Ovarian follicular development in cattle selected for twin ovulations and births12

Integration of transcriptomic and metabolomic analysis of the mechanism of dietary N-carbamoylglutamate in promoting follicle development in yaks

Yak is the main livestock in the highlands of China. The low reproductive rate of yaks is a serious constraint on their production and utility. N-carbamylglutamate (NCG) can increase arginine synthesis in mammals and has been shown to improve reproductive performance. Twelve multiparous and simutaneous anoestrous female yaks were randomly divided into two groups, one of which was fed the basal diet (Control, n = 6), and the other was fed the basal diet supplemented with NCG at 6 g/day/yak (NCG, n = 6). All yaks were slaughtered on the 32nd day (the time predicted for the selection of the last wave of dominant follicles), and their ovarian tissues were collected and follicles were classified. NCG supplementation increased the number of large ovarian follicles (diameter > 10 mm), as well as caused significant changes in the transcriptional and metabolic levels in yak ovaries which due to the differential expression of 889 genes and 94 metabolites. Integrated analysis of the transcriptomics and metabolomics data revealed that the differentially expressed genes and differential metabolites were primarily involved in the process of energy metabolism, amino acid metabolic pathways, carbohydrate metabolic pathways, and lipid metabolic pathways. The highlighted changes were associated with amino acid synthesis and metabolism, ovarian steroid hormone synthesis, the pentose phosphate pathway, and the tricarboxylic acid cycle, suggesting that NCG supplementation may promote estrogen synthesis and help regulate follicular development by altering the pathways associated with glucose catabolism. The results present important clues for understanding the mechanisms by which NCG supplementation promotes follicular development in yaks. The findings of this study provide a basis for the development and application of NCG in optimizing animal reproduction, including yak reproductive performance, which may help optimize livestock management and uplift the pastoral economy.

A Novel SNP in the Promoter Region of IGF1 Associated With Yunshang Black Goat Kidding Number via Promoting Transcription Activity by SP1

IGF1, a member of the insulin-like growth factor (IGF) superfamily, is also known as the growth-promoting factor (somatomedin C). IGF1 is involved in vertebrate growth and development, immunity, cell metabolism, reproduction, and breeding. However, there are relatively few studies on the relationship between IGF1 and goat reproduction. In this study, a new transcription factor SP1 bound to the IGF1 g. 64943050T>C promoted granulosa cell (GC) proliferation. A mutation g.64943050T>C located in the promoter region of IGF1 was identified. Association analysis revealed that the kidding number in the first and second litters and the average number of first three litters of the CC genotype (2.206 ± 0.044, 2.254 ± 0.056, and 2.251 ± 0.031) were significantly higher than those in the TC genotype (1.832 ± 0.049, 1.982 ± 0.06, and 1.921 ± 0.034) and TT genotype (1.860 ± 0.090, 1.968 ± 0.117, and 1.924 ± 0.062) (p < 0.05). The kidding number in the third litter of the CC genotype (2.355 ± 0.057) was significantly higher than that in the TT genotype (2.000 ± 0.107) (p < 0.05). Then, the function of this mutation was validated by the dual-luciferase reporter assay and EMSA. The results showed that the luciferase activity of IGF1-mutant-C was significantly higher than that of IGF1-Wild-T (p < 0.05). The EMSA also showed that the binding ability of IGF1-mutant-C was higher than that of IGF1-Wild-T (p < 0.05). Subsequently, the transcription factor SP1 was predicted to bind to the mutation of IGF1 (g.64943050T>C). Overexpression of SP1 promotes the expression of IGF1 in the primary granulosa cells (GCs). The results of the CCK-8 assay and the expression of GC proliferation factors (CDK4, cyclin D1, and cyclin D2) demonstrated that SP1 promoted GC proliferation by regulating IGF1 expression. Our results suggested that the IGF1 g.64943050T>C was significantly associated with the kidding number of Yunshang black goats, and SP1 as a transcription factor of IGF1 binding to the mutation T>C regulated the expression of IGF1. Furthermore, SP1 promoted goat GC proliferation by regulating the expression of IGF1, which provides a new insight for the goat fertility trait.

