Low-protein amino acid-supplemented diets in broiler chickens: effects on performance, carcass characteristics, whole-body composition and efficiencies of nutrient utilisation
✍ Scribed by Aletor, V?A; Hamid, I?I; Nie�, E; Pfeffer, E
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 112 KB
- Volume
- 80
- Category
- Article
- ISSN
- 0022-5142
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✦ Synopsis
Two concurrent trials were conducted to investigate the in¯uence of low-protein amino acidsupplemented diets on the performance, carcass characteristics, whole-body composition and ef®ciencies of nutrient utilisation by the male broiler chicken from age 3 to 6 weeks. The ®rst trial comprised ®ve isoenergetic (13.0 MJ kg À1 ) diets containing 225 (control), 210, 190, 172 or 153 g kg À1 crude protein (CP) supplemented with essential amino acids (EAAs) to meet the minimum National Research Council recommendations. In the second trial a composite mixture of non-essential amino acids (NEAAs) was added to the lower-CP diets (ie 210±153 g kg À1 ) such that they became isoproteinous (N Â 6.25) with the 225 g kg À1 control. Neither the lowering of dietary CP nor NEAA supplementation had any signi®cant in¯uence on weight gain or the relative weights of the various carcass cuts. However, chicks fed the lowest-CP diets consumed more feed (P 0.05) and had poorer (P 0.05) feed conversion ef®ciency (FCE). NEAA supplementation enhanced FCE to the control levels. Whole-body compositional analysis showed that lowering dietary CP increased (P 0.01) total body fat in a linear fashion (P 0.001; r = À0.72). Equalising dietary CP with the control (ie maintaining identical energy/ protein ratio) by NEAA supplementation did not correct for the fat deposition. Total body protein (g kg À1 ) was identical with the control with or without NEAA supplementation. Dietary energy, protein retention ef®ciency (PRE) and protein ef®ciency ratio (PER) were more ef®cient (P 0.01) in the lower-protein diets, while NEAA supplementation signi®cantly (P 0.01) decreased the ef®ciency of N utilisation. Reducing dietary CP from 225 to 153 g kg À1 decreased N excretion in a highly signi®cant linear fashion (P 0.001; r = 0.73). The nutritional and environmental implications of the increased body fat deposition on the one hand and the decreased N excretion on the other in the low-protein-fed chickens are discussed and the need to harmonise these apparently con¯icting interests is emphasised.