The influence of seasonal temperatures on meat quality characteristics of hot-boned, m. psoas major and minor, from goats and sheep I.T. Kadim * , O. Mahgoub, W. Al-Marzooqi, D.S. Al-Ajmi, R.S. Al-Maqbali, S.M. Al-Lawati Department of Animal and Veterinary Sciences, College of Agricultural and Marine Sciences, Sultan Qaboos University, P.O. Box 34, Al-Khoud 123, Muscat, Oman Received 8 April 2007; received in revised form 24 November 2007; accepted 26 November 2007 Abstract Samples of psoas major and minor muscles were randomly collected weekly from 203 (99 hot and 104 cool seasons) Omani goats, 215 (106 hot and 109 cool seasons) Omani sheep, 212 (104 hot and 108 cool seasons) Somali goats, 242 (127 hot and 115 cool seasons) Somali sheep and 211 (110 hot and 101 cool seasons) Australian Merino sheep slaughtered at the Central Slaughterhouse in Oman to investigate the effect of season on meat quality. The collection period was during November 2004–October 2005 and divided into two seasons according to ambient temperatures and relative humidity. These were termed: cool season (average temperature of 21 °C and 59% rel- ative humidity and hot season (average temperature of 35 °C and 47% relative humidity). Muscles collected during the hot season had significantly (P < 0.05) higher ultimate pH values (5.78) than those collected during the cool season (5.65). Myofibrillar fragmentation index was significantly (P < 0.05) higher for hot season samples (86.88%) than for cool season samples (85.59%). Expressed juice was significantly (P < 0.05) higher for cool season samples (36.84) than for hot season samples (35.74). Goat meat from the hot seasonal group was significantly (P < 0.05) darker than the cold season group based on L * (37.6 vs. 39.6), a * (20.0 vs. 23.3) and b * (3.6 vs. 4.2) colour measurements. These results indicated that high ambient temperatures had caused an increase in muscle ultimate pH leading to significant effects on meat quality. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Sheep; Goat; Psoas major and minor; Warner–Bratzler shear force; Meat quality; Sarcomere length; Myofibrillar fragmentation index 1. Introduction Animal performance is adversely affected with a combi- nation of any of high ambient temperatures, relative humid- ity, air movement and solar radiation (Hahn & Mader, 1997). Numerous energetic adaptations have evolved that attenuate the animal’s response to hot environments which may limit its ability to cope with specific types of environ- mental stressors (Nelson & Drazen, 2000). Body tempera- ture increases when the ambient temperature is above the upper critical temperature of 32 °C which may cause several physiological side effects and economic impact on animal output (Anderson, 1989; Degen & Young, 2002). High environmental temperatures depress utilisation of energy (Denek et al., 2006). However, there would be marked rise in energy expenditure from animal’s body reserves due to endocrine responses to encounter the effects of heat stress (Costa et al., 2006; Nelson & Drazen, 2000; Shinde, Raghavendra, Sankhyan, & Verma, 2002). This would lead to depletion of muscle glycogen the major source of energy for muscle metabolism low glycogen in muscles before slaughter subsequently increases the ulti- mate pH of meat, and results in low residual levels of glucose (Bray, Graafhuis, & Chrystall, 1989). A high post-mortem pH is accompanied with high water-holding 0309-1740/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2007.11.022 * Corresponding author. Tel.: +968 99279776; fax: +968 24413418. E-mail address: isam@squ.edu.om (I.T. Kadim). www.elsevier.com/locate/meatsci Available online at www.sciencedirect.com Meat Science 80 (2008) 210–215 MEAT SCIENCE