A study of factors that influence growth performance and carcass and meat quality of iberian pigs reared under intensive management systemsEstudio de los factores que influyen sobre la productividad y la calidad de la canal y la carne de cerdo Ibérico en intensivo

Resumen

The general aim of this Doctoral Thesis has been to study the influence of factors that influence growth performance and carcass and meat quality of Iberian (IB) pigs reared under intensive management systems. The influence of gender and castration of females, slaughter weight, feed restriction and terminal sire line were studied. To reach these goals, four trials were carried out. In the first trial a total of 360 IB dam x Spanish Duroc sire pigs was used to study the influence of gender and castration (intact females, IF vs. castrated females, CF vs. castrated males, CM) and slaughter weight (SW; 145 vs. 156 kg body weight, BW) on performance and carcass and meat quality. Pigs that were slaughtered with 145 kg BW (251 d of age) began the trial with 20 kg BW (80 d of age) and pigs that were slaughtered with 156 kg BW (268 d of age) began the trial with 30 kg BW (97 d of age). Meat samples were taken at m. Longissimus dorsi at the level of the last rib and backfat (BF) samples were taken at the tail insertion. Fatty acid profile of BF was not analysed in the pigs slaughtered at 156 kg BW and therefore only the fatty acid profile of each gender from pigs slaughtered at 145 kg BW were compared. There were six treatments with four replicates each. The experimental unit was a pen (15 pigs for productive performance and carcass quality, four pigs for meat quality and two pigs for fatty acid profile of BF). For the entire experiment, IF ate less feed (2.72 vs. 2.85 and 2.92 kg/d; P<0.01) and tended to be more efficient (3.75 vs. 3.92 and 3.92; P<0.10) than CF and CM. No differences were detected for average daily gain or SW between genders. Carcasses from IF were less fatter than carcasses from CF and CM (P<0.001). However, trimmed ham (18.2 vs. 16.8 and 17.2%), trimmed shoulder (11.6 vs. 10.9 and 10.9%) and untrimmed loin (4.0 vs. 3.5 and 3.6%) yield was higher (P<0.001) for IF than for CF and CM. Gender did not affect ham weight losses during ripening, meat chemical composition or fatty acid profile of BF (P>0,10). For the entire experiment (from 20 to 145 and from 30 to 156 kg BW, respectively), pigs slaughtered at 145 kg BW ate less feed (2.74 vs. 2.92 kg/d; P<0.001) and were more efficient (3.75 vs. 3.97; P<0.01) than pigs slaughtered at 156 kg BW. An increase in SW from 145 to 156 kg BW increased carcass weight and carcass yield (P<0.05) and pH2 and pH24 (P<0.01) and tended to reduce trimmed ham yield (17.6 vs. 17.3%; P<0.10). Slaughter weight did not affect ham weight losses during ripening or meat quality (P>0.10). It is concluded that intact females are an alternative to castrated females for intensive production of Iberian pigs. Also, the reduction in slaughter weight from 156 to 145 kg body weight is recommended for this type of production. In the second trial, IB × Duroc pigs (n=168), with an average age of 152 d (42 ± 2 kg) were used to investigate the influence of feeding regimen (ad libitum access to feed, AL vs. 82% of AL from 152 to 201 d of age and 72% from 202 to 263 d of age, FR) and gender (intact females, IF vs. castrated females, CF vs. castrated males, CM) on growth performance and carcass and meat quality. For the last 54 d before slaughter at 317 d of age, all pigs had AL access to feed. Meat samples were taken at m. Longissimus dorsi at the level of the last rib. Between 152 and 263 d of age, pigs consuming AL had greater (P<0.001) ADG and G:F than FR pigs. However, when all pigs received AL access to feed (264 to 317 d of age), ADFI (P<0.05), ADG (P<0.001), and G:F (P<0.01) were increased in FR pigs compared to AL pigs. Across the entire feeding period (152 to 317 d of age), ADG of FR pigs was less (P<0.001) than that of AL pigs. Feed restricted pigs tended to have greater (P<0.10) yields of trimmed hams and shoulders and less carcass fat than AL pigs; yet, feeding regimen did not (P>0.10) affect pork quality. Intact females tended (P<0.10) to have greater G:F and produced carcasses with less (P<0.05) fat, greater (P<0.01) proportions of primal cuts and increased (P<0.05) CP in the LM than CF and CM. It was concluded from this experiment that feed restriction applied from 152 to 263 d of age improved primal cut yields without affecting gain:feed, pork quality and cured ham production traits. Moreover, intact females were superior to their castrated counterparts (particularly castrated females) for performance and