Attainment Of Puberty Research Articles

Nutrition, Growth, and Age at Puberty in Heifers

Puberty onset and age at first calving have a critical impact on livestock production for good reproductive efficiency of the herd and to reduce the duration of the non-productive stage of the growing heifer. Besides genetic factors, sexual maturation is also affected by environmental factors, such as nutrition, which can account for up to 20% of the observed variability. The rate of body weight gain during growth is considered the main variable influencing the age at puberty, dependent on planes of nutrition in growing animals during the prepubertal-to-pregnancy stage. This paper reviews current knowledge concerning nutrition management and attainment of puberty in heifers, considering the relevance of some indicators such as body measurements and hormones strictly linked to the growth and puberty process. Puberty onset is dependent on the acquisition of adequate subcutaneous adipose tissue mass, as it is the main source of the hormone leptin. Until a certain level, body condition score and age at puberty are negatively correlated, but beyond that, for fatter animals, such correlation is gradually lost. Age at puberty in heifers was reported to be negatively related to IGF-1. Future research should be planned considering the need to standardize the experimental animals and conditions.

PSIII-10 Flaxseed oil-based supplement alters water consumption and plasma fatty acid profile of beef heifers

Abstract The objective of this study was to determine the effects of a flaxseed oil-based supplement (FlaxLic, New Generations, SD) on reproductive parameters, feeding behavior, and lipid profile in beef heifers. Crossbred Angus heifers [n = 60 body weight (BW) = 397kg ± 5.2 kg) were blocked by BW and antral follicle count and randomly assigned to two supplementation treatments: free-choice commercial lose mineral supplement (CON; n = 30) or free-choice flaxseed oil-based supplement (FLAX; n = 30) for 7 wk. Heifers were individually fed via the Insentec feeding system (Insentec RIC, Hokofarm, Marknesse, Netherlands), where basal diet (TMR) and supplements were provided in separate feeders to measure supplement intake and feeding behavior. Further, water intake and behavior were measured via Insentec water system. Individual intake was compiled over 24 h for each animal. Body weight, transrectal ultrasonography, and blood samples were collected weekly. On wk 5, heifers were enrolled in a fixed-time artificial insemination (FTAI) commercial protocol. Largest follicle diameter (LF) and corpus luteum (CL) presence were recorded weekly and on d of the FTAI protocol (d 0, d 7, and d 0). Pregnancy diagnosis was performed 30 d and 60 d following AI. Blood samples were analyzed for progesterone (P4) by radioimmunoassay (RIA) to determine puberty attainment before wk 5, and fatty acid profile was determined via gas chromatography-flame ionization detection. Heifers with a CL or P4 ≤ 1.0 ng/mL were considered pubertal. Data were analyzed using SAS 9.4. ADG was similar between groups (P = 0.90) but was affected by week (P < 0.01). TMR intake was similar in duration and quantity (P > 0.18) between groups. Supplement intake was greater (P < 0.01) for FLAX (0.73 ± 0.03 kg/d) compared with CON (0.18 ± 0.02 kg/d) and from wk 2 to wk 8 (P = 0.01). Time spent consuming the supplements was greater for FLAX compared with CON heifers (62.65 ± 2.11 vs 0.10 ± 0.11 min/d, respectively) over the entire trial (P < 0.01). Further, FLAX heifers consumed less water than CON heifers (32.2 ± 0.39 vs 33.93 ± 0.35 kg/d, respectively; P = 0.03) and from wk 2 to wk 7 (P = 0.03). LF was not different between groups on any of the days of the protocol (d 0, d 7, d 0; P > 0.20). Additionally, P4 (P ≤ 0.20), puberty attainment by wk 5 (P = 0.24), and pregnancy rates (P > 0.48) were similar between groups. Concentrations of arachidonic acid (3.00 ± 0.24 vs 2.32 ± 0.19 mg/mL; P = 0.04), linoleic (60.11 ± 4.34 vs 40.35 ± 4.04 mg/mL; P = 0.002), αLinolenic (16.73 ± 0.26 vs 15.86 ± 0.23 mg/mL; P = 0.02), and total polyunsaturated fatty acids (PUFA; 130.52 ± 5.97 vs 111.19 ± 5.56 mg/mL; P = 0.02) were greater on wk 8 for FLAX compared with CON heifers. Collectively, these findings did not show evidence that the flaxseed oil-based supplement affects variables that impact reproductive performance. However, it altered the plasma lipid profile, increasing omega-3, arachidonic, and linoleic fatty acids, as well as total PUFA.

PSIII-17 Relationship of toll-like receptor abundance in the boar reproductive tract with dihydrotestosterone prior to attainment of puberty

