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Posted by patricia sherman on April 12, 2003 at 11:57:46:
In Reply to: Rat breeding question......... posted by DMeyer20 on April 07, 2003 at 23:26:47:
How many babies do rats usually have with each litter ...
My rats average about 12 to 14 pups per litter. Over 15 is a large litter, although 16 or 17 isn't uncommon. 18 or more is exceptional, but the largest litter I've seen was 23. Under 11 is a small litter, the smallest litter I've seen was three. If a momma consistently throws litters of under ten, I don't keep her for long (she gets three or four tries). Some mommas are inconsistent and will give you litters of widely differing numbers of pups, most rats will produce litters of fairly similar size each time they're bred.
and what is their rate of growth.
A lot depends on how well they start out. Competition for milk when they're nursing, can be very stressful, and can result in the weaker babies being stunted. To ensure against this, I immediately reduce each litter to a maximum of eight pups. At four or five days old, I usually further reduce it, to a maximum of six. At two weeks old, the litter is culled down to a maximum of four. This ensures that all the babies are fat and healthy at weaning (three to four weeks old).
How long for the rat to reach the sizes of small, medium, large, and jumbo?
Pinkie rats will double their birth weight within 48 hours. Well-fed pups at age three weeks, are already larger than any mouse.
I classify them as very small if they're over 10 days, but still not weaned. From about four weeks to six or seven weeks, they're small. After they're six weeks old, you'll begin to notice a great difference in the growthrate between the males and females. A female at twelve weeks, will be about 2/3rds the size of her brother. By the time they're fully grown, she'll be less than half the size of a full-grown male.
Adult females (over four months) are what I call large. I also apply this label to males of about 12 to 20 weeks. By age five months, a male will achieve the small jumbo size. Some males will continue to grow a bit even up to age eight or nine months. Generally, a male over six or seven months will be a large jumbo.
As you've already been told, raising jumbos takes a lot of food and time, and generally isn't worth it.