Management of pre-pubertal small ruminants: Physiological basis and clinical approach

Metabolomics and transcriptomics analyses reveal the complex molecular mechanisms by which the hypothalamus regulates sexual development in female goats

BACKGROUND

The hypothalamus is a critical organ that regulates sexual development in animals. However, current research on the hypothalamic regulation of sexual maturation in female goats remains limited. In this study, we conducted metabolomic and transcriptomic analyses on the hypothalamic tissues of female Jining grey goats at different stages of sexual development (1 day old (neonatal, D1, n = 5), 2 months old (prepuberty, M2, n = 5), 4 months old (sexual maturity, M4, n = 5), and 6 months old (breeding period, M6, n = 5)).

RESULTS

A total of 418 differential metabolites (DAMs) were identified in this study, among which the abundance of metabolites such as anserine, L-histidine, carnosine, taurine, and 4-aminobutyric gradually increased with the progression of sexual development. These metabolites may regulate neuronal development and hormone secretion processes by influencing the metabolism of histidine and phenylalanine. Through combined transcriptomic and metabolomic analyses, we identified that differentially expressed genes such as mitogen-activated protein kinase kinase kinase 9 (MAP3K9), prune homolog 2 with BCH domain (PRUNE2), and potassium voltage-gated channel interacting protein 4(KCNIP4) may jointly regulate the development and energy metabolism of hypothalamic Gonadotropin-releasing hormone neurons in conjunction with DAMs, including LPC22:5, 2-Arachidonyl Glycerol ether, LPE22:5, and Lysops22:5. Additionally, we elucidated the molecular mechanism through which glutathione metabolism regulates sexual maturation in goats.

CONCLUSIONS

In summary, this study illustrates the dynamic changes in metabolites and mRNA within hypothalamic tissue during postnatal sexual maturation in female Jining grey goats. This research may provide significant scientific insights for future animal breeding.

Effects of Prenatal Herbal Methionine Supplementation on Growth Indices, Onset of Puberty, Blood Metabolites, and Fertility of Alpine Doelings

This study investigated the effects of prenatal herbal methionine supplementation on growth, puberty onset, reproductive efficiency, and blood metabolites in first-generation G1 Alpine doelings. Sixty pregnant multiparous goats (G0), each with at least three parturitions, were assigned during the last trimester of pregnancy to either herbal methionine (H-MET-G0; 1% Optimethione®; n = 30) or a control group (CTL-G0; n = 30). Only female offspring (G1 doelings) were studied (H-MET-G1:19; CTL-G1:25) from weaning (45 days old) to 10 months (first breeding). G1 doelings were weighed and monitored weekly for metabolites, IGF-1, insulin, and progesterone. Ovulation of the G1 doelings was induced using vasectomized bucks, followed by breeding with intact bucks. Postweaning growth, age at puberty (H-MET-G1:216 vs. CTL-G1:229 days), and live weight at puberty (H-MET-G1:20.5 vs. CTL-G1:21.0 kg) did not significantly differ (p > 0.05). Age at puberty and conception were negatively correlated with live weight (p < 0.001). First-cycle conception rates were 81% in CTL-G1 and 66% in H-MET-G1, with similar days to conception (p > 0.05). The number of pregnant doelings and the number of kids in utero did not significantly differ (p > 0.05) between treatments. Plasma IGF-1 and insulin levels were significantly higher (p < 0.001) in H-MET-G1 doelings, whereas plasma metabolites related to nutrition showed no differences between groups (p > 0.05). Prenatal herbal methionine supplementation had no carry-over effect on growth, puberty onset, or reproductive efficiency. Age at puberty and conception were negatively correlated with live weight and positively correlated with IGF-1 and insulin levels.

Response of maiden ewes to the 'ram effect' is a robust management practice and a candidate selection trait for enhanced reproductive performance in drylands

Management of reproduction that relies on naturally based solutions is extremely important to counter the negative perception around hormone-based interventions. In Mediterranean latitudes and wider regions of non-tropical drylands, sheep do not normally ovulate during spring but exposure to a ram can induce oestrus and ovulation. This study assesses the response of maiden Barbarine ewes in drylands to the 'ram effect' during springtime and estimates the genetic parameters of this response. The study uses a database documenting, for 24 consecutive years, the response of nulliparous 18-month-old ewes when mated after stimulation by the 'ram effect.' In addition to the oestrous and fertility database, a pedigree database was also available. Nearly half of the maiden ewes responded to the 'ram effect,' while 24% exhibited spontaneous reproductive activity and displayed oestrus during the first 14 days following the introduction of rams. Nearly 5% of females did not exhibit oestrus, and these animals are proposed for early culling. Average annual values of Normalised Difference Vegetation Index (NDVI), reflecting vegetation cover, and the percent of maiden ewes spontaneously cycling were positively correlated (P = 0.006). Interestingly, NDVI was negatively correlated with the percentage of anoestrus females that did not respond to the 'ram effect' but exhibited oestrus beyond the hypothetical time frame commonly used to describe it. Average fertility was 82.8% and was significantly affected by mating year, live weight at mating, and the response to the 'ram effect.' The highest fertility (88.39%) was for females spontaneously cycling at the time of ram introduction, and the lowest (83.35%) was for females coming into oestrus beyond the time frame for a ram-induced oestrus and ovulation. Heritability from a univariate logit-transformed analysis for fertility was 0.10 and the genetic correlation between fertility and the interval between ram introduction and oestrus was 0.26, suggesting that a shorter interval is associated with higher fertility. Thus, the interval between ram introduction and oestrus is a good candidate for selective breeding for high fertility of maiden ewes in drylands mated out-of-season using the 'ram effect.'