Abstract Fertile sperm production is crucial to the reproductive efficiency of swine operations; therefore, many factors impair quality semen production including hormonal imbalance and altered immune function. Toll-like receptors (TLRs) are a family of pattern recognition receptors which recognize and protect their host against pathogenic microorganisms through the regulation of inflammatory pathways. Recent data from our lab demonstrated greater expression of TLR2 mRNAs in the testes compared with other reproductive tissues (e.g., epididymis, seminal vesicles, and prostate) of pre-pubertal boars, suggesting TLR2 may aid early-in-life testes function or development. Expression of TLRs in various tissues has been shown to be influenced by hormones in rodents and humans. Dihydrotestosterone (DHT) is a sex steroid hormone and androgen that has a role in sexual development of males. However, little research has related TLRs with hormone concentration, which may help give insight to their physiological significance, particularly in the pre-pubertal male. Therefore, the objective of this project was to characterize relationships between expression of extracellular TLRs (TLR2, TLR4, TLR5 and TLR6) in the reproductive tissues (testes, epididymis, seminal vesicles, and prostate) with DHT concentrations in pre-pubertal boars. Intact reproductive tracts of pre-pubertal crossbred boars (Duroc x Landrace x Yorkshire; n = 4) were harvested at 2 mo of age and tissues were stored at –80°C for RT-qPCR analysis. From each boar, blood was collected postmortem and subsequent plasma samples stored at –20°C. Concentration of DHT in boar plasma was quantified using a competitive ELISA (MyBioSource, San Diego, CA) according to the manufacturer’s instructions. Expression of TLR2, TLR4, TLR5, and TLR6 mRNAs in the pre-pubertal boar tissues were quantified by RT-qPCR. Correlations of DHT concentration and TLR expression were calculated using Pearson Correlation within the PROC CORR function in SAS 9.4. The mean concentration of DHT was 9.32 ng/mL (range of 4.52 to 14.80 ng/mL). In the seminal vesicles, DHT concentration was significantly correlated with expression of both TLR2 (r = 0.95; P = 0.05) and TLR4 (r = 0.96; P = 0.04). In the testes, there was a tendency for a positive correlation between DHT concentration and expression of TLR2 mRNA (r = 0.92; P = 0.08). However, there were no correlations between DHT concentration and expression of any TLRs in the pre-pubertal boar epididymis or prostate (P > 0.10). These results suggest a relationship between androgens and TLR expression, particularly TLR2 and TLR4 mRNAs, in specific reproductive tissues of the pre-pubertal boar. Additional work will investigate TLR expression and androgen concentration in the pubertal boar.

26 Trace minerals to improve bull fertility

Abstract Bull fertility is paramount for reproductive success in cow-calf production systems and there are a variety of factors that influence bull fertility. Trace mineral requirements and recommendations have been established for growing and finishing steers, as well as lactating and pregnant cows, yet no specific requirements have been established for young or mature beef bulls. Nonetheless, trace minerals have been shown to have an important role in sexual maturation and semen quality of ruminants. Research performed in rams indicates that zinc deficiency results in reduced testicular development, decreased testicular concentrations of testosterone, and impaired development of seminiferous tubules. Deficiency of Zn has also been reported to negatively impact male fertility in humans, where men diagnosed with infertility responded positively to Zn supplementation. In growing bulls, diets with greater concentrations of organic forms of Zn, Cu, and Mn, tended to result in earlier attainment of puberty compared with control diets containing inorganic minerals. Furthermore, greater liver concentrations of Zn have been negatively correlated with sperm acrosomal damage in growing bulls, based on flow cytometry analyses. More recent research indicates that the use of hydroxichloride-based trace minerals results in greater liver concentrations of Zn and Cu compared with sulfate sources. While evidence indicates that trace mineral status has an important role in bull fertility, further research is required to better understand the contributions of trace minerals to semen quality. In addition, investigating the impact of trace mineral sources with greater bioavailability on semen quality may result in the development of practical recommendations that optimize bull fertility.

Effects of rate of body weight gain during the first trimester of gestation on beef heifer and offspring performance, concentrations of hormones and metabolites, and response to vaccination.

Our study objectives were to evaluate the effects of divergent rates of body weight (BW) gain during early gestation in beef heifers on F0 performance, metabolic and endocrine status, colostrum immunoglobulins, and subsequent F1 calf characteristics, growth performance, concentrations of hormones and metabolites, and response to vaccination. Angus-based heifers (n = 100; BW = 369 ± 2.5kg) were adapted to individual feeding for 14 d and bred using artificial insemination with female-sexed semen. Heifers were ranked by BW assigned to either a basal diet targeting 0.28kg/d gain (LG, n = 50) or the basal diet plus an energy/protein supplement targeting 0.79kg/d gain (MG, n = 50) until d 84 of gestation. Dam BW and blood samples were collected at 6 time points during gestation; body composition was evaluated at d -10 and 84; and fetal measurements were taken on d 42, 63, and 84. At calving (LG, n = 23; MG, n = 23), dam and calf BW were recorded; and colostrum, calf body measurements, and blood samples were collected. Cow-calf pairs were managed on a common diet from calving to weaning, followed by a common postnatal development period for all F1 female offspring. Growth performance, hormone and metabolite profiles, feeding behavior, and reproductive performance were assessed from birth to pre-breeding in F1 heifers. Offspring were vaccinated against respiratory disease and bovine viral diarrhea pathogens on d 62.3 ± 4.13 and 220.3 ± 4.13 post-calving. By design, MG dams were heavier (P < 0.0001) than LG at d 84, and the BW advantage persisted until subsequent weaning of F1 calves. Concentrations of serum IGF-1 and glucose were increased throughout gestation (P < 0.001) for MG dams, whereas concentrations of NEFA were decreased (P < 0.001) in LG dams. Calves from MG dams were 2.14kg heavier (P = 0.03) and had larger chest circumference (P = 0.04) at birth compared with LG cohorts. Heifers from MG dams continued to have greater (P ≤ 0.03) BW gain and feed efficiency during the development period, but no differences were observed (P ≥ 0.13) in body composition, concentrations of hormones and metabolites, feeding behavior, puberty attainment, and response to vaccination in F1 offspring. Hence, early gestation rate of gain impacted BW and concentrations of glucose and IGF-1 throughout gestation in the F0 dam, resulting in altered F1 calf BW and measurements at birth and increased gain and efficiency during the development period.

