Effect of Dietary Protein and Energy Levels on the Growth Rate, Feed Efficiency and Carcass Composition of Chicks

The main objective of feed formulation should be to maximize profits, the difference between returns (growth response) and costs [feed intake (FI)]. For broilers and growing turkeys it is necessary to predict the BW and feed intake responses in order to estimate which protein and energy levels maximize profits for the producer. Data from the literature were collected to evaluate whether growth and FI responses can be better predicted from the dietary protein to energy ratio than protein and energy levels. The Ordinary Least Squares method was applied to estimate the coefficients (Bn) of each model. The best model was selected through the J-test. The protein to energy ratio model was not selected in any case by the J-test. The model based on the protein and energy levels was selected by the J-test to predict the BW response in eight out of nine cases and to predict FI in six out of nine cases. A nested selection was performed to find models for each data set that only include coefficients that are significantly different from zero. The nested selection showed that BW and FI responses can be predicted successfully from protein and energy levels with coefficients of determination between .79 and .97 for broiler chickens and between .45 and .65 for turkeys. Nutritionists should consider the use of models, like the protein and energy levels model, that explain and predict BW and FI responses. Future modeling research should consider important factors in broiler production, like age, sex, and temperature.

Section: Discussionmentioning

confidence: 90%

Evaluation of the Protein to Energy Ratio Concept in Broiler and Turkey Nutrition

Gonzalez‐a

Pesti

1993

“…That Summers et al (1964) failed to consistently improve protein utilization (NPU) at deficient dietary levels of protein (i.e., 10or 14%from methionine-supplemented soybean meal) when caloric density was increased probably indicates that at these protein levels, dietary energy concentration was not limiting the rate of tissue protein synthesis. Other workers who have noted increased protein utilization upon adding fat to the diet, did so in all likelihood because the basal diet to which fat was added was deficient in energy for the protein level being fed (Combs, 1964;Yoshida et al, 1962;Rand etal., 1958;Forbes and Yohe, 1955). Indeed, between metabolizable energy concentrations of 3.05 kcal./g.…”

Section: Error Mean Squarementioning

confidence: 94%

Body Composition and Protein Utilization of Chicks Fed Graded Levels of Fat

Velu

Baker

1974

Two experiments involving chicks fed a complete crystalline amino acid diet from day 8 to day 21 posthatching were employed to evaluate body composition changes and protein utilization as a function of dietary caloric density. In experiment 1 graded levels of corn oil from 5 to 25% of the diet were fed. Chicks gained as rapidly and utilized the dietary nitrogen as efficiently when 5% corn oil was fed as when higher levels were fed. As caloric density of the diet increased, chicks ate to meet their energy need and therefore cut back on feed (hence, protein) intake. Nonetheless, each increment of protein intake was used at the same efficiency. Body fat increased and body protein decreased with each incremental increase in dietary corn oil. In experiment 2 it was established that protein utilization remained constant over a wide range of protein intake (below the requirement for maximal protein retention), regardless of whether protein intake differences resulted from a change in caloric density of the diet or from a change in the dietary concentration of the complete amino acid mixture. Energy retention appeared to reach a maxima at a dietary concentration of 15% corn oil or 4.19 kcal. M.E./g.

“…Dietary levels of protein and energy affected carcass fat independently over the levels employed. Research by Yoshida et al (1962) has demonstrated that the feeding of low energy-high protein diets acts to reduce the amount of carcass fat in the chicken. Kubena et al (1972) demonstrated that the amount of fat in chicken could be influenced by the feeding of isocaloric diets calculated to contain 80 to 110% of the values recommended by Combs (1970) for total sulfur amino acids.…”

Section: Introductionmentioning

confidence: 98%

The Influence of Dietary Energy and Amino Acid Levels on Abdominal Fat Pad Development of the Broiler Chicken

Mabray

Waldroup

1981

A study was conducted to determine the effects of dietary energy and amino acid content on the weight of the abdominal fat pad of broiler chicks. Diets containing 2970, 3190, and 3410 ME kcal/kg were formulated to contain 70 to 120% of the 1977 NRC amino acid requirements. These diets were fed to broiler chicks for 57 days. After slaughter in a commercial processing plant carcasses were evaluated.Through the dietary manipulations it was possible to produce carcasses of widely varying abdominal fat pad size. Although total fat pad weight was directly influenced by the dietary energy level of the diets, covariance adjustments for differences in body weight markedly reduced the influence of dietary energy. The degree of fatness could be significantly reduced by increasing the dietary amino acid levels within a given energy level. (