CARCASS TRAITS OF FATTENING PIGS IN RESPONSE TO HIGH AMBIENT TEMPERATURE

In the summertime in our climatic zone, the extreme increase in temperature occurs more frequently. The ambient temperature is one of the major factors that affect the production of pigs (Sirotkin et al., 2011) and it decreases the performance (Misztal et al., 2006). When the border zone of thermal neutrality is overpassed, it is impossible to achieve maximum performance. Kovalčiková, Kovalčik (1974) suggest that crossing the border zone of thermal neutrality is noticed by organism as a burden. The critical rate for pig is considered at 26 °C and more, depending on a category of pigs (Botto, 2011). Pigs are animals which are quite sensitive to high temperatures, and the thermoregulation mechanisms represent great expenses in energy (Fagundes et al., 2009). When pigs are exposed to a high ambient temperature, the possibility to dissipate heat to the environment is limited (Le Bellego et al., 2002). Renaudeau et al. (2006) also deals with the influence of high ambient temperature in growing pigs. Myer and Bucklin (2009) show that pigs can reduce their metabolic heat production by eating less feed. Souza (2009) considered the reduction of feed consumption as the primary response of animals when exposing to high temperatures because pigs do not have functional sweat glands like other livestock species. According to Hsia and Lu (2004), when pigs are given very restricted same amounts of feed, they may need less energy to maintain their body temperature under moderately high environmental temperature (30 °C). Pigs were significantly taller (P <0.05) and significantly longer (P <0.05) and the belly was significantly heavier than in pigs kept at 20 °C. Consequently, their performance is better than that of pigs under optimum environmental temperature. Huynh et al. (2005) indicate that animals respond to increased temperature by decreasing feed intake mainly as a form of reduction of metabolic heat. Quiniou et al. (2000) suggest that thermal stress has a significant negative effect on pigs with higher body weight. Voluntary feed intake depends on temperature and body weight with a marked negative effect of high ambient temperatures in heavier pigs. Hot weather alters pigs’ metabolic system and reduces the production performance and carcass quality. The relationship between growth potential and efficiency in lean meat of pigs is regulated by environmental conditions (Fagundes et al., 2009). Environmental temperature has an influence on the physical appearance and weight of internal organs of pigs (Lefaucheur et al., 1991). Rinaldo et al. (2000) indicate that high temperature had direct effect on fat compared to the cool season, it was also mentioned that in the warm season, fat percentage of the carcass was reduced (P <0.001), whereas less fat was deposited in backfat (P <0.001) and more fat retained in leaf fat (P <0.001). Backfat weight was not modified by indoor temperature or by winter temperature, but it was decreased by summer outdoor rearing (Lebret et al., 2002). Carcass fatness was higher (P <0.01) and lean content was lower (P <0.01) at 22 °C than at 29 °C (Le Bellego et al., 2002). Fagundes et al. (2009) suggest that longissimus thoracis muscle thickness was smaller in pigs under heat stress, but lean content was higher in those animals. Farrell (1978) implies that high temperature usually increases the length of pig carcass compared with that at lower temperatures. The degree of fatness tends towards a leaner carcass in a hot environment. According to Renaudeau (2006), the results showed an improved tolerance to heat stress with duration of exposure indicating an acclimation to heat, it was found out that the physiological reactions during heat acclimation are affected by breed. The aim of this work was to evaluate the impact of high temperature on carcass characteristics of fattening pigs.