The understated, yet immense, impact of the breeding boar on overall farm productivity is rarely discussed. Any factor related to nutrition or management that can improve boar reproductive performance is of great interest and should be studied extensively. After all, boars are responsible for 50 percent of end-market pig genetics!
In many commercial farms, boars are kept in poor hygienic conditions. Pens are of inadequate design or too small and lack room temperature and ventilation controls. In addition, such high-value stock is fed typical gestation diets that are not formulated for the specific biological purpose of boars, which is the frequent production of large volume of high-quality sperm.
Boar nutrition, libido
It should be noted from the onset that boar libido unlike sperm production, cannot be easily manipulated by changing dietary protein and energy levels. Despite the fact that this area needs to be further studied, currently it is well accepted that only prolonged conditions of over- or under-feeding, and therefore extreme cases of body condition change, can negatively impair boar libido.
Boar breeding is controlled by the thyroid gland, and in many cases a lack of libido has been reported when a decrease in the thyroid function has been observed. This needs particular attention, if certain anti-nutritional factors like glucosinolates (which are present in rapeseed meal, and are known to hinder the iodine fixation to the thyroid gland) are present in the feed. In such cases, extra iodine supplementation is suggested at levels of 750 -1,000 mg/ton complete feed to help avoid any malfunction of the thyroid gland.
In addition, one issue that is not related to nutrient specifications but is strongly associated with final nutrient availability is the in-feed presence of mycotoxins and zearalenone. Mycotoxins may negatively affect the boar's libido through their action of reducing testosterone production.
Boar health, sperm production
In contrast with boar libido, there is much scientific research, which proves that protein and amino acids lysine and methionine + cystine, play an important role in sperm production. In particular, the sulphur-containing amino acids (methionine/cystine) affect the secretory activity of the epididymis, thus significantly enhancing sperm volume.
This effect is more evident in intensively used boars, where sperm production has been shown to be positively influenced when extra protein and methionine was added to the diet. In addition to protein, adequate energy intake also is crucial for optimal sperm production!
When reporting on sperm quality, the most widely researched minerals are zinc and selenium. Zinc is directly involved in both the process of spermatogenesis and the maturation progress of the Leydig cells. It's advised to supplement breeding boar diets with 100-120 mg/kg Zn and ideally part of it, in a chelate form to avoid any interactions with other minerals and at the same time improve its digestibility.
Dietary selenium, apart from its role as an antioxidant, influences sperm cell development and sperm motility. According to scientific research and on farm trials, boars fed organic Se-supplemented diets (200 mg from organic form and 200 mg from inorganic sources per kg feed) produced greater volumes of sperm with higher levels of vitality and mobility.