الفهرس 
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Abstract
The experiment of this study was carried out at Private Breeding Farm of poultry production at Toukh city, Kaluobia Governorate, Egypt, during summer 2007, in order to investigate the relationship between the general immune response to SRBCS and some productive traits in broiler chicks. Two different commercial strains, namely ISA Hubbard and Ross 308, were used. Data collected from 500 chicks (250 chicks from each strain) were used. All chicks were brooded and reared under similar environmental conditions and raised on deep litter up to marketing age (7 weeks). Feed and water were provided ad libitum. They were fed a diet containing 23% crude protein and 3000 k.cal ME/kg in starter formula, 21% crude protein and 3050 k.cal ME/kg in grower formula and 19% crude protein and 3150 k.cal ME/kg in finisher formula. The load number was (intensity numbers 10 birds /m2).
The aims of study are:
1-To study the effect of Ab level, strain and sex on live body weight at different ages.
2- To study the effect of Ab level, strain and sex on carcass traits.
3- To study the effect of Ab level, strain and sex on blood components and both IgM and IgG.
4- To study the phenotypic correlations between live body weights at 7- wk of age and Ab titers at different ages in order to predict the live body weight of chickens.
5- To compute the expected response per generation due to phenotypic selection at different selection intensity in ISA Hubbard and Ross 308 strains.
This study showed the following results:
1. Live body weight:-
1- The statistical differences between the two strains and sex effect were highly significant (P<0.001) in live body weight at different ages (from hatch up to 4- wk of age). The interaction between strain and sex effects was highly significant (p≤ 0.001) in live body weight at 1st, 2nd, 3rd and 4th weeks of age.
2- Results showed that chicks had high antibody titers were low in body weight compared with low and, control antibody levels. The difference between both low line and control and high lines was significant (P≤ 0.05) at different age.
3- There were no significant differences for the interactions between strain x line, sex x line and strain x sex x line on body weight. However, these interactions were significant (P≤ 0.05) at only 7- wk of age.
2. Immunity
1- In genetically, the highest level of Ab- titers occurred at 7- days’ post- injection, then declined gradually to 21- days’ post- injection in all chickens of both strains. The difference of Ab titers between the strains was highly (P≤0.001) significant. The Ab titers of females were higher than males at 7, 14 and 21 days post injection, but the difference between them was not significant.
2- Results showed that, low and negative phenotypic correlations were obtained between antibody titers and live body weight at 7- wk of age.
3- The antibody levels effects were highly significant (P < 0.001) on the number of immune cells for Hubbard and Ross chicks at 49 days age. On other hand, the live body weight of chickens at 49 days of age did not have any significant effect on the number of immune cells.
4- The ISA Hubbard strain had higher immune white blood cells, heterophiles cells and lymphocytes cell numbers more than Ross strains, while the Ross strain had a higher red blood cell more than Hubbard at 49 days of chick’s age.
5- The effect of strain on immune cells numbers was statistically non significant for all measured immune cells, but all of white blood cells, red blood cells, heterophiles and lymphocyte cell were higher in the females of the two strains than the males, but without statistical significant difference between them.
6- The heterophiles cell percentage in ISA Hubbard strain was higher than Ross strain at 49 days of age. Opposite trend was noticed for lymphocytes percentage with a significant difference (p ≤ 0.01) of least-square means.
7- Ross 308 strain was significantly (P < 0.001) higher IgG anti-SRBCs antibody titer at 49 days from SRBCs injection compared to Hubbard one.
8- Both Hubbard and Ross females had higher IgG at 49 days of chicken’s age than males, but this difference were not significant.
9- There is no significant effect among control and selected line for high and low Ab titers on IgG percentage. The low immune response lines had the lowest mean compared to control and high ones.
10- Serum IgM percentage did not affected significantly by the levels of different selected line (low and high Ab titers) compared to control lines.
11- The body weight had highly significant effects (P < 0.001) on serum IgM percentage at 49 days of chicken age.
12- Bursa weight and relative weight were heavier in Ross and Hubbard females than males of both strains, but without any statistical significant differences among the two sexes.
13- Both low and high immune response levels gave bursa weight lower (1.609 g) than control level (1.65g) at 49 day chicks age, while low level was the mediated one (1.64g). Nevertheless, the three levels did not show any differences for bursa percentage (0.095%).