The Transcriptome Characterization of the Hypothalamus and the Identification of Key Genes during Sexual Maturation in Goats

Sexual maturation in goats is a dynamic process regulated precisely by the hypothalamic-pituitary-gonadal axis and is essential for reproduction. The hypothalamus plays a crucial role in this process and is the control center of the reproductive activity. It is significant to study the molecular mechanisms in the hypothalamus regulating sexual maturation in goats. We analyzed the serum hormone profiles and hypothalamic mRNA expression profiles of female goats during sexual development (1 day old (neonatal, D1, n = 5), 2 months old (prepuberty, M2, n = 5), 4 months old (sexual maturity, M4, n = 5), and 6 months old (breeding period, M6, n = 5)). The results indicated that from D1 to M6, serum hormone levels, including FSH, LH, progesterone, estradiol, IGF1, and leptin, exhibited an initial increase followed by a decline, peaking at M4. Furthermore, we identified a total of 508 differentially expressed genes in the hypothalamus, with a total of four distinct expression patterns. Nuclear receptor subfamily 1, group D, member 1 (NR1D1), glucagon-like peptide 1 receptor (GLP1R), and gonadotropin-releasing hormone 1 (GnRH-1) may contribute to hormone secretion, energy metabolism, and signal transduction during goat sexual maturation via circadian rhythm regulation, ECM receptor interactions, neuroactive ligand-receptor interactions, and Wnt signaling pathways. This investigation offers novel insights into the molecular mechanisms governing the hypothalamic regulation of goat sexual maturation.

Transcriptome analysis revealed the characteristics and functions of long non-coding RNAs in the hypothalamus during sexual maturation in goats

The hypothalamus is an essential neuroendocrine area in animals that regulates sexual development. Long non-coding RNAs (lncRNAs) are hypothesized to regulate physiological processes related to animal reproduction. However, the regulatory mechanism by which lncRNAs participate in sexual maturity in goats is poorly known, particularly from birth to sexual maturation. In this study, RNAseq analysis was conducted on the hypothalamus of four developmental stages (1day (D1, n = 5), 2 months (M2, n = 5), 4 months (M4, n = 5), and 6 months (M6, n = 5)) of Jining grey goats. The results showed that a total of 237 differentially expressed lncRNAs (DELs) were identified in the hypothalamus. Among these, 221 DELs exhibited cis-regulatory effects on 693 target genes, while 24 DELs demonstrated trans-regulatory effects on 63 target genes. The target genes of these DELs are mainly involved in biological processes related to energy metabolism, signal transduction and hormone secretion, such as sphingolipid signaling pathway, adipocytokine signaling pathway, neurotrophic signaling pathway, glutamatergic synapse, P53 signaling pathway and GnRH signaling pathway. In addition, XR_001918477.1, TCONS_00077463, XR_001918760.1, and TCONS_00029048 and their potential target genes may play a crucial role in the process of goat sexual maturation. This study advances our understanding of lncRNA in hypothalamic tissue during sexual maturation in goats and will give a theoretical foundation for improving goat reproductive features.

Application of the "echo-synch protocol" to advance pregnancy onset in ewe lambs at the first reproductive season

Introduction

This study assessed the efficacy and economic impact of a reproductive protocol based on repeated ultrasound scanning (US) associated with the use of GnRH to advance pregnancy onset in ewe lambs.

Methods

Prepubertal ewe lambs (n = 133) were divided into three weight groups (High: HW n = 35; Medium: MW n = 65; Low: LW n = 33). Thereafter, animals were randomly allocated into two subgroups: GnRH, ewe lambs treated with GnRH analog and then exposed to rams; CTR, ewe lambs exposed to rams only. CTR groups were joined with rams as a single flock. GnRH groups were kept separate from rams receiving a single dose of gonadorelin (40 μg/head) and then were evaluated after a week of US. Animals showing corpora lutea received an injection of PGF2α analog (100 μg/head) and then were joined with rams. The remaining ewe lambs received a second dose of gonadorelin and were kept separate from the rams. After another week, animals were checked again and the ones showing corpora lutea were injected with the PGF2α analog, while the others received a third injection of gonadorelin. On the same day, all the animals were joined with rams. Pregnancies were confirmed within 30 days by US. The efficacy of the protocol was determined by assessing differences in the number of days required to achieve pregnancy rates of 25, 50, and 75% and in the total costs and incomes from birth to the end of first lactation within the groups.

