Effect of gender, terminal sire line and age at slaughter on performance, carcass characteristics and meat quality of heavy pigs

Transcription

1 Animal Science 2003, 77: /03/ $ British Society of Animal Science Effect of gender, terminal sire line and age at slaughter on performance, carcass characteristics and meat quality of heavy pigs M. A. Latorre 1, P. Medel 1, A. Fuentetaja 2, R. Lázaro 1 and G. G. Mateos 1 1 Departamento de Producción Animal, Universidad Politécnica de Madrid, Ciudad Universitaria, Madrid, Spain 2 COPESE S. A., Sepúlveda, Segovia, Spain Present address : Imasde Agropecuaria S.L.Isabel Colbrand, 10, 4ª pl.local 90, Madrid, Spain. Corresponding author. ggmateos@pan.etsia.upm.es Abstract Two hundred and forty pigs of 56 ± 3 days of age were used to investigate the effects of sex (barrows; gilts), boar sire (DD, Danish Duroc; ND LW, Dutch Duroc Large White ; P LW, Pietrain Large White) and slaughter age (160; 175 days) on performance and carcass and meat quality. Treatments were arranged factorially (2 3 2) and there were four replicates (five pigs per replicate) per treatment. The female line was Landrace Large White in all cases. Barrows had greater daily food intake (P < 0 001) and average daily gain (P < 0 01) and had poorer food conversion ratio (P < 0 001) than gilts. Carcasses from castrates were fatter and had a lower yield of trimmed lean cuts than carcasses from females (P < 0 001). Longissimus muscle from barrows had more intramuscular fat and higher a* value than muscle from gilts (P < 0 05). Pigs from DD sire line grew faster (P < 0 05) and had a better food conversion ratio (P < 0 001) than pigs from the other two lines. Dressing proportion and backfat thickness were greatest for P LW sired pigs (P < 0 01) and proportion of trimmed lean cuts was greater for DD and P LW than for ND LW sired pigs (P < 0 01). Longissimus muscle from DD sired pigs had less protein (P < 0 01) and more intramuscular fat (P < 0 001) than muscle from the remaining lines. Longissimus muscle from P LW line had more intense colour than muscle from DD and ND LW lines (P < 0 01). Pigs slaughtered at 175 days had poorer food conversion ratio (P < 0 01) and less trimmed primal cut proportion (P < 0 001) than pigs slaughtered at 160 days. Also, increasing the age at slaughter increased intramuscular fat content (P < 0 01), a* value (P < 0 001) and colour intensity of the muscle (P < 0 01). Danish Duroc boars are a good alternative to ND LW or P LW boars for production of heavy pigs whether the crossbreds are sacrificed at 160 or 175 days. Also, an increase in age at slaughter impairs growth efficiency and yield of lean cuts but improves some aspects of meat quality, which might be of interest in the production of heavy pigs destined for the dry-cured product industry. Keywords: carcass quality, genotype, growth, meat quality, pigs. Introduction Sex, breed and age at slaughter influence growth performance, carcass quality and sensorial characteristics of meat (Cisneros et al., 1996; Ellis et al., 1996; Unruh et al., 1996; Lebret et al., 2001). Entire males are leaner and more efficient than castrates and gilts, but have a lower proportion of intramuscular fat (Barton-Gade, 1987) and develop boar taint with age (Diestre et al., 1990) both of which impair meat quality (Ellis and McKeith, 1993). A total of 36 million pigs were slaughtered in Spain in and the production was based largely on Landrace and Large White sows, with the slaughter generation produced by back-crossing the crossbred sows with lean purebreds or synthetic boars selected for carcass leanness. Moreover, 33 million hams and shoulders, mostly from gilts and entire males, with an average slaughter weight of around 100 kg, were destined to produce dry-cured hams (Ministerio de Agricultura, Pesca y Alimentación, 2002). Highly muscled pigs (i.e. Pietrain and Belgian Landrace) are leaner but less appropriate than other breeds for the production of

2 34 Latorre, Medel, Fuentetaja, Lázaro and Mateos dried hams because of the poor characteristics of the meat during the curing process (Candek-Potokar et al., 2002). In this respect, the Duroc is an attractive alternative to traditional lean lines because of its high proportion of intramuscular fat (Barton-Gade, 1987; Blanchard et al., 1999) and appropriate sensorial characteristics of the meat (Bejerholm, 1984). However, some reports indicate that these advantages may be offset by the greater carcass fatness and heavier shoulders (McGloughlin, 1988; Blanchard et al., 1999). On the other hand, the potential of the Duroc for lean meat production has improved dramatically over recent years (Danbred, 2003) and in fact, further improvements in this respect may even be deleterious for pork quality (Wood, 1993). It has been reported that marbling and backfat thickness are positively correlated (Huff-Lonergan et al., 2002) and that a low percentage of intramuscular fat reduces tenderness and juiciness of the meat (DeVol et al., 1988). However, Edwards et al. (1992) found that the regression of intramuscular fat proportion on subcutaneous backfat thickness differed among breeds, indicating that the Duroc has a more favourable partitioning between intramuscular and subcutaneous fat depots than the Large White. Therefore, there is a need to evaluate the genetic impact of alternative sire lines. It is widely accepted that quality of meat improves with age at slaughter (Candek-Potokar et al., 1998) but as age increases, carcass leanness and food efficiency decreased. Recently, a new rule of the European Union (Diario Oficial de las Comunidades Europeas, 1999) has prohibited the use of fresh hams weighing less than 9 5 kg for production of Serrano cured hams. Therefore, an increase in slaughter weight to at least 120 to 125 kg is needed to fulfil this requirement. It is advisable to test the adaptation of existing genetic lines to castration and slaughter at heavy weights with respect to growth and meat quality. The aim of this study was to investigate the effect of gender, sire line and age at slaughter