Follicular Size Threshold for Ovulation Reassessed. Insights from Multiple Ovulating Dairy Cows

Simple Summary

The selection of a single ovarian follicle able to differentiate and ovulate is a phenomenon common to monovular species including humans. The selected follicle acquires the capacity to ovulate when it reaches a diameter of about 10 mm. In cows with a single follicle of ovulatory size, the probability of ovulation significantly increases with follicle diameter. However, two or more follicles of ovulatory size are often present at estrus. In cows with one follicle of ovulatory size and another follicle of 7–9 mm, the small follicle may, under certain circumstances, ovulate producing a pregnancy.

Abstract

In Bos. taurus cattle, follicular deviation to dominance begins when the selected ovulatory follicle reaches a mean diameter of 8.5 mm. The dominant follicle acquires the capacity to ovulate when it reaches a diameter of about 10 mm. In this study, data derived from 148 cows in estrus with one follicle of ovulatory size and another of 7–9 mm, reveal that the small follicle has the capacity to ovulate alone or with the dominant follicle; thus, giving rise to a single or twin pregnancy. This indicates that a follicle of deviation size may ovulate in the presence of a follicle of ovulatory size.

Follicular development in livestock: Influencing factors and underlying mechanisms

Livestock farming development has become increasingly important in recent years. It not only provides us with meat nutrition and pet feeding but also increases the economic value by providing numerous employment opportunities, which improves our life quality. The livestock farming development depends on successful animal reproduction. As a vital process in animal reproduction, folliculogenesis and its influencing factors as well as their underlying mechanisms need to be understood thoroughly. This review is aimed at summarizing the factors such as cellular processes, gene regulation, noncoding RNAs and other endocrine or paracrine regulatory factors that affect follicular development, and their underlying mechanisms of action in livestock in order to provide novel insights for future studies. The above factors were found as significant determinants influencing the follicular development in livestock through various signaling pathways.

Transcriptomic data of bovine ovarian granulosa cells of control and High A4 cows

Microarray analysis using Affymetrix Bovine GeneChip 1.0 ST Array to determine RNA expression analysis was performed on somatic granulosa cells from two different groups of cows classified based on androstenedione concentration within the follicular fluid (Control vs High A4) of estrogen-active dominant follicles. The normalized linear microarray data was deposited to the NCBI GEO repository (GSE97017 - RNA Expression Data from Bovine Ovarian Granulosa Cells from High or Low Androgen-Content Follicles). Subsequent ANOVA determined genes that were enriched (≥ 1.5 fold more) or decreased (≤ 1.5 fold less) in the High A4 granulosa cells compared to Control granulosa cells and analyzed filtered datasets of these differentially expressed genes are presented as tables. MicroRNAs that are differentially expressed in Control and High A4 granulosa cells are also reported in tables. The standard deviation of the analyzed array data in relation to the log of the expression values are shown as a figure. Ingenuity Pathway Analysis determined upstream regulators of differently expressed genes as presented in a table. These data have been further analyzed and interpreted in the companion article "A High-Androgen Microenvironment Inhibits Granulosa Cell Proliferation and Alters Cell Identity" (McFee et. al., 2021 [1].

