The effect of varicocele on semen quality in boars exposed to heat stress.

Semen quality has a dramatic impact on reproductive efficiency in the swine industry, influencing both conception rate and litter size. The objective of this study was to assess whether the presence of varicocele hinders semen quality in both thermoneutral and heat stress (HS) conditions. At approximately 6 mo of age, ultrasonography was used to measure left and right pampiniform plexus area in order to detect varicocele in maternal line boars at the University of Nebraska-Lincoln. Between 10 and 12 mo of age, semen was collected from each boar (n = 28) twice weekly. Boars were collected under thermoneutral conditions, were then heat stressed for 7 d to exacerbate any semen quality issues, and semen was collected post-HS for 6 wk. Sperm characteristics were determined by computer-assisted semen analysis. The presence of varicocele had a significant effect on sperm concentration (P = 0.04) and trended toward significance for mean sperm head area (P = 0.06) throughout the duration of the study. An interaction existed between varicocele and collection time point at weeks 2-5 post-HS for distal droplet percentage, suggesting that boars with varicocele were possibly more susceptible to heat-stress-induced semen quality issues than boars without varicocele. Moreover, semen quality was reduced in boars with versus without varicocele under both thermoneutral and HS conditions. Therefore, detection of varicocele by ultrasound could represent a potential marker of fertility in young boars or as a component trait in selection indices for fertility.

Genetic relationships among sperm quality traits of Duroc boars collected during the summer season.

The goals of the study were to estimate the heritability and repeatability of boar sperm quality traits during the summer season, estimate phenotypic and genetic correlations between sperm quality traits, and assess the effect of these traits on total number born (TNB). Semen samples were collected and individually processed from Duroc boars (n = 363) from May through October 2017. Single sire litter information was available for 121 of the boars. Heritability, repeatability, genetic correlations, and phenotypic correlations were estimated for and among the following traits: total percentage of motile cells (MOT), total percentage of progressively motile cells (PROG), percentage of cells with a distal droplet (DIST), percentage of cells with a proximal droplet (PROX), percentage of cells with a bent tail (BENT), percentage of cells with a distal midpiece reflex (DMR), mean sperm head elongation (ELON), and total sperm cells per ejaculate (TOTSP). Heritability estimates ranged from 0.08 to 0.24 and repeatability estimates ranged from 0.21 to 0.62. The phenotypic and genetic correlations between sperm motility traits and morphological defects indicated a negative relationship. Sperm morphological defects had positive phenotypic and genetic correlations with each other. Total sperm per ejaculate showed positive genetic correlations with the motility traits. Positive phenotypic and genetic correlations existed between ELON and the motility traits. Total sperm motility (P < 0.001) positively affected TNB while DIST (P < 0.001), PROX (P < 0.001), BENT (P = 0.05) and DMR (P = 0.002) negatively affected TNB. Results indicate genetic selection could enhance sperm quality during the summer season in boars.

The heritability of pampiniform plexus vessel size and varicocoele in boars.

Ultrasonography was used to capture a coronal-sagittal image of the veins of the pampiniform plexus (PP) and the testicular artery of 327 maternal-line boars at approximately 6 months of age at the University of Nebraska-Lincoln. Varicocoele was diagnosed by two methods. Method 1 diagnosed varicocoele when the average vessel area on one side of the scrotum was 1.5 times larger than the average vessel area on the other side of the scrotum. Method 2 diagnosed varicocoele when the average vessel area on one side of the scrotum of a boar was 1.5 times larger than the average vessel on the same side of the scrotum of the boar's cohorts (same population and year). Varicocoele was diagnosed in 23.17% and 15.1% of boars measured using method 1 and method 2, respectively. Ultrasonography showed to be an effective means to measure PP vessel size in boars and may even allow for earlier detection of varicocoele than by using palpation. Animal models were employed to estimate the heritability for: average area of right PP vessels (0.52), average area of the left PP vessels (0.46), varicocoele presence using method 1 (0.26) and varicocoele presence using method 2 (0.25). These heritability estimates suggest that vessel size and varicocoele could be selected against in breeding programmes to potentially improve boar semen quality.

Longitudinal analysis of weight showed little relationship with age at puberty in gilts.

Continued selection for increased gilt body weight could negatively impact selection for age at puberty (AP) in gilts. The purpose of this study was to compare the genetic potential for growth to that for reducing age of puberty in swine. Females utilized (n = 1,079) were produced over a 6-yr period from a population developed to determine the impact of energy restrictions and genetic influences on sow development and longevity. From 120 to 235 d of age, BW was collected every 14 d and attainment of puberty tested. Age at puberty was defined as the first observed standing estrus in the presence of a mature boar. All females were genotyped with the Porcine SNP60K BeadChip and genotypes were used to construct a genomic relationship matrix. Univariate (AP), repeatability (BW), and random regression (BW; RR) models were fitted. Univariate analysis included the fixed effects of contemporary group (CG) and age at first boar exposure, and random direct additive and common litter effects. Repeatability analysis included the fixed effects of CG and random effects of direct additive, common litter, and permanent environmental (PE) effects. Random regression analysis included fixed effects of CG, and random direct additive, common litter, and PE effects. Proportion of phenotypic variation due to direct additive and common litter variance for AP were 0.33 and 0.06, respectively. Proportion of phenotypic variation due to direct additive, common litter, and PE variance estimated from the repeatability model for BW were 0.26, 0.11, and 0.40, respectively. Proportion of phenotypic variation due to direct additive, common litter, and PE variance estimated from the RR for BW ranged from (mean) 0.19 to 0.30 (0.27), 0.08 to 0.31 (0.19), and 0.42 to 0.62 (0.50), respectively. Direct additive correlations between test days for BW from RR ranged from 0.30 to 0.99. Rank correlations between estimated breeding values (EBV) for AP and BW from the RR were near zero across all age points ranging from -0.03 to 0.09. Rank correlations were higher (0.63) when BW was considered at the age at which puberty was reached. Correlations between AP and BW EBV from the repeatability model were low (-0.11). Growth appears to be less related to AP than previously reported, suggesting the need to either directly measure AP or investigate alternative indicator traits. Selecting gilts with most desirable BW EBV alone would not result in improvement in AP, at least in the current population.