I'll admit to knowing nothing about rats, and i do think Jason looks a stunner

Have you asked the Vet how long to wait after the op before putting him near your girls?

With my ferrets, all males castrated, occasionally vasectomised I was told to wait 6 weeks, so I do.
I did have one that wasn't vasectomised properly and i had serious doubts wether he had been done at all, so putting him to the in season girls, to bring them out of season, produced 4 litters So now I am extra extra careful!

OOOPS! Jason was put with the girks after 3 weeks

it is 6-8 weeks. 8 weeks in chinchillas and im pretty sure its 6 weeks in rats.

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the vet told me three weeks and thats when he joined his hareem and 3 months on we have had no pregnancies

I think you have been lucky I finished up with 27 unplanned for kits!!!!!!
All have happy and lifetime homes thankfully,

Really surprised at a vet only saying 3 weeks

im also shocked your vet has said 3 weeks it takes 6-8 weeks for he semen to lose it's potency.

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actually....its a little less than 2 weeks, as rats have much faster cell turnover and general bodily functions than other animals such as ferrets, chinchillas, dogs, cats etc.

Pholpramool and Sornpaisarn (1997) castrated 21 male rats. The authors found that for two days after castration, fertility in these castrated rats was normal. After the second day fertility started to drop quickly, and by the eighth day after castration all the rats in this study were sterile.

Specifically, Pholpramool and Sornpaisarn (1997) castrated 21 male rats and divided them into groups of 2-5 rats. Males from each group were then individually housed overnight with 2 females in heat on the day of castration or 1, 2, 3, 4, 5 or 8 days afterwards. Mating was judged by the presence of sperm in the vagina on the following morning. Males which didn't mate were given another opportunity the following night and were placed in the subsequent group.

Under normal circumstances, sperm leave the testes and enter a long tube called the epididymis. They travel down this tube, mature, and gain their fertilizing ability. Sperm are stored at the end of the epididymis, where they remain fertile for 42 days in the rat, then die (White 1932).

After neutering, sperm move rapidly through the epididymis (Sujarit and Pholpramool 1995). The epididymis atrophies, becomes hostile to sperm, and slowly destroys them (Arya and Vanha-Perttula 1985). Within 3-4 days after castration the sperm in the epididymis lose their mobility, lose the ability to fertilize, and die (Dyson and Orgebin-Crist 1973).



A rat rescue organization, Rattenvermittlung, which is part of the Swiss rat club named Club der Rattenfreunde Schweiz, neuters all healthy male rescue rats before finding homes for them. The neutered males are placed in cages with females 10 days after surgery. Over 100 males have been neutered and placed with females in this way. No pregnancies have occurred (C. Schenk, pers. comm. 1998).

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That was a very interesting read, thanks
I was just concerned as I had unwanted kits after a'failed' vasectomy, but still have doubts that it was ever done in the first place(long story) as the vet 'left' the practice

And each time i have the ferts castrated I'm usually told 6 weeks.