ORCID Profile
0000-0002-5202-216X
Current Organisation
Murdoch University
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Publisher: Elsevier BV
Date: 03-2016
DOI: 10.1016/J.THERIOGENOLOGY.2016.12.014
Abstract: 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 in idual 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 sub-s le of semen was separated into sperm and seminal plasma, by centrifugation and stored at - 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 sperm were 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.
Publisher: American Dairy Science Association
Date: 04-2018
Abstract: The aim of this study was to examine the effect of plane of nutrition (1) during the first 6 mo of life and (2) from 6 mo of age to puberty on early growth characteristics, age at puberty, and postpubertal semen production in Holstein-Friesian bulls. 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 (Hi) or low (Lo) plane of nutrition for the first 6 mo of life. The Hi and Lo calves received 1,200 and 450 g of milk replacer, respectively Hi calves were fed concentrate ad libitum and Lo were fed a maximum of 1 kg concentrate daily, and concentrate allowances remained the same after weaning. At 24 wk of age, bulls were reassigned within treatment to either remain on the same diet or to switch to the opposite diet until puberty, resulting in 4 treatment groups: Hi-Hi, Hi-Lo, Lo-Lo, and Lo-Hi. After puberty, all bulls were fed a moderate plane of nutrition until 60 wk of age thereafter, the diet was ad libitum concentrates until slaughter at 72 wk of age. Bulls were weighed weekly before weaning and every 2 wk after weaning. Scrotal circumference (SC) was measured every 2 wk, beginning at 15 wk of age. Beginning at a SC of 24 cm, electro-ejaculation was carried out every 2 wk to establish the onset of puberty. Semen collection continued monthly after puberty. Thermal images of the scrotum were taken monthly from 28 to 36 wk of age. Scrotal skin thickness (SST) was measured monthly (from 16 wk of age to puberty) using a digital calipers. Bulls on the Hi diet had a higher scrotal temperature and SST at each time point than those on the Lo diet. Average daily gain (ADG) was greatest in Hi-Hi bulls, with Hi-Lo and Lo-Hi having similar ADG but both being greater than Lo-Lo. Bulls on the Hi diet pre-6 mo of age were younger at puberty, regardless of diet offered post-6 mo of age. Bulls offered a Hi diet post-6 mo were heavier at puberty. Neither scrotal temperature nor dietary treatment affected postpubertal semen production variables. In conclusion, a high plane of nutrition during the first 6 mo of age hastened the onset of puberty and the availability of saleable semen, regardless of plane of nutrition post-6 mo of age.
Publisher: American Registry of Professional Animal Scientists
Date: 08-2021
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/RDV31N1AB43
Abstract: In cattle, uterine gland development (adenogenesis) occurs postnatally, beginning immediately after birth, and is normally complete by approximately 2 months of age. Normal development of uterine glands is essential for subsequent fertility. Early life plane of nutrition can impact age at puberty, but the impact of early postnatal nutrition on adenogenesis is unclear. The aim of this study was to examine the effect of enhanced nutrition during the first 21 weeks of life on heifer reproductive organ growth, endometrial gland development, and endometrial gene expression. To this end, Angus×Holstein-Friesian heifer calves with a mean (±s.d.) age and body weight of 19 (±5) days and 51.2 (±7.8) kg, respectively, were assigned to either a high (HIGH n=16 targeted average daily gain, ADG, 1.2 kg/d) or a moderate plane of nutrition (MOD n=16 targeted ADG 0.5 kg/d). Calves were slaughtered at five months of age, and their reproductive tracts were collected and dissected for analysis. To assess endometrial gland number, a cross-section of the midpoint of one horn (n=8 per group) was fixed in 10% neutral buffered formalin, embedded, and processed for histology. Slides were stained with haematoxylin-eosin. Five pictures were randomly taken on each slide using a stereomicroscope at 40× magnification and the number of glands was counted using ImageJ (j/) software. In addition, endometrial tissue s les were collected and snap frozen for subsequent quantitative RT-PCR analysis. At the time of slaughter, calves on the HIGH and MOD diets presented a body weight of 189.6 and 110.2kg, respectively (P& .001), indicating an ADG of 1.18 kg/d for the HIGH group and 0.50 kg/d for the MOD group (P& .001). Calves in the HIGH group had a greater (P& .001) total reproductive tract (mean±s.d. 114.01±35.56g v. 52.67±14.29g), isolated cervix (33.17±9.35g v. 16.14±5.27g), uterus (59.35±25.78g v. 27.46±10.61g), and ovarian (14.80±11.38g v. 5.40±1.94g) tissue weights compared with those in the MOD group. This difference was also present when organ weight was expressed on a per unit of body weight basis (P& .05). However, no differences were found in the number of endometrial glands between groups (HIGH: 453.50±94.18v. MOD: 482.38±124.69). In accordance with this result, transcript abundance of six paracrine mediators of gland development (ESR1, IGF1, IGFBP1, WNT5A, WNT7A, and FGF10) was not affected by diet. In conclusion, enhanced early-life plane of nutrition increased the size of the reproductive tract in heifer calves but did not affect endometrial gland development. Future studies will compare the global endometrial transcriptome between groups to explore other putative effects of diet on uterine development. Research was supported by EU, Horizon 2020 Marie Sklodowska-Curie, REPBIOTECH 675526, Science Foundation Ireland 13/IA/1983, and São Paulo Research Foundation (FAPESP) 2017/21415-5.
