Evaluation of biochemical parameters and genetic markers for association with meat tenderness in South African feedlot cattle L. Frylinck a, * , G.L. van Wyk a , T.P.L. Smith c , P.E. Strydom a , E. van Marle-Köster b , E.C. Webb b , M. Koohmaraie d , M.F. Smith a a Agricultural Research Council of South Africa, Private Bag X2, Irene 0062, South Africa b Department of Animal and Wildlife Science, University of Pretoria, South Africa c US Meat Animal Research Centre, ARS, USDA, Clay Centre, P.O. Box 166, Spur 18-D, NE 68933-0166, USA d IEH Laboratories and Consulting Group, 15300 Bothell Way NE, Lake Forest Park, WA 98155, USA article info Article history: Received 21 May 2009 Received in revised form 22 July 2009 Accepted 24 July 2009 Keywords: Beef crossbreds Tenderness Calpain proteolytic system Genetic markers Cold shortening/toughening abstract A large proportion of South African feedlot cattle are crossbreds of Brahman (BrX, Bos indicus), and Sim- mental (SiX, Bos taurus). A sample of 20 grain fed bulls from each of these crossbreeds was used to com- pare meat quality with that of the small frame indigenous Nguni (NgX, Sanga) by evaluating a variety of biochemical and genetic parameters previously shown to be associated with meat tenderness. Shear force values were generally high (5.6 kg average at 14 days post mortem), with SiX animals higher than BrX or NgX (P = 0.051) despite higher calpastatin:calpain ratio in BrX (P < 0.05). Calpain activity and cold short- ening were both correlated with tenderness for all classes. The sample size was too small to accurately estimate genotypic effects of previously published markers in the CAST and CAPN1 genes, but the allele frequencies suggest that only modest progress would be possible in these South African crossbreds using these markers. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction Meat tenderness has received much attention in South Africa over the past decade (Frylinck, Strydom, & Scholtz, 2007; Frylinck, Strydom, Smith, & Heinze, 2001; Strydom, Frylinck, Mongomery, & Smith, 2009; Strydom, Naudé, Smith, Scholtz, & Van Wyk, 2000). Many researchers have focused their studies on the difference in tenderness between Bos indicus and Bos taurus breeds (Campo, Sanudo, Panea, Alberti, & Santolaria, 1999; Gregory, Cundiff, & Koch, 1995; O’Connor, Tatum, Wulf, Green & Smith, 1997; Sher- beck, Tatum, Field, Morgen, & Smith, 1995) due to variation in the properties of the muscle proteolytic calpain enzyme system, (Koohmaraie, 1996; Shackelford, Koohmaraie, Miller, Crouse, & Reagan, 1991; Whipple et al., 1990) and the related effects on the myofibrillar properties of the muscle. Two enzymes responsi- ble for this process are the micro molar calcium-activated neutral protease l-calpain (CAPN1), which is encoded by the CAPN1 gene, and its inhibitor, calpastatin (CAST), which is encoded by the CAST gene (Koohmaraie, 1996). Several markers have been developed at the CAST gene (Barendse, 2002) and three markers (marker 316, marker 530 and marker 4751) have been developed at the CAPN1 gene (Casas et al., 2006; Page et al., 2002; White et al., 2005). Mark- ers 316 and 530 can be used to guide selection in Bos taurus cattle, but do not segregate at high frequencies in Brahman cattle (Bos indicus). White et al. (2005) extended the tenderness marker (CAPN1-4751) test to include cattle of Bos taurus, Bos indicus and crossbred descent. It was concluded that marker 316 may continue to be useful in a variety of populations with a high percentage Bos taurus background, and that a multi marker system provides an optimal solution in cattle of all subspecies background. Markers 316 and 4751 are generally preferred as a tool to guide selection, because they show association with tenderness in a wide variety of populations compared to marker 530 (White et al., 2005). The CAST A/T marker at the CAST gene in Bos taurus and Bos indicus cat- tle (Barendse patent) and a T/A polymorphism called CAST-Brah- man (that is fixed in Bos taurus a little further down in the 3 0 UTR from the C/T) were associated with tenderness (Casas et al., 2006; Schenkel et al., 2006). According to the South African Feedlot Association, a large pro- portion of weaners finished in South African feedlots for beef pro- duction include Brahman- and Simmental-crosses. The Nguni that is known as a tropically adapted Taurus breed (Sanga) indigenous to Southern Africa is a popular breed used extensively by commer- cial and resource poor farmers to produce grass fed beef in South Africa. Due to their smaller carcass size, these animals are not pop- ular with commercial feedlotters, although their adaptability in the feedlot is acceptable (Strydom, Frylinck, Van der Westhuizen, & 0309-1740/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2009.07.016 * Corresponding author. Tel.: +27 12 672 9385; fax: 27 12 665 1551. E-mail address: Lorinda@arc.agric.za (L. Frylinck). Meat Science 83 (2009) 657–665 Contents lists available at ScienceDirect Meat Science journal homepage: www.elsevier.com/locate/meatsci