Results

The GnRH-MW group showed the best performances in reaching the threshold pregnancy rates of 25, 50, and 75%, but the effect of treatment was significant only at the 25% threshold (p < 0.01). Both low groups displayed an overall poorer performance at 50 and 75% thresholds than medium and high-weight groups (p = 0.01 and p < 0.01, respectively). The GnRH administration did not advance pregnancy onset in GnRH-HW compared with CTR-HW. In the balance between costs and income, the HW-CTR and MW-GnRH groups showed higher gross margins than the other groups.

Conclusion

Using the US/GnRH protocol in ewe lambs appears technically and economically effective in animals that have not reached the optimal weight at the first breeding season, advancing ewe lambs' pregnncies and increasing farm profitability.

Review: Feeding strategies for rearing replacement dairy goats - from birth to kidding

Goat kid rearing is a key profit driver and the cornerstone of future herd productivity in dairy systems. As goat kids get older, and progress from liquid (i.e., colostrum, milk) to solid feed (i.e., concentrate, hay, pasture), there is a reduction not only in feed cost but also in labour cost, disease susceptibility and mortality rates. Hence, research on rearing dairy goats has traditionally focused on improving early neonatal performance. However, recent research reveals that early-life nutrition may have long-term effects, and consequently, impact the lifetime productive performance and health of dairy goats. Therefore, this literature review has collected research on the various aspects of rearing replacement dairy goat kids in different production systems. It summarises research on areas such as colostrum management (i.e., colostrum quality, time, volume and frequency of colostrum feeding), liquid feeding in preweaned kids (i.e., maternal suckling vs artificial, restricted vs unrestricted), weaning strategies (i.e., abrupt vs step-down), and postweaning to postpubertal nutrition in replacement dairy goats, whilst highlighting gaps in the existing literature, and areas where it would be beneficial to refine and validate current recommendations. Such information can be used in the development of management plans to maximise the benefits of early-life nutrition on the long-term productivity of dairy goats.

Pregnancy in Slaughtered Lambs and Sheep—A Cross-Sectional Study in Three Abattoirs in Switzerland

Simple Summary

The slaughtering of pregnant livestock and its relevance to animal welfare has become an ethically controversial topic. In this study, the prevalence of sheep and lambs being slaughtered while pregnant in Switzerland was assessed as well as the stage of pregnancy and the life signs of the fetuses. Data collection was carried out over one year in three Swiss abattoirs. Overall, 7.6% of the female animals were pregnant at slaughter, and 25.5% of them were in the third trimester of pregnancy, where 81.1% of the fetuses showed signs of life, such as a heartbeat or umbilical artery pulsation. To assess the relevance of animal welfare, it is discussed whether fetuses feel pain and stress. Even though science disagrees as to whether fetuses are capable of feeling conscious pain, it cannot certainly be ruled out, which is why the slaughter of pregnant sheep and lambs should be minimized as much as possible.

Abstract

The slaughter of pregnant sheep and goats is not restricted in Switzerland. The aim of this study was to assess the prevalence of pregnant sheep and lambs being slaughtered in Switzerland and to determine the state of gestation and vital signs of the fetuses in order to assess the need to take measures and raise awareness of this issue. The data collection was carried out from March 2021 to February 2022, comprising 115 days in three abattoirs. A total of 18,702 sheep and lambs were included in this cross-sectional study, and 8770 were female (46.9%), 663 of which were pregnant at slaughter (7.6%). The pregnancy rate varied by age category: 404 lambs (6.1%) and 259 sheep (11.9%) were pregnant. The highest pregnancy rate was found in winter (25.7%). Among the 663 pregnancies, more than a quarter were multiple pregnancies (28.2%). A total of 169 animals were in the third trimester of pregnancy (25.5%), where living fetuses were mainly found (81.1%). As it cannot be definitively ruled out that fetuses feel conscious pain, the data from this study underline that, from an ethical point of view, there is a need for action and that measures must be taken to reduce the number of pregnant slaughtered animals.

Reproductive Management of Rams and Ram Lambs during the Pre-Breeding Season in US Sheep Farms

In sheep farms, achieving economic and productive efficiency and sustainability goals is directly related with the reproductive management of the animals. Genetically, the male contribution to the offspring is 50%, but in practical terms, there is a greater potential impact of the ram on reproductive results, because one male has the potential to affect a large group of females and therefore greatly affects the entire flock. Unfortunately, the selection of males for breeding in the US sheep industry has been traditionally conducted based on phenotypical traits, without a genetic/reproductive evaluation, and/or health assessment or records. Therefore, it is important to establish integrative management practices to select the rams and ram lambs to be used in the breeding season. Among these practices are genomic testing, a comprehensive breeding soundness evaluation and assessment of health status and records of the males before the breeding season, to detect and correct potential issues.

