Effects of dietary retinol on hepatic retinol storage and on plasma and tissue alpha-tocopherol in pigs.

A feeding experiment was carried out with pigs to investigate the effects of graded dietary retinol supplements on hepatic and plasma retinol and on alpha-tocopherol in plasma and selected tissues. Four groups of twelve weanling pigs each with a mean body weight of 7 kg were fed a complete ration containing 54 IU vitamin E/kg and supplemented with 5, 10, 20 or 40 x 10(3) IU retinol/kg for Treatments 1 to 4, respectively. The feed was fed in restricted amounts for 150 days when the pigs were slaughtered at 105 kg body weight. Overall daily body weight gain and feed conversion ratio were 660 g and 2.49, respectively, without treatment differences (p less than 0.01). Hepatic retinol concentration (y, IU/g fresh weight) was linearly related to dietary retinol concentration (x, IU/kg feed) as expressed by y = -88.9 + 0.077 x [r2 = 0.94]. Total hepatic retinol (y, IU) and total retinol intake (x, IU) were linearly related as expressed by y = -194.9 x 10(3) + 0.4585 x [r2 = 0.98]. Hepatic retinol retention relative to intake ranged from 30.0% to 44.9%. Plasma retinol concentration was not affected by dietary retinol (p less than 0.01). Plasma alpha-tocopherol levels remained on a plateau for 42 days in all treatments. After 150 days plasma levels exceeded those at 42 days in Treatments 1 to 3, but not in Treatment 4. The effect of retinol on tissue alpha-tocopherol varied with tissues. While there was no effect on M. Longissimus and backfat, alpha-tocopherol levels in heart and liver showed an inverse relationship with dietary retinol.(ABSTRACT TRUNCATED AT 250 WORDS)