Sexual Development and Puberty in Bulls

Brito, Leonardo F.C.

doi:10.1002/9781119602484.ch6

Cited by 8 publications

(6 citation statements)

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“…Continual selection of bulls with high reproductive capacity can ensure breeding success after decreasing bull:cow ratios. Scrotal circumference is one such trait to select for, as it is a moderately heritable trait and positively correlated with semen output and semen quality (Brito, 2015). Yearly breeding soundness exams for producers using only one bull are highly Translate basic science to industry innovation recommended for maintaining good pregnancy rates, especially if choosing increase the number of females exposed.…”

Section: Discussionmentioning

confidence: 99%

58 A retrospective analysis of bull:cow ratio effects on pregnancy rates of beef cows previously enrolled in fixed-time artificial insemination protocols

Timlin

Hungerford

Redifer

et al. 2019

Journal of Animal Science

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This retrospective study analyzed the effect of bull:cow ratio on pregnancy rates of cows returning to estrus after enrollment in fixed-time artificial insemination (TAI). Data were compiled over the course of 6 breeding seasons between 2014 and 2017 from the Virginia Department of Corrections herd containing 15 farms and 141 groups of cows (average 44 cows/group). Multiparous cows aged 2 years and older (n = 6002) were exposed to estrus synchronization. Non-pregnant cows after TAI (n = 3079, average 21 cows/group) were exposed to natural service with bulls diagnosed as fertile by a breeding soundness exam. Percent data were given an arcsine transformation. A one-way ANOVA evaluated TAI rates by season and a linear regression was performed to compare conception rates to the bull:cow ratio. Pregnancy rate to TAI among groups averaged 53% and ranged from 11% to 83%. First bull pregnancy rate of cows returning to estrus was 47% overall, with fall seasons having greater conception rates than spring (51.1% vs. 44.5%, P = 0.03). The ratio of bulls to total number of cows ranged from 1:8 to 1:68 with an average ratio of 1:28. The ratio of bulls to the number of open cows ranged from 1:2 to 1:39 with an average ratio of 1:14. There was no correlation between the bull:cow ratio and return to estrus pregnancy rate (r = -0.12), and there was no correlation between the number of open cows per bull and return to estrus conception rates (r = -0.17). Thus, higher bull:cow ratios (between 1:8 and 1:68) did not effect return to estrus pregnancy rate; producers may consider a lower number of bulls needed for natural service breeding post TAI, decreasing bull related costs and increasing the economic feasibility of adopting TAI protocols

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Section: Discussionmentioning

confidence: 99%

58 A retrospective analysis of bull:cow ratio effects on pregnancy rates of beef cows previously enrolled in fixed-time artificial insemination protocols

Timlin

Hungerford

Redifer

et al. 2019

Journal of Animal Science

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“…Moreover, calves submitted to different nutritional food qualities reach puberty at different ages (Garcia et al, 1987). In animals fed with low food quality, puberty is later, and in the other growth phases, the nutritional factor did not influence the reproductive characteristics (Abdel-Raouf, 1960;Brito, 2014;Krieck et al, 2022). The feeding quality also modulates the central nervous system, including the endocrine system (Durlinger et al, 1999), which directly affects the reproductive functions, influencing both ages at puberty and seminal characteristics (Rekwot et al, 1988;Krieck et al, 2022).…”

Section: Serum Profile Of The…mentioning

confidence: 99%

Serum profile of the anti-müllerian hormone of Nelore bulls in the peripuberty

Pereira,

Satrapa,

Gomes

et al. 2024

Arq. Bras. Med. Vet. Zootec.