Melatonin Treatment in Rams and Their Replacement with Novel Treated Rams Advance First Lambing and Increase Fertility in Sarda Ewe Lambs

Simple Summary

The goals of this study were to advance first mating in ewe lambs and to shorten the period ranging from weaning to first lambing. Sarda ewe lambs (n = 400) were separated into four groups of 100 and exposed for a 50-day breeding period to fertile, adult rams as follows: (1) RMR (Rams–Melatonin–Replacement) group: exposed to melatonin-treated rams which were replaced every 10 days; (2) RM (Rams–Melatonin) group: exposed to melatonin-treated rams which were not replaced; (3) RCR (Rams–Controls–Replacement) group: exposed to untreated rams which were replaced every 10 days; and (4) RC (Rams–Controls) group: exposed to untreated rams which were not replaced. In each group, lambing dates, fertility rate, litter size, and distance in days from ram introduction to lambing (DRIL) were recorded. The RMR group showed the highest fertility rate, whilst shorter DRIL and higher number of ewes that lambed in a shorter time frame were recorded both in RM and RMR groups, compared to controls. The findings highlighted that melatonin treatment in rams and their replacement allowed advancing first mating, increasing fertility rate, and improving lambing concentration.

Abstract

This study aims to find reliable strategies for advancing first mating and shortening the period from weaning to first lambing in ewe lambs. Sarda ewe lambs (n = 400) were selected from two farms and allocated into four separated groups of 100, all of which were exposed to fertile, adult rams over the course of a 50-day breeding period. The first treatment group (RMR) was exposed to four melatonin-treated rams which were replaced every ten days, whilst the second treatment group (RM) was exposed to four melatonin-treated rams which were not replaced. Alternatively, the first control group (RCR) was exposed to four untreated rams which were replaced every ten days, whilst the second control group (RC) was exposed to four untreated rams which were not replaced. In each group, lambing dates, fertility rate, litter size, and distance in days from ram introduction to lambing (DRIL) were recorded. The highest fertility rate was recorded in the RMR group (p ≤ 0.05). Shorter DRIL (p ≤ 0.01) and higher lambing concentrations were recorded in the RM and RMR groups as compared to the controls. The findings indicate that melatonin treatment of rams and their replacement at 10-day intervals results in earlier onset of first mating, increased fertility rate in ewe lambs, and a higher number of ewes that lambs in a shorter time frame.

Dentition can predict maturity in young Merino sheep

Context A unique population of Merino sheep recorded for a range of production and reproduction traits presented an opportunity to calculate sire variation in dentition which may indicate maturity and influence marketing and selection decisions. A change in the definition of ‘lamb’ in the Australian sheep industry warranted an investigation of the relationship between production, reproduction and dentition. Aims To assess the variation in timing of dentition changes in Merino sheep and determine whether there are associations with key production and reproduction traits. Methods A population of 2150 pedigree-recorded Merino sheep were studied to analyse the sire variation in progeny for a range of dentition changes and production and reproduction traits. Dentition phenotypes included the age animals started to lose the deciduous lamb teeth, the age when one permanent incisor was in wear and the amount of time between these two events. Production records included bodyweight, fat and muscle traits. Reproduction records from the female progeny included the outcome of pregnancy scanning after the first joining opportunity. Sire variation for the age dentition changed was analysed. The effect of progeny age at hogget categorisation on production and reproduction was analysed. Key results Progeny that were heavier, fatter and with higher muscle measurements matured earlier. Female progeny were more likely to be pregnant if classed as hoggets earlier in life. Conclusions Dentition records provided useful indicators of maturity in Merino sheep in this study and can be used to inform decisions regarding the timing of marketing options and the likelihood of success when assessing female progeny for suitability to join at ~18 months of age. Implications Merino sires can exhibit a wide range of variation with respect to the age at which their progeny will mature, as indicated by their dentition. If animals are heavier at an earlier age, they are more likely to mature earlier, which has to be considered when planning nutritional requirements for growing out young male progeny, and females could be more successful as young breeders. Dentition is a useful tool to indicate maturity in young Merino sheep.

Is it time to reconsider the relative weight of sociosexual relationships compared with photoperiod in the control of reproduction of small ruminant females?

In goats and sheep from the temperate and subtropical latitudes, the breeding season lasts from early autumn to late winter, whereas the anestrous season lasts from late winter to late summer. In prepubertal or postpartum females, the duration of the quiescent period depends mainly on the season of parturition and of nursing duration. In both situations, the ovulatory activity starts only during the breeding season. Photoperiod has been generally considered as a major regulator of all these periods of reproductive activity/inactivity in female sheep and goats (ie puberty, seasonal anestrus, postpartum anestrus). In particular, regarding seasonal anestrus, the sociosexual interactions between males and females have been considered to have only a modulatory role, limited to few weeks preceding the onset or after the offset of the breeding season. Nonetheless, we recently showed that the use of sexually active males plays a crucial role to trigger ovulatory and estrous activities during the anestrous season and also in prepubertal and postpartum females. In fact, in females exposed to sexually active males, puberty is strikingly advanced in comparison with females exposed to sexually inactive castrated males or to isolated females (6 mo vs 7.5 mo). Most females (>85%) exposed during the anestrous season to sexually active males ovulated, whereas a low proportion of them ovulated when in contact with sexually inactive males (<10%). Interestingly, the presence of these sexually active males allows females to ovulate all the year round and prevents the seasonal decrease of LH plasma concentrations in ovariectomized females treated with an estradiol implant. Finally, the presence of sexually active males triggers ovulation in postpartum anestrous females nursing their offspring. All these findings show that sexually active males can play an important role to reduce anestrous periods. We need, therefore, to reconsider the relative weight of sociosexual relationships, compared with photoperiod, in the management of reproduction of goat does and ewes.

