الفهرس 
RATIONALE and OBJECTIVES
Genetic–nutrient interactionsOnly 14 pages are availabe for public view
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Abstract
General Summary and Conclusions
Two trials ,each of 180 one-day old broiler chicks (Ross) were conducted till 42 days of age to evaluate the effect of low available phosphorus or high lysine level throughout first ten days after hatch on the adaptability of broilers as nutritional imprinting to low available phosphorus or low protein level during the finishing stage in relation to their productive performance and environment pollution. In the first experiment from day one to day 10 of age, all chicks assigned to 3 equal treatments .Chicks in T1 (control) were fed a diet containing an optimal level of available phosphors (0.46%) according to NRC. Chicks in T2 were fed a diet containing a low level of available phosphorus (0.23 %). However; chicks in T3 were fed a diet containing a high level of available phosphorus (0.69 %) . from day 11 to day 28 of age, chicks of all treatments were fed grower diet containing, 0.9 % Ca. and 0.46% av. P. from day 29 to day 42 of age, chicks of each treatment were distributed into 2 subtreatments. In subtreatment 1 chicks were fed a diet containing 0.35 % av. phosphorus, while those of subtreatment 2 were fed a diet containing 0.18 % av. P. In the second experiment, chicks were assigned to two treatments. During the first ten days of age, Chicks in T1 (control) were fed a diet containing an optimal level of lysine (1.2 %) according to NRC. Chicks in T2 were fed a diet containing high level of lysine (1.5 %).. from day 11 to day 28 of age; Chicks of both treatments were fed a diet containing 1.1 % lysine. from day 29 to day 42 of age: Chicks of each treatment were divided into two subtreatments . Chicks of subtreatment 1 were fed a diet containing 19 % protein and 0.9 % lysine, while chicks of subtreatment 2 were fed a diet containing, 16 % protein and 0.9 % lysine..
During the experimental period of the two experiments (6wks), the following parameters were recorded or calculated: weekly body weight, body weight gain, weekly feed consumption, feed conversion ratio, and daily mortality. At 28 and 42 days of age of experiment 1 three birds of each replicate were taken, slaughtered and prepared to record organs, cutup parts and dressing percentage. Blood samples were taken and serum was separated to determine Ca, phosphorus and alkaline phosphatase. Also, left tibias were taken and dried to determine tibia ash and calcium and phosphorus. At 42 days of age of experiment 1, all replicates of the experiment, were prepared to carry out phosphorus retention experiment. Similarly, in experiment 2, at 42 days of age, three birds of each replicate were taken, slaughtered and prepared to record organs, cutup parts and dressing percentage. Also, all replicates of the experiment were prepared and used to carry out nitrogen retention experiment.
The results of exp.1 revealed that birds fed low level of available P during the early and the late periods of age achieved average BW and BWG which amounted to 1617 and 1561 g; respectively, versus 1407 and 1353 g for their control within the same treatment. No significant effects on feed conversion ratio were detected. The values of breast weight reveal that it was insignificantly affected by phosphorus level of subtreaments1 and 2in treatments 1 and 2 but it was significantly affected by phosphorus level of subtreaments1 and 2 in treatment 3.The results of breast % of LBW and breast % of CW reveal that it was insignificantly affected by phosphorus level when comparing between subtreatments1 and 2 in treatments 1, 2 and 3. The results of legs % of LBW and legs % of carcass weight reveal that they were significantly affected by phosphorus level of subtreaments1 and 2 in treatment 1.Whereas,they were insignificantly affected by phosphorus level of subtreaments1 and 2 in treatments 2 and 3. The results of carcass weight and carcass percentage reveal that it was insignificantly affected by phosphorus level when comparing between subtreaments1 and 2of treatments 1,2 and 3. The results of dressed weight showed that chicks fed the low level of phosphorus (0.23 %) during the period from 1-10 days of age in treatment 2 (subtreatment 1) achieved dressed % (87 %) at 42 days of age which is numerically similar to that of subtreatment 2 in the same treatment. Tibia calcium (%) at 28 and 42 days of age was insignificantly affected by available phosphorus level, while tibia phosphorus (%) was significantly affected. However, birds fed the highest level of phosphorus (0.69 %) achieved the lowest phosphorus level in tibia at 28 days of age (12.1 %) compared to 13 % tibia phosphorus for birds fed the lowest level of available phosphorus. Serum phosphorus at 28 days of age was significantly affected by available phosphorus level in treatments 1, 2 and 3. Birds fed the lowest level of available phosphorus (0.18 %) during the first ten days of age and during the last two weeks of age exhibited the highest level of phosphorus retention percentage (65.8%) compared with the other two treatments (51.8 % and 48.3 %)