Publisher: Elsevier BV
Date: 06-2016
Publisher: Elsevier BV
Date: 05-2023
Publisher: Oxford University Press (OUP)
Date: 08-2017
Publisher: Elsevier BV
Date: 04-2022
DOI: 10.1016/J.THERIOGENOLOGY.2022.01.030
Abstract: Younger bulls typically produce lower volumes of semen per ejaculate with a lower sperm concentration than older more mature, bulls and often fail to meet semen demand using standard collection frequency schedules. The objective of this study was to assess the effect of ejaculate collection frequency on semen output, sperm quality and field fertility in young bulls under commercial conditions. Holstein Friesian bulls aged 366 ± 8 days (mean ± SEM) were assigned one of two ejaculate collection frequencies: (i) HF (n = 14 bulls), where ejaculates were collected twice a day, five days in each two-week period or (ii) LF (n = 12 bulls), where ejaculates were collected once a day, two days per week. The trial period continued until each bull reached both 20 ejaculates and 1000 marketable frozen semen straws. Subjective motility was assessed on all ejaculates pre-freeze and post-thaw (at 0 and 2 h). A subset of ejaculates were assessed post-thaw by computer-assisted sperm analysis for motility, kinematics and morphological defects and by flow cytometry for viability, membrane fluidity, acrosome integrity, reactive oxygen species and DNA fragmentation. A total of 13,846 inseminations (9,541 for HF and 4,305 for LF) were carried out on dairy cows and heifers. HF reached the 1000 straw threshold 41 days earlier than LF (P < 0.01) with the same number of ejaculates. Ejaculate volume and sperm concentration were not affected by treatment but the first ejaculate of the day (HF only) had a greater volume (P < 0.001) and sperm concentration (P < 0.05) than the second ejaculate. HF had higher pre-freeze total (P < 0.01) and gross (P < 0.05) motility than LF. HF had higher post-thaw (2 h) total and gross motility than LF (P < 0.05). Ejaculate rejection rates did not differ between treatments. There was no effect of treatment, week or ejaculate number of the day (HF only) on post-thaw motility and kinematic parameters or sperm viability, membrane fluidity, acrosome integrity and DNA fragmentation. However, HF had lower superoxide production than LF (P < 0.05). Pregnancy per artificial insemination was 64.5 ± 1.0% and 59.9 ± 1.1% for the HF and LF bulls, respectively (mean ± SEM P = 0.05). In conclusion, collecting ejaculates more frequently from young bulls significantly reduced the number of days required to obtain 1000 straws, increased semen quality in terms of lower superoxide production and increased field fertility.
Publisher: Bioscientifica
Date: 08-2018
DOI: 10.1530/REP-17-0671
Abstract: The objective of this study was to examine the effect of nutrition during the first 18 weeks of life on the physiological and transcriptional functionality of the hypothalamic, anterior pituitary and testes in Holstein Friesian bull calves. 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, to achieve an overall target growth rate of 1.2 or 0.5 kg/day, respectively. At 126±1.1 days of age, all calves were euthanised. Animal performance (weekly) and systemic concentrations of metabolic and reproductive hormones (at four week intervals) were assessed. Testicular histology, targeted gene and protein expression of the arcuate nucleus, anterior pituitary and testes were also assessed using qPCR and immunohistochemistry, respectively. Testicular tissue from post pubertal 19 month old Holstein Friesian bulls (n=10) that were reared under similar conditions was also available for comparative gene expression analysis. The metabolites and metabolic hormones generally reflected the improved metabolic status of the calves on HIGH bull calves (P .001). Only ghrelin receptor was upregulated in the anterior pituitary (P .05) and arcuate nucleus (P .10) in LOW compared to HIGH bull calves. Calves offered a high plane of nutrition were heavier at slaughter (P .001), had larger testes P .001), larger seminiferous tubule diameter P .001), more mature spermatogenic cells P .001) and more Sertoli cells (P .05) in accordance with both morphological and transcriptional data. This study indicates that a high plane of nutrition during early calf-hood alters gene expression which advances testicular development and hastens spermatogenesis
Publisher: Public Library of Science (PLoS)
Date: 21-11-2019
Publisher: Elsevier BV
Date: 2018
Publisher: Elsevier BV
Date: 2017
Publisher: American Dairy Science Association
Date: 04-2018
Abstract: The 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 s les 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 s le. Blood s les 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 s les 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 bulls.
