Short communicationEffects influencing boar semen
Introduction
Monitoring and analyzing the quality and quantity of boar semen has great economic importance for pig breeders. The boar's impact on the herd reproductive performance is high, particularly if the male is mated to many females. According to Robinson and Buhr (2005) the economic return of an AI centre primarily depends on the boar's ability to produce spermatozoa during the period. This ability is limited by testicular capacity, libido and physical soundness (feet, legs, back). A lot of studies indicate that the reproductive fitness of boars depends on the following factors: heritability (Pavlík, 1988, Oh et al., 2003), testicular size (Clark et al., 2003), nutrition (Khan et al., 2005), age of the boar (Jankeviciute and Zilinskas, 2002), intensity of sexual exploitation (Frangez et al., 2005), photoperiod (Sancho et al., 2004) and outdoor temperature and social environment (Hemsworth, 1996, Kunavongkrit et al., 2005). The aim of the present study was to analyze the influence of some important effects on the quality and quantity of boar semen.
Section snippets
Materials and methods
Data from 22 insemination stations for boars in the Czech Republic were analyzed. The data set consisted of 230,705 records of semen collections from 2712 boars obtained during the period from 2000 to 2005. The collection and processing of semen was standardized using the methods described in the respective standard (ČSN, 1996) in all selected stations. The boars belonged to the following breeds: Czech Meat Pig (CM; 89♂), Duroc (D; 105♂), Hampshire (H; 22♂), Landrace (L; 477♂), Large White (LW;
Results
The effect of breed or hybrid combination was statistically significant (P < 0.001) for all the traits. Other effects included into the linear model (the effects of the month; the year within the month; the collection interval; the boar within the breed and the age of the boar at collection) were also statistically significant (P < 0.001). The least square means (LSMs), standard errors and estimated heterotic effects of the observed semen traits are summarized in Table 1 for seven of the breeds and
Discussion
The comparison with our previous work (Smital et al., 2004) shows that the boars recently investigated had higher values in the traits related to semen quantity (VO, CO, NOT, NOC) and lower values in traits related to semen quality (MO, AB) than the boars that were kept in the AI centres during 1990–1997. Moreover, it is noticeable that the manifestation of heterosis in the present crossbred combinations was less expressive than in the combinations which occurred 10 years ago.
No breed proved to
Acknowledgements
Financial support for this study was provided through the project MZE 0002701401of the Czech Republic Ministry of Agriculture. The author thanks to the Association of Pig Breeders in the Czech Republic for making available the data and Miss. Pavlína Chadrabová for excellent technical assistance.
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