Relationship between carcass quality characteristics and semen quality in Piétrain boars

In several countries, Piétrain boars are indispensable as a terminal commercial sire and constitute a large group of boars kept by the AI centers. Selection of these boars is mainly based on fattening performance and meat quality characteristics. However, the effects of a such narrowly focused selection on semen quality have been poorly investigated. The main objective of this study was to assess the semen quality of Piétrain boars originating from Flemish AI centers and to correlate the results with the carcass quality characteristics of these boars. Additionally, the storability of the semen doses during the 5 different days of storage was investigated.

 

Freshly diluted semen doses from 147 boars (age: 6.5 to 87.5 months) originating from 10 artificial insemination (AI) centers were used and stored for five days at 17°C. Motility was assessed daily with CASA (Hamilton-Thorne), morphology and concentration were assessed on day of semen collection (D0) by eosin-nigrosin staining and the Bürker counting chamber, respectively. The above mentioned data were correlated with the lean meat percentage, loin eye depth and backfat thickness using linear mixed models taking into account the clustering of boars within AI centers (the effect of age was included in the models) and the repeated measurements for each semen dose.

 

The 5-day average motility (±SD) across all AI centers was 76.3±12.4%. Average values (±SD) for morphology and concentration on D0 were: live spermatozoa 91.0±4.9%, live normal spermatozoa 83.2±8.4%, and concentration 28.9±10.7 (x106 spermatozoa/ml). Backfat thickness (cm) and loin eye depth were significantly associated (p<0.05) with both motility and progressive motility. Boars having more backfat showed higher semen motility from D0-2 (1.16% of extra motility for every 1 cm backfat), while backfat was negatively related to motility during D3-4, indicating a more pronounced negative impact of longer storage duration on semen motility of boars with more backfat. Backfat thickness was positively associated with progressive motility from D0-4. Loin eye depth was positively associated with motility and progressive motility from D1-4 (p<0.05). Lean meat percentage was not found to be significantly associated with motility and progressive motility (p>0.05). None of the carcass quality characteristics were found to be significantly associated with semen morphology and concentration.

 

Boar studs could maximize the potential of creating Piétrain sire lines that combine good productivity with high fertility by avoiding a strict selection based on reduced backfat, and by including in the selection criteria the loin eye depth. Additionally, the expiry dates provided by some Belgian AI centers should be revised.