Onset of puberty and regularity of oestral cycles in ewe lambs of four breeds under high-altitude conditions in a non-seasonal country

Twenty-four Colombian Creole, Romney Marsh, Hampshire and Corriedale ewes raised under high-altitude conditions in a non-seasonal country were used to determine and to characterize the onset of puberty and of regularity ovarian function since the age of 3months. They underwent blood collection for determination of progesterone and monthly weight assessment. Oestrus was assessed daily by a teaser ram. In all breeds, age at onset of puberty ranged from 5.4 to 6.9 months and age at onset of regular ovarian function ranged from 7.4 to 8.6 months. Colombian Creole showed a higher body development at onset of puberty: 73.5 ± 8.3% versus 56.2 ± 7.4 in Romney Marsh, 58.8 ± 10.4 in Hampshire, and 57.3 ± 8.0 in Corriedale (p < 0.05), as well as a higher relative daily weight gain (+17%, p < 0.05). A negative correlation between daily weight gain and age at onset of puberty was established. Progesterone at onset of puberty and of regularity did not differ between breeds, but characterization of the luteal phase by the progesterone area under the curve (P4-AUC) revealed at both time points significantly lower values for Creole lambs (p < 0.05). Decreased P4-AUC paralleled a higher proportion of short oestral cycles observed prior to onset of regularity in Creoles, whereas an increased proportion of extra-long cycles were recorded in Romney Marsh (p < 0.05). These results establish first reference data for economically important breeds raised under tropical conditions. In comparison with other breeds, Colombian Creole requires a higher body development to achieve puberty and that an important proportion of short characterizes its prepubertal period cycles.

An historical view of the experimental leptospiral infection in ruminants

The first experimental infections with Leptospira in ruminants were conducted in the 1950s, primarily assessed the pathogenesis caused by serovar Pomona in cows. Throughout the decades, experimental infections have also demonstrated the clinical aspects of the infection by other strains, mainly Hardjo. Despite the important outcomes observed in experimental infections in ruminants, there is still a large discrepancy regarding the ideal dose, route, strain, model species or animal age that should be used to reproduce the acute and chronic leptospirosis in ruminants. In this context, the present study aimed to review the historical processes involved on the experimental leptospiral infection in ruminants. The inclusion criteria were papers that clearly described inoculation route, strain, dose, clinical signs and animal age. Overall, 37 experiments were noted. The most frequently reported clinical signs were fever, prostration, hematuria and death, with the majority of them occurring in young animals infected by incidental strains. Regarding reproductive problems, they occurred in the majority of the experiments and were also more related to incidental strains. In this context, abortions, retained placenta and weak fetuses were the most frequent symptoms. Noteworthy that although the mechanisms of the clinical acute disease either systemic or reproductive, is reasonably well understood, the physiopathology involved on reproductive problems due to the silent chronic infection is less discussed and remains to be elucidated. In this context, it is evident the need for studies focused on the genital infection and reproductive aspects of leptospiral infection in ruminants.

Effects of letrozole administration on growth and reproductive performance in Markhoz goat bucklings

This study evaluated the growth performance, testicular and semen characteristics, and hormonal profile of Markhoz (Iranian Angora) bucklings injected with letrozole (LTZ). Twenty-eight 4-4.5 month old bucks were randomly assigned into four groups and received either 0.25 mg/kg body weight (BW) LTZ subcutaneously (sc LTZ) or intramuscularly (im LTZ), and also sc (sc CONT) or im (im CONT) controls every week for 3 months. The study was performed at the beginning of the breeding season in Sanandaj Animal Husbandry Research Station (46.99 °E, 35.31 °N). The results showed that LTZ causes increased final body weight (25.78 ± 1.61 kg), higher average daily gain (104 ± 0.03 g/days), and decreased feed conversion ratio (7.81 ± 2.57) (P < 0.05). The pre-slaughter, hot, and cold carcass weights (27.56 ± 2.40, 11.45 ± 1.07 and 11.11 ± 1.05 kg, respectively) were (P < 0.05) heavier in LTZ groups while other carcass characteristics did not differ between groups. No differences occurred between the groups in biochemical parameters, except high-density lipoprotein levels (35.47 ± 2.43 mg/dL) which was higher in LTZ treatments (P < 0.05). LTZ-treated bucks had larger scrotal circumference (20.12 ± 5.75 cm), higher relative testicular weight (560.91 ± 78.59 mg/100 g BW) and volume (175.5 ± 29.71 cm³), greater diameter of seminiferous tubules (224.5 ± 5.21 μm), and number of Sertoli cells (8.39 ± 0.77) (P < 0.05). Semen volume (0.74 ± 0.16 mL), sperm concentration (2.64 ± 0.19 × 10^-9/mL), total sperm per ejaculate (1.95 ± 0.49 × 10^-9), and semen index (1248 ± 323) increased (P < 0.05) by LTZ treatments, while semen pH (6.77), motility (80.91%), progressive motility (76.75%), viability (83.35%), abnormality (13.70%), acrosome integrity (78.06%), and membrane integrity (80.05%) of sperm remained unaffected. Intratesticular and serum testosterone (T) levels (7.97 ± 0.89 ng/mg protein and 2.47 ± 0.59 ng/mL, respectively), serum luteinizing hormone (LH), growth hormone (GH) levels (1.71 ± 0.24 and 3.62 ± 0.33 ng/mL, respectively) of LTZ groups were elevated, whereas intratesticular and serum estradiol (E2) levels (84.14 ± 8.15 pg/mg protein and 32.33 ± 2.16 pg/mL, respectively) decreased (P < 0.05). No differences were recorded between the sc and im routes of LTZ administration in the measured parameters. To conclude, we have found that LTZ treatment improves growth and reproductive functions of goat bucklings associated with increased serum LH and GH, elevated T and reduced E2 levels in both serum and testis.