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This study aimed to investigate the profile of AMH serum concentrations during the period of prepuberty in young bulls. The bulls were selected and evaluated for 150 days to assess their sexual development. The semen and blood collection, body weight (kg), and scrotal measurements were performed every 30 days, and puberty (D0) was considered when at least 50×106 spermatozoa/mL, and 10% of progressive motility were verified for the first time. After the blood collection, plasma was separated and used to determine the AMH concentration by ELISA, presenting values of 611.4a (±94.5), 555a (±181.99), 621.6ab (±133.44), 370.4ab (±59.36) and 51.7b (±7.94) for moments of -60, -30, 0, +30 and +60 of puberty, respectively. During the evaluated period, there was a progressive increase in body weight (kg), scrotal circumference (cm), and semen characteristics. The AMH mean plasma concentration decreased 60 days after puberty onset. There was no correlation with the andrological parameters analyzed; however, there was a positive and strong correlation between the testicular height and width at puberty onset with plasma concentrations of AMH. We concluded that AMH is not a helpful tool for the early prediction of puberty in Nelore bulls.

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“…The higher the increase of luteinizing hormone, the earlier calves enter puberty (Brito, 2021). Testosterone then increases further during rapid testicular growth in the pubertal period and further during puberty (Brito, 2021). There is evidence for the involvement of gonadotropin-independent hormonal pathways like the influence of insulin-like growth factor 1 (IGF-1) promoting Leydig cell and testicular development (Spiteri-Grech & Nieschlag, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…To produce sperm at the onset of puberty, the interaction of different endocrinological axes plays an important role in the development of a bull (Bollwein et al., 2016; Brito, 2021). The prepubertal phase (8–20 weeks) is characterized by a transient increase of gonadotropins and concurrently testosterone (Brito et al., 2007).…”

Section: Introductionmentioning

confidence: 99%

“…The prepubertal phase (8–20 weeks) is characterized by a transient increase of gonadotropins and concurrently testosterone (Brito et al., 2007). The higher the increase of luteinizing hormone, the earlier calves enter puberty (Brito, 2021). Testosterone then increases further during rapid testicular growth in the pubertal period and further during puberty (Brito, 2021).…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of hormones as candidate early biomarkers of Holstein bull performance around the first semen collection at artificial insemination centres

Leiter,

Mittmann,

Schaper

et al. 2024

Reprod Domestic Animals

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Artificial insemination (AI) centres select bulls as calves according to their genetic breeding values and raise them until the first semen collection; yet, a high dropout rate of reared bulls is a problem for AI centres. Potential hormonal indicators of bull sexual maturation (cortisol, dehydroepiandrosterone (DHEA), testosterone, oestradiol, insulin‐like growth factor 1 (IGF‐1)) were observed and evaluated in relation to the performance parameters to perhaps identify candidate biomarkers allowing an early selection of bulls as suitable sires. Blood samples from 102 German Holstein calves at 4 ± 1, 8 ± 1 and 12 ± 2 months of age from six AI centres were analysed using validated immunoassays for cortisol, DHEA, testosterone, oestradiol and IGF‐1. Semen analyses included native and thawed diluted semen. Bulls were classified at the first semen collection into groups with good versus poor performance (GP vs. LP). After 2 years, the subsequent differentiation was done in high (HPP), medium (MPP) and low performance persistency (LPP). Age at first semen collection was an important factor for sperm quality. Cortisol concentrations decreased with age, but the cortisol/DHEA ratio decreased with age only in GP bulls (p < .05). Oestradiol and testosterone concentrations both correlated with libido behaviour (p < .05). Testosterone and IGF‐1 concentrations were higher at the time of first semen collection in GP bulls and increased with age (p < .05). In conclusion, testosterone and IGF‐1 concentrations at first semen collection are associated with performance at first semen collection and future performance persistency, and might be useful early biomarkers for consistent sperm producing bulls on AI centres.

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Sexual Development and Puberty in Bulls

Cited by 8 publications

References 115 publications

58 A retrospective analysis of bull:cow ratio effects on pregnancy rates of beef cows previously enrolled in fixed-time artificial insemination protocols

58 A retrospective analysis of bull:cow ratio effects on pregnancy rates of beef cows previously enrolled in fixed-time artificial insemination protocols

Serum profile of the anti-müllerian hormone of Nelore bulls in the peripuberty

Evaluation of hormones as candidate early biomarkers of Holstein bull performance around the first semen collection at artificial insemination centres

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