Publisher: Elsevier BV
Date: 07-2017
DOI: 10.1016/J.THERIOGENOLOGY.2017.04.002
Abstract: The onset of puberty in the bull is regulated by the timing of early GnRH pulsatility release from the hypothalamus, which has been demonstrated to be affected by plane of nutrition during calf-hood. The aim of this study was to determine the effect of plane of nutrition on growth rate, scrotal development, metabolite concentrations and exogenous gonadotrophin (GnRH) induced release of luteinizing hormone (LH), follicle stimulating hormone (FSH) and testosterone (TT) in pre-pubertal bulls of two contrasting dairy breeds. Holstein-Friesian and Jersey bull calves were assigned to either a high or low plane of nutrition from 3 to 49 weeks of age. Intensive blood s ling was conducted at 16, 24 and 32 weeks of age, every 15 min from 30 min prior to intravenous administration of exogenous GnRH to 135 min after. Monthly blood s les were also collected and analyzed for insulin like growth factor 1 (IGF-1), insulin, leptin, adiponectin and metabolite concentration. Insulin and IGF-1 were higher in bulls on a high plane of nutrition (P 0.05). Leptin was not affected by plane of nutrition or breed (P > 0.05). Adiponectin tended to be higher in bulls on a high plane of nutrition (P = 0.05), but was not affected by breed (P > 0.05). Bulls on a high plane of nutrition had a greater concentration of LH in response to GnRH (P 0.05). FSH concentration was not influenced by breed or plane of nutrition but FSH concentrations did decrease with age (P 0.05). Jersey bulls, particularly those on a high plane of nutrition, had higher TT production in the pre-pubertal period (P < 0.001). Using 28 cm as a proxy for age at puberty, bulls on a high plane of nutrition were predicted to reach puberty earlier than bulls on a low plane. In conclusion, the data clearly demonstrate that a high plane of nutrition positively affects several key nutritional and reproductive hormones which are critical to the endocrinological functionality of the hypothalamic-pituitary-testicular axis in dairy-bred bull calves.
Publisher: Elsevier BV
Date: 06-2016
Publisher: CSIRO Publishing
Date: 2018
DOI: 10.1071/RD17376
Abstract: Advancing the age at which puberty and subsequent sexual maturation is attained in cattle is central to the reproductive and economic efficiency of both beef and dairy production systems worldwide. Onset of puberty in both male and female cattle is regulated by a complex network of biochemical processes and involves interaction among many key metabolic, neuroendocrine and reproductive tissues. Although our understanding of the biochemical interplay that conditions and eventually triggers the pubertal process has improved in recent years, much of the intricate mechanistic detail still eludes us. Environmental factors, such as nutritional management, as well as the genetic makeup of the animal undoubtedly affect the timing of puberty in cattle. In particular, there is now overwhelming evidence to support the importance of early life nutrition in regulating the timing of puberty in both bulls and heifers. For both genders, there is significant evidence that an improved metabolic status, early in calfhood, advances maturation of the hypothalamic–pituitary–gonadal axis, therefore facilitating earlier sexual development. Although advancing sexual maturation is a desirable goal, it is important that any strategy used does not impinge upon normal gametogenesis or postpubertal fertility potential. To this end, the aim of this review is to discuss the underlying biology of puberty in cattle with particular emphasis on the role of nutritional management during early calfhood in: (1) advancing the maturity of the hypothalamic–pituitary–gonadal axis and (2) implications for the quality of gametes and subsequent fertility.
Publisher: American Registry of Professional Animal Scientists
Date: 12-2018
No related grants have been discovered for Colin Byrne.