on growth performance, carcass characteristics and meat quality of heavy pigs destined for the dry-cured ham industry. Material and methods Productive performance A total of 240 pigs of 56 ± 3 days (25 ± 0 7 kg) was used to study the influence of sex (castrates v. gilts), sire line (coded DD, ND LW and P LW) and slaughter age (160 v. 175 days) on performance and carcass and meat quality traits. Sire line semen used was Danish Duroc (DanBred INT, Denmark) for DD, Dutch Duroc Large White (Stamboek, The Netherlands) for ND LW and Pietrain Large White (Gene +, France) for P LW. The female line was Landrace Large White in all cases. The pigs were placed in pens ( m) in an environmentally controlled finishing barn, and had ad libitum access to water and pelleted food throughout the trial. Each of the 12 treatments was replicated four times and the experimental unit was a pen with five pigs. The routine of animal care and experimental procedures used in this study conformed to regulations and guidelines of Boletin Oficial del Estado (1988). Diets were formulated to meet or exceed the nutrient requirements recommended by the National Research Council (1998) for pigs at this age. The ingredient composition, the estimated nutrient value (Fundación Española para el Desarrollo de la Nutrición Animal, 1999) and the determined analyses of the diets (Association of Official Analytical Chemists, 2000) are indicated in Table 1. Live weight and food consumption were recorded per pen at 14-day intervals to determine daily gain, daily food intake and food to gain ratio. Carcass quality At planned age (160 or 175 ± 3 days), pigs were weighed and immediately transported to a slaughterhouse located at 70 km from the experimental station. During the 17 h of waiting time at the slaughterhouse, water, but not food, was provided. Pigs were stunned (225 to 380 V, 0 5 A, 5 to 6 s) and killed by exanguination. Following evisceration, carcasses were split down the midline and hot weights were recorded to calculate carcass yield. Afterwards, the head was removed at the atlanto-occipital junction. At 45 min post mortem, carcass length (from the posterior edge of the Symphysis pubis to the anterior edge of the first rib), ham length (from the anterior edge of the Symphysis pubis to the hock joint), ham perimeter (at its widest side), backfat thickness (between the 3rd and 4th last ribs level) and fat thickness at gluteus medius muscle (at the thinnest point) were measured in the left side of each carcass using a ruler with a precision of 0 5 mm. Also, ph 45 was measured at the semimembranosus muscle using a ph meter (CRISON 507, Crison Instruments SA, Barcelona, Spain) fitted with a glass electrode. A chop of 150 ± 15 g of the longissimus muscle was taken from the left side loin of the carcass at the last rib level, placed in a plastic bag and frozen (-20ºC) for meat quality analysis. The remaining cuts of the carcasses were chilled (4ºC overnight) until measurements. At 24 h post mortem, ultimate ph (ph 24 ) was measured at the semimembranosus muscle. Also, untrimmed ham and shoulder weights from

3 Carcass and meat quality of heavy pigs 35 Table 1 Ingredient composition and estimated and determined analysis of the diets (g/kg diet) 56 to 63 days 63 to 105 days 105 days to slaughter Ingredient Barley Wheat Rye Soya-bean meal (0 47 CP) Bakery by-product meal Full-fat soya beans 80 0 Blended fat Sugar-beet molasses L-lysine, (0 50) DL-methionine, (0 99) L-threonine, (0 25) Sodium chloride Calcium carbonate Dicalcium phosphate Vitamin and mineral Estimated nutrient content Net energy (MJ/kg) Crude protein (CP; N 6 25) Lysine Neutral-detergent fibre Ether extract Ash Calcium Total phosphorus Sodium Determined nutrient content Moisture Ash Crude protein (N 6 25) Ether extract Supplied (mg/kg diet): retinol 2 1; cholecalciferol 0 03; DL-α-tocopherol 7 37; menadione 0 5; thiamin 0 2; riboflavin 2 5; pantothenic acid 8; niacin 15; choline 350; pyridoxine 0 2; cyanocobalamin 0 015; Cu 75; Fe 80; Mn 50; Zn 110; Co 0 1; Se 0 2; I 0 5. Estimates from tables of Fundación Española para el Desarrollo de la Nutrición Animal (1999). each carcass were recorded before and after chilling to estimate cooler shrink (dripping losses). At 48 h post mortem, hams, shoulders and the right side loin from each carcass were trimmed and weighed for yield evaluation. The weight of the loins was calculated by duplicating the weight of the right-side loin. The experimental unit was the pen with five pigs penned together. Meat quality Weights of loin samples were recorded before freezing and after defrosting (24 h at 4ºC and then blotted dry) to estimate thawing losses. Meat colour was evaluated with a chromameter (CM 2002 Minolta, Minolta Camera, Osaka, Japan) using objective measurements (Commission International de l Eclairage, 1976). Average of three observations of lightness (L*) and two colour co-ordinates (a* and b*) were used for further analysis. Also, the chroma value (c* = (a* 2 + b* 2 )) that describes the intensity of the colour, was calculated. In addition, pigment content (myoglobin) was measured in two slices from each chop with a spectrophotometer (Beckman DU -640, Beckman Instrument, Fullerton, USA) by the method of Hornsey (1956) as modified by Boccard et al. (1981). Each slice was evaluated twice and the average value was used for further analyses. A sample of 5±0 1 g of minced meat was taken into an extraction vessel and a mixture of 20 ml acetone and 1 ml water was added and stirred for 30 s with a glass rod. Afterwards, 0 5 ml HCl (12 mol/l) was added and the suspension was kept in a sealed vessel, overnight in the dark and then filtered. Absorbance of the clear solution was measured at 510 nm in cells of 1 cm patch length. The concentration of myoglobin, in mg/g fresh weight, was obtained by multiplying the absorbance reading by the factor