134 A 12-year summary of effects of body weight at breeding and synchronization protocols on reproductive success of Bos indicus-influenced beef heifers grazing warm-season grasses

Abstract A retrospective analysis of 5 studies (2011 to 2022) evaluated the effects of body weight and synchronization protocols before the start of breeding season on reproduction of Bos indicus-influenced beef heifers. Data were collected from 594 Brangus crossbred heifers weaned on average at 280 ± 26 d of age, allocated to bahiagrass pastures (4 to 5 heifers and 0.8 to 1.0 ha/pasture), and supplemented with soybean hulls-based concentrate (0.5 to 1.8% of body weight, (BW); dry matter basis] from 2 weeks post-weaning until the end of the breeding season (189 ± 24 days of supplementation). Heifers were initially sorted into those that were supplement (S) and were not supplemented (NS) assigned to an estrous synchronization protocol before the start of the breeding season. Then, within each synchronization group, heifers were sorted into those that were below (BE) or above (AB) the average BW of all heifers (300 kg) at the start of the breeding season (n = 130, 126, 146, and 192 for BE+NS, BE+S, AB+NS, and AB+S heifers, respectively). Data were analyzed using GLIMMIX procedure of SAS using synchronization, BW at breeding, and resulting interaction as fixed effects, and heifer (synchronization × BW), study, and pasture(study) as random effects. Effects of synchronization × BW at breeding and synchronization were not detected for heifer BW and overall average daily gain (ADG). However, AB heifers were always (P &amp;lt; 0.0001) heavier from post-weaning until the end of the breeding season and had (P &amp;lt; 0.0001) greater overall ADG than BE heifers. Effects of synchronization × BW at breeding tended (P = 0.07) to detected for puberty attainment at the start of the breeding season, which was least (P &amp;lt; 0.01) for BE+NS, did not differ between BE+S vs. AB+NS (P = 0.37), and was greatest for AB+S heifers (31, 66, 60, and 81 ± 7.4%, respectively). However, final pregnancy and calving percentages differed (P &amp;lt; 0.01) only for BE vs. AB heifers (68 vs. 81 ± 4.4% and 63 vs. 75 ± 5.2%, respectively). Effects of synchronization × BW at breeding tended (P = 0.10) to detected for percent of heifers calving within the first 30 days of the calving season, which was least (P &amp;lt; 0.03) for BE+NS and did not differ (P = 0.20) among BE+S, AB+NS, and AB+S heifers (48, 69, 61, and 64 ± 5.9%, respectively). Hence, in Bos indicus-influenced beef heifers, BW above 300 kg at the start of the breeding season led to improved overall reproductive performance compared to BW &amp;lt; 300 kg, whereas estrous synchronization protocols had positive effects to puberty attainment (regardless of heifer BW) and improved early calving distribution only when heifers were below 300 kg at the start of the breeding season.

101 Effects of moderate exercise regimen on reproductive development of replacement beef heifers reared in drylots at a high stocking density

Abstract This experiment evaluated growth and reproductive development of beef heifers reared at a high stocking density and provided with access to an exercise area. The experiment was replicated over 2 yr, with a total of 180 Angus × Brahman heifers. Each year, 90 heifers were ranked by age (264 ± 1 d) and body weight (BW; 200 ± 2 kg) on d 0, and assigned to a) 1 of 6 drylot pens (10 × 14 m pens; 10 heifers/pen) resulting in a stocking density of 14 m2/heifer (DENS), or b) 1 of 3 paddocks (2-ha paddocks; 10 heifers/paddock) resulting in a stocking density of 2,000 m2/heifer (CON). On d 15, 3 DENS pens were randomly selected and given access to an exercise area (DENS-EX) for 1 h three times weekly. Negligible forage was available for CON heifers, whereas all heifers received the same limit fed diet which averaged 13 kg/heifer daily of a corn-based diet. Heifer shrunk BW was recorded after 16 h of feed and water withdrawal on d -3 and 225 for BW gain calculation. Heifer temperament (chute score, exit velocity, and temperament score) were evaluated on d 0 and 225. Heifers were also fitted on d 0 with a pedometer behind their shoulder and an ear tag (CowManager, Select Sires, Plain City, OH) to record behavioral responses. Each week, pedometer results were recorded, and blood samples were collected for puberty evaluation via plasma progesterone. Heifers from CON had more (P &amp;lt; 0.05) steps per week compared with DENS and DENS-EX (23,973, 6,706, and 12,354 steps/week, respectively; SEM = 1,247), and DENS-EX heifers had more (P &amp;lt; 0.05) steps per week compared with DENS. Heifers from CON spent more (P &amp;lt; 0.05) time ruminating and eating compared with DENS and DENS-EX. No treatment effects (P ≥ 0.91) were detected for heifer BW gain (0.820, 0.815, and 0.824 kg/d for CON, DENS, and DENS-EX, respectively; SEM = 0.016). Heifers from DENS had greater (P ≤ 0.05) exit velocity and temperament score on d 225 compared with DENS-EX and CON. Heifers from DENS experienced delayed puberty attainment (treatment x day; P &amp;lt; 0.01) compared with DENS-EX and CON. A greater (P ≤ 0.05) proportion of CON heifers were pubertal by day 105 compared with DENS and DENS-EX (30.0, 11.6, and 15.0%, respectively; SEM = 6.5), whereas a greater (P &amp;lt; 0.05) proportion of CON and DENS-EX heifers were pubertal by d 154 compared with DENS (61.7, 66.7, and 43.3%, respectively; SEM = 6.5). Results from this experiment demonstrate that providing heifers with an exercise area alleviated the negative effects associated with high stocking density on their reproductive development. This work is supported by the USDA-NIFA AFRI program (#2021-67015-34083).

