COBISS: 1.08 Agris category code: L01 INFLUENCE OF GENDER AND SLAUGHTER WEIGHT ON MEAT QUALITY TRAITS OF HEAVY PIGS Ivona DURKIN Mima DADIC 2, Dijana BRKIC Boris LUKIC Goran KUSEC Marijan MIKOLIN 3, Ines JERKOVIC 3 abstract The investigation was carried out on 99 PIC pig carcasses (49 gilts and 50 barrows) divided into six groups according to their slaughter weight (120, 130, 140, 150, 160 and >170 kg), with the aim to investigate the influence of gender and slaughter weight on meat quality traits. At the slaughter line and in laboratory following meat quality traits were measured: initial and ultimate pH in MS and LD muscle, drip loss, EZ drip, colour parameters, cooking loss and instrumental tenderness. Out of all investigated meat quality traits, gender influenced only cooking loss, while differences between slaughter weight groups were found for almost all meat quality traits measured. However, increasing slaughter weight to >170.00 kg had no major benefit on technological meat quality traits. Key words: pigs / gender / slaughter weight / meat quality 1 INTRODUCTION In order to produce pig carcasses with high lean meat content and simultaneously to save on feed, pig producers aspire to decrease the fattening period. As a consequence, pigs are slaughtered at younger age when meat does not have necessary characteristics for processing into dry-cured or certain traditional fermented products. In Croatia, it is generally accepted that meat from older animals, slaughtered at high live weight is more suitable for processing into dry-cured hams and kulen, a traditional PGI (protection of geographical indication) protected dry-fermented sausage. Indeed, an increase of age/ slaughter weight can improve some meat quality traits, such as IMF(intramuscular fat content) content, flavour profile, juiciness, colour and cooking loss (Candek-Potokar et al., 1998; Weatherup et al., 1998; Toldra, 2002; Latorre et al., 2004), but due to reduced growth and feed efficiency the cost of production is increased. In addi- tion, meat from older animals is often characterised as having less desirable meat quality traits (Cisneros et al., 1996; Candek-Potokar et al., 1998; Latorre et al, 2004; Latorre et al., 2009) and the production of heavy pigs in most cases results in overly fatty primal cuts with lower added value. Thus, it is important to determine slaughter weight/age at which the pig meat will have suitable quality traits for further processing into dry-cured or fermented products at optimal costs of production such as feeding. Therefore, the aim of this study was to evaluate the effects of sex and slaughter weight of finishing pigs on meat quality traits. 2 MATERIAL AND METHODS The investigation was carried out on 99 P337xC23 PIC (Pig Improvement Company) pigs in 2x6 factorial arrangement. Pigs were grouped based on gender and 1 Fac. of Agriculture in Osijek, Kralja Petra Svačica 1d, 31000 Osijek, Croatia, e-mail: idurkin@pfos.hr 2 Ministry of Agriculture, Ulica grada Vukovara 78, 10000 Zagreb, Croatia 3 Belje Inc., Industrijska zona 1, Mece, 31326 Darda, Croatia average slaughter weight (120, 130, 140, 150, 160 and >170 kg). Animals were reared in the test station under controlled conditions and had ad libitum access to feed and water. The pigs were fed ST-1 diet (till 58th day of the fattening), ST-2 diet (from 58th till 100th day of the fattening) and ST-3 diet (from 100th until the last day of the fattening). These diets were designed to meet the nutritional requirements of the pigs at mentioned phases of fattening. Live weight of the pigs was recorded at the beginning and at the end of the investigation; after the pigs reached 100 kg live weight the weighing was performed at two weeks interval. When the animals reached the planned average slaughter weight (±3 kg), they were transported to slaughter house, so the pigs within each treatment were slaughtered at the same day. After stunning using CO2, the pigs were exsanguinated and further processed according to the common practice used in commercial abattoirs. At the slaughter line and in laboratory, following meat quality traits were measured: initial pH values (pH45) measured 45 minutes after slaughter and ultimate pH values measured after 24h of cooling at m. longis-simus dorsi (LD) and m. semimembranosus (MS) of primarily processed pig carcasses. Drip loss was measured by bag method according to Honikel (1987) after 24h of cooling at 4 °C, while EZ drip was measured as described by Christensen (2003). Light reflectance scores for