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The aim of this experiment was to compare non-carriers and heterozygous carriers of the dominant RN − allele (Rendement Napole) for carcass composition, muscle distribution and technological meat quality in pigs. Crossbred slaughter pigs ( n = 79), from Hampshire sires, heterozygous for the RN − allele, and Swedish Yorkshire X Swedish Landrace dams were used. The animals were classified into RN − genotype according to the estimated glycogen level at slaughter (glycolytic potential) in the longissimus dorsi muscle. Carriers of the RN − allele had higher daily gain, fewer days on test and produced carcasses with higher lean meat content, and a larger proportion of ham. The major ham muscles were larger in the RN − carriers than in the non-carriers. The proportions between the individual muscles were changed due to the RN − allele, with a greater content of glycolytic ham muscles ( M. semimembranosus et adductor, M. biceps femoris, M. gluteus ) and a smaller content of M. quadriceps femoris in RN − carriers. RN − carriers had lower values for ultimate pH, Napole yield (yield after curing and cooking), crude protein, and dry matter, and higher values for glycolytic potential, drip losses, filter paper wetness, internal reflectance and ash content. No effect of the RN − allele was found regarding lactate and surface reflectances.

The effects of outdoor rearing and sire breed on carcass composition and technological and sensory meat quality in pigs were studied in a trial with 102 crossbred slaughter pigs (Yorkshire, or Yorkshire × Landrace sows and Duroc or Yorkshire as terminal sire). Half of each litter were reared conventionally indoors, while the remainder were reared outdoors in a 50 000 m(2) area, as a single group. All pigs were fed ad libitum. Yorkshire sired pigs had significantly leaner carcasses and meat with lower IMF content and marbling scores, and higher shear force and water content. The sire breeds did not differ regarding pH(u), water-holding capacity, or colour. Meat from the Yorkshire crosses was more acid, less tender and gained lower overall acceptance scores in the sensory test. The outdoor-reared pigs had lower daily gain values and leaner carcasses. They produced meat with lower pH(u), higher drip loss, higher shear force values and higher internal reflectances. Their meat contained more lactate and crude protein and had a higher glycolytic potential, less IMF and less water. Regarding the sensory qualities, outdoor rearing impaired tenderness, juiciness and overall acceptance.