Effects of amoderate exercise regimen on development and puberty attainment of beef heifers reared in drylots at a high stocking density.

This experiment evaluated growth, physiological responses, and puberty attainment in beef heifers reared in drylots with a high stocking density, and provided or not with a moderate exercise regimen. A total of 180 heifers (75% Angus × 25% Brahman) were used in this experiment replicated over 2 yr. Each year, 90 heifers were ranked by age (264 ± 1 d) and body weight (BW on day -3; 200 ± 2kg) on day 0, and assigned to a) one of six drylot pens (10 × 14 m pens; 10 heifers per pen) with a stocking density of 14 m2/heifer (DENS), or b) one of three pastures (2-ha pastures; 10 heifers per pasture) with a stocking density of 2,000 m2/heifer (CON). Beginning on day 15, three DENS pens were given access to an exercise area (DENS-EX) 3 times/wk (1h). Negligible forage was available for CON, whereas heifers from all treatments received the same limit-fed diet (~13kg/heifer daily). Shrunk BW was recorded after 16h of feed and water withdrawal on days -3 and 225 to calculate BW gain. Temperament was evaluated on days 0, 128, and 224. Heifers were fitted with a pedometer behind their shoulder on day 0 to record physical activity. Pedometer results and blood samples were collected weekly for progesterone analysis. Hair samples from the tail switch were collected every 28 d. Data were analyzed with pen or pasture as an experimental unit, via ANOVA using the MIXED or GLIMMIX procedures of SAS (SAS Inst. Inc., Cary, NC). Heifers from CON had more (P < 0.01) steps per week compared with DENS and DENS-EX (23,973, 6,706, and 12,354 steps/wk, respectively; SEM = 1,247), and DENS-EX heifers had more (P < 0.01) steps per week compared with DENS. No treatment effects (P ≥ 0.91) were detected for heifer BW gain (~0.820kg/d). Hair cortisol concentrations were greater (P ≤ 0.05) in DENS and DENS-EX compared with CON beginning on day 56. Exit velocity and temperament score were greater (P ≤ 0.05) in DENS compared with DENS-EX and CON on day 224. Puberty attainment was delayed (treatment × day; P < 0.01) in DENS compared with DENS-EX and CON. A greater (P ≤ 0.05) proportion of CON were pubertal by day 105 compared with DENS and DENS-EX (30.0%, 11.6%, and 15.0%, respectively; SEM = 6.5), while a greater (P < 0.05) proportion of CON and DENS-EX were pubertal by day 154 compared to DENS (61.7%, 66.7%, and 43.3%, respectively; SEM = 6.5). Rearing replacement heifers in drylots with high stocking density has detrimental effects on their puberty attainment, and the moderate exercise regimen partially alleviated this negative outcome.

24 Effects of Gestational and Postweaning Nutrition on Brain Development and Puberty in Beef Heifers

Abstract Approximately 5 million beef heifers enter the U.S. cow herd annually, and their lifetime productivity is largely dependent upon their ability to attain puberty and produce a calf by 24 mo of age. However, a considerable proportion of heifers within existing U.S. production systems fail to achieve these goals, particularly in southern regions where Bos indicus-influenced cattle predominate. Consequently, managerial approaches are needed that employ nutritional programming of the reproductive neuroendocrine axis, while minimizing feeding costs and optimizing the consistent attainment of puberty by approximately 14 mo of age. Our previous research has clearly demonstrated that increased BW gain between 4 and 8 mo of age facilitates pubertal development by programming hypothalamic centers that regulate gonadotropin releasing-hormone (GnRH) secretion. Among the different metabolic hormones, leptin has a critical role in conveying nutritional information to the hypothalamus and controlling puberty. Two hypothalamic neuronal populations that express the orexigenic peptide neuropeptide Y (NPY) and the anorexigenic peptide alpha melanocyte-stimulating hormone (αMSH; a product of the POMC gene) are key components of afferent pathways that convey inhibitory (NPY) and excitatory (αMSH) inputs to GnRH and kisspeptin neurons. Our studies have demonstrated that short-term increases in dietary energy intake after early weaning at 4 mo of age result in epigenetic, structural, and functional modifications in these hypothalamic pathways to promote high-frequency, episodic release of GnRH and luteinizing hormone. However, integrating the foundational knowledge of metabolic imprinting of the brain for early puberty with issues related to lifetime performance is complex. One approach has been to employ a novel stair-step nutritional regimen involving alternating periods of dietary energy-restriction and re-feeding during juvenile development. This approach is designed to support early onset of puberty by imprinting functional alterations in the hypothalamus during key periods of brain development while optimizing other aspects of growth and performance. Finally, while several key processes of fetal brain development occur during late gestation, neither maternal undernutrition (BCS 3.0-3.5) nor maternal obesity (BCS 7.5-8.0) during the last two trimesters of gestation impacted the organization of hypothalamic neurocircuitries controlling GnRH/LH secretion or age at puberty in the heifer offspring. Collectively, these results indicate that the adult reproductive phenotype in Bos indicus-influenced females is resilient to significant degrees of nutritional stress imposed during prenatal development, particularly if early gestation (first trimester) is avoided. These findings are in contrast with reports in Bos taurus females in which late gestation nutritional extremes result in delayed puberty in heifer offspring, suggesting that potential genotype-specific differences may exist. Research support: USDA-NIFA-AFRI (2018-67015-27595 and 2021-67015-33676).