CIE L*, a* and b* were obtained using a Minolta CR-410 colorimeter (Minolta Camera Co. Ltd., Osaka Japan) with a D65 light source and eight-degree standard observer. Instrumental tenderness was measured on at least four subsamples of 2.54 cm thick LD chops. Prior to measurements chops were defrosted for 24h, sealed in plastic bags and cooked in water bath until an internal temperature of 73 °C. The samples were cooled at 4 °C overnight. Shear force was measured using a TA.XTplus Texture Analyser fitted with a 1 mm thick Warner-Bratzler shear attachment. The mean value of maximal strength necessary for cutting the samples was calculated with a Texture Exponent 4.0 Software (Stable Micro Systems Ltd., UK) and presented as Warner-Bratzler Shear Force (WBSF, N). Cooking loss was established from LD chops used for shear force determination. It was calculated from weights taken before and after cooking and expressed as a percentage. Data were analysed using GLM procedure of Sta-tistica 8.0. The model included gender, slaughter weight (SW) as fixed effects. The differences between investigated groups were determined by Fisher LSD test, where P < 0.05 was classified as significant difference. 3 RESULTS AND DISCUSSION The effect of gender and slaughter weight on meat quality traits are presented in Table 1. No significant differences between sexes were obtained in pH values measured 45 minutes and 24h post mortem in LD and MS muscles. This is in accordance with the results of Latorre et al. (2004), Jaturasitha et al. (2006), Renaudeau and Mourot (2007), Peinado et al. (2008) and Palomares-Cuellar et al. (2011). Contrary, Larzul et al. (1997) reported higher pH values in LD muscle in barrows than in gilts, while Barton-Gade (1987) reported higher ultimate pH values in SM muscle in barrows than in gilts. The inconsistency between these two studies can be explained by the difference in genotypes, body weight as well as pre-slaughter handling and handling of the carcasses. Furthermore, there was no difference between genders neither in drip loss and EZ drip nor in Minolta colour (CIE-L*, a*, b*) values. Opposite to our results, Renaudeau and Mourot (2007) reported significant effect of sex on drip loss values, while Cisneros et al. (1996) and Palomares-Cuellar et al. (2011) reported higher CIE-a* values in gilts than in barrows. In addition, Cisneros et al. (1996) reported that subjective colour, firmness, and marbling scores were higher for barrows, indicating that they had darker, firmer muscle with more visible marbling compared to gilts. Finally, in the present study, the only difference between sexes was found for cooking loss values. This could be a consequence of higher intramuscular fat level usually found in barrows, which is in negative correlation with cooking loss (Huff-Lonergan et al., 2002). Our results are in agreement with the results of Eikelenboom and Hov-ing-Bolink (1993), Piao et al. (2004) and Latorre et al. (2004), who also found that meat from gilts had greater cooking losses than meat from barrows. Most studies which investigated influence of slaughter weight on meat quality traits did not find any effect of slaughter weight on pH values (Leach et al., 1996; Candek-Potokar et al., 1998; Correa et al., 2006). This is in agreement with our results on pH24, but not pH45 values. Pigs slaughtered at 140 kg (Table 1) had higher pH45 in MS muscle than pigs slaughtered at 120 kg and >170 kg, while the other groups did not differ significantly. The same group also had the highest pH45 measured in LD muscle. Although we could not establish significant differences between groups in pH values measured 24h post mortem in MS or LD muscle, in the table it can be seen that the highest pH24 values in MS muscle was recorded in groups slaughtered at 130 kg and 140 kg LW (live weight). Also, the difference between these two groups and the group slaughtered at 150 kg with the lowest pH24 values was close to significant (P = 0.0511 and 0.0501, respectively). It is well known that a higher pH is associated with better water holding capacity of meat. Thus, the pig group slaughtered at 140 kg had the lowest drip loss and EZ drip values. Drip loss decreased significantly with an increase of slaughter weight from 73 to 137 kg reported by Martin et al. (1980) and 100 to 130 kg determined by Piao et al. (2004). The results could not be confirmed in our investigation. However, the slaughter weights in the present study were markedly higher than slaughter weights in those investigations. Meat