4 36 Latorre, Medel, Fuentetaja, Lázaro and Mateos Ether extract, crude protein and moisture content of the loin samples were determined by using a NIT meat analyser (Infratec 1265, Tecator, Höganäs, Sweden). Chops were trimmed of all visible external fat and then minced. The readings were made by spectroscopy in near infrared between 700 and 1100 nm. Cooking losses were determined by the method described by Honikel (1998). A fresh slice of 80 ± 5 g from each chop was bagged in a thin-walled plastic bag, placed in a water bath (Precisterm, J. P. Selecta SA, Barcelona, Spain) and heated at a constant temperature of 75ºC. The temperature of the meat was controlled by a probe (Hanna Instruments, Woonsocket, RI 02895, USA). When the end-point temperature in meat was attained (70ºC), samples were removed from the water bath, left to cool for 30 min and blotted dry. Weights of loin samples were recorded before and after cooking to estimate cooking losses. The Warner-Bratzler force of cooked meat was measured using a texture meter (TA-XT2, Stable Micro Systems, Surrey GU 1YL, England) by the method described by Honikel (1998). Samples were cut with a cross-section of 100 mm 2 (10 10) with the fibre direction parallel to a long dimension of at least 30 mm. The full scale load was set at 5 kg, the crosshead speed was 6 mm/s and the fibre axis was perpendicular to the direction of the blade. Eight slices per meat sample were analysed. The experimental unit was comprised by the chops from the five pigs penned together in the performance trial. Statistical analysis Data were analysed as a completely randomized design with treatments arranged factorially (2 3 2), using the General Linear Model program of the SAS statistical package (Statistical Analysis Systems Institute, 1990). Model included sex, sire line and slaughter age as main effects and also the interactions. Data in tables are presented as means. Results Productive performance No significant interactions among gender, boar line and slaughter age were detected for any of the performance traits studied and therefore only main effects are presented (Table 2). At the beginning of the trial, castrates were heavier than gilts (24 9 v kg; P < 0 01) because pigs were allotted to treatments on the basis of age and not on initial body weight. From 56 to 105 days, barrows ate more food (P < 0 01) and had a poorer food conversion ratio (P < 0 05) than females. Similar results were recorded at 160 days but no differences between sexes were observed from 160 to 175 days. At the end of the trial, barrows ate more food (2 62 v kg/day; P < 0 001), grew faster (943 v. 917 g/day; P < 0 01) and had a poorer food conversion ratio (2 78 v g/g; P < 0 001) than females. Initial weight of the pigs differed among sire lines (24 0, 24 9 and 25 3 kg for DD, ND LW and P LW lines, respectively; P < 0 001) although the age was similar (56 ± 3 days). From 56 to 105 days, progeny of DD had lower daily food intake than progeny of ND LW or P LW pigs (1 90 v and 2 02 kg/ day; P < 0 01) but no differences were detected from 105 days to slaughter. Also, DD line had the best food conversion ratio from 56 to 160 days (P < 0 05) but the differences among lines disappeared thereafter. At the end of the trial, food intake was similar among lines but DD sired pigs grew faster (950 v. 920 and 920 g/day; P < 0 05) and had better food conversion ratio (2 63 v and 2 76 g/g; P < 0 001) than ND LW or P LW sired pigs. Pigs slaughtered at 175 days had greater daily food intake (2 58 v kg/day; P < 0 001) and had poorer food conversion ratio (2 76 v g/g; P < 0 01) than pigs slaughtered at 160 days, but daily gains were similar. Carcass traits The influence of treatment on carcass characteristics is presented in Table 3. Castrates had heavier carcasses (102 2 v kg; P < 0 01) but similar carcass yield (782 v. 781 g/kg; P > 0 05) than females. Also, barrows had fatter carcasses (23 7 v mm for backfat thickness and 21 7 v mm for fat at gluteus medius muscle) and greater hams (37 9 v cm for length and 78 4 v cm for perimeter) than gilts (P < 0 001). No effect of sex on carcass length, ph 45, ph 24 or cooler shrink was detected. Sire breed did not affect carcass weight, but P LW had more carcass yield (787 v. 777 and 781 g/kg) and backfat thickness (23 7 v and 21 4 mm) than DD or ND LW (for each, the overall effect of sire line was P < 0 01). Fat thickness at gluteus medius muscle was greatest for ND LW and lowest for DD, with P LW line intermediate (P = 0 06). Hams and carcasses were longer for DD and ND LW sired pigs than for P LW sired pigs (P < 0 001) whereas the greater ham perimeter was observed for DD and P LW lines (P < 0 05). Progeny from P LW had lower ph 45 than progeny from DD or ND LW (5 92 v and 6 02; P < 0 05) but no influence of genotype on ph 24 or shrink at cooling was observed. Increasing age at slaughter increased carcass weight (106 5 v kg), fat thickness at gluteus medius muscle (21 7 v mm), carcass length (88 4 v cm), ham length (38 3 v cm) and ham perimeter (79 0 v cm) (P < 0 001). However,

5 Carcass and meat quality of heavy pigs 37 Table 2 The effect of sex and sire line on average daily gain (ADG), average daily food intake (ADFI) and food conversion ratio (FCR) Sex (S) Sire line genotype (G) Slaughter age (SA, days) Significance C F s.e. DD ND LW P LW s.e s.e. S G SA Initial weight (kg) a 24 9 b 25 3 c ** *** Final weight (kg) ** *** From 56 to 105 days ADG (g/day) ADFI (kg/day) a 2 02 b 2 02 b ** ** FCR (g/g) a 2 09 b 2 04 ab * * From 105 to 160 days ADG (g/day) a 850 b 853 b ** ** ADFI (kg/day) *** FCR (g/g) a 2 77 b 2 79 b ** ** From 160 to 175 days ADG (g/day) a 1162 ab 962 b ADFI (kg/day) FCR (g/g) From 56 days to slaughter ADG (g/day) a 920 b 920 b ** * ADFI (kg/day) *** *** FCR (g/g) a 2 76 b 2 76 b *** *** ** a,b,c Mean values within a row with different superscripts were significantly different (P < 0 05). C=castrated males; F=females; DD=Danish oc; Dur ND LW=Dutch Dur oc Large White; P LW=Pietrain Large White. No. =24 for sex ef fect and no. =16 for sire line effect from 56 to 105 days and from 105 to 160 days. No. =12 for sex ef fect and no. =8 for sire line effect from 160 to 175 days. There were no significant interactions (P > 0 05). Approaching significance (P=0 08).