181 Effects of Moderate Exercise Regimen on Reproductive Development of Replacement Beef Heifers Reared in Drylots at a High Stocking Density

Abstract This experiment evaluated the physiological and reproductive responses of beef heifers reared at a high stocking density and provided with access to an exercise area. Ninety Angus × Brahman heifers were ranked by age (257 ± 2 days), body weight (BW; 216 ± 2 kg), and temperament score on day 0 and assigned to a) 1 of 6 drylot pens (10x14 m pens; 10 heifers/pen) resulting in a stocking density of 14 m2/heifer (DENS), or b) 1 of 3 paddocks (2-ha paddocks; 10 heifers/paddock) resulting in a stocking density of 2,000 m2/heifer (CON). On day 15, 3 DENS pens were randomly selected and given access to an exercise area (DENS-EX) for 1 hour three times weekly. Negligible forage was available for CON heifers, whereas all heifers received the same limit fed diet which averaged 13 kg/heifer daily of a corn-based diet. Heifer shrunk BW was recorded after 16 h of feed and water withdrawal on days -3 and 225 for average daily gain calculation. On day 0, heifers were fitted with a pedometer behind their shoulder and an ear tag (CowManager, Select Sires, Plain City, OH) to record behavioral responses. Each week, pedometer results were recorded, and blood samples were collected for puberty evaluation via plasma progesterone. Heifers from CON had more (P &amp;lt; 0.05) steps per week compared with DENS and DENS-EX, and DENS-EX heifers had more (P &amp;lt; 0.05) steps per week compared with DENS. Heifers from CON spent more (P &amp;lt; 0.05) time ruminating and eating compared with DENS and DENS-EX. No treatment effects (P ≥ 0.12) were detected for heifer BW gain or temperament variables. Heifers from DENS experienced delayed puberty attainment given a greater (P &amp;lt; 0.05) proportion of CON heifers were pubertal by day 98 compared with DENS and DENS-EX, whereas a greater (P &amp;lt; 0.05) proportion of DENS-EX heifers were pubertal by day 154 compared with DENS heifers (treatment × day interaction, P &amp;lt; 0.01). Collectively, results from this experiment demonstrate that providing heifers reared at a high stocking density access to an exercise area does not result in similar reproductive responses as those reared on pasture at a low stocking density. This work is supported by the USDA National Institute of Food and Agriculture (#2021-67015-34083).

Growth and Puberty Attainment of Girls with Human Immunodeficiency Virus.

Pattern of physical growth and pubertal changes among 59 girls, aged 8-15 years, diagnosed as cases of HIV on anti-retroviral therapy was cross-sectionally studied. Besides, measurement of body weight, height, and body mass index, breast development stage, presence or absence of pubic and axillary hair, and age of attainment of menarche were also noted in these subjects in the growth clinic of the department. With the advancement of age, the weight and height of HIV girls increased; however, they were lighter and shorter compared to their normal peers. 15.3% of HIV girls were short-statured and underweight. None of the study participants were found to be overweight or obese. 40.7% of HIV girls had attained menarche (mean age: 12.58 ± 1.349 years). The appearance of pubic (13.45 ± 1.64 years) and axillary hair (13.73 ± 1.41 years) occurred around 1 year later. The delayed physical growth and puberty attainment of HIV girls than their normal counterparts may be due to the influence of the disease.

Physical traits, performance data, and reproductive tract maturity score can be used to predict fertility and likelihood of early conception in beef replacement heifers consigned to a heifer development program in the southeastern United States.

To identify growth and reproductive measurements that can be used to select heifers with the potential to be more reproductively efficient. A total of 2,843 heifers consigned to the Georgia Heifer Evaluation and Reproductive Development program between 2012 and 2021 with a mean (min, max) age of heifers at delivery of 347 days (275, 404). Reproductive tract maturity score (RTMS), weight at delivery as a percentage of target breeding weight, hip height 3 to 4 weeks after delivery, and average daily gain during the first 3 to 4 weeks after delivery were evaluated as potential predictors of the variables of interest. The model-adjusted odds of pregnancy were 1.40 to 1.67 times higher for heifers with an RTMS of 3, 4, or 5 when compared to heifers with an RTMS of 1 or 2. For every 2.5-cm increase in hip height and every 1-month increase in age at the beginning of the breeding period the model-adjusted odds of pregnancy were 1.10 and 1.16 times higher, respectively. The model-adjusted pregnancy hazard rate for heifers with an RTMS of 3, 4, or 5 was 1.19 to 1.25 times higher than that of heifers with an RTMS of 1 or 2. For every 2.5-cm increase in hip height, the model-adjusted hazard rate for pregnancy was 1.04 times greater. Physical traits related to animal maturity and attainment of early puberty can be used to select heifers that are more likely to become pregnant early in their first breeding season.

