Genetic parameter estimation for beef bull semen attributes.

Improvements in bull reproductive performance are necessary to optimize the efficiency of cattle production. Female fertility has been enhanced through assisted reproductive technologies as well as genetic selection; however, improving beef bull fertility has been largely ignored. Phenotypes routinely collected at bull semen collection facilities are believed to affect fertility and provide the phenotypes necessary for a genetic evaluation. The first objective of this study was to determine the significant fixed effects for modeling beef bull fertility using data from bull semen collection facilities. The second objective was to estimate variance components, heritabilities, repeatabilities, and correlations between beef bull semen attributes. Beef bull fertility phenotypes including volume (VOL), concentration (CONC), number of spermatozoa (NSP), initial motility (IMot), post-thaw motility (PTMot), 3-h post-thaw motility (3HRPTMot), percentage of normal spermatozoa (%NORM), primary abnormalities (PRIM), and secondary abnormalities (SEC) were obtained from two bull semen collection facilities. A total of 1,819 Angus bulls with 50,624 collection records were analyzed. Of the fixed class and covariate effects tested, the significant class effects were collection location and collection day within year and the significant covariate effects included age at collection, days since previous collection, and cumulative comprehensive climate index (CCI). For this study, the CCI was calculated for a 75-d period including the 61-d spermatogenesis cycle and 14-d epididymal transit time. The 75 d prior to collection accounted for the environmental stress a bull may have experienced over the course of development of the spermatozoa, which was more significant than the CCI calculated for collection day or spermatogenesis start date. Pre-thaw beef bull semen traits had low heritability estimates of 0.11 ± 0.02 (VOL), 0.09 ± 0.02 (CONC), 0.08 ± 0.02 (NSP), and 0.12 ± 0.03 (IMot). Heritabilities of post-thaw beef bull semen attributes were more variable at 0.10 ± 0.02 (PTMot), 0.05 ± 0.04 (3HRPTMot), 0.10 ± 0.04 (%NORM), 0.03 ± 0.03 (PRIM), and 0.18 ± 0.04 (SEC). Correlations of breeding values for these traits with scrotal circumference (SC) expected progeny difference (EPD) are low. The low to moderate heritability estimates indicate that genetic improvement can be made in beef bull semen quality traits if new tools are developed to augment the scrotal circumference EPD that are currently available within the industry.

Selection for bull fertility: a review.

Fertility is a critically important factor in cattle production because it directly relates to the ability to produce the offspring necessary to offset costs in production systems. Female fertility has received much attention and has been enhanced through assisted reproductive technologies, as well as genetic selection; however, improving bull fertility has been largely ignored. Improvements in bull reproductive performance are necessary to optimize the efficiency of cattle production. Selection and management to improve bull fertility not only have the potential to increase conception rates but also have the capacity to improve other economically relevant production traits. Bull fertility has reportedly been genetically correlated with traits such as average daily gain, heifer pregnancy, and calving interval. Published studies show that bull fertility traits are low to moderately heritable, indicating that improvements in bull fertility can be realized through selection. Although female fertility has continued to progress according to increasing conception rates, the reported correlation between male and female fertility is low, indicating that male fertility cannot be improved by selection for female fertility. Correlations between several bull fertility traits, such as concentration, number of spermatozoa, motility, and number of spermatozoa abnormalities, vary among studies. Using male fertility traits in selection indices would provide producers with more advanced selection tools. The objective of this review was to discuss current beef bull fertility measurements and to discuss the future of genetic evaluation of beef bull fertility and potential genetic improvement strategies.

Follicular expression of follicle stimulating hormone receptor variants in the ewe.

BACKGROUND: Several alternatively-spliced mRNA transcripts of the follicle stimulating hormone receptor (FSHR) have been identified in sheep, including FSHR-1 (G protein-coupled form), FSHR-2 (dominant negative form), and FSHR-3 (growth factor type-1 form). Our objective was to determine which of these variants is predominantly expressed in follicles collected from ewes at various times after estrus. METHODS: Suffolk-cross ewes (n = 8) were allowed to come into estrus naturally and were euthanized 24 (n = 3), 36 (n = 3), or 48 (n = 2) hours after the onset of estrus. All visible follicles were measured, aspirated and pooled according to follicular diameter: small (<= 2.0 mm), medium (2.1-4.0 mm), large (4.1-6.0 mm), and preovulatory (> = 6.1 mm). Aspirated cells were separated from follicular fluid by centrifugation. Total RNA was extracted from cell pellets and reverse transcribed. The resulting cDNA was subjected to qPCR, using primer sets designed to amplify each variant specifically. Gene expression was normalized to that of beta-actin within samples, and compared by analysis of variance with the level of significant differences set at p < .05. RESULTS: Relative expression of FSHR-3 exceeded that of both FSHR-1 and FSHR-2 in medium follicles, and tended to be higher in small follicles (p = .09) regardless of time after onset of estrus, and thus results from different time points were pooled. Expression of FSHR-3 was greater than that of FSHR-2 and luteinizing hormone receptor (LHR) in small and medium follicles. Expression of LHR was greatest in preovulatory follicles. CONCLUSIONS: These experiments show that in addition to the well characterized G protein-coupled form of the FSHR, alternatively spliced variants of the FSHR may participate in follicular dynamics during follicular waves of the sheep estrous cycle. Furthermore, these results indicate that an "alternatively" spliced form of the FSHR (FSHR-3) is the predominant form of the FSHR in the sheep.

PVD9902, a porcine vas deferens epithelial cell line that exhibits neurotransmitter-stimulated anion secretion and expresses numerous HCO3(-) transporters.

Epithelial ion transport disorders, including cystic fibrosis, adversely affect male reproductive function by nonobstructive mechanisms and by obstruction of the distal duct. Continuous cell lines that could be used to define ion transport mechanisms in this tissue are not readily available. In the present study, porcine vas deferens epithelial cells were isolated by standard techniques, and the cells spontaneously immortalized to form a porcine vas deferens epithelial cell line that we have titled PVD9902. Cells were maintained in continuous culture for >4 yr and 200 passages in a typical growth medium. Frozen stocks were generated, and thawed cells exhibited growth characteristics indistinguishable from their nonfrozen counterparts. Molecular and immunocytochemical studies confirmed the origin and epithelial nature of these cells. When seeded on permeable supports, PVD9902 cells grew as electrically tight (>6,000 ohms x cm2), confluent monolayers that responded to forskolin with an increase in short-circuit current (I(sc); 8 +/- 1 microA/cm2) that required Cl-, HCO3(-), and Na+, and was partially sensitive to bumetanide. mRNA was expressed for a number of anion transporters, including CFTR, electrogenic Na+-HCO3(-) cotransporter 1b (NBCe1b), downregulated in adenoma, pendrin, and Cl-/formate exchanger. Both forskolin and isoproterenol caused an increase in cellular cAMP levels. In addition, PVD9902 cell monolayers responded to physiological (i.e., adenosine, norepinephrine) and pharmacological [i.e., 5'-(N-ethylcarboxamido)adenosine, isoproterenol] agonists with increases in I(sc). Unlike their freshly isolated counterparts, however, PVD9902 cells did not respond to glucocorticoid exposure with an increase in amiloride-sensitive I(sc). RT-PCR analysis revealed the presence of both glucocorticoid and mineralocorticoid receptor mRNA as well as mRNA for the alpha- and gamma-subunits of the epithelia Na+ channels (alpha- and gamma-ENaC), but not beta-ENaC. Nonetheless, PVD9902 cells recapitulated most observations in freshly isolated cells and thus represent a powerful new tool to characterize mechanisms that contribute to male reproductive function.