الفهرس 
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Abstract
In Egypt as well as in many other countries there is a continuous increase in the demand for animal protein. Local meat production has failed to satisfy increased consumption needs. Rabbit meat could be a very important source of protein for humans, not only because of its quality but also because rabbits can utilize high fiber feed and transform it into high quality low fat meat. Generally, the rabbit farming is increasing in most of the developing countries due to their smaller body size, short gestation period, high production potential, rapid growth rate and the ability to utilize forage and by-products as major diet components.
This study was planned to investigate the effect of breed, sex and dietary sodium butyrate on productive traits, carcass traits, mortality rate, biochemical change and histological changes. The obtained results are summarized under the following titles:
I. Productive traits:
a. Body weight:
1. New Zealand white rabbits were only significantly higher body weight during 3rd week than Flander (1336.6±36.9 vs. 1221.6±26.9g, respectively).
2. With considering the difference between males and females at the start of experiment by analysis of covariance to the initial weight, females also were significantly lower body weight than males during 3ndweek (1254.6±36.3 vs. 1303.6±32.3g); 6thweek (1580.9±36.2 vs. 1650.7±34.9, respectively); 7thweek (1701.6+37.1 vs.1772.5+36.20 and during 8thweek (1833.64 ± 37.69 vs. 1903.41± 36.93g).
3. The addition of Sodium butyrate to ration of rabbits (300 g/ton) improved the body weight of rabbits from the 1stweek (1076.9+29.5 vs. 1036.5+44.4 g) till the end of experiment after 8th week (1851.5±49.82g vs.1882.71+26.45g).
b. Weight gain:
1. New Zealand White rabbits were higher weight gain than Flander during 1st week (104.3+5.2 vs. 99.6+2.3 g/week), 2nd week (112.7+8.4 vs. 101.1+4.5 g/week); 7th week (125.0+2.8 vs. 117.5+3.1 g/week) and significantly weight gain were during the 8th week (136.1+3.5 vs. 126.8+1.8 g/week).
2. Males gained more than females during 1st week (102.1+3.3 vs. 101.8+4.7 g/week), 2nd week (116.1+4.9 vs. 102.7+7.9g/week), 4th week (110.2+2.9 vs. 105.8+1.9 g/week), a significant difference during5th week (117.6+4.4vs. 106.8+1.9g/week), 6th week (119.2+4.2 vs. 114.6+3.7 g/week), 7th week (121.8+2.7 vs. 120.7+3.3 g/week).
3. Dietary sodium butyrate improved rabbits’ weight gain of rabbits during 1st week, 2nd week, and 8thweek of experiment However, weight gain lowered during 5th week (115.8+5.3 vs. 109+1.3 g/week),6th week (122.5+5.6 vs. 112.2+1.8 g/week) and 7th week (123.3+3.9 vs. 119.6+2.1g/week).
c. Feed conversion ratio:
1. With respect to Feed conversion ratio of New Zealand White rabbits was better than those of Flander during 1st week (3.07+0.16 vs. 3.12+0.10); 2nd week (3.17+0.11 vs.3.40+0.13); 5th week (3.91+0.13 vs. 3.93+0.10); 7th week (5.38+0.16 vs. 5.56+0.14) and 8th week (5.54+0.16 vs. 5.76+0.07, respectively).
2. The female feed conversion ratio were better than males during 1st week of experiment (3.03+0.13 vs. 3.16+0.13) and 8th week of experiment (5.48+0.11 vs. 5.82+0.13), while males were better than females with significant difference during the 5th week of experiment (3.70+0.11 vs. 4.14+0.10).
