Optimising the use of fresh semen: insights for use with young genomically-selected bulls

With the advent of genomic selection, bulls are being used in the artificial insemination industry during early puberty. These young bulls produce ejaculates of low volume and low spermatozoa concentration that are highly valued. The objective of this thesis was to investigate methods that best utilise the semen from young genomically-selected bulls. As a result of the characterisation of in vitro quality of sex-sorted (SS) and non-sex-sorted (NS) fresh and frozen spermatozoa there was ~40% of the SS fresh spermatozoa agglutinated while the SS (fresh and frozen) had lower levels of oxidative stress. Both motility and viability positively correlated to field fertility of SS spermatozoa, however, no functional assessments correlated to field fertility of NS spermatozoa. Different seminal plasma (SP) components were correlated to field fertility for both SS and NS cohorts. The effect of seminal plasma from high and low fertility bulls on the function of caudal epididymal spermatozoa was investigated via a number of in vitro assessments. Results from these assessment demonstrated a beneficial effect of SP on the motility of caudal epididymal spermatozoa (P<0.05). There was no effect of SP from high or low fertility bulls on fresh or frozen-thawed parameters assessed of caudal epididymal spermatozoa, or the fertilising ability of caudal epididymal spermatozoa. Seminal plasma reduced the osmotic resistance of caudal epididymal spermatozoa regardless of source form high or low fertility bull. Finally, this study sought to prolong the functional lifespan of spermatozoa in fresh egg yolk based diluent through the addition of antioxidants; l carnitine (0 to 20 mM), crocin (0 to 2 mM), α-tocopherol (0 to 1 mM), quercetin (0 to 250 µM) and catalase (0 to 500 IU). Following 4h at 39 o C incubation all catalase treated spermatozoa had greater acrosome intact populations compared to the control. When fresh semen was stored in the presence of antioxidants motility, lipid peroxidation and membrane fluidity decreased with time but there was no effect of treatment on any other the in vitro parameters assessed during the storage period. In conclusion, this thesis provides new insights into the physiological effects of sex-sorting on spermatozoa physiology

The in vitro addition of docosahexaenoic acid (DHA) improves the quality of cooled but not frozen-thawed stallion semen

The aim of this study was to assess the effect of the addition of docosahexanoic acid (DHA) on the in vitro quality of cooled and frozen-thawed stallion semen. In Experiment 1, semen from 10 stallions was collected (3 ejaculates per stallion). Semen was diluted to 100 x 106 spermatozoa/mL with 0.02 mM of vitamin E (VE) and 0, 1, 10 or 20 ng of DHA/mL and frozen. Semen was thawed and total motility (TM), acrosome integrity and morphology were assessed. In Experiment 2, semen from 3 stallions was collected (3 ejaculates per stallion) and frozen as in Experiment 1, but VE and DHA were added after thawing. Total motility and progressive linear motility (PLM) were assessed at 30, 60 and 120 min and viability, acrosome integrity and membrane fluidity at 30 min. In Experiment 3, semen from 5 stallions was collected (1-3 ejaculates per stallion), diluted to 20 x 106 spermatozoa/mL and stored at 4ºC. After 1, 24, 48 and 72 h, TM, PLM, viability, membrane fluidity and lipid peroxidation were assessed. The addition of DHA had no effect on frozen semen (Experiments 1 and 2) but improved TM, PLM and membrane fluidity in cooled stallion semen

Effect of seminal plasma from high- and low-fertility bulls on cauda epididymal sperm function

The aim of this study was to characterise the effect of seminal plasma (SP) from bulls of high or low fertility on sperm function. First, the effect of SP on the motility of fresh cauda epididymal spermatozoa (CES) and frozen–thawed ejaculated spermatozoa was assessed (Experiment 1a). Seminal plasma was then collected from bulls of known high and low fertility. Pooled CES were incubated in the SP from each bull, diluted and assessed for motility and viability on Days 1, 2, 3 and 5 after packaging as fresh semen (Experiment 1b). Also assessed were motility, kinematics, viability and mitochondrial membrane potential after thawing (Experiment 1c) as well as hypotonic resistance (Experiment 2) and fertilisation potential using in vitro fertilisation (Experiment 3). Seminal plasma increased the motility of CES (P  0.05). The hypotonic resistance of CES was reduced by SP (P  0.05). In conclusion, SP affects the physiological function of CES but there is no difference between SP from high- or low-fertility bulls

Dietary polyunsaturated fatty acid supplementation of young post-pubertal dairy bulls alters the fatty acid composition of seminal plasma and spermatozoa but has no effect on semen volume or sperm quality

