A total of 120 crossbred [synthetic line x (Large White x Landrace)] pigs (castrated males and females) were used to evaluate the influence of rearing conditions for growing-finishing pigs on growth performance, carcass, stress reactions at slaughter, and meat eating quality. At approximately 35 kg of live weight (LW), littermates were allocated to either a conventional (fully slatted floor, 0.65 m2/pig, considered as control, CON) or an alternative (sawdust bedding with free access to an outdoor area, 2.4 m2/pig, OUT) system, until slaughter at approximately 110 kg of LW. Pigs had free access to standard growing and finishing diets. The trials were conducted in spring, summer, and winter, with each season involving 2 pens of 10 pigs in each system. Compared with the CON, the OUT pigs exhibited a greater growth rate (+10%, P < 0.001) due to their greater feed intake (+0.23 kg/d, P < 0.01), resulting in a greater body weight at slaughter (+7 kg, P < 0.001). The OUT pigs had thicker backfat (+2.4 mm, P < 0.01) and lower lean meat content (- 2.0% points, P < 0.001) than the CON pigs. The OUT system did not (P > 0.10) influence the behavioral activities of pigs during lairage at the slaughterhouse, or the urinary levels of catecholamines and cortisol, and plasma levels of ACTH, cortisol, lactate, creatine kinase, and FFA immediately after slaughter. The OUT pigs had similar (P > 0.10) pH values 30 min postmortem (pH1) in the LM, biceps femoris (BF), and semimembranosus (SM) muscles, similar ultimate pH (pHu) in LM, but lower pHu in SM (- 0.07 unit, P < 0.001) and in BF (- 0.03 unit, P = 0.029). Despite nonsignificant effects of production system on stress reactions at slaughter, assessed by urine and plasma indicators and muscle metabolism at 30 min postmortem, meat from OUT pigs had more LM drip loss after 2 (+1.0%, P = 0.003) and 4 (+1.1%, P = 0.010) d than did meat from the CON pigs. The OUT system slightly increased meat yellowness (b* value) in the LM (+0.7 unit, P = 0.001), BF (+0.5 unit, P = 0.014), and SM (+0.5, unit P = 0.041), whereas redness (a*) and lightness (L*) of the 3 muscles were unaffected (P > 0.07). Intramuscular fat content was greater in the LM (+17%, P = 0.001), BF (+14%, P = 0.004), and SM (+17%, P = 0.003) of the OUT pigs. Outdoor rearing during summer and winter improved meat juiciness, whereas odor, flavor, and tenderness were unaffected (P > 0.10). Influence of rearing conditions on all the other traits studied did not depend on the season.

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De nombreux travaux ont été conduits au cours de ces dernières années afin de réduire l’excrétion d’azote, de phosphore, du cuivre et de zinc par les porcs. Les voies envisagées consistent d’une part à mieux ajuster les apports aux besoins des animaux et d’autre part à améliorer la biodisponibilité de ces nutriments dans les aliments. L’alimentation par phases combinée à une amélioration de l’équilibre en acides aminés du régime permet de réduite de façon substantielle les rejets d’azote. L’utilisation de régimes moins riches en protéines permet également de réduire les émissions d’ammoniac et dans une certaine mesure la production d’odeur. L’alimentation par phase est aussi efficace pour réduire l’excrétion de P. Cependant la faible digestibilité du P reste le principal problème, même si elle peut être significativement améliorée grâce à l’incorporation de phytases d’origine microbienne et l’utilisation de phosphates hautement digestibles. De la même manière la réduction des apports alimentaires de Cu et de Zn est très efficace pour en réduire l’excrétion. Au niveau de l’exploitation ces différentes approches permettent de réduire l’entrée de nutriments, en particulier d’azote de phosphore et d’éléments traces métalliques, et elles contribuent ainsi à réduire l’impact environnemental.