Probability and Animal Pregnancy

If a randomly selected pair of male and female adult humans have intercourse without any kind of contraceptive, the fact is that she will probably not get pregnant, even on the most fertile days of her cycle. The odds are way too high to rely on this as a method of birth control, but still, I am under the impression that the odds are something less that 50%.

If I am correct in the above, is it any different for animals? We hear all the time about various animals being used for stud purposes. I remember once my father was paid for using our pet schnauzer to make other schnauzers. Somehow, I’ve gotten the impression that breeders presume that every act of sex will lead to a pregnancy. Does it really?

I don’t have a source, but I recall from somewhere that if fertile couples have unprotected sex for a year, 85% of them will get pregnant. Of course, I’m sure that’s an average over the fertility of the whole group; some couples may be more fertile. It would be wrong to say that YOUR chance of concieving a child after a year of unprotected sex is 85%. It might be greater or less.

Human women are wierd though. (You already knew that, right?). They have a menstrual cycle instead of estrus. We have sex all the time, but fertility is much more hit-and miss. When an animal is in heat, she is much more definitely fertile. I don’t know if that explains the assumption of breeders that a mating will result in pregnancy, but I’m sure it’s a big part.

OK, Keeves, since no one has directly addressed your “stud fee” question, I’ll take a shot at it.

I am under the impression that there are various types of stud contracts. Some contracts take a “pay your money, take your chances” approach. This is along the lines of what you mentioned. A mating fee is paid reguardless of the outcome. With other contracts, payment is based on impregnation. Still others are a hybrid of the two. In large part, the fee and type of contract are based on the renown of the stud (supply and demand). These days, most commercial breeding operations, especially horses and cattle, rely on artificial insemination. It tends to be much more efficient than mother nature.

The overwhelming majority of people have more than the average (mean) number of legs. – E. Grebenik

sows have an incedible farrowing rate of 85% (this is a fairly standard rate used for planning and projections at pig farms.) but given human greed, they’re pressuring the poor sows some more. MBAs will note that sows cannot farrow 54 days in a year which is a big loss, so they say, but what they mean is 54 days is already an operational nightmare since unproductive days often go unrecognized, while natural mating limits sow:boar ratio to 10X.

contrary to what people think, artificial insemination doesn’t increase farrowing rate. it increases sow:boar ratio.