Genomic identification, expression profiling, and functional characterization of CatSper channels in the bovine

peer-reviewedCation channels of sperm (CatSper) are sperm-specific calcium channels with identified roles in the regulation of sperm function in humans, mice, and horses. We sought to employ a comparative genomics approach to identify conserved CATSPER genes in the bovine genome, and profile their expression in reproductive tissue. We hypothesized that CATSPER proteins expressed in bull testicular tissue mediates sperm hyperactivation and their rheotactic response in the reproductive tract of the cow. Bioinformatic analysis identified all four known CATSPER genes (CATSPER 1-4) in the bovine genome, and profiling by quantitative real-time polymerase chain reaction identified site-specific variation in messenger ribonucleic acid (mRNA) expression for all four genes along the reproductive tract of the bull. Using a novel antibody against CATSPER 1, protein expression was confirmed and localized to the principal piece of bull sperm, in agreement with what has been reported in other species. Subsequent treatment of bull sperm with either the calcium chelator ethylene glycol tetraacetic acid; mibefradil, a specific blocker of CatSper channels in human sperm; or CATSPER1 antibody all significantly inhibited caffeine-induced hyperactivation and the rheotactic response, supporting the concept that the calcium influx occurs via CatSper channels. Taken together, the work here provides novel insights into expression and function of CatSper channels in bull testicular tissue and in the function of ejaculated sperm.peer-reviewe

Plane of nutrition before and after 6 months of age in Holstein-Friesian bulls: II. Effects on metabolic and reproductive endocrinology and identification of physiological markers of puberty and sexual maturation

peer-reviewedThe aim of this study was (1) to examine the effect of plane of nutrition during the first and second 6 mo of life on systemic concentrations of reproductive hormones and metabolites in Holstein-Friesian dairy bulls, and (2) to establish relationships with age at puberty and postpubertal semen production potential. Holstein-Friesian bull calves (n = 83) with a mean (standard deviation) age and body weight of 17 (4.4) d and 52 (6.2) kg, respectively, were assigned to a high or low plane of nutrition for the first 6 mo of life. At 24 wk of age, bulls were reassigned, within treatment, either to remain on the same diet or to switch to the opposite diet until puberty, resulting in 4 treatment groups: high-high, high-low, low-low, and low-high. Monthly blood samples were analyzed for metabolites (albumin, urea, total protein, β-hydroxybutyrate, glucose, nonesterified fatty acid, triglycerides and creatinine), insulin, insulin-like growth factor-1, leptin, adiponectin, FSH, and testosterone. A GnRH challenge was carried out at 16 and 32 wk of age (n = 9 bulls per treatment). Blood was collected at 15-min intervals for 165 min, with GnRH administered (0.05 mg/kg of body weight, i.v.) immediately after the third blood sample. Blood samples were subsequently analyzed for LH, FSH, and testosterone. Stepwise regression was used to detect growth and blood measurements to identify putative predictors of age at puberty and subsequent semen quality traits. Metabolic hormones and metabolites, in general, reflected metabolic status of bulls. Although FSH was unaffected by diet, it decreased with age both in monthly samples and following GnRH administration. Testosterone was greater in bulls on the high diet before and after 6 mo of age. Testosterone concentrations increased dramatically after 6 mo of age. Luteinizing hormone was unaffected by diet following GnRH administration but basal serum LH was greater in bulls on a high diet before 6 mo of age. In conclusion, the plane of nutrition offered before 6 mo of age influenced metabolic profiles, which are important for promoting GnRH pulsatility, in young bull

Effect of early calf-hood nutrition on the transcriptomic profile of subcutaneous adipose tissue in Holstein-Friesian bulls

peer-reviewedBackground: Adipose tissue is a major endocrine organ and is thought to play a central role in the metabolic control of reproductive function in cattle. Plane of nutrition during early life has been shown to influence the timing of puberty in both male and female cattle, though the exact biological mechanisms involved are currently unknown. The aim of this study was to investigate the effect of early calf-hood nutrition on the transcriptomic profile of subcutaneous adipose tissue in Holstein-Friesian bulls to identify possible downstream effects on reproductive physiology. Results: Holstein-Friesian bull calves with a mean (±S.D.) age and bodyweight of 19 (±8.2) days and 47.5 (±5.3) kg, respectively, were assigned to either a high (n = 10) or low (n = 10) plane of nutrition. Calves were fed in order to achieve an overall growth rate of 1.08 and 0.57 kg/day for the high and low plane of nutrition treatments, respectively. At 126 days of age, the bulls were euthanized, subcutaneous adipose tissue samples were harvested and RNAseq analysis was performed. There were 674 genes differentially expressed in adipose tissue of calves on the low compared with the high plane of nutrition (P 2.0). High plane of nutrition positively altered the expression of genes across an array of putative biological processes but the most dominant cellular processes affected were cellular energy production and branched chain amino acid degradation. A high plane of nutrition caused upregulation of genes such as leptin (LEP) and adiponectin (ADIPOQ), which are known to directly affect reproductive function. Conclusions: These results provide an insight into the effect of augmenting the plane of nutrition of Holstein-Friesian bull calves in the prepubertal period on the transcriptome of adipose tissue