Long-acting injectable progesterone treatment prior to puberty induction in gilts

Progesterone (P4) has a pivotal role on female puberty attainment in most farm animals. However, there are no studies evaluating the effect of P4 treatment previously to boar exposure for puberty induction in gilts. Therefore, serum P4 concentration, estrus expression and reproductive performance after boar stimuli were evaluated in gilts intramuscularly treated with long-acting P4 before boar exposure. In Experiment I, prepubertal gilts received either 1 mL of saline (control) or intramuscular (I.M.) P4 treatment (150 mg, 300 mg or 600 mg; n=6 per treatment). Serum P4 concentration for P4-treated gilts was greater than for control gilts for at least 8 d for P4300 and P4600 groups (P < 0.05), but greater until after 16 d only for those treated with 600 mg (P < 0.05). In Experiments II (prepubertal) and III (peripubertal), gilts received either saline (control) or 300 mg P4 I.M. and those showing estrus signs were artificially inseminated (AI), whereas gilts without estrus expression were culled. In prepubertal gilts (Exp. II), estrus expression rate did not differ (P < 0.05) for control (79.1%; n=110) and P4-treated gilts (81.5%; n=108). In peripubertal gilts (Exp. III), although estrus expression did not differ between control (77.6%; n=106) and P4-treated (69.6%; n=102) gilts (P > 0.05), P4-treated gilts presented longer (23.1 ± 1.4 days) interval from treatment to estrus expression than control gilts (17.1 ± 1.3 days; P < 0.05). In Experiments II and III, the proportion of culled gilts with ovarian structures consistent with normal estrous cycles, farrowing rate, and litter size did not differ between treatments (P > 0.05). In conclusion, I.M. treatment with 300 or 600 mg of long-acting P4 was efficient in maintaining high P4 concentrations in prepubertal gilts for at least 8 days. However, P4 treatment over this time interval did not benefit the reproductive performance of prepubertal and peripubertal gilts.

The Impacts of Supplemental Protein during Development on Amino Acid Concentrations in the Uterus and Pregnancy Outcomes of Angus Heifers.

Replacement heifer development is one of the most critical components in beef production. The composition of the ideal uterine environment could maximize fertility and reproductive efficiency. Our hypothesis was that protein supplementation would affect the uterine environment of beef heifers without inhibiting development or reproduction. To test the effects of dietary supplementation on these outcomes, a randomized complete block design with repeated measures was implemented. Angus heifers (n = 60) were blocked by body weight (BW) and randomly assigned to one of three supplemental protein treatment groups (10% (CON), 20% (P20), and 40% (P40)). Mixed model ANOVAs were used to determine whether protein supplementation treatments, time, and the interaction or protein supplementation, semen exposure, and the interaction influenced uterine luminal fluid (ULF) and pregnancy outcomes. Amino acids (AAs) were impacted (p < 0.001), specifically, the essential AAs: Arg, Iso, Leu, Val, His, Lys, Met, Phe, Trp. Protein supplementation influenced multiple AAs post-insemination: Arg (p = 0.03), CC (p = 0.05), 1-MH (p = 0.001), and Orn (p = 0.03). In conclusion, protein supplementation did not affect the reproductive development via puberty attainment or the timing of conception even with alterations in growth. However, uterine AA concentrations did change throughout development and protein supplementation influenced ULF d 14 post-insemination, which may affect the conception rates.

Suitability of a universal electroporation device for genome editing and production of transgenic rats.

Mammalian genome editing has utilized expensive and highly specialized electroporator devices. The "Gene Pulser XCell," a modular electroporation system for transfecting all cell types, has not been used extensively in mammalian embryo genome editing. The present experiment was undertaken to determine the usefulness of the Gene Pulser XCell for inserting the CRISPR/Cas9 system into intact zygotes in order to obtain the enhanced green fluorescent protein reporter rats (eGFP-R). An electroporation pulse response test using mCherry mRNA was performed to optimize the settings of the electroporator. Forty-five combinations of five pulse voltages (15, 25, 30, 35 and 40V), three pulse durations (5, 10 and 25ms), and three pulse frequencies (2, 5 and 6 pulses) applied at a constant 100-ms pulse interval and temperature of 37.5°C were evaluated. The test revealed that the 35V was the only voltage suitable for insertion of mCherry mRNA into intact rat zygotes and the only one that resulted in the production of embryos attaining the blastocyst stage. The incorporation of mCherry mRNA increased but the survival of the electroporated embryos declined with an increment in the number of pulses. Subsequent transfer of 1112 surviving Sprague Dawley rat embryos (after 8h of incubating 1800 zygotes electroporated with the CRISPR/Cas9) resulted in the production of 287 offspring (25.8%). Ensuing PCR and phenotypic evaluation confirmed that twenty animals (6.96%) expressed eGFP in all body organs/tissues except for blood and blood vessels. The mortality of males and females before the attainment of puberty was 2 and 3 pups, respectively, and the final number/ratio of male to female of offspring was 9:11. All the surviving rats mated naturally and successfully transmitted the GFP transgene to their progeny. The Gene Pulser XCell total system with the settings predetermined in the present experiment can effectively be used to produce transgenic rats through the CRISPR/Cas9-mediated genome editing of zygotes.

Effect of sires' expected progeny difference for scrotal circumference and juvenile ADG on the puberty of crossbred beef heifers.

