الفهرس 
Chapter I : IntroductionOnly 14 pages are availabe for public view
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Abstract
This study was performed in the rabbitry of the college of agriculture (Moshtohor), Benha University during the period from September 2000 to September 2001.
A total number of 90 New Zealand with does and 18 bucks were purchased with an average age of 5.5 months. The total number was equally divided into two groups, each group cosisting of 45 does and 9 bucks, one group was housed in closed building with controlled ventilation, while the other group was housed in open house.
The animals in both housing systems were classified into three district groups each of 15 does and 3 bucks to be submitted to one of the following reproduction system :
1- Intensive system of reproduction, in which does were mated immediately after kindling
2- Semi- intensive system of reproduction, in which does were mated 10-14 days after kindling
3- Extensive system of reproduction, in which does were mated after weaning of their bunnies {30 days after kindling }.
Blood samples :
Samples were collected from doe rabbits and serum was separated to study the hormonal profile of progesterone (P4), Tri- iodo thyronin (T3) and thyroxin (T4), the first sample was collected at the time of mating, the second sample was collected at mid pregnancy while the last one was collected 28 days for the the date of mating.
Does of the intensive system of reproduction were subjected to blood sampling for the first, sixth and last parity, while these under semi- intensive system were subjected to sampling from the fist, fourth & seventh parity. On the other hand does under the extensive system of reproduction were sampled at the first, third & fifth parity.
Results :
1-Effect of different system of reproduction on serum hormonal profile of doe rabbits:
A significant effect was reported for the system of reproduction on hormonal profile of all of the three studied hormones. Intensively mated does were found to have a significantly higher level of P4 and lower T3 level at the mating time compared to their counterparts under either extensive or semi- intensive system of reproduction.
At late pregnancy, intensively mated does were found to have a significantly lower P4 level compared to those of the extensive system, but not with the does under the semi- intensive system of reproduction; on the other hand the level of T3 was significantly higher at late pregnancy in the intensively mated does compared to the extensively mated group.
The level of T4 hormone was found to be the least influenced by the system of reproduction, as the significant effect was only at time of mating during which the highest level was for the semi- intensive system of reproduction, while the lowest was recoded for the extensively mated does.
2-Effect of some environmental factors on serum hormonal level of doe rabbits :
A significant effect was reported for housing system on all hormonal levels; does reared in the closed building were found to have higher levels of T4 during all stages of pregnancy compared to those reared in the opened building .
Hormonal profile was significantly influenced by seasonal variatoin, a general improvement of the hormonal level was recorded during winter while the least values were reported during summer season.
Parity was found to have a highly significant effect on the hormonal level of all the studied hormones, as the fourth parity had the highest level of both T3 and T4; On the other hand the lowest level of T4 was reported for the ninth parity. Hormonal changes in P4 level were inconsistent as the highest level was recorded for the third and fourth parities at late pregnancy; but the level was generally stable from the fourth parity till ninth parity the period of mid pregnancy.
3-Effect of diffirent systems of reproduction on some performance paramiters :
System of reproduction had a significant effect on all the studied pregnancy parameters except for the mortality percent, which was not significantly affected extensively mated does recorded the highest litter size and weight at both birth & meaning also had the highest milk yield, compared to their counterparts under either the semi- extensive or intensive system of reproduction. On the other hand intensively mated does were found to have the least performance compared to the other two groups of does.
4- Effect of some environmental factors on performance parameters of doe rabbits :
Housing system was found to house a highly significant effect on all the studied performance parameters, does reared in closed building were found to have improved performance compared to those reared in opened building.
In the meantime all performance parameters were found to be significantly influenced by seasonal variations as the highest records for performance & lowest mortality were reported during autumn, while the least performance levels and highest mortality were during the summer.
Parity was also found to have a significant effects on all performance parameters as the best performance was reported for the third parity, while the highest mortality was reported for the eighth and ninth parities, in the meantime milk yield was found to show dramatic DROP at the seventh parity.
The interactive effect of different environmental factors and system of reproduction was found to have a significant effect on all performance parameters. The which points to the importance of taking all the environmental parameters into consideration during planning a system for reproduction in a rabbitry.
Conclusion:
from the above results we conclude that there is a significant effect of the system of reproduction on serum levels of both metabolic hormones (T3 and T4) and reproductive hormone (progesterone) with different grades, which intern will be reflected on the performance parameters of doe rabbits.
It is recommended for rabbit producers to choose the suitable system of reproduction in order to get an optimum doe performance. All the environment factors and their interactive effects should be taken into consideration.