With natural mating, a prime reason to cull boars is the animal’s size. Boars often get too large to service sows naturally. So it can be to your benefit to limit feed those boars to keep their weight at a manageable level.
However, in an artificial insemination breeding program, weight gain is much less a concern than semen quality and quantity. So, consider feeding the boar to help him maintain optimal reproductive performance. You can worry less about cutting protein and energy levels to limit weight gain.
Two University of Missouri studies evaluated the effects of dietary protein on sperm production. The results showed that protein intake didn’t have much impact on sperm production per se when energy intake remained relatively high.
But low protein intake, in this case 10.5 percent crude protein, increased the time the boar required to complete ejaculation and decreased his libido.
Effects of energy levels were more complex. If boars maintained high daily energy intake, low protein levels dropped sperm volume by 38 percent. Libido suffered as well.
The trials found 363 grams (about 0.75 pounds) of protein and 77 megacalories of energy per day produced the best boar performance. That nutrition level equates to a daily consumption of 5.3 pounds of a 14 percent crude-protein diet. That’s similar to many gestation diets.
The point to remember is that low energy intake can limit boar performance. And low-protein diets, such as the 10.5 percent protein diet, can increase semen collection time and curb your animal’s libido.