primal cuts yield traits. Therefore, feed restriction, coupled with the use of intact versus castrated females, can be recommended as acceptable practices for the production of Iberian pigs under intensive conditions. In the third trial a total of sixty crossbred (IB dam x Duroc sire) females, 80 d of age (17.6 ± 0.13 kg body weight, BW), was used to investigate the effect of castration on productive performance, carcass and meat quality and fatty acid profile of backfat (BF). There were two treatments (intact females, IF vs. castrated females, CF) and five replicates of six pigs per treatment. Pigs were ovariectomized at 92 d of age (26.1 ± 0.19 kg BW) and slaughtered at 267 d of age (143.6 ± 6.49 kg BW). Meat samples were taken at m. Longissimus dorsi at the level of the last rib and BF samples were taken at the tail insertion. For the global experiment (18 to 144 kg BW), IF ate less feed and were more efficient than CF (P<0.05). Also, IF had less carcass yield (P<0.01) and fat thickness at the m. Gluteus medius (P<0.05) and tended to have lower carcass BF depth (P<0.10) than CF. However, IF had higher shoulder yield at 2 and at 24 h post mortem (P<0.05) and after trimmed (P<0.10) than CF. The pH24 of the m. Semimembranosus tended to be lower for IF than for CF. Also, IF had more moisture (71.0 vs. 69.1%) and less fat (6.64 vs. 9.12%) in the m. Longissimus dorsi than CF (P<0.05). Meat from IF was more lightness (L*; P<0.01), redder (a*; P<0.001) and had more intensive colour (c*; P<0.001) than meat from CF. Backfat was more saturated in CF than in IF (P<0.05), mostly because of the higher palmitic acid (P<0.05) and the lower linolenic acid (P<0.05) content. It is concluded that intact females have better productive performance and shoulder yield but less carcass yield than castrated females and that castration does not improve meat quality. Therefore, when animal welfare, cost of castration, productive performance and carcass and meat quality traits are considered, the use of intact females rather than castrated females is recommended for the production of Iberian pigs reared under intensive management systems. In the fourth trial a total of 180 pigs (19 ± 2.5 kg body weight, BW and 80 ± 10 d of age) was used to study the effect of sex (intact female, IF vs. castrated male, CM) and terminal sire line (Danish Duroc, DD vs. Spanish Duroc, SD vs. Retinto IB, RIB) on performance and carcass and meat quality of pigs sacrificed at 145 kg BW (262 and 311 d of age for Duroc crossbreds and for pure IB pigs, respectively). The female line used was pure IB in all cases. Meat samples were taken at m. Longissimus dorsi at the level of the last rib and backfat (BF) samples were taken at the tail insertion. Fatty acid profile of BF was not analysed in the RIB sired pigs and therefore only the two Duroc sire lines (DD vs. SD) of each sex were compared. There were six treatments with five replicates each. The experimental unit was a pen (six pigs for productive performance and carcass quality, three pigs for meat quality and five pigs for fatty acid profile). From 19 to 145 kg BW, IF ate less feed (2.61 vs. 2.81 kg/d; P<0.05) and were more efficient (4.10 vs. 4.41; P<0,05) than CM. Also, IF had lower carcass yield (P<0.01) and less carcass (P<0.05) and muscular fat (P<0.01) than CM. However, IF had higher trimmed ham (18.4 vs. 17.8%; P<0.10), trimmed shoulder (11.7 vs. 11.3%; P<0.05) and loin (4.3 vs. 3.8%; P<0.001) yields than CM. Gender did not affect fatty acid profile of BF (P>0.10). Duroc sired pigs grew faster (689 vs. 549 g/d; P<0.001) and had better feed conversion (3.90 vs. 4.99; P<0.001) than RIB sired pigs. Pure IB pigs needed 49 d more than Duroc sire line pigs to reach the pre-planned slaughter weight. No differences were detected for productivity between the two Duroc lines used (DD vs. SD). Pure IB pigs had fatter carcasses (P<0.001) and higher pH at 2 and 24 h post mortem (P<0.001) than Duroc crossbreds. Iberian x Duroc pigs had higher trimmed ham (19.7 vs. 14.8%) and trimmed shoulder (12.3 vs. 9.9%) yields and higher ham weight losses during ripening than pure IB pigs (P<0.001). Meat from IB pigs had more fat (P<0.05) and was redder (a*; P<0.001) and had higher intensity of colour (higher c* and lower Hº; P<0.01) than meat from IB x Duroc pigs. No differences were detected between the fatty acid profile of BF from DD and SD sire lines (P>0.10). It is concluded that productive performance and primal cuts yield are higher for intact females than for castrated males. Danish Duroc sires are a good alternative to Spanish Duroc and Retinto Iberian sires for production of Iberian pigs under intensive systems.