Sex before a fight in my opinion makes No difference. The only factor could be time.. with humans that is. If you give a two minutes qnd done performance... (we've all been there ), then we should be fresh as a Daisy... now if you went on a two hour bang her lights out session... you may be a little tired. But it wouldn't be from the ejaculation, it would be from excercise... when a dog mates... he's looking to nut as fast as he can, (some humans too... especially after marriage ), so it wouldn't hurt in a show afterward.... just my opinion.