Maintenance threonine requirement and efficiency of its use for accretion of whole-body threonine and protein in young chicks.
Broiler chicks were fed on chemically-defined crystalline amino acid diets containing graded levels of L-threonine (Thr) during the period 10-20 d post-hatching. Doses of Thr represented 5, 10, 15, 40, 55, 70 and 95% of its ideal level for maximal weight gain and feed efficiency. Other amino acids were maintained at minimized excess levels that were 15% (of ideal) above the various doses of Thr. Following 10 d of feeding and a 24 h fast, chicks were killed for whole-body protein and amino acid analysis. Using pen accretion means, weight gain (r2 0.98), protein accretion (r2 0.99), and Thr accretion (r2 0.99) were linear (P < 0.01) functions of Thr intake. Slope of the Thr accretion regression line indicated that 82% of the Thr intake was recovered in whole-body protein. At zero Thr intake, chicks lost 11.9 mg Thr/d. The Thr maintenance requirement was 45.7 mg/d per kg body weight 0.75. Increasing doses of Thr resulted in increased (P < 0.05) concentrations of methionine, isoleucine, histidine and lysine in whole-body protein. Other indispensable amino acids, including Thr, also tended to increase. Whole-body glycine, proline, serine and cystine concentrations decreased (P < 0.05) as Thr was increased in the diet. The maintenance need for Thr represented 5.5% of the total need for Thr. The data suggest that efficiency of Thr utilization is constant at all levels of Thr intake between 5 and 95% of the level required for maximal weight gain and feed efficiency.
Edwards
H M
HM
Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
Baker
D H
DH
Fernandez
S R
SR
Parsons
C M
CM
D000704:Analysis of Variance; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D002645:Chickens / Q000378:metabolism*; D003553:Cystine / Q000378:metabolism; D002149:Energy Intake; D005998:Glycine / Q000378:metabolism; D008297:Male; D009751:Nutritional Requirements; D011392:Proline / Q000378:metabolism; D011506:Proteins / Q000378:metabolism*; D012044:Regression Analysis; D012694:Serine / Q000378:metabolism; D013912:Threonine / Q000378:metabolism*; D015430:Weight Gain
D011506:Proteins; D013912:Threonine; D012694:Serine; D003553:Cystine; D011392:Proline; D005998:Glycine