Similar effects of lysine deficiency in muscle biochemical characteristics of fatty and lean piglets.

The main objective of this work was to investigate the effects of feeding Lys-deficient diets on muscle biochemical characteristics, particularly intramuscular fat concentration and fatty acid profile, in a fatty (Iberian) and a conventional pig genotype (Landrace × Large White [LDW]) maintained in identical experimental conditions. Performance and plasma metabolite changes were also monitored. Twenty-eight barrows of 10 kg initial BW, 14 of Iberian and 14 of LDW breed, were randomly assigned to each of 2 experimental diets in a 2 × 2 factorial arrangement (2 breeds × 2 diets). Seven pigs were allocated to each treatment combination. Diets (isonitrogenous and isoenergetic; 200 g CP/kg DM and 14.7 MJ ME) based on barley, corn, corn gluten meal, and soybean meal, with identical composition, except for their Lys content (10.9 g/kg for the diet adequate in Lys and 5.2 g/kg for the diet deficient in Lys), were assayed. Pigs were housed in individual 2 m pens and fed at 85% of ad libitum intake of the Iberian genotype, of greater intake capacity. Daily feed allowance was based on BW individually measured each week. At 25 kg BW, pigs were slaughtered by exsanguination after electrical stunning. Blood samples were taken and longissimus dorsi and biceps femoris muscles were rapidly dissected and stored frozen prior to analysis. Performance was reduced in both pig breeds when fed Lys-deficient diets, particularly in LDW pigs (breed × diet interaction, < 0.05). Intramuscular fat content increased in longissimus dorsi of Iberian ( < 0.05) and in biceps femoris of both pig genotypes ( < 0.01) when fed Lys-deficient diets. Oleic acid increased ( < 0.05) and PUFA acid decreased ( < 0.01) in longissiumus dorsi and biceps femoris of pigs of both genotypes fed Lys-deficient diets. The proportion of oxidative fibers ( < 0.001) and free carnitine content ( < 0.05) increased in longissimus dorsi of both pigs types fed Lys-deficient diets. Plasma creatinine was greater in LDW pigs compared with Iberian pigs ( < 0.01). Urea and total cholesterol increased in pigs consuming Lys-deficient diets ( < 0.01). The plasma free carnitine concentration was higher in Iberian pigs than in LDW pigs ( < 0.059). No changes in plasma carnitine status due to dietary Lys supply were detected. Feeding Lys-deficient diets could be a suitable strategy for increasing intramuscular fat content in fatty and lean pigs.