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 gr owth responses that were superior to those resulting from supplementation w ith any pairs of deficient nutrients. In Assay 2, single addition of Zn but not of methionine or riboflavin produced a growth response, but the combin ation of either Zn and Met or Zn and riboflavin resulted in growth response s that were greater than the response elicited by Zn alone. Assay 3 involve d individual or multiple deficiencies of choline, riboflavin and vitamin B- 6, and individual additions suggested that choline was first limiting. Chol ine + 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 combinatio n 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 unsuppleme nted negative-control diet. In Assay 4, chicks responded to individual addi tions 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 th an those occurring with any single addition. The data from these experiment s show that unlike the situation with three deficient amino acids, the expe cted responses to first-, second- and third-limiting B-vitamins or deficien t vitamins combined with deficient levels of Zn or Met do not follow the ex pected pattern of response to first-, further response to first- and second - and an even further response to first-, second- and third-limiting nutrie nts.