colour represents one of the most important meat quality traits because of its direct influence on consumer acceptance and high correlation to functional characteristics of meat, such as pH and water holding capacity. Results presented in Table 1 show that pigs slaughtered at 130 and 150 kg had higher CIE-L* values than pigs slaughtered at 140 and 160 kg, while pigs slaughtered at 120 and >170 kg LW did not differ statistically from other pig groups. Contrary to these results, other studies (Candek-Potokar et al., 1998; Piao et al., 2004; Correa et al., 2006) reported that slaughter weight did not influence luminosity. Increase of slaughter weight is accompanied with an increase of age and due to higher pigment content, meat from older animals usually produce redder meat (Martin et al., 1980; Piao et al., 2004; Latorre et al., 2004). Our results are in agreement with the results of these authors. A pig meat should have CIE-L* values between 42 and 50, drip loss less than 5% and pH24 less than 6.00 in order to be classified into RFN (Red, Firm, Non-exudative) quality class (Warner et al. (1997)). In Table 1, it can be noticed that mean CIE-L*, drip loss, and EZ drip values were to some extent higher than normal in all investigated pig groups. This could be due to scalding process and depressed heat transfer during chilling of the carcasses originated from pigs slaughtered at higher live weights. The slaughter weight influenced significantly cooking loss and WBSF values. The highest cooking loss was found in group slaughtered at 120 kg live weight, while the lowest was in group slaughtered at >170 kg. Instrumental tenderness, by WBSF was higher in groups slaughtered at 140 and 160 kg than in groups slaughtered at 120, 130, 150 and >170 kg. These differences between investigated groups might be a consequence of different calpain status and CAST genotype of the animals as it has been reported that activity of calpain system, as well as genetic background of the animal represents the key determinant of meat tenderness (Koohmariae, 1992; Taylor et al., 1995; Maltin et al., 2003; Durkin, 2011). 4 CONCLUSIONS In the present study, no significant differences between genders were found for any of investigated technological meat quality traits, except for cooking loss. Although we found significant differences between groups for pH45 in MS and LD muscle, drip loss, EZ drip, Minolta colour parameters, cooking loss and instrumental tenderness, these differences actually have no practical importance. Therefore, from technological aspect, slaughtering animals at higher live weights has no major benefit on quality of their meat. However, further investigations which will include chemical composition and Table 1: Influence of gender (G) and slaughter weight (SW) on investigated meat quality traits Gender (G) Slaughter weight (SW) Variable Barrows Gilts MSE 120 kg 130 kg 140 kg 150 kg 160 kg >170 kg MSE G SW Number 50 49 15 17 15 17 18 17 pH45 MS* 6.14 6.15 0.03 6.07b 6.17* 6.29a 6.18ab 6.13ab 6.05b 0.06 n.s. <0.001 pH45 LD** 6.21 6.21 0.04 6.23* 6.16b 6.37a 6.19ab 6.23ab 6.12b 0.06 n.s. n.s. pH24 MS 5.69 5.66 0.02 5.64 5.73 5.73 5.62 5.72 5.63 0.04 n.s. n.s pHM LD 5.61 5.59 0.08 5.61 5.62 5.64 5.58 5.60 5.57 0.03 n.s. n.s. Drip loss (%) 6.12 6.31 0.37 5.70bc 5.66b 4.67c 7.73a 7.09ab 6.14abc 0.64 n.s. <0.01 EZ drip (%) 6.46 6.55 0.41 5.85b 5.92b 5.21b 9.11a 6.31b 6.40b 0.71 n.s. <0.01 CIE-L* 53.54 54.10 0.32 54.31* 54.50a 52.73b 54.51a 52.85b 53.99ab 0.55 <0.1 n.s. CIE-a* 17.28 17.23 0.13 16.16c 17.11b 17.04b 17.11b 17.86a 18.05a 0.23 n.s. <0.001 CIE-b* 7.52 7.62 0.11 7.13c 7. 8 6.96c 8.08a 7.47bc 7.83ab 0.19 n.s. <0.001 Cooking loss (%) 31.85? 33.03x 0.21 33.66a 32.01bc 33.09* 32.19b 32.69ab 31.15c 0.36 <0.001 <0.001 Shear force (N) 50.83 50.96 1.05 50.56b 47.66b 56.99a 46.71b 54.85a 49.04b 1.81 n.s. <0.001 a, b, c, d, x, y P < 0.05; n.s.-not significant; *m.. semimembranosus, **m. . longissimus dorsi sensory aspects of meat quality, such as IMF level, juiciness and flavour profile are recommended. 5 ACKNOWLEDGMENT Results presented in this paper are the result of the scientific project "Early prediction of Pig Carcass and Meat Quality" investigations. The project was granted by Ministry of Science, Education and Sports, Republic of Croatia. 6 REFERENCES Barton-Gade P. A. 1987. Meat and fat quality in boars, castrates and gilts. Livestock Production Science, 16: 187-196 Cisneros F., Ellis M., McKeith F. K., McCaw J., Fernando R. L. 1996. 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