6 38 Latorre, Medel, Fuentetaja, Lázaro and Mateos Table 3 The effect of treatment on carcass traits Sex (S) Sire line genotype (G) Slaughter age (SA, days) Significance s.e. s.e. s.e. C F (no. =24) DD ND LW P LW (no. =16) (no. =24) S G SA Carcass weight (kg) ** *** Carcass yield (g/kg) a 781 a 787 b ** Backfat thickness (mm) a 21 4 a 23 7 b *** ** Fat thickness at m. gluteus medius (mm) a 21 3 b 20 7 ab *** P = 0 06 *** Carcass length (cm) a 87 6 a 85 8 b *** *** Ham length (cm) a 37 6 b 36 8 c *** *** *** Ham perimeter (cm) a 77 2 b 78 1 a *** * *** ph a 6 02 a 5 92 b * ph * Cooler shrink (g/kg) a,b,c Mean values within a row with different superscripts were significantly different (P < 0 05). C=castrated males; F=females; DD=Danish oc; Dur ND LW=Dutch Dur oc Large White; P LW=Pietrain Large White. Interaction slaughter age sire line (P < 0 01) for carcass length; there were no other significant interactions (P > 0 05). Calculated from hams and shoulders, exclusively. Table 4 The effect of interaction of slaughter age and sire line on carcass length (cm) Slaughter age (days) Sire line genotype DD ND LW P LW s.e.(no. =8) 0 42 Significance of interaction ** DD=Danish Dur oc; ND LW=Dutch Dur oc Large White; P LW=Pietrain Large White. carcass yield and backfat thickness were not modified by age. Pigs slaughtered at 160 days had higher ph 24 than pigs slaughtered at 175 days (5 87 v. 5 78; P < 0 05) but no effect of age was detected for ph 45 or cooler shrink. For each age (160 v. 175 days), all the pigs were sacrificed on the same day. Therefore, the effects of age and day of slaughter on ph might be confounded. A significant interaction (slaughter age genotype) was detected for carcass length (P < 0 01); the increase in length observed with age was more pronounced for DD than for ND LW and P LW sired pigs (Table 4). The influence of treatment on weight and yield of lean cuts of the carcasses is shown in Table 5. Gilts had a similar proportion of shoulders but greater proportion of loins (73 v. 70 g/kg; P < 0 001) and hams (264 v. 261 g/kg; P < 0 01) than barrows, and as a consequence, combined lean cut proportion was higher for females (489 v. 482 g/kg; P < 0 001). Weights of primal lean cuts were higher for progeny of DD and P LW than for those of ND LW (49 7 and 49 1 v kg; overall effect of sire line was P < 0 01). Loin yield was greater for P LW sire line than for DD or ND LW sire lines (73 v. 71 and 70 g/kg; P < 0 01). However, DD sired pigs had higher ham yield than ND LW or P LW sired pigs (266 v. 261 and 261 g/kg; P < 0 01). As a consequence, ND LW sired pigs had the lowest yield of combined lean cuts (481 v. 489 and 486 g/kg, for DD and P LW, respectively; P < 0 01). As expected, the weight of trimmed lean cuts increased with age (51 1 v kg; P < 0 001) but their proportions in the carcass were reduced (480 v. 491 g/kg; P < 0 001). Meat traits The influence of treatment on meat quality is shown in Table 6. Meat from barrows had more intramuscular fat than meat from gilts (27 6 v g/ kg; P < 0 05). No effects of sex were detected for L*, b* and c* values, but meat from castrates was redder

7 Carcass and meat quality of heavy pigs 39 Table 5 The effect of treatment on trimmed lean cuts Sex (S) Sire line genotype (G) Slaughter age (SA, days) Significance s.e. s.e. s.e. C F (no. =24) DD ND LW P LW (no. =16) (no. =24) S G SA Trimmed cut weight (kg) Loin a 6 9 b 7 4 a ** *** Ham a 26 0 b 26 3 b ** *** Shoulder a 15 1 b 15 4 ab ** * *** Loin+ham+shoulder a 48 0 b 49 1 a ** *** Trimmed cut yield (g/kg carcass) Loin a 70 a 73 b *** ** *** Ham a 261 b 261 b ** ** *** Shoulder *** Loin+ham+shoulder a 481 b 486 a *** ** *** a,b Mean values within a row with different superscripts were significantly different (P < 0 05). C=castrated males; F=females; DD=Danish oc; Dur ND LW=Dutch Dur oc Large White; P LW=Pietrain Large White. There were no significant interactions (P > 0 05). Table 6 The effect of treatment on meat traits Sex (S) Sire line genotype (G) Slaughter age (SA, days) Significance s.e. s.e. s.e. C F (no. =24) DD ND LW P LW (no. =16) (no. =24) S G SA Chemical composition (g/kg) Moisture a 739 b 737 ab ** P = 0 08 Fat a 23 8 b 24 9 b * *** ** Protein a 240 b 241 b ** Colour parameters L* a* * *** b* a 9 19 a 9 89 b ** c* a 10 2 a 10 9 b ** ** Pigment content (mg myoglobin perg) Warner-Bratzler force (kg) Cooking losses (g/kg) Thawing losses (g/kg) *** a,b Mean values within a row with different superscripts were significantly different (P < 0 05). C=castrated males; F=females; DD=Danish oc; Dur ND LW=Dutch Dur oc Large White; P LW=Pietrain Large White. Interaction of sex sire line (P < 0 05) for protein content; there were no other significant interactions (P > 0 05).

