الفهرس 
The objectives of this study wereOnly 14 pages are availabe for public view
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Abstract
The present study was carried out at the Rabbits Production Unit
(RPU), Faculty of Agriculture, Ain Shams University, Cairo, Egypt. The aim
of this study was to investigate the effects of supplemental vitamin A or zinc
and their combinations on growth performance, nutrients digestibility
coefficients, carcass traits, some blood constituents and economic evaluation
of growing Rex rabbits.
A total number of 135, unsexed Rex Rabbits, (5 weeks) with an
average initial body weight of 645.46±77.85gm, were randomly allotted in a
factorial design into nine experimental groups (3*3), there were three
replicates of five rabbits for each experimental treatment. The experimental
groups included three vitamin A levels (6000,1000 or 14000 IU/kg diet) and
three Zn levels (50,100 and 150 ppm/kg) in factorial (3*3) design. The basal
experimental diet was formulated and pelleted at Egyptian Canadian
Company to cover the nutrient requirements of rabbits recommended by
NRC (1977) and Lebas et al. (1997). The added premix in the growing
rabbit diets was vitamin A and Zn free.
The rabbits were housed in galvanized metal wire cages provided
with feeders and automatic drinking system and were kept under the same
managerial and hygienic conditions. The experimental period was extended
for 8 weeks. Individual live body weight, feed consumption, feed conversion
ratio and mortality rate were weekly recorded.
The main results could be summarized as follows:
1- Live body weights and body weight gain of rabbits were increased
significantly throughout the experimental period in a linear manner due
to supplemental vitamin A and Zn.
2- Zn supplementation at any level did not affect on feed consumption of
growing rabbits, while vitamin A tended to reduce it, especially with
the mid-level (10000 IU/kg).3- Rabbits group received the control diet contained 50 ppm Zn plus 6000
IU vitamin A gave the worest overall feed conversion ratio as
compared with those given the other experimental diets.
4- The interaction between Zn and vitamin A was highly significant
during the whole experimental period indicating the presence of
reciprocal positive synergism between both supplements.
5- No significant differences were observed in the digestibility
coefficients of dry matter, organic matter and crude protein, ether
extract, crude fiber, nitrogen free extract and nutritive values (TDN &
DCP) among experimental diets.
6- There were insignificant improvements in most nutrients digestibility
coefficients and nutritive values for rabbits fed diets containing 14000
IU vitamin A. The same trend was noted with rabbits received diet
contained 50 ppm zinc.
7- No significant differences were observed in dressing percentage and
relative weights of hot carcass, head, liver and heart due to feeding
rabbits on different levels of zinc, regardless of vitamin A in the rabbit
diets.
8- Dietary Zn levels did significantly affect (P<0.05 or 0.01) relative
weights of kidneys, kidneys fat and spleen.
9- significant differences were noted in dressing percentage and relative
weights of hot carcass, liver, kidneys fat and spleen for rabbit groups
given diets containing different levels of vitamin A (6000, 10000 and
14000 IU).
10- Rabbits fed diet containing 10000 IU vitamin A gave the highest
dressing percentage than those received 6000 and 14000 IU vitamin A
diets. While head, heart and kidneys relative percentages were not
significantly affected by vitamin A addition.
11- Rabbits fed 14000 IU/kg diet have significantly (P>0.05) higher total
protein and globulin than those fed 6000 or 10000 IU/kg diet. In addition, no significant differences were observed in total protein of
rabbits fed diets containing different levels of zinc.
12- Rabbits fed the control diet contained 50 ppm recorded higher
(P≤0.05) Albumin (g/dl) than those received diets containing 100 or
150 ppm.
13- Supplementation vitamin A had no significant effect of on blood
albumin.
14- Lower (P≤0.05) values of A/G ratio were obtained for rabbit groups
fed diet containing 150 zinc ppm or 14000 IU vitamin A /kg as
compared to the control and other treated groups.
15- Rabbit groups fed diets containing either 100 or 150 ppm zinc had
lower (P≤0.01) values of total cholesterol than those of (50 ppm
zinc).
16- Higher level of total lipids was recorded for rabbits group fed diet
contained 14000 IU vitamin A as compared to the other vitamin A
levels.
17- Rabbits group fed 10000 IU vitamin A diet recorded higher
cholesterol and lower triglyceride in the blood plasma compared with
the other treated groups ( 6000 or 14000 IU Vitamin A diets).
18- Feeding on diet containing, elevated the 150 ppm Zn plasma level of
AST as compared with the other Zn level (50 and 100 ppm).
19- Rabbits group fed high level (14000 IU) of Vitamin A had higher
plasma urea (P≤0.05) than those received 6000 or 10000 IU vitamin
A diets. ALT enzyme was significantly the highest for rabbits fed
10000 IU vitamin A diet.
20- There were highly significant differences (P≤0.01) in protease,
cellulase and xylanase enzymes due to feeding rabbits with different
levels of zinc and vitamin A.
21- Economic efficiency (%), relative economic efficiency and
performance index were increased by feeding rabbits on diet with 150 ppm zinc plus 14000 IU vitamin A, while feeding on control diet ( 50
ppm zinc plus 6000 IU vitamin A) resulted in worse economic indices.
The general conclusion indicated that, vitamin A, zinc or their
interaction could be successfully for feeding growing rabbits at various
levels without any deleterious effects on the rabbit performance and
economic evaluation. We concluded from this study that, provision of
rabbit level diet with 150 ppm zinc plus 14000 IU vitamin A/kg is
practically good procedure and could recommended in formulating rabbit
diets in order to achieve better productive and physiological performance
with less feeding cost.