country. However, limited research studied the effect of breed or genotype on the carcass characteristics and meat quality; and reported having no national information, in which the animals completed under the same system of feeding and management (Núñez et al. 2005). Thus, the aim of the present study was to evaluate the influence of breed of six genotypes of tropical young bulls (Zebu, European Brown Swiss, Holstein, Zebu · European Brown Swiss, Zebu · American Brown Swiss, and Zebu · Holstein) on carcass characteristics and beef chemical composition of bullocks finished in the temperate-tropical region of the central Mexico. Materials and methods Animal handling, management and sampling The study was conducted at the Experimental Farm of the Autonomous University of Chapingo, located in Texcoco, CSIRO PUBLISHING Animal Production Science http://dx.doi.org/10.1071/AN141037 Journal compilation Ó CSIRO 2016 www.publish.csiro.au/journals/an