Sperm selection by rheotaxis improves sperm quality and early embryo development

peer-reviewedThe objective of this work was to elucidate whether a sperm selection method that combines rheotaxis and microfluidics can improve the selection of spermatozoa over density gradient and swim-up. For this purpose human sperm selected by rheotaxis were compared against density gradient, swim-up and a control group of non-selected spermatozoa in split frozen-thawed (FT) and fresh (F) semen samples. Sperm quality was assessed in terms of motility, morphology, DNA fragmentation index (DFI), viability, acrosome integrity and membrane fluidity. Using a mouse model, we compared fertilisation and embryo development rates after performing ICSI with spermatozoa, sorted using rheotaxis or swim-up. Selection by rheotaxis yielded a sperm population with reduced DFI than the control (P < 0.05), improved normal morphology (P < 0.001) and higher total motility (TM; P < 0.001) than the other techniques studied in F and FT samples. Swim-up increased TM compared to density gradient and control in FT or F samples (P < 0.001), and yielded lower DFI than the control with F samples (P < 0.05). In FT samples, selection by rheotaxis yielded sperm with higher viability than control, density gradient and swim-up (P < 0.01) while acrosomal integrity and membrane fluidity were maintained. When mouse spermatozoa were selected for ICSI using rheotaxis compared to swim-up, there was an increase in fertilisation (P < 0.01), implantation (P < 0.001) and foetal development rates (P < 0.05). These results suggest that, in the absence of non-destructive DNA testing, the positive rheotaxis can be used to select a population of low DNA fragmentation spermatozoa with high motility, morphology and viability, leading to improved embryo developmental rates

Review: Understanding the causes of variation in reproductive wastage among bulls

The ability to predict the fertility of bulls before semen is released into the field has been a long-term objective of the animal breeding industry. However, the recent shift in the dairy industry towards the intensive use of young genomically selected bulls has increased its urgency. Such bulls, which are often in the highest demand, are frequently only used intensively for one season and consequently there is limited time to track their field fertility. A more pressing issue is that they produce fewer sperm per ejaculate than mature bulls and therefore there is a need to reduce the sperm number per straw to the minimum required without a concomitant reduction in fertility. However, as individual bulls vary in the minimum number of sperm required to achieve their maximum fertility, this cannot be currently achieved without extensive field-testing. Although an in vitro semen quality test, or combination of tests, which can accurately and consistently determine a bull’s fertility and the optimum sperm number required represent the ‘holy grail’ in terms of semen assessment, this has not been achieved to date. Understanding the underlying causes of variation in bull fertility is a key prerequisite to achieving this goal. In this review, we consider the reliability of sire conception rate estimates and then consider where along the pregnancy establishment axis the variation in reproductive loss between bulls occurs. We discuss the aetiology of these deficiencies in sperm function and propose avenues for future investigation

Human resources analytics: A legitimacy process

Taking a grounded theory approach, this paper explores human resources (HR) Analytics legitimacy in three organisations over a period of 3 years. The research aims to investigate (i) how the HR Analytics legitimacy process presents and develops and (ii) what decisions, activities, and events can shape the legitimacy of HR Analytics in organisations. We draw on institutional theory and industry creation literatures to understand what constitutes HR Analytics legitimacy through a three-dimensional perspective: cognitive, socio-political, and technological. A process theory lens as an analytical tool allowed for the mapping of the institutional process in order to isolate key individual decisions, activities, and events over time. Three related, non-linear sub-processes of HR Analytics legitimation are identified, namely, HR Analytics as a strategic commitment, the HR data infrastructure decision, and the focus of HR Analytics projects in addition to a number of delaying, enabling, and accelerating elements that influence this process

The effect of the in vitro supplementation of exogenous long-chain fatty acids on bovine sperm cell function