The aim of this study was to examine the effects of dietary supplementation with rumen protected n-6 or n-3 polyunsaturated fatty acids (PUFA) on the quantity and quality of semen from young post-pubertal dairy bulls. Pubertal Holstein-Friesian (n= ­ 43) and Jersey (n= 7) bulls with a mean ± s.e.m. age and bodyweight of 420.1 ± 5.86 days and 382 ± 8.94 kg, respectively, were blocked on breed, weight, age and semen quality (based on the outcomes of two pre-trial ejaculates) and randomly assigned to one of three treatments: (i) a non-supplemented control (CTL, n = 15), (ii) rumen-protected safflower (SO, n= 15), (iii) rumen-protected n-3 PUFA-enriched fish oil (FO, n = 20). Bulls were fed their respective diets, ad libitum for 12 weeks; individual intakes were recorded using an electronic feeding system for the initial 6 weeks of the feeding period. Semen was collected via electro-ejaculation at weeks 2, 1, 0, 7, 10, 11 and 12 relative to the beginning of the trial period (week 0). On collection, semen volume, sperm concentration and progressive linear motility (PLM) were assessed. On weeks 2, 1, 0, 10, 11, 12, semen was packaged into 0.25 mL straws and frozen using a programmable freezer. On weeks 1, 7 and 11; a subsample of semen was separated into sperm and seminal plasma, by centrifugation and stored at e 20 C until analysis of lipid composition. Semen from 10 bulls per treatment were used for post-thaw analysis at weeks 10, 11 and 12 (3 straws per ejaculate). Sperm motility was analysed by computer assisted semen analysis (CASA). In addition, membrane fluidity, acrosome reaction and oxidative stress were assessed using flow cytometry. Sperm from bulls fed SO had a 1.2 fold higher total n-6 PUFA content at week 11 compared to week 1 (P < 0.01) while bulls fed FO had a 1.3 fold higher total n-3 PUFA content, in sperm by week 11 (P < 0.01). There was no effect of diet on semen volume, concentration or PLM of sperm when assessed either immediately following collection or post-thawing. Membrane fluidity and oxidative stress of spermwere also not affected by diet. The percentage of sperm with intact-acrosomes was lower in CTL bulls compared to those fed SO (P < 0.01). In conclusion, while the lipid composition of semen was altered following dietary supplementation with either n-6 or n-3 based PUFA, this did not lead to measurable improvements in the quantity or quality of semen produced by young post-pubertal dairy bulls

Relationship between in vitro sperm functional assessments, seminal plasma composition, and field fertility after AI with either non-sorted or sex-sorted bull semen

The hypothesis of this study was that different in vitro parameters are required to predict the in vivo fertility of non-sorted (NS) and sex-sorted (SS) semen. Thus, the aim was to correlate in vitro bull sperm functional parameters (experiment 1) and seminal plasma composition (experiment 2) with pregnancy rates using 2 cohorts of bulls (NS and SS). Experiment 1: ejaculates from each bull (n = 3 ejaculates per bull; n = 6 bulls for both NS and SS) were assessed for motility, thermal stress tolerance and morphology using microscopy, and viability, osmotic resistance, mitochondrial membrane potential, and acrosome integrity using flow cytometry. Fertilizing ability was assessed using IVF. Experiment 2: ejaculates (n = 3 per bull; n = 8 and 6 bulls for NS and SS, respectively) were collected, seminal plasma harvested and frozen and later analyzed for amino acid and fatty acid composition using gas chromatography mass spectrometry. In the NS cohort of bulls, there was no correlation between pregnancy rate and any of the sperm functional parameters assessed. However, within the SS cohort, motility and viability were correlated with pregnancy rate (r = 0.84 and 0.80, respectively; P < 0.05). There was no correlation between IVF outcome and pregnancy rate in either the SS or NS cohort of bulls. In the NS cohort of bulls, concentrations of the amino acid isoleucine and the fatty acid tricosylic acid (C23:0) were correlated with pregnancy rate (r = 0.80 and 0.74, respectively; P < 0.05). Within the SS cohort of bulls, the amino acid glutamic acid and the fatty acid arachidic acid (C20:0) were correlated with pregnancy rate (r = 0.84 and 0.82, respectively; P < 0.05). In conclusion, this study suggests that different in vitro markers of fertility are required to predict the fertility of NS and SS sperm

The effect of dietary supplementation of algae rich in docosahexaenoic acid on boar fertility

The objective of this study was to assess the effects of dietary supplementation of a commercial algal product rich in docosahexaenoic acid (DHA) on boar fertility as assessed in vitro and in vivo. Boars were fed one of three experimental diets for 19 weeks: (i) Control (Ctl) diet (n = 31), (ii) Ctl diet plus 75g All-G-Rich per day (n = 31) or (iii) Ctl diet plus 150g All-G-Rich per day (n = 30). Parameters assessed were (i) raw semen quality; volume, sperm concentration, total motility and morphology (ii) liquid semen quality; progressive motility, viability, hypotonic resistance and acrosomal integrity (iii) frozen-thawed semen quality; motility, thermal stress, viability, membrane fluidity and mitochondrial activity (iv) sperm and seminal plasma (SP) fatty acid composition (FAC) (v) total antioxidant capacity (TAC) of SP and (vi) farrowing rates and litter sizes of sows (n = 1158) inseminated with liquid semen. Boars consuming 75g All-G-Rich had a larger semen volume (P 0.05). There was no effect of dietary treatment on the FAC and TAC of SP or on farrowing rate and litter size (P > 0.05). There was an effect of dietary treatment on the FAC of sperm, represented by an 1.72 and 1.60 fold increase in the DHA content for 75 and 150g treatments, respectively, compared to the Ctl treatment. In conclusion, a significant increase in semen volume and total sperm number in boars supplemented 75g All-G-Rich daily, resulted in an increase in production of 3 to 4 more doses per ejaculate, thus, indicating that the feeding regime described within this study has the potential for increasing the output of boar studs. (c) 2016 Elsevier Inc. All rights reserved