THE EFFECT OF GENOTYPE ON RESPONSE IN BODY COMPOSITION TO VARIATION IN DIETARY PROTEIN : ENERGY RATIOS

An experiment with 480 day-old chicks of four commercial strains was conducted to study theeffect of genotype on response in body composition to variation in dietary protein: energy ratios. Thechicks were randomly allocated into 4x2x4 factorial and fed on a commercial starter diet (250 g CP and12.5 MJ of ME /kg) from hatching to 5 d of age and divided into two groups with three replicationseach of 16 birds and given either the such starter diet (S) or a finisher diet (F) containing 190 g CP and13.0 MJ of ME /kg. The birds were reared in strain-and sex-intermingled groups in brooders and followoncages until they reached the target body weight of 600-650 g (females) or 650-700 g (males) andtransferred to single cages and fed S or F diet until 1200-1300 g (females) or 1300-1400 g (males). Thelighting program was 23 h light for the first two days, and reduced to 18 h/d for the remainder of theexperiment. There were considerable variations in relative growth performance, FCR, carcass fat andabdominal fat due to genotypes and dietary regimen. Although birds tend to response in similar waywhen dealing with the excesses and insufficient supply, the nutrient requirements in relation to theprotein: energy ratios should be designed according to genetic background.The accumulation of fatduring the growing period was primarily due to the genetic variation whereas beyond this age, variationin abdominal fat was due principally to dietary effects

THE EFFICIENCY OF PROTEIN UTILIZATION IN DIFFERENT BROILER STRAINS

The objective of this work was to study the protein utilization and protein turnover of different broilerstrains and was carried out in completely randomized design. One hundred and forty four sexed doc fromeach strain (Cobb =A, Ingham = B and Steggels = C) were divided into a factorial arrangement (threedietary protein, two sexes and three strains). Two regimens of composite mixes of a summit and dilution dietand a free choice between these two diets. Diets were changed weekly, with notional crude protein levelsat one day-old of 240g/kg for all chickens, and at 42 days of age of 120 or 180 g/kg in the low and highprotein. Protein utilization efficiency (PRE) was measured from 39-42 d of age. PRE increased with theincreasing of dietary protein in strains A and C and had much higher response than in strain B. The moisture:protein ratios were 2.51, 2.65 and 2.58 in strains A, B and C, indicating strain B contained higher moistureand body fat and less protein. Involvement of genetic controls as the selection effect seems to increase thecapacity of chickens in improving nutrient utilizatio

AN EVALUATION OF THE EFG GROWTH MODEL IN ITS CAPACITY TO PREDICT AMINO ACID REQUIREMENTS IN BROILERS

An experiment imposing the multi continuous phase feeding was carried out to evaluate the EFG(Emman, Fisher and Gous) Growth Model in its capacity to predict amino acid requirements in broilers.Birds were fed using blended summit (247.91g/kg CP, 3200 kcal of ME /kg) and dilution (166.26 g/kgCP, 3200 kcal of ME g/kg ) diets and offered to 2-4 or 8 phases. Two hundred male day-old broilerchicks of two commercial strains (A=Ingham and B = Steggles) were used. The predicted responseswere greater than the observed both gain (g/d) and feed intake (g/d). The discrepancy between theobserved and predicted gain in the strain A and B birds, showed a different pattern, with a markeddifference during the early growing period, with a degree of convergence in the late growing period forthe strain A but the reverse picture for the strain B. This shows that strain characterization is notaccurate due to an inadequate definition of the genotypes by the model. Non agreement betweenpredicted and determined gain and feed intakes provided little benefit in moving towards a morefrequent change in diet to accommodate predicted growth-related changes in amino acid requirements

CHOICE FEEDING AND AMINO ACID REQUIREMENTS FOR BROILERS

The study was conducted as a completely randomized design, with a factorial arrangement todetermine the response of commercial broilers to choice feeding and limiting amino acids on growth andcarcass performance. A total of 432 male birds were weighed at one-d-old and randomly distributed to48 wire-floored brooder cage each 1.0 m2. There were 2 sexes and 4 dietary treatments with 6 replicateseach of 9 birds. Birds were given one of three dietary regimens with dietary change every 7 days. Allgroups were fed free choice of summit and dilution diets. The estimated dietary level of crude protein atday-old was 240 g/kg and the level at 42 d was either 120, 150 or 180 g/kg for females or 130, 160 and190 g/kg for males. At 43 d of age, all birds from each dietary treatment were slaughtered formeasurement of body composition. Results reveal that lysine requirement for maximum gain in thisstudy was higher than NRC recommendation. The free choice-fed bird was significantly higher, in termsof growth and body composition than that obtained on the low dietary protein regimen