The ovarian follicle of ruminants: the path from conceptus to adult

This review resulted from an international workshop and presents a consensus view of critical advances over the past decade in our understanding of follicle function in ruminants. The major concepts covered include: (1) the value of major genes; (2) the dynamics of fetal ovarian development and its sensitivity to nutritional and environmental influences; (3) the concept of an ovarian follicle reserve, aligned with the rise of anti-Müllerian hormone as a controller of ovarian processes; (4) renewed recognition of the diverse and important roles of theca cells; (5) the importance of follicular fluid as a microenvironment that determines oocyte quality; (6) the 'adipokinome' as a key concept linking metabolic inputs with follicle development; and (7) the contribution of follicle development to the success of conception. These concepts are important because, in sheep and cattle, ovulation rate is tightly regulated and, as the primary determinant of litter size, it is a major component of reproductive efficiency and therefore productivity. Nowadays, reproductive efficiency is also a target for improving the 'methane efficiency' of livestock enterprises, increasing the need to understand the processes of ovarian development and folliculogenesis, while avoiding detrimental trade-offs as greater performance is sought.

A high-androgen microenvironment inhibits granulosa cell proliferation and alters cell identity

A naturally occurring bovine model with excess follicular fluid androstenedione (High A4), reduced fertility, and polycystic ovary syndrome (PCOS)-like characteristics has been identified. We hypothesized High A4 granulosa cells (GCs) would exhibit altered cell proliferation and/or steroidogenesis. Microarrays of Control and High A4 GCs combined with Ingenuity Pathway Analysis indicated that High A4 GCs had cell cycle inhibition and increased expression of microRNAs that inhibit cell cycle genes. Granulosa cell culture confirmed that A4 treatment decreased GC proliferation, increased anti-Müllerian hormone, and increased mRNA for CTNNBIP1. Increased CTNNBIP1 prevents CTNNB1 from interacting with members of the WNT signaling pathway thereby inhibiting the cell cycle. Expression of CYP17A1 was upregulated in High A4 GCs presumably due to reduced FOS mRNA expression compared to Control granulosa cells. Furthermore, comparisons of High A4 GC with thecal and luteal cell transcriptomes indicated an altered cellular identity and function contributing to a PCOS-like phenotype.

Thermal Mechanisms Preventing or Favoring Multiple Ovulations in Dairy Cattle

Simple Summary

While cows are usually monovular, the incidence of dizygous twin births has recently increased considerably alongside increasing milk production. Genetic progress and improvements in nutrition and management practices have led to a continuous increase in milk yield and thus also to multiple ovulations and twin pregnancies. Twin pregnancies are undesirable as they seriously compromise the welfare of the cow and herd economy. A better understanding of the processes associated with multiple ovulations should help to reduce rates of twinning. During the stages of the sexual cycle, temperature gradients are established within the ovary and throughout the genital tract. Pre-ovulatory local cooling of the reproductive system favors male and female gamete maturation and subsequent fertilization. In fact, thermal mechanisms may prevent or favor multiple ovulations and thus twinning. The purpose of this review was to update this topic.

Abstract

While cows are predominantly monovular, over the past 30 years the incidence of multiple ovulations and thus twinning has increased considerably alongside milk production. Multiple pregnancies are not desirable as they negatively affect the health of cows and the herd economy. Although causal mechanisms associated with multiple ovulations have been extensively revised, the process of multiple ovulations is not well understood. Recent studies on the thermal biology of the reproductive system have shown how thermal mechanisms may prevent or favor multiple ovulations. This review focuses on this relationship between thermal dynamics and multiple pregnancies. Cooling of the pre-ovulatory follicle is able to regulate ovulation. In effect, pre-ovulatory local cooling of the female reproductive system favors male and female gamete maturation and promotes fertilization. Thermal stress is proposed here as a model of stress. Periods of high ambient temperature affect the processes of pre-ovulatory follicular cooling and multiple ovulations. While the ratio between unilateral and bilateral multiple pregnancies is normally close to one, under heat stress conditions, this ratio may be 1.4 favoring unilateral multiple pregnancies. A ratio approaching unity is here proposed as an indicator of cow wellbeing.