The early attainment of puberty in heifers is essential for the profitability of the cow-calf farm. This study aimed to evaluate the impact of juvenile average daily gain (ADG) and sire's expected progeny difference (EPD) on puberty of crossbred beef heifers. Sixty Angus × Nellore heifers early weaned (age = 102 ± 4.3 d; initial BW = 103 ± 4.7kg) were used in a 2 × 2 factorial arrangement. The factor 1 was the sire's EPD for scrotal circumference, in which heifers born from sires with positive EPD were considered precocious (P), and heifers born from sires with negative EPD were considered non-precocious (NP). The factor 2 was the high (HG; ADG = 0.9kg; ad libitum) and medium ADG (MG; ADG = 0.7kg) from 3rd to 7th month of age (1st phase). After 1st phase until puberty, all heifers were fed ad libitum (2nd phase). Statistical analysis was performed by SAS. There was an interaction between factors for DMI in the 1st phase (P = 0.02), which PHG heifers had higher DMI than NPHG. There was no effect on puberty rate, BW, age and BCS at puberty comparing HG vs. MG. However, favorable sires' EPD for scrotal circumference induced a higher proportion of puberty (P 87% vs. NP 59%) at 15months of age. Thus, the ADG in juvenile age did not affect puberty rate, but sires with positive EPD increased puberty rate of Angus × Nellore heifers in heifers fed a high gain diet.

Puberty attainment and growth performance in male rabbits fed zinc sulphate supplemented diets

Micronutrients are essential for reproductive performance in farm animals but often deficient in their diets especially in the tropics. This study was conducted to assess the effect of zinc supplementation on puberty attainment and growth indices in male rabbits. The experimental diets were supplemented with zinc as zinc sulphate at 0, 50, 100 and 150 mg/kg of diet and fed to twenty-four growing male rabbits aged 9-10 weeks old allotted to four groups in a Completely Randomized Design. Puberty attainment in the male rabbits was monitored at 72hours interval from 12weeks of age till sperm cells were first seen in their preputial fluid examined under a microscope. Body weight gain and feed intake were monitored weekly; and the feed conversion ratio was estimated. The study lasted for 10weeks. The data obtained were subjected to general linear model of analysis of variance at p&lt;0.05. An insignificant impact of zinc supplementation on puberty attainment was recorded. Among all the growth parameters assessed, only feed intake was significantly (p&lt;0.05) influenced by zinc supplementation. Average daily feed intake was higher (86.55g) in male rabbits fed Z150 compared to those on other groups. Weight gain was lower in rabbits fed zinc supplemented diets. It can be concluded that dietary zinc supplementation did not result in early attainment of puberty and no significant (p&gt;0.05) effect on pubertal weight. Dietary, zinc supplementation did not improve growth performance, puberty attainment or pubertal weight in male rabbits. However, to meet nutritional requirement of growing rabbits, supplementation may be needed as many conventional feeds do not meet the recommended level.&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; Les micronutriments sont essentiels pour les performances de reproduction des animaux de ferme mais souvent déficients dans leur alimentation, en particulier sous les tropiques. Cette étude a été menée pour évaluer l’effet de la supplémentation en zinc sur l’atteinte de la puberté et les indices de croissance chez les lapins mâles. Les régimes expérimentaux ont été complétés avec du zinc sous forme de sulfate de zinc à 0, 50, 100 et 150 mg/kg de régime et donnés à vingt-quatre lapins mâles en croissance âgés de 9 à 10 semaines répartis en quatre groupes dans un plan entièrement randomisé. L’atteinte de la puberté chez les lapins mâles a été surveillée à intervalle de 72 heures à partir de l’âge de 12 semaines jusqu’à ce que les spermatozoïdes soient vus pour la première fois dans leur liquide préputial examiné au microscope. Le gain de poids corporel et la consommation d’aliments ont été surveillés chaque semaine; et le taux de conversion alimentaire a été estimé. L’étude a duré 10 semaines. Les données obtenues ont été soumises à un modèle linéaire général d’analyse de variance à p&lt;0,05. Un impact insignifiant de la supplémentation en&#x0D; zinc sur l’atteinte de la puberté a été enregistré. Parmi tous les paramètres de croissance évalués, seule la prise alimentaire était significativement (p&lt;0,05) influencée par la supplémentation en zinc. La consommation alimentaire quotidienne moyenne était plus élevée (86,55 g) chez les lapins mâles nourris au Z150 par rapport à ceux des autres groupes. Le gain de poids était plus faible chez les lapins nourris avec des régimes enrichis en zinc. On peut conclure que la supplémentation alimentaire en zinc n’a pas entraîné l’atteinte précoce de la puberté et aucun effet significatif (p&gt;0,05) sur le poids pubertaire. La supplémentation alimentaire en zinc n’a pas amélioré les performances de croissance, l’atteinte de la puberté ou le poids pubertaire chez les lapins mâles. Cependant, pour répondre aux besoins nutritionnels des lapins en croissance, une supplémentation peut être nécessaire car de nombreux aliments conventionnels ne répondent pas au niveau recommandé.

