Single versus multiple deficiencies of methionine, zinc, riboflavin, vitamin B-6 and choline elicit surprising growth responses in young chicks.

A soy-protein isolate diet that was deficient in methionine (Met), zinc (Zn), riboflavin, vitamin B-6 and choline for chick growth (Assay 1) was used to study individual or multiple deficiencies of several of these nutrients. In all cases, adding all three deficient nutrients together resulted in growth responses that were superior to those resulting from supplementation with any pairs of deficient nutrients. In Assay 2, single addition of Zn but not of methionine or riboflavin produced a growth response, but the combination of either Zn and Met or Zn and riboflavin resulted in growth responses that were greater than the response elicited by Zn alone. Assay 3 involved individual or multiple deficiencies of choline, riboflavin and vitamin B-6, and individual additions suggested that choline was first limiting. Choline + riboflavin supplementation, however, produced marked growth and gain:food responses that were far greater than those resulting from supplemental choline or riboflavin alone. Moreover, the growth response to a combination of choline + pyridoxine (PN) was also greater than that obtained from any of the three nutrients fed alone; even PN + riboflavin (in the absence of choline) produced responses greater than those observed with the unsupplemented negative-control diet. In Assay 4, chicks responded to individual additions of riboflavin, PN or Met, and in Assay 5, to either riboflavin or PN; all two-way combinations resulted in growth rates that were far greater than those occurring with any single addition. The data from these experiments show that unlike the situation with three deficient amino acids, the expected responses to first-, second- and third-limiting B-vitamins or deficient vitamins combined with deficient levels of Zn or Met do not follow the expected pattern of response to first-, further response to first- and second- and an even further response to first-, second- and third-limiting nutrients.