Liver L-gulonolactone oxidase activity and tissue ascorbic acid concentrations in nursing pigs and the effect of various weaning ages

In Experiment I,we evaluated liver L-gulono-gamma -lactone oxidase (GLO) ac tivity and tissue concentration of ascorbic acid in young pigs from birth t o weaning (14 d) and through a 28-d postweaning period; in Experiment 2, we evaluated the effect of three weaning ages on these measurements. Sow colo strum and milk collected in both experiments demonstrated a linear decline (P < 0.01) in ascorbic acid concentration as lactation progressed. In Exper iment 1, three pigs were killed at 0, 3, 7, 14, 21, 28, 35 and 42 d of age for determining liver GLO activity and serum and tissue ascorbic acid. Live r GLO activity decreased by 80% from 0 to 3 d of age and remained low until d 14 (weaning). After weaning, liver GLO activity increased linearly (P < 0.01). Tissue ascorbic acid concentrations decreased during the nursing per iod and again after weaning, but then increased to 42 d of age (P < 0.01). in Experiment 2, pigs were weaned at 10, 17 or 24 d of age. Three pigs from each group were killed at weaning and at each week postweaning until 38 d of age. Liver GLO activity was low during the nursing period but increased linearly (P < 0.01) for each group during the subsequent postweaning period . Pig serum and tissue ascorbic acid concentrations increased postweaning i n each group. These results suggest that a factor in sow's milk, possibly a scorbic acid, suppressed liver GLO activity of nursing pigs but upon weanin g, liver GLO activity of pigs increased in a linear manner (P < 0.01).