8 40 Latorre, Medel, Fuentetaja, Lázaro and Mateos Table 7 The effect of interaction of sex and sire line on protein content of loin (g/kg) Sex Sire line genotype C F DD ND LW P LW s.e.(no. =8) 1 2 Significance of interaction * C=castrated males; F=females; DD=Danish oc; Dur ND LW=Dutch Dur oc Large White; P LW=Pietrain Large White. than meat from females (4 63 v. 4 34; P < 0 05). No influence of gender was observed for resistance to cutting or cooking and thawing losses. Meat from DD sired pigs had less protein (238 v. 240 and 241 g/kg; overall effect of sire line was P < 0 01) and more fat (30 4 v and 24 9 g/kg; P < 0 001) than meat from ND LW or P LW sired pigs. Moisture content was lowest for DD and highest for ND LW line pigs with an intermediate value for P LW (735, 739 and 737 g/kg; P < 0 01). Pigs from P LW line had a higher b* value (9 89 v and 9 19) and more intense colour of the meat (10 9 v and 10 2) than pigs from DD and ND LW sire lines (P < 0 01). No differences among breeds were observed for Warner-Bratzler shear force or losses during cooking or thawing. A significant interaction (sex genotype) was detected for protein content of the meat which was independent of breed for females but lower for DD sired barrows than for ND LW or P LW sired barrows (P < 0 05) (Table 7). An increase in slaughter age increased intramuscular fat (27 9 v g/kg; P < 0 01) and tended to decrease moisture content of the loin (736 v. 738 g/ kg; P = 0 08). Also, redness score (4 75 v. 4 21; P < 0 001) and intensity of colour (10 7 v. 10 3; P < 0 01) increased with age. Thawing losses were highest for pigs slaughtered at 160 days (87 v. 64 g/ kg; P < 0 001) but no influence of age on shearing force and cooking losses was observed. Discussion Productive performance Irrespective of experimental treatment, pigs grew less and had a poorer food conversion ratio than expected from 105 to 160 days of age. In fact, pigs grew faster from 56 to 105 days than from 105 to 160 days, a period that coincided with a time of extreme ambient temperatures. In fact, from 142 to 156 days of age the temperature occasionally reached 34ºC inside the building. Consequently, food intake was reduced and daily gains and food conversion ratio were penalized in this period. From 160 to 175 days, daily gains increased as a consequence of more appropriate temperatures or the presence of compensatory growth. The effects of gender. Barrows grew faster and had poorer food conversion ratio than gilts, results that agree with previous research (Leach et al., 1996; Weatherup et al., 1998; Augspurger et al., 2002) and are consistent with the higher voluntary food intake and greater backfat thickness of castrates (Friesen et al., 1994; Weatherup et al., 1998). The effects of breed of sire. DD sired pigs exhibited greater weight gains than the ND LW and P LW sired pigs. McGloughlin et al. (1988) found that American and Irish Duroc boars grew faster than Large White boars and Tibau et al. (1997) reported for purebreds that Duroc grew more than Pietrain but less than Large White. In the present study progeny from DD boars had a better food conversion ratio than progeny from ND LW or P LW boars, which is opposite to findings of Edwards et al. (1992) and Blanchard et al. (1999) comparing Duroc and Large White sired pigs, and of Tibau et al. (1997) comparing Duroc, Pietrain and Large White pigs. The DD line used in our trial had been intensively selected for food efficiency and lean carcasses which might have resulted in better growth performance than expected on the basis of results obtained with other Duroc lines (Kuhlers et al., 1996). In fact, DD sired pigs had similar appetites and were leaner at slaughter than the other lines studied, results that are consistent with the food conversion data. The effects of slaughter age. Age at slaughter did not affect growth rate which agrees with Johnston et al. (1993) and Candek-Potokar et al. (1998) with pigs from 100 to 130 kg body weight (BW). However, Albar et al. (1990) with castrates and gilts of similar weights reported that daily gains decreased with age. Also, Ellis et al. (1996) found a significant deterioration in growth rate as the final weight increased from 80 to 120 kg. The reasons for these discrepancies are unclear but might be related, at least in part, to the genetic potential of the lines used and the management conditions and temperature during the trial. For example, Tibau et al. (1997) observed a reduction in daily gains of pure Pietrain pigs once they reached 90 kg BW. Also, 1 10 m 2 per pig was allowed in the current trial whereas Albar et al. (1990) housed the pigs in cages with a surface area

9 Carcass and meat quality of heavy pigs 41 of 0 80 m 2 /pig which might have limited the actual growth of the pigs at the end of the trial. Our data indicate that food intake increased and food conversion ratio deteriorated with age, which agrees with Albar et al. (1990) and Weatherup et al. (1998). In fact, Cisneros et al. (1996) found that from 100 to 160 kg BW, food intake increased linearly with age and Leach et al. (1996) observed similarly a linear increase for food conversion ratio. Carcass traits The effects of gender. Barrows had fatter carcasses than gilts which agrees with Friesen et al. (1994) and Weatherup et al. (1998) and is consistent with the higher growth rate and poorer food conversion ratio observed for castrates. No differences in dressing proportion were detected between sexes, which is in accordance with Leach et al. (1996), Weatherup et al. (1998) and Lebret et al. (2001). However, Friesen et al. (1994) and Ellis et al. (1996) reported that carcass yield was greater for gilts than for castrates, a discrepancy that might have been caused by the distinct methodology used for the dissection of the reproductive tissues and the concomitant changes in the amount of saleable meat eliminated with the genitals. In the present trial, carcass length was similar in barrows and gilts, in spite of castrates being heavier. This observation agrees with Cisneros et al. (1996) but not with Leach et al. (1996) who found that females were longer than castrates when they were slaughtered at same weight. In accordance with most previous studies, sex did not affect ph 45 (Edwards et al., 1992; Cisneros et al., 1996; Leach et al., 1996) or ph 24 (Cisneros et al., 1996; Leach et al., 1996; Weatherup et al., 1998). In the present trial, no significant difference was detected between sexes for cooler shrink which disagrees with Cisneros et al. (1996) and with Lebret