Effects of long-term parenteral administration of vitamin B6 on B6 status and some aspects of the glucose and protein metabolism of early-weaned piglets
2001
Matte, J.J. | Girard, C.L. | Seve, B.
The present experiment aimed to determine the effect of feeding level and parenteral supplements of vitamin B6 (pyridoxine) on B6 status as well as on glucose, C-peptide, insulin, alpha-amino-N and urea after a gastric bolus of glucose in weaned piglets; the plasma tryptophan, xanthurenic acid and kynurenine responses to a gastric bolus of tryptophan were also measured. Forty-two piglets weaned at 2 weeks of age were distributed in seven blocks of six animals each. Within each block, the animals were assigned to the following factorial treatments: two levels of feeding (28 (F28) and 56 (F56) g/kg0.75 per d) administered by gastric-tube feeding and three levels of parenteral (intramuscular injections) vitamin B6 (0 (B6(0)), 15 (B6(15)) and 30 (B6(30)) mg/d). In B6(0) piglets, a decrease of 30% and 20% in erythrocyte and plasma pyridoxal-5-phosphate respectively, were observed during the 2 weeks post-weaning. In supplemented piglets, the erythrocyte pyridoxal-5-phosphate was maximised in B6(15) piglets at a level 3-4 times higher than in B6(0) piglets (P < 0.003). However, in plasma the maximal pyridoxal-5-phosphate concentration was reached in F28-B6(30) piglets (P < 0.058). The glucose and insulin responses to a gastric bolus of glucose were lower, and the post-bolus decrease of glucose was slower, in F28 than in F56 piglets (P < 0.0001). The insulin:C-peptide ratio was 25% greater in B6(15) piglets (P < 0.082). After the bolus of glucose, the aminoacidaemia decreased differentially according to treatments (P < 0.047) while the uraemia was at least 2-fold higher (P < 0.001) in F28 piglets than in F56 piglets and tended to be maximised in B6(30) piglets (P < 0.074). The response of plasma tryptophan to the gastric bolus of tryptophan was 11% lower in B6(30) piglets (P < 0.057). The plasma concentration of kynurenine increased continuously during the post-bolus period and this response was more marked in F56 (P < 0.002) and in B6(30) piglets (P < 0.02). Xanthurenic acid was undetectable in any of the treatments. The measurements on pyridoxine status suggest that the present basal dietary level of B6 (7.7 mg/kg) was not sufficient to cover the metabolic needs. For many criteria, an optimal level was reached at 15 mg/d parenteral B6 but the response of urea to glucose bolus suggests that 30 mg/d was detrimental. Further studies are necessary to determine the dietary level of B6 equivalent to the present optimal parenteral supplements and its eventual effects on B6 status and post-weaning growth performance of piglets.
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