Dh. Baker et al., MAINTENANCE REQUIREMENT FOR VALINE AND EFFICIENCY OF ITS USE ABOVE MAINTENANCE FOR ACCRETION OF WHOLE-BODY VALINE AND PROTEIN IN YOUNG CHICKS, The Journal of nutrition, 126(7), 1996, pp. 1844-1851
Experiments were conducted with chicks during the period 10-20 d posth
atching to assess valine accretion and protein accretion as a function
of incremental valine intakes between 5 and 95% of its ideal level (r
equirement for maximal growth). Chemically defined crystalline amino a
cid diets were fed, and amino acids other than valine were maintained
at minimized excess levels as valine was increased. With dietary valin
e concentrations representing 5, 10, 40, 55, 70 and 95% of the ideal l
evel, weight gain (r(2) = 0.98), protein accretion (r(2) = 0.98) and v
aline accretion (r(2) = 0.99) increased linearly (P < 0.01) as a funct
ion of valine intake. Slope of the valine accretion curve was 0.73 +/-
0.02, and there was no indication of decreased valine utilization as
valine intake increased to 95% of its required level for maximal growt
h. Using the linear regression equation, i.e., valine accretion (Y) re
gressed on valine intake (X), the maintenance valine requirement (X at
Y zero) was 18.4 mg/d or 48.8 mg/d per kg body weight(3/4). Whole bod
y valine was 4.72 g/100 g whole body protein accreted and was constant
at all levels of valine intake. At zero protein accretion, however, v
aline accretion was negative (-3.8 mg/d). Thus, the valine requirement
for zero valine accretion (48.8 mg/d per kg(3/4)) was higher than the
valine requirement for zero protein accretion (32.4 mg/d per kg(3/4))
. In a subsequent experiment, also involving whole body valine and pro
tein accretion, valine doses of 40, 55 and 70% of ideal were compared
using amino acid-balanced diets (amino acids other than valine at 55,
70 and 85% of ideal levels, respectively) or imbalanced diets (amino a
cids other than valine at a constant 100% of their ideal levels). Stra
ight-line (P < 0.01) valine and protein accretion responses occurred,
but slope of the response curves (accretion vs. valine intake) was low
er in the imbalanced series than in the balanced series. The results o
f these studies suggest a constant utilization above maintenance of ab
sorbed valine over a wide range of valine intakes.