et al. (2001) who reported lower dripping losses for barrows than for gilts. Castrates had more carcass fat than females which may be responsible for the lower cooler shrink observed. However, in our trial backfat was 2 9 mm thicker in barrows than in gilts but no differences in shrink at cooling were observed. Also, the proportion of dripping losses reported by Cisneros et al. (1996) and by Lebret et al. (2001) ranged from 20 to 30 g/kg, which are higher than the losses found in our trial (from 9 5 to 10 g/kg). Shrink at cooling was studied in the current trial from hams and shoulders exclusively, whereas Cisneros et al. (1996) and Lebret et al. (2001) worked with whole carcasses. Cooling losses increase with the area of exposure and consequently, shrinking will be greater when measured in the whole carcass than when measured in hams and shoulder, exclusively. The influence of sex on proportion of lean cuts is unclear and depends on feeding regime, breed and age at slaughter (Martin et al., 1980). In our study, the proportion of trimmed ham and loin but not of shoulder was greater for gilts than for barrows, which is consistent with data of Unruh et al. (1996). Lebret et al. (2001) found that the proportions of ham, loin and shoulder were greater in gilts than in barrows whereas Fortin (1980) did not find any effect of gender on primal lean cuts. The effects of breed of sire. Breed affected carcass traits in many ways. Carcass yield was lower for DD and ND LW sired lines than for the P LW sired line, in agreement with Tibau et al. (1997) comparing pure Duroc and Pietrain. Backfat thickness was lower for DD and ND LW sired line than for P LW sired line in accordance with McGloughlin et al. (1988) and Candek-Potokar et al. (1998) comparing Duroc and Large White crossbreds. However, Blanchard et al. (1999) observed that backfat thickness and killing-out proportion, in Large White (Large White Landrace) crossbreds increased as the proportion of Duroc increased at the expense of Large White. All this information indicates the need to be cautious when comparing the effects of breed on carcass characteristics because variability among lines within breeds might be wider than variability among breeds which may distort the value of the data. Our results indicate that the DD line used had better productive performance and less carcass fat than previously reported for Duroc. The higher lean content of the carcasses from the DD line compared with the other lines found in the present study is consistent with the food conversion data recorded. Also, progeny from DD and ND LW had longer carcasses than progeny from P LW, which agrees with Tibau et al. (1997) comparing Duroc, Pietrain and Large White purebreds. In the current study, ph 45 was higher for DD and ND LW than for P LW sired pigs which is in accordance with Edwards et al. (1992) comparing Duroc and Large White crossbreds and with Tibau et al. (1997) working with Duroc, Pietrain and Large White purebreds. Wood (1993) has reported that Pietrain pigs are very susceptible to stress and had lower ph 45 and higher frequency of pale, soft and exudative condition of the meat than other breeds. The proportion of trimmed lean cuts was higher for DD and P LW than for ND LW crossbred. Most of the advantage was due to the higher proportion of hams in the DD line and of loins in the P LW line. Traditionally, the proportion of hams has been consistently higher for Pietrain than for Duroc. In

10 42 Latorre, Medel, Fuentetaja, Lázaro and Mateos fact, Tibau et al. (1997) studied the lean proportion of three different breeds and reported the highest value for Pietrain and the lowest for Duroc with Large White in an intermediate position. Also, Blanchard et al. (1999) observed that carcass lean in Large White (Large White Landrace) decreased as the proportion of Duroc in the final product increased at the expense of Large White. The greater proportion of hams observed for the DD progeny in the current report might have been caused by the nature of the Duroc line used, as evidenced by the high lean content of their carcasses. Moreover, in our study Pietrain and Dutch Duroc breeds were introduced at a proportion of 0 25 whereas Danish Duroc was included at 0 50, which could have affected the yield of primal lean cuts. The effects of slaughter age. Pigs slaughtered at 175 days had 4 g/kg higher carcass yield than pigs slaughtered at 160 days but the differences were not significant. Gu et al. (1992) indicated that the allometric coefficient of carcass is greater than unity and therefore carcass yield increases with age which agrees with Ellis et al. (1996) and Weatherup et al. (1998). Although backfat thickness was 0 7 mm thicker in pigs slaughtered at 175 days than in pigs slaughtered at 160 days of age, the difference did not reach significance. This observation agrees with Albar et al. (1990), but not with Ellis et al. (1996) and Cisneros et al. (1996) who observed that backfat increased linearly with age. However, fat thickness at gluteus medius muscle increased with age which agrees with Albar et al. (1990) and Candek-Potokar et al. (1998). As expected, carcass and ham length and ham perimeter increased with age in concordance with Albar et al. (1990) and Candek-Potokar et al. (1997). The influence of age on cooler shrink and ph of the meat is the subject of debate (Leach et al., 1996). In our study, cooler shrink and ph 45 were not affected by age, but ph 24 decreased which agrees with Cisneros et al. (1996) who found a linear decrease of ph 24 with age. However, Albar et al. (1990) and Candek-Potokar et al. (1998) reported no effect of age on ph. On the other hand, lean cut proportion decreased with age, which agress with Carr et al. (1978) and Cisneros et al. (1996). However, other studies have found little effect of age on primal cut distribution (Martin et al., 1981; Albar et al., 1990). Meat traits The effects of gender. In general, sex had little influence on meat traits, except for intramuscular fat that was higher for barrows, which is consistent with the backfat thickness data. Similar results have been reported by Barton-Gade (1987) and Leach et al. (1996) comparing castrates and gilts. Most previous studies have not detected any effect of gender on meat colour as determined by subjective scores (Ellis et al., 1996; Nold et al., 1997), objective parameters (Leach et al., 1996; Weatherup et el., 1998) or pigment content (Barton-Gade, 1987). However, in our study, meat from castrates was redder than meat from females. Opposite