3. Feeding Sodium butyrate (30g/ton) for rabbits improved significantly feed conversion ratio during 1st week of experiment (2.85±0.07 vs. 3.30±0.15); 2ndweek, (2.89 ±0.11 vs. 3.62±0.15); 3rdweek (2.94±0.09 vs. 3.63±0.09); 4thweek (3.42±0.13 vs. 3.94±0.13); 5thweek (3.63±0.12 vs. 4.16±0.07); 6th week (4.64±0.2 vs. 5.25±0.08); 7th week (5.20±0.14 vs. 5.69±0.14) and 8th week (5.51+0.12 vs. 5.77+0.12).
II. Carcass traits:
1. With regard to the effect of breed on the carcass traits, New Zealand White rabbits had significantly higher (P<0.05) dressing percentage (0.53±0.02 vs. 0.51±0.02), fore quarter (0.17+0.007 vs. 0.16+0.005), loin (0.13 ±0.005 vs. 0.12 ±0.004), hindquarter (0.23±0.009 vs. 0.22±0.007) and gastrointestinal tract percentage (0.23+0.009 vs. 0.22+0.007) than Flander.
2. Males of rabbits were higher dressing percentage (0.53±0.02 vs. 0.52±0.02), While, other parameter were nearly similar.
3. Under an ad libitum condition feeding sodium butyrate to rabbits resulted in higher dressing percentage than control group (0.53+0.02vs. 0.52+0.02).
III. Serum biochemical traits:
1. Breed had no effect on Triglycerides, enzymatic activity of Alanine Aminotransferase (A.L.T) or Aspartate Aminotransferase (A.S.T) where, levels of biochemical parameters were (157.67±8.4 vs. 150.33±7.31mg/dl, respectively), (14.1±0.65 vs. 15.4±0.41 IU, respectively) and (21.27±0.42 vs. 22.18±0.22 IU, respectively).
2. Sex had no significant effect on T.G and A.S.T however, means of male and female were(156±6.13 vs. 152±9.46mg/dl, respectively), (21.69±0.45 vs. 21.77±0.24 IU, respectively)
3. Dietary sodium butyrate (300 g/ton) had no effect on T.G and the enzymatic activity of Alanine Aminotransferase (A.L.T) Aspartate Aminotransferase (A.S.T) where means of treatment and control rabbits were (147.67±9.04 vs. 160.33±6.22mg/dl, respectively), (15.17±0.54 vs. 14.33±0.58 IU, respectively) and (21.84±0.41 vs. 21.61±0.3 IU, respectively).
4. Present results clearly indicate that supplementation of rabbit diet with acidifier (sodium butyrate) has no deleterious effects on liver or kidney functions since levels of enzymatic activity of Alanine Aminotransferase Aspartate Aminotransferase were not significantly changed in response to dietary treatment.
IV. Mortality rate:
The results of the current experiment showed that feeding rabbits with sodium butyrate reduced mortality rate to zero% in comparing with incidence of mortality in control group (0.16%).
V. Histological changes:
from the previous results it was obvious that breeds of rabbits did not influence the histological structure of the small intestine of rabbits where the control New Zealand White and Flander were nearly similar and the treated groups were nearly the same however, feeding rabbits sodium butyrate in both breeds increase the duodenal villi height and prominently increase the submucosal gland (Brunner’s glands).This findings support the improvement in the productive traits of rabbits.
from the present results, it is concluded that:
1. New Zealand white rabbits were better than Flander breed where New Zealand rabbits were higher body weight, weight gain, better feed conversion ratio and higher carcass traits during experiment.
2. Males’ rabbits were better than female rabbits where males’ rabbits were higher body weight, weight gain, better feed conversion ratio and higher carcass traits during experiment than females’ rabbits.
3. Addition of sodium butyrate (300g / ton ) ratio improved the body weight , weight gain, feed conversion, higher dressing percentage and the major important result was reducing mortality rate to zero% in comparing with incidence of mortality in control group (0.16%).
4. Supplementation of rabbit diet with acidifier (sodium butyrate) has no deleterious effects on liver or kidney functions since levels of enzymatic activity of Alanine Aminotransferase Aspartate Aminotransferase were not significantly changed in response to dietary treatment.