Abstract
The digestible lysine requirement for the growth performance of broilers fed diets with decreasing energy to protein ratio and reared under subtropical summer conditions were determined. Treatments consisted of five wheat-based diets with five levels (0.90, 0.95, 1.00, 1.05 and 1.10%) of digestible lysine (DL) and lowering energy to protein ratio (EPR; 13.6, 12.8, 12.0, 11.4 and 11.0), with five replicates of 80 birds each (n = 2000). Body weight gain (BWG) significantly increased by increasing DL levels during wk 1 (p<0.001), while 1.05% DL promoted the highest BWG during the whole experimental period (p<0.01). Increasing DL level resulted in significant reduction in feed intake (FI) and BWG to DL intake ratio (BWG:DLI) during wk 1-3 (p<0.05). Feed:gain ratio (FGR) significantly (p<0.01) improved with DL levels up to 1.05% during the whole experimental period, except for wk 5. The increasing ambient temperature had a linear effect on the all growth parameters. It is inferred that best growth performance can be obtained at 1.05% DL, maintaining all other AA constant under subtropical summer conditions.
Highlights
Several studies have been carried out to establish total amino acid (AA) requirements of modern fast-growing broiler chickens
During wk 1, a significant linear increase in body weight gain (BWG) was observed as dietary digestible lysine (DL) level increased (p
During the last week, BWG was not affected by DL level (p>0.05)
Summary
Several studies have been carried out to establish total amino acid (AA) requirements of modern fast-growing broiler chickens. Amino acids in most feed ingredients are not completely digested, and knowledge on the efficiency of AA utilization is imperative for the formulation of broiler diets (Leeson & Summers, 2001). This knowledge can be used to reduce absorption efficiency differences among feedstuff sources (Emmert & Baker, 1997). Sklan & Noy (2003) estimated digestible lysine (DL) requirements of 0.92 and 0.96% for BWG and feed efficiency, respectively, for 7-d-old broilers. Mushtaq et al (2007) suggested that DL can be lowered to 0.8% when the other AA were in definite ratio to DL, according to the ideal AA ratio, in canola meal based diets
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