findings have been reported by Warriss et al. (1990) and by Lindahl et al. (2001) who detected higher haem pigment concentration and darker muscles in gilts. In the present trial, no differences were detected for thawing losses, Warner- Bratzler shear force or cooking losses between castrates and females confirming previous data (Martel et al., 1988; Cisneros et al., 1996; Ellis et al., 1996; Weatherup et al., 1998). The effects of breed of sire. In general, all the breeds gave acceptable quality of the meat. The greatest intramuscular fat content was recorded for Duroc sired pigs, an observation which is consistent with previous research (Barton-Gade, 1987; Edwards et al., 1992) comparing Duroc and Large White crossbreds. The extent to which proportion of intramuscular fat affects organoleptic properties of pig meat is the subject of debate (DeVol et al., 1988; Martel et al., 1988). Blanchard et al. (1999) studied the influence of the inclusion of Duroc at levels of 0, 0 25 and 0 50 at the expense of Large White in Large White (Large White Landrace) crossbreds and found that intramuscular fat, tenderness and overall acceptability of the meat increased as the inclusion level of Duroc increased. An interesting finding of our trial was that DD boars produced crossbreds with leaner carcasses, that had more intramuscular fat in the loin than ND LW or P LW. Therefore, the use of DD as a boar line might improve meat quality of heavy weight crossbreds without jeopardizing the proportion of lean cuts of the carcass. In the present study P LW sired pigs had a higher yellow score and more intense colour of meat than DD and ND LW sired pigs whereas most of the recent reports have not been able to detect any effect of genotype on meat colour as measured by visual score (Ellis et al., 1996; García-Macías et al., 1996), objective parameters (García-Macías et al., 1996; Nieuwhof et al., 1991) or pigment content (García- Macías et al., 1996). Breed did not influence resistance to cutting or water holding capacity, which agrees with Martel et al. (1988) and Nieuwhof et al. (1991). However, Blanchard et al. (1999) found that shear force and cooking losses were reduced as the level of inclusion

11 Carcass and meat quality of heavy pigs 43 of Duroc in the final product at the expense of Large White increased from 0 to The effects of slaughter age. Age reduced moisture and increased fat content of the loin in agreement with most published studies (Candek-Potokar et al., 1998; Weatherup et al., 1998). In fact, Cisneros et al. (1996) reported that the decrease in moisture and the increase in intramuscular fat of the meat were linear with age. Also, in the current trial, the a* and c* values of the meat increased with age indicating that the meat got redder and had a more intense colour as the pigs matured, which agrees with Gacía-Macías et al. (1996) and Candek-Potokar et al. (1998). However, Cisneros et al. (1996) reported a reduction in subjective colour score with weight whereas no changes were observed by Leach et al. (1996) and Unruh et al. (1996). Thawing losses were reduced with age but no effect was observed for Warner-Bratzler force or cooking losses in agreement with Candek-Potokar et al. (1998). Most researchers have not found any effect of age on these parameters (Ellis et al., 1996; Weatherup et al., 1998), although Leach et al. (1996) indicated that the resistance of meat to cutting increased linearly with age. Conclusions Barrows had greater daily food intake and average daily gain and had a poorer food conversion ratio than gilts. Also, carcasses from castrates were fatter and had more intramuscular fat and a lower proportion of primal cuts than females. Progeny from DD boars performed better and had less backfat and more intramuscular fat than progeny from P LW and ND LW boars. Also, DD and P LW sired pigs had more trimmed primal cut yields than ND LW sired pigs. Therefore, DD boars can be used advantageously as an alternative to P LW and ND LW boars for the production of heavy weight crossbreds destined for the dry-cured ham industry. Slaughtering pigs at 175 days led to a deterioration in productive traits and increased carcass fat but improved some aspects of meat quality which in heavy pigs, destined for the Serrano dry-cured ham industry, may be of benefit. Acknowledgements This work was supported by CDTI project number (MCYT). The authors would like to thank Emilio Gómez Izquierdo (Centro de Pruebas de Porcino, Hontalbilla, Segovia, Spain) for care of the animals and María Dolores García Cachán (Estacion Tecnológica de la Carne, Guijuelo, Salamanca, Spain) for help in the analyses of the meat. References Albar, J., Latimier, P. and Granier, R Poids d abattage: évolution des performances d engraissement de carcasse de porcs abattus au delá de 100 kg. Journées de la Recherche Porcine en France 22: Association of Official Analytical Chemists Official methods of analysis, 17th edition. AOAC, Arlington, VA. Augspurger, N. R., Ellis, M., Hamilton, D. N., Wolter, B. F., Beverly, J. L. and Wilson, E. R The effect of sire line on the feeding patterns of grow-finish pigs. Applied Animal Behaviour Science 75: Barton-Gade, P. A Meat and fat quality in boars, castrates and gilts. Livestock Production Science 16: Bejerholm, C Experience in taste testing fesh pork at the Danish Meat Research Institute. Proceedings of the 30th European meeting of meat research workers, Bristol, UK, pp Blanchard, P. J., Warkup, C. C., Ellis, M., Willis, M. B. and Avery, P The influence of the proportion of Duroc genes on growth, carcass and pork eating quality characteristics. Animal Science 68: Boccard, R., Buchter, L., Casteels, E., Cosentino, E., Dransfield, E., Hood, D. E., Joseph, R. L., MacDougall, D. B., Rhodes, D. N., Schön, I., Timbergen, B. J. and Touraille, C Procedures for measuring meat quality characteristics in beef production experiments. Report of a working group in the Commission of the European Communities (CEC) beef production research programme. Livestock Production Science 8: Boletín Oficial del Estado Real Decreto Español 223/ 88 sobre la protección de los animales utilizados para experimentación y otros fines científicos. Boletín Oficial del Estado 67: Candek-Potokar, M., Monin, G. and Zlender, B Pork quality, processing, and sensory characteristics of dry-cured hams as influenced by Duroc crossing and sex. Journal of Animal Science 80: Candek-Potokar, M., Zlender, B. and Bonneau, M Effets du poids et de l abattage sur la composition chimique du muscle long dorsal de porcs croisés Duroc (Landrace Large White). Journées de la Recherche Porcine en France 29: Candek-Potokar, M., Zlender, B. and Bonneau, M Effects of breed and slaughter weight on longissimus muscle biochemical traits and sensory quality in pigs. Annales de Zootechnie 47: Carr, T., Walters, L. E. and Whiteman, J. V Carcass composition changes in growing and finishing swine. Journal of Animal Science 47: Cisneros, F., Ellis, M., McKeith, F. K., McCaw, J. and Fernando, R. L Influence of slaughter weight on growth and carcass characteristics, commercial cutting and curing yields, and meat quality of barrows and gilts from two genotypes. Journal of Animal Science 74: Commission International de l Eclairage Colorimetry: official recommendations of the International Commission on Illumination. Publication CIE no. 15 (E ). Bareau Central de la CIE, Paris, France. Danbred http: //www. danbred. dk