15 Search for Non-Genomic Markers as Puberty Predictors inBos Indicus Cattle

Abstract Brahman cattle are used for crossbreeding due to their maternal ability, heat, and parasite tolerance. Brahman displays delayed attainment of puberty compared with taurine breeds. The objective was to identify molecular markers in the blood of prepubertal heifers and bulls that predict early puberty attainment. We hypothesize that Brahmans that attains puberty have a blood metabolite signature that differs from animals that remain prepubertal. Plasma was collected 90 (-90d) and 30 (-30d) days prior to the beginning of the breeding season from 156 yearling Brahman heifers and 28 bulls. Animals were classified as pubertal (pub) or prepubertal (prepub) based on reproductive variables such as the reproductive tract score and pregnancy to insemination for heifers and scrotal circumference and semen quality for bulls. Plasma from 48 pub and 48 prepub heifers and 9 pub and 7 prepub bulls were submitted for quantitative mass spectrometry metabolomics analysis. There was a clear clustering of animals according to puberty status (orthogonal projections of latent structures discriminant analysis). Concentrations of the top three metabolites explaining clustering were analyzed by t-tests. As heifers approached maturity, there was a 3.03-, 11.76- and 2.08-fold change (P &amp;lt; 0.0001) in the concentrations of PC ae C42:3, ProBetaine, and PC ae C42:2 measured at -30 vs. -90 days. Similarly, for bulls, concentrations of HipAcid, C4 and SM (OH) C24:1 were 1.52-, 1.53-, and 1.45-fold greater (P &amp;lt; 0.0001), respectively. Comparing pub vs. prebub heifers on -90 d, there was a 1.26- (P &amp;lt; 0.001), 0.62- (P &amp;lt; 0.01) and 1.11-fold change (P &amp;lt; 0.05) for hArg, Putrescine and AABA concentrations, respectively. Regarding bulls on -90 d, there was a 1.57- (P &amp;lt; 0.01), 1.32- (P &amp;lt; 0.03) and 1.15-fold change (P &amp;lt; 0.03) for FA(18:1), FA(18:2) and DG(16:1_18:2) concentrations, respectively. In conclusion, we discovered potential markers for the prediction of puberty attainment based on plasma metabolomic signatures in Brahman.

Review: Gestational and postnatal nutritional effects on the neuroendocrine control of puberty and subsequent reproductive performance in heifers.

Pubertal attainment is an intricate biological process that involves maturation of the reproductive neuroendocrine axis and increased pulsatile release of gonadotropin-releasing hormone (GnRH) and luteinizing hormone. Nutrition is a critical environmental factor controlling the timing of puberty attainment. Nutrient restriction during early postnatal development delays puberty, whereas increased feed intake and adiposity during this period hasten pubertal maturation by imprinting the hypothalamus. Moreover, the dam's nutrition during gestation can program the neuroendocrine system in the developing fetus and has the potential to advance or delay puberty in the offspring. Leptin, a hormone produced primarily by adipose cells, plays an important role in communicating energy status to the brain and regulating sexual maturation. Leptin's regulation of GnRH release is mediated by an upstream neuronal network since GnRH neurons do not contain the leptin receptor. Two groups of neurons located in the arcuate nucleus of the hypothalamus that express neuropeptide Y (NPY), an orexigenic peptide, and alpha melanocyte-stimulating hormone (αMSH), an anorexigenic peptide, are central elements of the neural circuitry that relay inhibitory (NPY) and excitatory (αMSH) inputs to GnRH neurons. Moreover, KNDy neurons, neurons in the arcuate nucleus that co-express kisspeptin, neurokinin B (NKB), and dynorphin, also play a role in the metabolic regulation of puberty. Our studies in beef heifers demonstrate that increased rates of BW gain during early postweaning (4-9 mo of age) result in reduced expression of NPY mRNA, increased expression of proopiomelanocortin and kisspeptin receptor mRNA, reduced NPY inhibitory inputs to GnRH neurons, and increased excitatory αMSH inputs to KNDy neurons. Finally, our most recent data demonstrate that nutrition of the cow during the last two trimesters of gestation can also induce transcriptional and structural changes in hypothalamic neurocircuitries in the heifer progeny that likely persist long-term after birth. Managerial approaches, such as supplementation of the dam during gestation (fetal programming), creep feeding, early weaning, and stair-step nutritional regimens have been developed to exploit brain plasticity and advance pubertal maturation in heifers.

Genetic relationships among yearling fertility, body composition and weight traits in tropically adapted composite cattle

Context Reproduction is an economically important trait in both males and females; however, the relationships between fertility and body composition traits are little researched, but essential to breeding programs, as they will help inform selection decisions and allow the greatest opportunity for genetic gain. Aims Estimate genetic and phenotypic correlations between male and female yearling fertility traits and investigate their relationship with yearling body composition traits, which have an effect on the attainment of puberty. Methods Genotype and phenotype data were obtained from a tropical composite commercial cattle population and imputed to 27 638 single nucleotide polymorphisms. A series of univariate and bivariate linear mixed models using a genomic relationship matrix were run to estimate genetic parameters, genetic and phenotypic correlations for a series of male and female fertility and body composition traits. These parameters were then compared to help understand the genetic relationships. Key results Scrotal circumference was favourably genetically correlated with weight (0.34), fat traits (0.06–0.24), muscle (0.24) and heifer days to calving (−0.32). Heifer days to calving was favourably correlated with muscle (−0.18) but not fat traits (0.11 to 0.21). The genetic correlations between heifer days to calving and sperm morphology traits were generally unfavourable (−0.32 to 0.25). Sperm morphology traits were favourably genetically correlated with fat traits (−0.84 to 0.31) and muscle (−0.61 to 0.31) but not weight (−0.15 to 0.09). Conclusions and implications Yearling sperm morphology traits were unfavourably correlated with heifer days to calving, indicating that they are not good candidates for indirect selection on improving female fertility in the herd. A different trend was found for yearling scrotal circumference and heifer days to calving, identifying it as a good candidate for indirect selection of heifer fertility as it is easy to measure and heritable. The genetic correlations estimated between composition traits with male and female fertility traits allow breeding programs to make an informed selection decision to optimise genetic gain across all traits.