How long should I keep does for?
  
To answer this question three main issues need to be considered;
  

1.

 Reproductive performance
2. The does genetic merit and overall genetic progress of the rabbitry
3. The age structure of the rabbitry
 
I will attempt to illustrate these issues using data that we have collected over the last four years in our rabbitry. I am in no way suggesting that this will be exactly the same in all situations however the principles should remain the same.
  
1) Reproductive performance
 
There is a distinct relationship between both the age of the doe and the number of parities she has had with her reproductive performance. The most important determinant appears to be number of parities (litters) that the doe has mothered. I have illustrated the average number born, weaned and overall litter weight at weaning in Figure 1.
  
Figure 1. The relationship between the number of rabbits born, weaned and overall litter weight at weaning ( x ) with the number of litters mothered by the doe
 

 
This graph clearly illustrates that the doe does not reach her maximum level of production until her third or fourth litters and then starts to decline. While the number of kittens weaned per parity drops off dramatically after about the seventh parity the total litter weight weaned does not decline as dramatically.
 
2) The does genetic merit and overall genetic progress of the rabbitry
 
It is important to establish the value of the genes of each breeding doe. It does not make sense genetically or financially to persist with in-superior does. Once a doe has mothered three to four litters you will be able to have a good indication of its performance. Using this information and that of its relatives you can gain an indication of its genetic merit. The aim must be to get the greatest number of litters and possible replacement does out of your best breeding does. However it must be noted that only a small percentage (approximate 10%) of the variation between animals in reproductive performance is due to the genes of the animal. Therefore the majority of the variation between does in their reproductive performance is due to environmental factors such as nutrition, health and climatic conditions.
 
This issue is further complicated by the fact that the quicker does are replaced with genetically superior does the more rapidly the overall genetic merit of the rabbitry with improve. If there is a young doe that is not producing after three litters it would be much more beneficial to cull this doe and replace her with a genetically superior one.
 
3) The age structure of the rabbitry
 
It is important for all breeding flocks to have breeding animals covering a range of ages. This also applies to rabbits and with correct management a rabbitry should be able to have a large proportion of their animals near the ages of maximum production and thereby improve the continuity of production throughout the year.
 
The number of replacements that are required can be simply calculated for each production system. Lets us consider a 100 doe rabbitry that produces 5000 sellers per year as an example. Examining the graph presented above the average doe should be replaced after she has weaned 7 litters, which would be approximately every 56 weeks. This calculation assumed that does are selected at 12 weeks of age and on average wean a litter every 50 days. Therefore this means that each fortnight approximately 4 rabbits should be selected to replace the oldest or most unproductive does. This will result in the majority of does being replaced after 7 litters.