Effects of Feeding Low Protein Diets with Different Energy-to-Protein Ratios on Performance, Carcass Characteristics, and Nitrogen Excretion of Broilers

Abstract

This study shows the effects of feeding low protein (LP) diets with different energy-to-protein ratios were evaluated on the production parameters, carcass composition, meat quality, nitrogen retention, and excreta composition of broilers. A total of 576-day-old Ross 308 broilers were fed a control diet (C) and three LP diets containing 1.5% less crude protein than diet C for 41 days. The LP1 treatment was isocaloric with diet C, while the dietary apparent metabolizable energy corrected by nitrogen (AMEn) levels in the case of the LP2 and LP3 treatments were reduced by 1.5% and 3%, respectively. The LP diets were supplemented with six crystalline essential amino acids (AA) to meet the standardized ileal digestible AA requirements of broilers. The LP1 treatment did not affect the performance parameters of broilers and increased the breast meat yield, the nitrogen retention and decreased drip loss of breast meat and the total-N and uric acid-N nitrogen excretion of birds in comparison with the C group. Although the energy-reduced LP2 and LP3 diets resulted in lower final body weight, they did not affect the carcass composition, breast meat quality, nitrogen retention, and excreta composition of birds compared with the control treatment.

Effects of different dietary threonine and glycine supplies in broilers fed low-protein diets

“…The uric acid concentration of excreta in broilers fed the control C diet was already quite low (12.54 mg/g dry matter), and maybe a further decrease was not possible by feeding LP diets. In our previous two experiments, the LP diets reduced the uric acid levels in the excreta when higher uric acid levels than in the present trial were measured in the excreta of broilers fed normal CP diets (17.65 and 15.30 mg/g dry matter) (31,43).…”

“…The starch-to-CP ratio increased in the LP treatments compared to the C treatment, and it was the highest in the LP3 diet containing swine meat meal. The higher starch-to-CP ratio deteriorated the FCR value in the starter phase of our previous experiment in a quadratic manner ( 43 ). A similar quadratic relationship was observed between these two factors from 7 to 35 days in two studies ( 44 , 45 ).…”

“…The negative relationship between drip loss and ultimate pH in poultry meat is well known ( 52 , 59 ). The feeding of LP diets can result in higher ultimate pH and decreased drip loss ( 43 , 60 ). The higher drip loss of the meat proved to be more acidic with a higher level of glucose, glycogen, and glycolytic potentials ( 52 , 53 , 59 ).…”

“…Most of the ammonia released from poultry manure originates from the breakdown of uric acid ( 65 ). The feeding of LP diets can decrease the uric acid level of blood plasma ( 21 ) and the concentrations of total and urinary N and uric acid in broiler excreta ( 15 , 31 , 43 ). However, the results of the present experiment failed to confirm the advantageous results of previous studies associated with N emission.…”