A good place to find out about how to optimize sperm is the dairy and beef industries. Basically, the whole purpose of a bull (stud) is to produce sperm of high quality, and lots of it, so that all the heifers and cows on the farm can make calves, which grow into beautiful heifers, then have calves of their own, become a cow, and then have more calfs. It goes without saying that it is a fundamental requirement to optimize semen quality.
A conclusion made in a study published in the Journal of Animal Science states that low protein diets reduced the amount of fructose in the semen samples of the bulls being observed. Fructose is a simple sugar present in semen necessary to feed the sperm so that their mitochondria can produce ATP. Simply put, sperm needs this sugar to get the energy required to whip their tail so they can swim.
Therefore, men need to make sure they are getting enough protein. Usually this is not an issue for most men, but for some it is. My advice is that men try to get as much protein as they can from fish and vegetable sources. That doesn't mean that a good steak (happy cattle only please) shouldn't be a part of the diet, but cholesterol should also be paid close attention to. Remember, what is bad for your heart is bad for your penis. Basically, the more fish you eat, the more fatty four legged animal muscle one can consume, as their good and bad cholesterol help each other in many ways. If you are a vegetarian or vegan, and having trouble conceiving, TCM would counsel you to begin including some animal protein in your diet, meat as medicine. You would augment your diet to train for a marathon right?
Research source: https://www.journalofanimalscience.org/content/22/1/14.full.pdf
*Further reading: Foods that improve sperm motility and morphology