33 Animal Science 2003, 77: 33-45 1357-7298/03/23840033$20·00 © 2003 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, 28040 Madrid, Spain 2 COPESE S. A., 40300 Sepúlveda, Segovia, Spain † Present address : Imasde Agropecuaria S.L.Isabel Colbrand, 10, 4ª pl.local 90, 28050 Madrid, Spain. ‡ Corresponding author. E-mail : 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 2001 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