Differential role of r-met-hu G-CSF on male reproductive function and development in prepubertal domestic mammals

The understanding of mammalian spermatogenesis niche factors active during sexual development may be leveraged to impact reproduction in farm animals. The aim of this study was to evaluate the effects of r-met-hu/G-CSF (filgrastim) on prepubertal sexual development of guinea pigs (Cavia porcellus) and ram lambs (Ovis aries). Individuals of both species were administered r-met-hu/G-CSF daily for 4 days. During and after administration protocols, testicular function and development were assessed through hematological responses, hormonal profiles (gonadotropins, testosterone and cortisol) testicular morphometry and germ cell kinetics. As expected, r-met-hu/G-CSF acutely mobilized white-lineage blood cells in both species. LH was increased by r-met-hu/G-CSF in guinea pigs (P<0.01) but T remained unchanged. In ram lambs gonadotropins and T increased in dose-response fashion (P<0.01) while cortisol values were stable and similar in treated and control animals (P>0.05). In guinea pigs there were no differences in testicular weights and volumes 2-mo after r-met-hu/G-CSF application (P>0.05). However, ram lambs showed a dose-response effect regarding testis weight (P<0.05). 66.66% of ram lambs had initial testes not yet in meiosis or starting the first spermatogenic wave. After 60-days only 25% of control animals were pubertal while all treated animals (1140-μg) had reached puberty. We propose an integrated hypothesis that G-CSF can stimulate spermatogenesis through two possible ways. 1) r-met-hu/G-CSF may go through the brain blood barrier and once there it can stimulate GnRH-neurons to release GnRH with the subsequent release of gonadotrophins. 2) a local testicular effect through stimulation of steroidogenesis that enhances spermiogenesis via testosterone production and a direct stimulation over spermatogonial stem cells self-renewal. In conclusion, this study shows that r-met-hu/G-CSF differentially affects prepubertal sexual development in hystricomorpha and ovine species, a relevant fact to consider when designing methods to hasten sexual developmental in mammalian species.

Effect of selenium supplementation on attainment of puberty in Saanen male goat kids

The aim of the study was to evaluate the effect on selenium supplementation on attainment of puberty in Saanen male goat kids. Forty Saanen male goats kids were divided into two groups: selenium supplemented (n = 20) and control (n = 20). The treatment group received sodium selenite at a ninety days interval for an experimental period of 150 days. All experimental Saanen male goat kids were fed Lucerne hay deficient in selenium. The development of the reproductive functions of the male goat kids was monitored until puberty. At the age of 5.5 months motile spermatozoa were collected from 65% of the supplemented group compared to 35% of the control. At 140 days following supplementation the treated group showed significantly higher semen volume per ejaculate and improved semen quality in the form of improved spermatozoa motility and concentration and a decreased percentage of dead spermatozoa, spermatozoa abnormalities and acrosome damage compared to the control. Supplementation with selenium significantly (P < 0.05) improved body weight, testicular measurements and decreased age at puberty. Selenium supplementation also led to higher (P < 0.05) LH and testosterone concentrations. It is concluded that selenium supplementation hastened age at attainment of puberty to 5.5 months in male Saanen kids as the control group attained puberty at 6 months. It also improved semen quality and reproductive hormones concentration of Saanen kids.

Productive performance and reproductive characteristics of Morada Nova male lambs fed with high-energy diet

Morada Nova breed sheep are without wool, tropicalized, small-sized animals, known for their high-quality meat and skin. Their body development naturally depends on the genetic potential and adequate nutritional support, which suggests that the offer of high-energy density diets positively influences their productive indicators. Thus, the present study investigated the effect of a high-energy diet for the Morada Nova lambs on body development and testicular function, considering their histomorphometric characteristics and seminal quality. Forty-two males (19.2 weeks, 20.7 ± 3.5 kg) were equally divided into two groups and fed with 2.05 Mcal (G7, n = 21) or 2.37 Mcal (G24, n = 21) of metabolizable energy/day, equivalent to 7% and 24% above the minimum for growing lambs. The animals were confined for 23 weeks (W0 to W23). Weight and body score differed significantly from the W1 (P < 0.05). From the W5, thoracic perimeter, body length, wither height, and rump attributes were higher in G24 (P < 0.05). The scrotal circumference and testicular volume were higher in G24 from the W3 (P < 0.05). Although testosterone levels were not affected (P = 0.05), the highest energy intake increased the diameter of the seminiferous tubules and the development of the epididymal epithelium (P < 0.05). This positively influenced the seminal quality and reduced the minor defects (21.87% vs. 17.13%) and the total spermatic defects (26.34% vs. 21.78%, P < 0.05). Thus, it is possible to employ higher levels of dietary energy for Morada Nova young males to express higher productive efficiency and earlier reproductive attributes of interest.