Benefits and Risks of Preventing Twin Pregnancies

Clinical problems associated with twin pregnancies have been well established, and twin births are now considered undesirable or even disastrous for the dairy cattle industry and the individual cow. The high incidence of early fetal loss, abortion during the mid-lactation period, dystocia, stillbirth, and placenta retention should be considered a preventable consequence of management, as these disorders greatly compromise the welfare and productive lifespan of a cow carrying or delivering twins. The use of sexed semen generates herd replacements and additional heifers, so a proposed strategy for twin pregnancy prevention is the transfer of a single in vitro-produced female beef cow embryo to cows not suitable for producing replacements. Another proposed strategy is drainage at insemination of co-dominant follicles to prevent twin pregnancies in cows with genetic merit. As a result, embryo survival should improve, economic losses associated with twin pregnancies will be prevented, beef output from the herd will be increased, and the health and welfare of the cow will certainly benefit. In this review, the clinical prospects of preventing or avoiding twin pregnancies using both procedures are discussed.

Twin Pregnancies in Dairy Cattle: Observations in a Large Herd of Holstein-Friesian Dairy Cows

Simple Summary

Cows have two ovaries, two uterine horns, two oviducts, and a uterine body. Although they are commonly monovular, they can sustain twin or other multiple pregnancies to term. In cows with a single pregnancy, the embryo implants in the uterine horn that is on the side of ovulation where a corpus luteum develops. Multiple pregnancies are classified into bilateral (one or more embryos in each uterine horn) and unilateral (all embryos in the same uterine horn, right or left) and, in both cases, embryos occur on the side of their corresponding corpus luteum or corpora lutea. Multiple pregnancies are undesirable in dairy herds as they compromise the reproductive performance and productive lifespan of cows. The present study sought to: (a) gain information on the incidence of twin pregnancies, (b) assess and expand information on the relative incidence of bilateral twins compared to unilateral twins, (c) confirm corresponding laterality between embryos and corpora lutea, (d) tabulate the frequency of triplets or quadruplets, and (e) evaluate possible effects of environmental heat stress conditions on the incidence of multiple pregnancies. The data for this study were derived from the ultrasonographic examination of 1130 cows carrying twins, triplets, or quadruplets, and 3160 cows carrying singletons.

Abstract

Multiple pregnancies have devastating consequences on the herd economy of dairy cattle. This observational study examines incidence patterns based on data from the ultrasonographic examination of 1130 multiple pregnancies in cows in their third lactation or more carrying twins (98.8%), triplets (1.1%), or quadruplets (0.08%), and 3160 of their peers carrying singletons. Cows became pregnant following a spontaneous estrus with no previous hormone treatments. Irrespective of a significant decrease (p < 0.0001) in the conception rate (28–34 days post-insemination) during the warm period of the year, the multiple pregnancy rate was similar for both warm (26.5%) and cool (26.3%) periods. The incidence of unilateral multiple pregnancies (all embryos in the same uterine horn) was higher than that of bilateral pregnancies (at least one embryo in each uterine horn): 54.4% versus 45.6% (p < 0.0001). This difference rose to 17% during the warm season (p = 0.03). Pregnancy was monitored in unilateral multiple pregnancies until abortion or parturition (n = 615). In the warm period, the parturition rate was 43% compared to 61% recorded in the cool period (p < 0.0001). Thus, a warm climate is the main factor compromising the fate of multiple pregnancies. Some clinical suggestions are provided.

Twins in Dairy Herds. Is It Better to Maintain or Reduce a Pregnancy?

Simple Summary

In dairy herds, twin or other multiple pregnancies are not desirable as they compromise the health and productive lifespan of the cows. The mean productive lifespan of primiparous and secundiparous dairy cows delivering twins is about 300 and 200 days shorter, respectively, than that of cows delivering singletons. In addition, the long-term negative effects of twinning are not limited to the early lactation but continue for a period of up to 800 days after calving. Herd management options after diagnosing a twin pregnancy are discussed from an animal health and economic perspective.

