Threonine needs of broiler chickens with different growth rates.
The Thr needs in 3 commercial broiler strains (A, multipurpose; B, high yield; C, high yield) known to differ in terms of feed intake, growth rate, and breast yield were evaluated. Birds were randomized across 96 floor pens (12 birds/pen), received a common diet from d 1 to 20, and were fed graduations of Thr (0.52 to 0.87% total Thr in 0.07% increments) from d 21 to 42. Treatments (3 x 6 factorial) were replicated 5 or 6 times. The corn, soybean meal, and peanut meal test diet contained 0.43 and 0.96% digestible Thr and Lys, respectively. An additional group of strain C birds (6 pens) was maintained on a corn-soybean meal diet containing surfeit Thr (0.73% of diet). Birds fed the corn and soybean meal diet performed similarly (P < or = 0.05) to birds fed peanut meal diets. A feed conversion interaction (P < or = 0.05) occurred indicating that strain C was more sensitive to Thr deficiency than strains A and B. The abdominal fat interaction (P < or = 0.05) indicated that strain A had more relative abdominal fat than strains B and C. All strains differed (P < or = 0.05) in terms of BW gain (A, 78.2; B, 75.1; C, 72.9 g/d). Strain C had the lowest (P < or = 0.05) feed intake, which resulted in the lowest (P < 0.05) Thr intake, but it had the highest (P < or = 0.05) breast meat yield. Most parameters tested yielded quadratic (P < or = 0.05) models whereby Thr estimates could be predicted. Namely, BW gain and breast meat yield resulted in total Thr estimates (95% of maximum response) of 0.74 and 0.71%, respectively, which are in close agreement with the 1994 NRC (0.74%). The plasma Thr sigmoid response verified the former estimates. Analysis of strain intercepts and slopes as affected by Thr differed (P < or = 0.05) in terms of feed intake but not BW gain or breast meat yield. The 21 to 42 d Thr need across strains was estimated as 0.74% total or 0.65% digestible. Because dietary Lys was not in excess of the bird's needs, the former digestibility estimate equated to a Thr/Lys of 0.68.
Kidd
M T
MT
Department of Poultry Science, Mississippi State University, Mississippi State, MS 39759-9665, USA. mkidd@poultry.msstate.edu
Corzo
A
A
Hoehler
D
D
Kerr
B J
BJ
Barber
S J
SJ
Branton
S L
SL
D000005:Abdomen; D000273:Adipose Tissue; D000818:Animals; D001823:Body Composition; D002645:Chickens / Q000235:genetics / Q000254:growth & development*; D004032:Diet; D004435:Eating; D005260:Female; D005838:Genotype; D016014:Linear Models; D008239:Lysine / Q000008:administration & dosage; D008297:Male; D008460:Meat; D015233:Models, Statistical; D009751:Nutritional Requirements; D013045:Species Specificity; D013912:Threonine / Q000008:administration & dosage* / Q000097:blood; D015430:Weight Gain
D013912:Threonine; D008239:Lysine