14- The statistical analysis of LSM of bursa weight and percentage revealed that there is a highly significant (P≤ 0.001) effect due to strains and live body weight on both bursa weight and relative weight.
15- Ross broiler chicks were significantly (P≤ 0.05) heavier spleen weight (1.64 g) and relative weight (0.09%) compared to Hubbard broiler chicks at 49 days of age. Statistically, there was a highly significant (P ≤ 0.001) difference among the two strains due to spleen weight and relative weight.
16- Broiler females of the two strains showed heavier spleen weight and percentage compared to the males chicks. These differences were not significant for spleen weight and relative weight.
17- There was a highly significant (P≤ 0.001) effect for live body weight on spleen weight and percentage.
18- Strains effect on thymus weight and percentage revealed highly significant (P < 0.001) on both thymus weight and relative weight. The Hubbard chicks had significantly higher thymus relative weight compared to Ross.
19- Ross and Hubbard males chicks had lower thymus weight and percentage compared to females chicks. But these differences were not significant.
20- The low immune response level chicks had significantly (P< 0.05) heavier thymus weight (2.34gm) and percentage (0.137%) compared to high and control levels.
21- The live body weight showed a highly significant (P≤ 0.001) effects on thymus absolute and relative weight.
3.Carcass traits
1- Ross broiler chicks had heavier blood weight compared to ISA Hubbard strains. Also with respect to relative blood weight, it was noticed that Ross broiler chicks were heavier blood percentage compared to ISA Hubbard.
2- Males had significantly (p≤0.05) heavier blood weight compared to females. Also with respect to relative blood weight, it was noticed that males had heavier blood percentage compared to females.
3- ISA Hubbard broiler chicks had significantly (p≤0.001) heavier feather weight compared to Ross strain. Also with respect to relative feather weight, it was noticed that ISA Hubbard broiler chicks had heavier feather percentage compared to Ross.
4- Females had heavier feather weight compared to males. But there were no significantly difference between males and females. Also with respect to relative feather weight, it was noticed that females were heavier feather percentage compared to males.
5- ISA Hubbard broiler chicks had heavier leg weight compared to Ross strains; there were no significantly difference between strains. Also with respect to relative leg weight, it was noticed that ISA Hubbard broiler chicks were heavier leg percentage compared to Ross.
6- Females had heavier leg weight compared to males. But there were no significantly difference between males and females. Also with respect to relative leg weight, noticed that males were heavier leg percentage compared to females.
7- ISA Hubbard broiler chicks had heavier head weight compared to Ross strains. But there was no significantly difference between strains. Also with respect to relative head weight, it was noticed that ISA Hubbard broiler chicks were heavier head percentage compared to Ross.
8- Males had heavier head weight compared to females. But there were no significantly difference between males and females. Also with respect to relative head weight, it was noticed that males were heavier head percentage compared to females.
9- ISA Hubbard broiler chicks had heavier inedible weight compared to Ross strains. But there was no significantly difference between strains. Also with respect to relative inedible weight, noticed that ISA Hubbard broiler chicks were heavier head percentage compared to Ross.
10- Males were heavier inedible weight compared to females. But there were no significantly difference between males and females. Also with respect to relative inedible weight, it was noticed that males were heavier head percentage compared to females.
11- Ross strain was significantly (P≤0.05) heavier dressing weight than Hubbard. Furthermore, the Ross broiler showed dressing percentage higher than Hubbard. Males of both strains were heavier in dressing weight and percentage compared to the females.
12- The high Ab-level immune response chicks were the lowest dressing weight compared to low and control levels. While control level showed the lowest dressing percentage compared to high and low levels.
13- Statistically there were no significant effects for strain, sex and levels on both dressing weight and percentage. But there were a highly significant effect for body weight on dressing weight and percentage.
14- There was a slight increase in heart weight of Ross strain than Hubbard at 49 days of chick’s age. Inversely, ISA Hubbard broiler was significantly higher in heart percentage than Ross one. These differences between the two strains statistically were not significant.
15- The females of Ross and ISA Hubbard broiler had heavier heart weight and percentage than males’ broiler. But there was no significant effect for sex on heart weight and percentage.