Abstract

Multiple ovulations and so multiple pregnancies have increased recently in dairy cattle. The incidence of the double ovulation impact in high producers at insemination may be over 20%. Twin pregnancies are undesirable as they seriously compromise the welfare and productive lifespan of the cow and herd economy. Clinical problems extend from the time of pregnancy diagnosis to pregnancy loss, abortion or parturition. Early pregnancy loss or abortion of multiple pregnancies lead in most cases to culling. In cows reaching their term, mean productive lifespan is up to about 300 days shorter for cows delivering twins than for cows delivering singletons. While there is an urgent need to address multiple pregnancy prevention procedures in the foreseeable future, the incidence of twin pregnancies continues to rise in parallel with increased milk production. Herein, we review two contrasting measures proposed for the time of twin pregnancy diagnosis: (1) gonadotropin-releasing hormone treatment for pregnancy maintenance, or (2) embryo reduction. These options are discussed in terms of their implications for individual animal health and herd economy. Our main conclusions find that manual twin reduction has proven to be the best management option, whereas the use of prostaglandin F_2α for inducing abortion may be a better option than doing nothing.

Selection of fewer dominant follicles in Trio carriers given GnRH antagonist and luteinizing hormone action replaced by nonpulsatile human chorionic gonadotropin†

Studying selection of multiple dominant follicles (DFs) in monovulatory species can advance our understanding of mechanisms regulating selection of single or multiple DFs. Carriers of the bovine high fecundity Trio allele select multiple DFs, whereas half-sib noncarriers select a single DF. This study compared follicle selection during endogenous gonadotropin pulses versus during ablation of pulses with Acyline (GnRH antagonist) and luteinizing hormone (LH) action replaced with nonpulsatile human chorionic gonadotropin (hCG) treatment in Trio carriers (n = 28) versus noncarriers (n = 32). On Day 1.5 (Day 0 = ovulation), heifers were randomized: (1) Control, untreated; (2) Acyline, two i.m. doses (Days 1.5 and D3) of 3 μg/kg; (3) hCG, single i.m. dose of 50 IU hCG on Day 1.5 followed by daily doses of 100 IU; and (4) Acyline + hCG. Treatments with nonpulsatile hCG were designed to replace LH action in heifers treated with Acyline. Acyline treatment resulted in cessation of follicle growth on Day 3 with smaller (P < 0.0001) maximum follicle diameter in Trio carriers (6.6 ± 0.2 mm) than noncarriers (8.7 ± 0.4 mm). Replacement of LH action (hCG) reestablished follicle diameter deviation and maximum diameter of DFs in both genotypes (8.9 ± 0.3 mm and 13.1 ± 0.5 mm; P < 0.0001). Circulating follicle stimulating hormone (FSH) was greater in Acyline-treated than in controls. Finally, Acyline + hCG decreased (P < 0.0001) the number of DFs from 2.7 ± 0.2 to 1.3 ± 0.2 in Trio carriers, with most heifers having only one DF. This demonstrates the necessity for LH in acquisition of dominance in Trio carriers (~6.5 mm) and noncarriers (~8.5 mm) and provides evidence for a role of GnRH-induced FSH/LH pulses in selection of multiple DFs in Trio carriers and possibly other physiologic situations with increased ovulation rate.

To What Extent Does Photoperiod Affect Cattle Reproduction? Clinical Perspectives of Melatonin Administration – A Review

The seasonality of reproduction in most mammals is dictated by photoperiod, temperature and nutrition. Melatonin, mainly synthesized in the pineal gland, is generally accepted as the active mediator of photoperiod responses including reproduction. While non-pregnant heifers and cows show continuous sexual activity and are therefore not seasonal breeders, it has been suggested that photo-periodicity may influence the appearance of puberty in heifers and the onset of parturition. Further, the light/dark ratio may influence endocrine patterns of gestation and a shorter light period correlates with the incidence of twin pregnancies. This review considers specific aspects of the effects of photoperiod and melatonin on reproduction in dairy cattle and discusses the clinical applications of melatonin.

