On the basis of previous results, it has been hypothesized that the actual recommendations for vitamin supplementation were not sufficient to maximize the reproductive performances of boars with regards to semen production and quality, in particular when increasing the semen collection frequency. The purpose of this study was to determine the effects of an important feed supplement of vitamins (both lipid soluble and water-soluble) on the quality and quantity of semen, in an insemination centre. This study was also meant to evaluate the efficiency of this vitamin supplement for maintaining semen quality when the collection frequency is increased (3 times per week, versus 3 times every two weeks). The results showed that the vitamin feed supplement did affect the vitamin concentration of the plasma, seminal fluid and sperm, but the increased collection frequency only slightly affected these parameters. The vitamin supplement affected the hormonal profile of the boar during breeding, but without any marked repercussion on the semen production or quality of the ejaculate. The increased semen collection frequency decreased the semen production per ejaculate, but increased the cumulative semen production by 20%, without affecting the semen quality. As well, the semen quality was little affected by a daily collection during 14 days: the spermatozoids’ motility was reduced but their morphology remained unchanged. The numerous correlations observed between hormonal, seminal and/or plasmatic profiles and between the morphological criteria and semen production deserve further research to explore their efficacy as predictors of semen production. With that regard, testicular volume seems a promising production predictor.