16- The high immune response level chicks had heavier heart weight compared to control and low levels. The low level was the mediated one. But there was no significant effect for levels on heart weight and percentage.
17- Live body weight showed a highly (P≤ 0.01) significant effect on heart weight, but no significant effect on heart percentage.
18- The liver weight and percentage of ISA Hubbard strain was significantly heavier than Ross one. Moreover, the liver weight of the two strain females was heavier than males one. The same trend was observed for liver percentages.
19- The high level of immune response was significantly (P≤ 0.05) heavier in liver weight and percentage followed by low level and the control was the lowest one. Statistically there was a highly (P≤ 0.01) significant effects due to strain and live body weight on liver weight.
20- Ross strain showed gizzard weight and percentage significantly (P< 0.05) heavier than ISA Hubbard one at 49 days of broiler age.
21- There were no noticeable differences between males and females of Ross and ISA Hubbard strain in gizzard weight and percentage. The analysis of variance no significant differences due to sex on gizzard weight and percentage.
22- The high immune response Ab- level chicks was significantly (P≤ 0.05) heavier gizzard weight and relatively gizzard percentage compared to low and control Ab- levels. Control level was the mediated one.
23- Ross broiler was significantly (P≤ 0.05) heavier giblets weight more than ISA Hubbard strain at 49 days of chick’s age. The same trend was observed for giblets relative weight. But these differences statistically were not significant.
24- The Ab- level broiler chicks was significantly lower in giblets weight when compared to the high level, while it was heavier giblets than control level. There was no significant difference between the three Ab-levels in giblets percentage.
25- Live body weight showed highly significant (P ≤ 0.01) effects on giblets weight and without significances on the relative weight.
26- The edible meat parts of Ross broiler were significantly heavier than Hubbard broiler chicks. Also Ross broilers were significantly (P≤ 0.05) higher relative edible meat parts weight than ISA Hubbard ones.
4. Blood components:-
1- Hubbard strain had higher total plasma proteins than Ross. The other blood components (Albumins, Globulins and A/G ratio) were higher in Ross than Hubbard strain. Statistically, there is a highly significant difference between Hubbard and Ross strains in total plasma proteins at (P≤ 0.001). But the differences between the two strains were not significant in the other total plasma proteins (Al, Gl and A / G).
2- The females of both strains were higher in albumin and Albumin to globulin ratio values than males, but the males have the higher values of the total plasma proteins and globulins.
3- The low levels of Ab titer had higher total plasma proteins compared with the control and high levels of Ab titer. While the high levels of Ab titer had highest value of plasma albumins followed by control and low levels.
4- Both sex and Ab titer have non-significant statistical effects on the total plasma proteins. But the live body weight has highly significant (P≤0.001) effects on this parameter except A/G ratio didn’t affected by line body weight at this age.
5- Total Plasma lipids mean values were higher in ISA Hubbard strain than Ross one at 49 days of age.
6 -Sex has a significant effect on total plasma lipids and cholesterol. The males of both strains gave higher mean value for plasma total lipids than females.
7- The analysis of variance of strain, sex, Ab level and live body weight clearly shown that these factors have not significant effects on plasma total lipids at 49 days of chicks’ age. But both of sex and live body weight have a highly significant effect on plasma cholesterol.
8- Liver function revealed that ISA Hubbard was significantly lower in GOT than Ross strain at 49 days of age, while GPT gave on opposite. But statistically these differences between the two strains were not significant for both GOT and GPT.
9- The females of both ISA Hubbard and Ross chicks gave a higher GOT and GPT than males chicks. This effect was not significant from the statistical view.
10- At 49 of chicks age, liver function affected by Ab levels for both GOT and GPT low levels shown the lower GOT, results compared with control and high levels, the last gave the higher significantly higher than control and high ones.
11- Live body weight effect on liver functions revealed that both of GOT and GPT affected significantly (P ≤ 0.001) by live body weight.
5. selection parameters.
1- The ISA Hubbard higher average of body weight in selected parent the Ross 308, the average of body weight in selected parents expected to reach 1786.8 g.
2- In ISA Hubbard, where it expected to reach 1616.6 g for Ross 308 at 10% selection intensity. These values expected to reach 1705.10 and 1569.00 g at 50% selection intensity in both ISA Hubbard and Ross 308, respecti.