Ovarian follicular development, hormonal and metabolic profile in prepubertal ewe lambs with moderate dietary restriction and lipid supplementation

To evaluate the effects of moderate dietary restriction and lipid supplementation on ovarian follicular development, hormonal and metabolic profile, thirty-five prepuberal ewe lambs were blocked by body weight and randomly assigned to treatments: ALUS (control) - unsupplemented-diet ad libitum (3.5% ether extract, n = 9); R-US - intake restricted to 85% of the ALUS diet (n = 9); AL-LS - lipid-supplemented-diet ad libitum (9.8% ether extract, n = 8); R-LS - intake restricted to 85% of the ALLS diet (n = 9), from 95 ± 8 days of age until estrus or 7 months of age. Lipid supplementation did not reduce dry matter intake. Daily weight gain was greater in lambs fed ad libitum. Plasma glucose was greater in the RLS treatment group, while serum insulin was less with lipid supplementation. There was a treatment by age interaction on total cholesterol, HDL cholesterol and triglyceride serum concentrations. Estrus was detected in 43% of the animals and the overall ovulation rate was 60%. The number of follicles, diameter of the largest follicle, body weight, age and serum progesterone at puberty did not differ among treatment groups. The mean diameter of the largest follicle was greater in lambs having than in those not having ovulations and increased with age in both groups. There was an interaction between the effects of occurrence of ovulation and age on the number of follicles between 3 and 5 mm and > 5 mm. Lipid supplementation and dietary restriction altered the metabolic profile in ewe lambs with no concomitant changes in values for reproductive variables.

Effects of dietary ferulic acid on reproductive function and metabolism of pre-pubertal hairbreed ewes during the anestrous season

This study aimed to evaluate the effects of dietary supplementation of ferulic acid (FA) on reproductive tract weight (RTW), ovarian activity and serum concentrations of some metabolites and thyroid hormones of pre-pubertal hairbreed ewe lambs during the natural anestrous season. Twenty Dorper x Pelibuey crossbred ewe lambs (initial body weight = 28.5 ± 0.5 kg and age = 5.0 mo) were fed a basal diet and assigned to two treatments (n = 10) under randomized complete block design: FA supplementation to dosages of 0 (control) or 300 mg of FA/d animal^-1. Females were treated with FA during 34 d and then slaughtered to evaluate RTW and ovary. Blood samples were collected at days 1 and 34 to determine serum concentrations of metabolites (i.e. glucose, cholesterol, triglycerides, urea and total protein) and thyroid hormones. Final weight, dry matter intake, and serum concentrations of metabolites (except glucose) and thyroid hormones were unaltered by FA. Compared to control, FA-fed ewe lambs had lower (P = 0.05) serum glucose level but higher (P ≤ 0.05) RTW, ovarian mass, number of larger follicles and corpus luteum (CL). While percentage of ewe lambs with small follicles and number of small follicles per female did not vary, percentage of ewe lambs with large follicles and CL increased (P = 0.02) with FA. In conclusion, FA supplementation improves the reproductive tract development and ovarian activity of pre-pubertal hairbreed ewe lambs during the natural anestrous season. An improvement in functionality of the glucose-insulin system could be related with this benefic effect of FA.

Influences of different dietary energy level on sheep testicular development associated with AMPK/ULK1/autophagy pathway

Energy balance is an important feature for spermatozoa production in the testis. The 5'-AMP-activated protein kinase (AMPK) is a sensor of cell energy, has been implicated as a mediator between gonadal function and energy balance. Herein, we intended to determine the physiological effects of AMPK on testicular development in feed energy restricted and compensated pre-pubertal rams. Lambs had restricted feeding for 2 months and then provided compensatory feeding for another 3 months. Feed levels were 100%(control), 15% and 30% of energy restriction (ER) diets, respectively. The results showed that lambs fed the 30% ER diet had significantly lower testicular weight (P < .05) and spermatids number in the seminiferous tubules, but there were no differences between control and 15% ER groups. Meanwhile, 15% ER and 30% ER diets induced testis autophagy and apoptosis through activating AMPK-ULK1(ULK1, Unc-51 like autophagy activating kinase) signal pathway with characterization of increased Beclin-1 and Light chain 3-Ⅱ/Light chain 3-Ⅰ (LC3-II/LC3-I) ratio, up-regulated the ratio of pro-apoptotic Bcl-2-associated X protein (BAX) and anti-apoptotic B-cell lymphoma 2 (Bcl-2), as well as activated AMPK, phosphorylated AMPK(p-AMPK) and ULK1. Furthermore, a compensation of these parameters occurred when the lambs were re-fed with normal energy requirement after restriction. Taken together, dietary energy levels influence testicular development through autophagy and apoptosis interplay mediated by AMPK-ULK1 signal pathway, which also indicates the important role of the actions of AMPK in the testis homeostasis.

