wet the slip stream

[Danijela.Krajisnik]

What does the following phrase mean: "You’re not wetting the slip stream."
A breed expert tells this to a pig farmer who has a boar that won't mate. He suggests to try to take some semen from the boar next time he actually does have a go with the sows. Then the following piece of conversation takes place:
So when he’s up I should catch some?
Well you can you try if you like and I can come on…
Well I think it’d be better for you…
It’s not you’re not catching you’re not you’re not wetting the slip stream. OK lads here we go.
Obviously it's meant to be funny in some way, but what does he mean? Could he really be referring to the physics term "slip stream"?

Thanks

[Ouisch]

I'm not well versed in the nuances of animal husbandry, so I can't help you in deciphering this phrase.

Times have certainly changed since I was in school. When we studied a foreign language, we learned sentences about going to the pool, or going to school, or what time will lunch be served. I don't think we ever practiced by using sentences about pig insemination.

[Dr. Jamshid Ibrahim]

A slipstream written either one word or hyphnated is a current or an assisting force to drive sth along. So you follow close behind so that the resistance of the air to your progress is less. Metaphorical use.