This study aimed to investigate the effects of long-chain fatty acids (α-linolenic acid (ALA), docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), linoleic acid (LA), oleic acid (OA) and palmitic acid (PA)) at concentrations of 10-100 µM, on extended bull spermatozoa stored in vitro for up to 7 days. Progressive linear motion (PLM), viability (Experiments 1-3), ability to penetrate artificial mucus (Experiment 1), reactive oxygen species (ROS; Experiment 2) and superoxide production (Experiment 3) were assessed. Spermatozoa maintained the ability to penetrate artificial mucus up to Day 4, irrespective of treatment. In Experiments 2 and 3, DHA and EPA had detrimental effects on PLM and viability. PA preserved PLM and viability at levels greater than the control (P<0.05), whilst keeping ROS levels to a minimum, particularly on Days 1 and 3 (P<0.01) when ROS generation peaked in other treatments. In contrast, superoxide production peaked on Day 0 (Experiment 3) and declined thereafter with no significant effect of fatty acid. This study supports the notion that superoxide dominates on Day 0, whereas its breakdown products, hydrogen peroxide and the hydroxyl radical as assessed by CM-H2DCFDA, contribute to ROS generation on subsequent days

Effect of exposing rams to a female stimulus before semen collection on ram libido and semen quality

Rams with strong libido and desirable semen characteristics can provide more insemination doses per ejaculate and produce more progeny, improving population genetic linkage to improve the accuracy of EBV. The objective of this study was to determine if teasing rams, either by sight and smell alone (Exp. 1), or physical contact (Exp. 2), could improve libido and semen quality of rams. In Exp. 1, there were 3 treatments in which rams were exposed to the sight and smell of the ewe for 1 h: control treatment (n = 5) in which rams were exposed to a ewe not in estrus; non-novel treatment (n = 6) in which rams were exposed to a ewe in estrus and the same ewe was used for semen collection; and novel treatment (n = 6) in which rams were exposed to a ewe in estrus and a different ewe in estrus was used for semen collection. In Exp. 2, rams were individually given full access to a ewe, which had a cotton apron fi tted to cover her vulva, for 15 min. The 3 treatments in Exp. 2 were: control treatment (n = 5) in which rams were placed in a pen with a ewe not in estrus; a nonnovel treatment (n = 5) in which rams were placed in a pen with a ewe in estrus and the same ewe was used for semen collection; novel treatment (n = 6) in which rams were placed in a pen with a ewe in estrus and a different ewe in estrus was used for semen collection. Experiment 1 was repeated for 5 consecutive days and Exp. 2 was repeated for 4 consecutive days. Data on reaction time, number of mounts, semen volume, semen concentration, sperm wave motion, and progressive linear motion (Exp. 1 only) were collected and analyzed as a randomized complete block design, where rams were initially blocked for breed and age. In Exp. 1, there was an effect of day (P < 0.05) and a treatment × day interaction (P < 0.05) on semen volume, whereas there was also an effect of treatment (P < 0.05) and day (P < 0.01) on semen concentration, which was most evident on d 1. In Exp. 2, there was an effect of treatment on reaction time (P < 0.05) and semen volume (P = 0.08), which was most evident on d 1. This study demonstrates an acute effect on d 1 on semen concentration when rams were exposed to the sight and smell of a ewe in estrus. Alternatively, when rams were stimulated with physical contact of a ewe in estrus, an acute increase in semen volume was evident on d 1. These effects were not evident on subsequent days and thus the overall benefi ts on ram libido and semen quality of exposing rams to ewes in estrus are minimal

The biological mechanisms regulating sperm selection by the ovine cervix

In species where semen is deposited in the vagina, the cervix has the unique function of facilitating progress of spermatozoa towards the site of fertilisation while also preventing the ascending influx of pathogens from the vagina. For the majority of species, advances in assisted reproduction techniques facilitate the bypassing of the cervix and therefore its effect on the transit of processed spermatozoa has been largely overlooked. The exception is in sheep, as it is currently not possible to traverse the ovine cervix with an inseminating catheter due to it\u27s complex anatomy, and semen must be deposited at the external cervical os. This results in unacceptably low pregnancy rates when frozen-thawed or liquid stored (>24h) semen is inseminated. The objective of this review, is to discuss the biological mechanisms which regulate cervical sperm selection. We assess the effects of endogenous and exogenous hormones on cervical mucus composition and discuss how increased mucus production and flow during oestrus stimulates sperm rheotaxis along the crypts and folds of the cervix. Emerging results shedding light on the sperm-cervical mucus interaction as well as the dialogue between spermatozoa and the innate immune system are outlined. Finally, ewe breed differences in cervical function and the impact of semen processing on the success of fertilisation, as well as the most fruitful avenues of further investigation in this area are proposed