The results of Exp2, revealed insignificant differences in BW, BWG and feed conversion ratio between subtreatments 2 of T1 and T2 at 42 days of age. Carcass weight and carcass percentage were insignificantly affected by early dietary lysine level between subtreatments 1 and 2 of treatment 1, whereas, it was significantly affected by early dietary lysine level between subtreatments 1 and 2 of treatment 2. The results of breast and legs weight reveal that it was insignificantly affected by lysine level between subtreatments (1 , 2 ) in treatments (1) but it was significantly affected by lysine level in subtreatments (1, 2) in treatment (2). The results of carcass weight and carcass percentage reveal that it was insignificantly affected by lysine level between subtreatments (1 , 2) in treatment (1).Whereas, carcass weight was significantly affected by lysine level between subtreatments (1 , 2) in treatment ( 2 ). The results of dressed percentage showed that chicks fed the lowest level of lysine (1.2 %) during the period from 1-10 days of age in treatment 1 (subtreament 2) and were fed the lowest level of protein (16 %) during the last two weeks of age achieved insignificant higher dressed % (81.8 %) versus 79.4 % for subtreatment 1. Nitrogen retention at 42 days of age revealed that it was insignificantly affected by the high level of lysine during the first ten days accompanied by low level of protein in the last two weeks. However, nitrogen retention % was to some extent better in treatment 2 subtreatment 2 (90.3 %) that was fed highly early dietary lysine level (1.5 %) together with late low protein level (16 %).
In conclusion, broilers fed a dietary low level of av.P from hatch to 10 days of age demonstrated the ability to adapt to the low level (Experiment one). Since broilers fed the low level P diet during the first ten days of age were better able to handle a low level of P in the finisher phase (29 to 42 days of age) than those fed a control diet in the first ten days of age. This was shown in the improved growth of treatment 2 subtreatment 2, however, birds fed deficient in P from hatch to 10 days of age demonstrated the ability to adapt to the deficiency and achieved slightly best body weight at 42 days of age (1617g) versus 1407g for birds fed low P in early period and optimum av.P in later period, and improvement in body weight gain (1561g vs 1353g) and improved feed conversion ratio ( 2.5 vs 3.1) and improvement in some bone measures including tibia phosphorus content ( 15.4 % vs 14.7 %).In the second experiment, broilers fed a high lysine diet in the early phase were able to tolerate a decrease in protein in the finisher phases. Body weight and body weight gain of 42 day old broilers fed a high lysine pre-starter and a low protein finisher diets (Treatment 2, subtreatment 2) was slightly higher, but insignificantly higher than the body weight of birds fed the control diet (1786 g versus 1765g ) and 1732 g versus 1712 g for body weight gain . However, feed conversion ratio, carcass yield and breast yield percentage were not affected by the low protein diets. Additionally N retention percentage from birds fed the low protein diets was 90.3 % compared to the N excretion from birds fed the control diets (88.8 %). The reviews Based on the results of the two experiments , it may be stated that early low level of dietary available phosphorus has led to some improvements in live bodyweight ,body weight gain , feed conversion ratio by reducing feed consumption and increasing body gain . Also , it siguficanty increase phosphorus percent in tibia at 42 days of age, Moreover, the early high level of dietary lysine along with late low level . of protein has feed to some improvements in carcass weight , breast weight , legs weight and percent of nitrogen retention at 42 days of age. in conclusion , more work is needed to determine if there is a nutritional imprinting of dietary manipulation through molecular biology and gene experssion studies.