12 44 Latorre, Medel, Fuentetaja, Lázaro and Mateos DeVol, D. L., McKeith, F. K., Bechtel, P. J., Novakofski, J., Shanks, R. D. and Carr, T. R Variation in composition and palatability traits and relationships between muscle characteristics and palatability in a random sample of pork carcasses. Journal of Animal Science 66: Diario Oficial de las Comunidades Europeas Reglamento Europeo 2419/1999 relativo a la inscripción de determinadas denominaciones en el registro de certificaciones de características específicas de los productos agrícolas y alimenticios. Pliego de condiciones para la elaboración del jamón serrano. Diario Oficial de las Comunidades Europeas L 291: Diestre, A., Oliver, M. A., Gispert, M., Arpa, I. and Arnau, J Consumer responses to fresh meat and meat products from barrows and boars with different levels of boar taint. Animal Production 50: Edwards, S. A., Wood, J. D., Moncrieff, C. B. and Porter, S. J Comparison of the Duroc and Large White as terminal sire breeds and their effect on pigmeat quality. Animal Production 54: Ellis, M. and McKeith, F. K Factors affecting the eating quality of pork. In Growth of the pig (ed. G. R. Hollis), pp CAB International, Wallingford, UK. Ellis, M., Webb, A. J., Avery, P. J. and Brown, I The influence of terminal sire genotype, sex, slaughter weight, feeding regime and slaughter-house on growth performance and carcass and meat quality in pigs and on the organoleptic properties of fresh pork. Animal Science 62: Fortin, A The effect of slaughter weight on the carcass characteristics of Yorkshire barrows and gilts. Canadian Journal of Animal Science 60: Friesen, K. G., Nelssen, J. L., Unruh, J. A., Goodband, R. D. and Tokach, M. D Effects of the interrelationship between genotype, sex, and dietary lysine on growth performance and carcass composition in finishing pigs fed to either 104 or 127 kilograms. Journal of Animal Science 72: Fundación Española para el Desarrollo de la Nutrición Animal Normas FEDNA para la formulación de piensos compuestos (ed. C. de Blas, G. G. Mateos and P. G. Rebollar). FEDNA, Madrid, Spain. García-Macías, J. A., Gispert, M., Oliver, M. A., Diestre, A., Alonso, P., Muñoz-Luna, A., Siggens, K. and Cuthbert- Heavens, D The effects of cross, slaughter weight and halothane genotype on leanness and meat and fat quality in pig carcasses. Animal Science 63: Gu, Y., Schinckel, P. and Martin, T. G Growth, development, and carcass composition in five genotypes of swine. Journal of Animal Science 70: Honikel, K. O Reference methods for the assessment of physical characteristics of meat. Meat Science 49: Hornsey, H. C The colour of cooked cured pork. I. Estimation of the nitric oxide-haem pigments. Journal of the Science of Food and Agriculture 7: Huff-Lonergan, E., Bass, T. J., Malek, M., Dekkers, J. C. M., Prusa, K. and Rothschild, M. F Correlations among selected pork quality traits. Journal of Animal Science 80: Johnston, M. E., Nelssen, J. L., Goodband, R. D., Kropf, D. H., Hines, R. H. and Schricker, B. R The effects of porcine somatotropin and dietary lysine on growth performance and carcass characteristics of finishing swine fed to 105 or 127 kilograms. Journal of Animal Science 71: Kuhlers, D. L., Jungst, S. B. and Gamble, B. E Indirect selection for lean feed conversion in Duroc swine. Journal of Animal Science 74: 119 (abstr.). Leach, L. M., Ellis, M., Sutton, D. S., McKeith, F. K. and Wilson, E. R The growth performance, carcass characteristics, and meat quality of Halothane carrier and negative pigs. Journal of Animal Science 74: Lebret, B., Juin, H., Noblet, J. and Bonneau, M The effects of two methods of increasing age at slaughter on carcass and muscle traits and meat sensory quality in pigs. Animal Science 72: Lindahl, G., Lundström, K. and Tornberg, E Contribution of pigment content, myoglobin forms and internal reflectance to the colour of pork loin and ham from pure breed pigs. Meat Science 59: McGloughlin, P., Allen, P., Tarrant, P. V. and Joseph, R. L Growth and carcass quality of crossbred pigs sired by Duroc, Landrace and Large White boars. Livestock Production Science 18: Martel, J., Minvielle, F. and Poste, L. M Effects of crossbreding and sex on carcass composition, cooking properties and sensory characteristics of pork. Journal of Animal Science 66: Martin, A. H., Fredeen, H. T., Weiss, G. M., Fortin, A. and Sim, D Yield of trimmed pork products in relation to weight and backfat thickness of the carcass. Canadian Journal of Animal Science 61: Martin, A. H., Sather, A. P., Fredeen, H. T. and Jolly, R. W Alternative market weights for swine. II. Carcass composition and meat quality. Journal of Animal Science 50: Ministerio de Agricultura, Pesca y Alimentación Anuario de Estadística Agraria. MAPA, Madrid, Spain. National Research Council Nutrient requirements of swine. National Academy Press, Washington DC. Nieuwhof, G. J., Kanis, E., Hel, W. van der, Vestergen, M. W. A., Huisman, J. and Wal, P. van der Effect of recombinant porcine somatotropin on body composition and meat quality in growing pigs; interactions with genotype, sex and slaughter weight. Meat Science 30: Nold, R. A., Romans, J. R., Costello, W. J., Henson, J. A. and Libal, G. W Sensory characteristics and carcass traits of boars, barrows, and gilts fed high- or adequateprotein diets and slaughtered at 100 or 110 kilograms. Journal of Animal Science 75: Statistical Analysis Systems Institute SAS user s guide: statistics, version 6, fourth edition. SAS Institute Inc., Cary, NC. Tibau, J., Puigvert, X., Soler, J., Trilla, N., Diestre, A., Gispert, M., Fernandez, J. and Manteca, X Incidencia de factores genéticos y de comportamiento en la eficiencia