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A total of 144 pigs were used to study the effects of sex (barrows or gilts) and terminal sire line (Iberian or three genetic lines of Duroc: Duroc 1, Duroc 2 and Duroc 3) on performance and carcass and meat quality traits. Gilts showed slightly lower average daily gain, shoulder weight and trimming losses, but slightly better primal cuts yields and higher loin weight, while there was no significant effect of sex on meat quality traits or on the fatty acid composition of lard and muscle. There were important differences in performance and in carcass and primal cuts quality traits between pure Iberian pigs and all Iberian × Duroc crossbreeds evaluated, partly due to the lower slaughter weights reached by the formers. The different sire lines showed differences in several traits; Duroc 1 group showed lower backfat thickness and ham and shoulder trimming losses, and higher primal cut yields than Duroc 2 and Duroc 3 groups. Intramuscular fat (IMF) content remained unaffected by crossbreeding, but meat color resulted more intense and redder in crosses from the Duroc 1 sire line. The accumulation of fatty acids in lard was not affected by Duroc sire line, while animals of the group Duroc 2 showed higher levels of monounsaturated fatty acid and lower of polyunsaturated ones in IMF. These results highlight the importance of considering not only performance, but also carcass and meat quality traits when deciding the Duroc sire line for crossbreeding in Iberian pig production.

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One hundred forty four ovine embryos and feti were used in an investigation to determine mathematical models describing the histomorphometric growth of tissues and compartments of the ruminant stomach. The results indicate that during prenatal life the diameter of the gastric chambers increase more slowly than the length. The tissue layers of the gastric walls, particularly the muscular tunic of all compartments demonstrated a uniform tendency toward more rapid development than the compartment walls proper.

Two production systems and several ages at slaughter were used: 12, 14 and 16 months for outdoor rearing (with the final finishing phase in the Montanera system, in which fed was based on natural resources, mainly acorns and grass) and 8, 10 and 12 months for animals reared indoors (intensive system: with feed based on commercial fodder) to evaluate their effect on the muscle fibre population and size of the Longissimus thoracis, (LT) muscle, as well as fresh loin quality traits. Animals that were older at slaughter revealed increased fibre sizes of the LT muscles in the pigs reared in the Montanera system. The LT muscles of the animals reared in intensive systems had a lower percentage of type I fibres and higher size of type IIB than those reared in the Montanera system. The approximate composition and instrumental colour of Montanera fresh loins were affected by the animal slaughter age. In the case of the intensive system, the effect of animal slaughter age had an impact on the approximate composition, instrumental colour, water loss and textural properties. Therefore, different ages at slaughter of Iberian pigs showed variations in some quality parameters in the fresh loins in both the Montanera and Intensive systems, thus proving to be a factor of variability and homogeneity of the Iberian products. The meat from Iberian pigs reared in an intensive system and slaughtered at a younger age proved to be more tender. The production system affected all the above quality traits, with the exception of water loss.