Interactions between parasitic infections and reproductive efficiency in sheep

This review article summarises the many reports in the literature, confirming that, in sheep, parasitic infections can adversely affect reproductive efficiency; examples, which refer to all parts of the reproductive cycle of sheep, are as follows: trichostrongylosis in ewe-lambs (which can lead to delayed attainment of puberty), myiosis of the prepuce (which can cause impediment of mating), chorioptic mange or trypanosomosis in rams (which can lead to testicular degeneration or azoospermia, respectively), trypanosomosis or sarcoptic mange in pre-conceptual ewes (which can lead to poor conception rates or reduced number of ovulations, respectively), toxoplasmosis or neosporosis in pregnant ewes (which are causes of abortion), trichostrongylosis or trematode infections in lactating ewes (which can cause reduction of milk yield and can be a risk factor for mastitis, respectively), cryptosporidiosis in newborn lambs (which can be a cause of deaths), coccidiosis in growing pre-weaned lambs (which can cause suboptimal growth rate). In other cases, the reproductive status of the animal can influence the parasitic infection; examples are as follows: the increase in faecal parasitic output during the peri-parturient period (as a consequence of the peri-parturient relaxation of immunity), the heavier trichostrongylid infections of twin lambs compared to lambs from single parities (as a consequence of developmental origin issues in twin lambs). All the above examples support the idea of presence of interactions between parasitic infections and reproductive efficiency in sheep.

Correlations among ultrasonographic and microscopic characteristics of prepubescent ram lamb testes

The onset of spermatogenesis during prepubertal development is accompanied by dynamic changes in testicular microstructure. Computer-assisted analysis of scrotal ultrasonograms may allow us to track these changes in a noninvasive manner; however, the echotextural characteristics of different histomorphological variables remain unclear. Hence the objective of this study was to compare echotextural and microscopic attributes of the testis over the first wave of spermatogenesis in prepubescent ram lambs. Bi-weekly ultrasound examinations and weekly testicular biopsies were carried out in 22 ram lambs from 9.5–10 weeks of age or the attainment of 15 cm3 in testicular volume, respectively, to the first detection of elongated spermatids (ESt). Testicular echogenicity was highly variable with age; however, after the alignment of data to the first detection of ESt, there was an initial increase followed by a decline, corresponding to the mitotic and postmitotic phases of spermatogenesis in prepubescent ram lambs. Testicular echotextural attributes (mean numerical pixel values and pixel heterogeneity) correlated with seminiferous tubule (ST) diameter, the number of degenerating cells/ST cross-section (XS), and the number of ubiquitin C-terminal hydrolase L-1 (a marker for prespermatogonia and undifferentiated spermatogonia) staining cells/ST XS during the mitotic and postmitotic phases. Additionally, in the postmitotic phase, significant correlations were recorded between the quantitative echotextural characteristics and ST cell density, nuclear:ST area and percentages of STs with different spermatogenic cells as the most mature germ cell type present. These results indicate that ram testes exhibit distinctive echotextural characteristics during the mitotic and postmitotic phases of germ cell differentiation. It is concluded that scrotal ultrasonography in conjunction with computerized image analysis holds potential as a noninvasive alternative to testicular biopsy in monitoring the reproductive status throughout different stages of testicular development.

Ovarian and uterine characteristics and onset of puberty in adolescent offspring: effects of maternal diet and selenium supplementation in sheep

The aim of this study was to determine the effects of maternal diet with adequate (A) or high (H) selenium (Se) supplementation on ovarian and uterine characteristics, and onset of puberty in adolescent offspring. Sheep were fed a maintenance (M) diet with ASe or HSe levels from breeding to parturition. From Day 50 to parturition, a portion of the ewes from ASe and HSe groups was fed restricted (R, 60% of M) or excess (E, 140% of M) diet. Immediately after birth, lambs were separated from their dams and given artificial colostrum for 20 hours, followed by milk replacer. From Day 57.3 ± 0.6, ewe lambs were fed a pelleted grower diet until Day 116.3 ± 0.6 when they were transitioned to a finisher diet. From Day 99 to 180, serum samples were collected weekly from jugular vein for progesterone analysis to determine onset of puberty. Reproductive tissues were collected on Day 180.1 ± 0.4 of age. Maternal diet or Se supplementation did not affect uterine or ovarian weight and onset of puberty. However, area under the curve for progesterone was greater (P = 0.05) in ASe compared with HSe groups, and was greater in ASeM than HSeM group. In CLs, labeling index (LI; a proportion of proliferating cells) was less (P < 0.04) in HSeM than ASeM group, and in stroma was less (P < 0.05) in R and E groups than M group. Maternal diet did not affect the LI of any follicle types. For all groups combined, LI was the greatest (P < 0.001) in antral, less in early antral and secondary, and the least in atretic follicles. Our results demonstrate that maternal diet influenced ovarian but not uterine characteristics or onset of puberty. These results indicate that maternal plane of nutrition and/or Se supplementation may have specific effects on reproductive function in offspring.