Factors that influence on boar semen quality
Due to the important
role that boars represent both in productive and economical questions in a
pig company, the different factors that influence sperm production and
quality must be known and controlled. These factors can be classified as
external to the boar or exogenous and those with origin in the own boar or
endogenous.
Exogenous factors
- Seasonal effects:
Seasonal effects refer to environment temperature and photoperiod that vary with seasons. In winter and spring it can be observed a higher ejaculate volume and sperm concentration than in summer and the beginning of autumn.
During autumn, an increase of abnormal sperm and different sizes in sperm heads and tails can be observed. Sperm maturation in the epididymis and testicular activity become altered. During summer, semen volume is significantly lower, sperm motility decrease, the activity of sexual accessory glands and also the sperm maturation in the epididymis become altered.
With regards to critical temperature, the highest temperature to maintains intact boar metabolism, is around 27ºC. environment temperature never must reach 29ºC. It is advisable to have maximum-minimum thermometers, placed in different sites in the boar pen in order to know exactly the temperature variations along the day. The ideal range of temperature for boars is 18-20ºC., with a relative humidity between 60-70% and a ventilation rate around 25 m3/h/boar in winter and 200 m3/h/boar in summer. Air speed at animals level must be between 0,2-0,7 m/s. Cool temperatures do not seem to affect remarkably semen quality or boars fertility, but it is detrimental to libido.
With reference to photoperiod, it has a high influence on sperm production, semen volume, steroid production and libido that suffer an increase in short days (10 h) and a decrease in long days (16 h). Long days affect boar sperm production with a decrease of number of total sperm per ejaculate, motility and fertilizing ability. Therefore, it can be concluded that 10-12 h/light/day, is more beneficial than 16 h/light/day. Continuous darkness, although rarely absolute, produce a decrease of sperm concentration, a lesser percentage of alive sperm and a higher percentage of abnormal sperm. Regarding to light intensity , it is recommended 300 lux.
- Facilities:
Other important factors are facilities and housing. Boars must never be housed in groups, avoiding fighting and physical aggressions. However nose contact is advisable since it helps to enhance libido. Regarding to the type of housing facilities, there should be semi-open systems, pen of 10-11 m2 with exercise area, simple pen with a surface of approximately 8 m2, stall with dimensions of 70-80 cm wide and 2 m long, cheaper but with less space for boar's movement (to be soon banned within UE) that makes necessary to have other exercise areas. Floor type can be ground, concrete, with or without straw bed, slatted floor, etc. It is important to choose a suitable floor to avoid problems in legs like lameness that affect semen quality. Facilities must be cleaned once per week and disinfected at least with the arrival of a new boar.
- Handling:
As to boar handling, we can say that the rhythm of semen collection has influence on their performance. With a higher frequency of ejaculations, the number of spermatozoa decreases and biochemical parameters of semen becomes affected.
Spermatogenesis needs between 45-55 days approximately to complete. During the longer part of this period, the spermatozoa are into the testicle. Later it suffers a period of maturation into the epididymis, of about 10-14 days, travelling along its three zones, caput, corpus and cauda, where it is stored. With every ejaculation, a 60 % of the volume of the semen stored in cauda epididymis is emptied, after 3 or 4 consecutive collections, this zone is completely empty and the spermatozoa from caput and corpus move to it, and a higher proportion of immature and aberrant spermatozoa appear in the ejaculate.
It is recommended a frequency of collection of 1 or 2 times per week or 2 to 3 times per fortnigth eeks, depending on the boars' age , because the frequency recommended for boars younger than 1 year must be once a week. When frequency of semen collection is higher and without rest, it can be observed a decrease of mature spermatozoa, the presence of spermatozoa with distal droplet and the increase of immature sperm with proximal droplet. Inactivity is also detrimental, and it is recommended to discard first collections when a boar has not worked in 1 month.
- Nutrition and feeding:
Correct nutrition and feeding have a significant influence on libido, sperm production, and semen quality. For this reason it is necessary to supply a specific feed for boars. The use of supplements with vitamins E and C, selenium, zinc, biotin, enhance sperm production. A correct level of proteins is necessary to favour libido, sperm production and body maintenance and growing.
On the other hand, it must be taking into account the presence of fibre, because its lack produces constipation and abnormal fermentations with toxins production. These toxins can reach testicle and produce disturbances in spermatogenesis. It is advisable to take into account the conditions of the raw materials, manufacture and storage to avoid bad effects on semen quality caused by the presence of micotoxins like zearalenone or aflatoxin B.
It is also recommended to regulate the amount of feed according to the weight and age of the animals, in order to avoid unbalanced weight in excess or in default, that could provoke problems libido and locomotive problems at the time of semen collection. It must be adjusted in cold seasons or when semen collection is more frequent.
Another important factor is water that must be always of good quality, clean and fresh. This is very important in summer, when boars drink a lot (5-30 l/day), depending on the type of feeding, and health status. The suitable flow in the drinker must be at least 1.5 l/min.
Several studies have shown that the highest percentage of boars is eliminated for overweight problems (47%), followed by reproductive problems (18%), locomotive problems (12%), disease(4%).