Abstract
Simple SummaryThe efficiency of swine production measured as litter size influences the profitability of the pig industry. Furthermore, sow fertility potential depends in part on the boar semen quality and reproductive efficiency. The objective of this study is to compare boar sperm head size and morphometric features of shape to evaluate their relationships with reproductive success after artificial insemination (AI). A morphometric analysis of boar ejaculate reveals morphometrically separate sub-populations. The differences between sub-populations are displayed for sperm head size. In addition, sperm clustering into sub-populations did not have a predictive capacity on litter size variables. Nevertheless, the morphometric variables of the sperm may have a predictive, albeit reduced, capacity regarding litter size variables. The results of this study therefore open up possibilities for future assessments of fertility. The aim of the study was to compare the morphometric features of sperm head size and shape from the Pietrain line and the Duroc × Pietrain boar crossbred terminal lines, and to evaluate their relationship with reproductive success after artificial insemination of sows produced from crossbreeding the York, Landrace and Pietrain breeds. Semen samples were collected from 11 sexually mature boars. Only ejaculates with greater than 70% motility rate and <15% of abnormal sperm were used for artificial inseminations (AI) and included in the study. Samples were analyzed using an ISAS®v1 computer-assisted sperm analysis system for eight morphometric parameters of head shape and size (CASA-Morph). Sub-populations of morphometric ejaculates were characterized using multivariate procedures, such as principal component (PC) analysis and clustering methods (k-means model). Four different ejaculate sub-populations were identified from two PCs that involved the head shape and size of the spermatozoa. The discriminant ability of the different morphometric sperm variables to predict sow litter size was analyzed using a receiver operating characteristics (ROC) curve analysis. Sperm head length, ellipticity, elongation, and regularity showed significant predictive capacity on litter size (0.59, 0.59, 0.60, and 0.56 area under curve (AUC), respectively). The morphometric sperm sub-populations were not related to sow litter size.
Highlights
The efficiency of pig livestock production, measured as piglets born alive, total born per litter, and the number of piglets weaned by a sow per year, influence the profitability of the pig industry [1]
Some studies have described a correlation between the fertility of males used for artificial insemination (AI) and sperm morphometry [12], and head size has been associated with factors predisposing fertility [16]
Current computer-assisted sperm morphometric analysis CASA-Morph systems can be used to analyze individual sperm morphometrics more accurately, and this information can be submitted to a multivariate procedure such as cluster analysis for an overview of distinct sperm patterns grouped into sub-populations (SPs) or clusters [20]
Summary
The efficiency of pig livestock production, measured as piglets born alive, total born per litter, and the number of piglets weaned by a sow per year, influence the profitability of the pig industry [1]. The morphometric variables of the size and shape of the sperm head exhibit a relevant variability among species, among males of different species [14,15], and between breeds or selected lines within a species [6,10]. Some studies have described a correlation between the fertility of males used for artificial insemination (AI) and sperm morphometry [12], and head size has been associated with factors predisposing fertility [16]. Other authors refer to an association between the head size and shape of the spermatozoa and semen or ejaculate variables [17,18,19]. A limited number of studies have focused on the size and head shape of sperm and the characterization of sperm sub-populations on litter size in livestock species such as pigs [30,31]. The aim of the present study was to compare the morphometric features of the head size and shape of spermatozoa from the Pietrain and
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