Improved embryo survival following follicular drainage of subordinate follicles for twin pregnancy prevention in bi-ovular dairy cows

To prevent twin pregnancies in cattle, a simple transvaginal device can be used for follicular drainage. This study examines embryo survival following follicular drainage of the smaller pre-ovulatory follicle at timed artificial insemination (AI) in cows with a pre-ovulatory follicle in each ovary. The study groups established were a control group of 289 monovular cows, a non-drainage group of 114 bi-ovular cows and a follicular drainage group of 113 bi-ovular cows. All cows undergoing drainage developed a corpus luteum (CL) in the drained ovary. Pregnancy loss was recorded 56 days post-AI in 19.5% of the 149 cows that became pregnant. Pregnancy loss in the drainage group cows not suffering heat stress (3.8%) was significantly lower (P < 0.05) than in control non-heat stressed cows (20.9%) and heat-stressed non-drainage group cows (25%). Results indicate that CL induction by follicular drainage for twin pregnancy prevention may reduce the incidence of pregnancy loss.

Developmental Programming of Fertility in Livestock

Developmental programming became an area of interest to understand negative environmental impacts on progeny performance. Recently, the concept that we may be able to harness developmental programming to target animals to their niche in the production system has gained recognition. Female fertility is an area where developmental programming has been moderately successful; however, the mechanisms remain unclear. Although some studies have demonstrated differences in gonadal development and attainment of puberty in response to developmental programming, these have not translated to improved fertility. To improve response to developmental programming, it is critical to identify factors that contribute to inconsistencies across studies.

Trio a novel bovine high-fecundity allele: II. Hormonal profile and follicular dynamics underlying the high ovulation rate

The newly discovered Trio high-fecundity allele produces multiple ovulations in cattle. This study evaluated (1) size and growth rates of follicles in Trio carriers during a synchronized follicular wave, induced by follicle aspiration; (2) follicle-stimulating hormone (FSH) patterns associated with the follicular wave; (3) size of corpora lutea (CL) and circulating progesterone; and (4) intrafollicular estradiol concentrations prior to normal deviation. Trio carriers had mean dominant follicles that were significantly smaller in diameter and volume than noncarriers. Onset of diameter deviation occurred at ∼3 days after the last follicle aspiration in both genotypes despite Trio carriers having much smaller individual follicles. Follicles of Trio carriers grew at a slower rate than noncarrier follicles (∼65% in mm/day or ∼30% in mm3/day) resulting in much smaller individual dominant follicles (∼25% volume). However, total dominant follicle volume, calculated as the sum of all dominant follicles in each animal, was similar in carriers and noncarriers of Trio throughout the entire follicular wave. Circulating FSH was greater in Trio carriers during the 24 h encompassing deviation. Trio carriers had significantly more ovulations than noncarriers, and individual CL volume was smaller, although total luteal tissue volume and circulating P4 were not different. Thus, increased ovulation rate in Trio carriers relates to smaller individual follicles (one-third the volume) near the time of deviation due to slower follicle growth rate, although time of deviation is similar, with increased circulating FSH near deviation leading to selection of multiple dominant follicles in Trio carriers with similar total follicle volume.

Trio, a novel bovine high fecundity allele: III. Acquisition of dominance and ovulatory capacity at a smaller follicle size

The acquisition of dominance and ovulatory capacity was evaluated in follicles from cows that were carriers or half-sibling noncarriers of the Trio allele. Follicle size at acquisition of follicular dominance was determined by evaluating whether follicles ovulate after GnRH challenge (ovulatory capacity-experiment 1) and by determination of intrafollicular concentrations of estradiol and free insulin like growth factor 1 (IGF1) and relative mRNA expression of cytochrome P450 family 19 subfamily A member 1 (CYP19A1), luteinizing hormone/choriogonadotropin receptor (LHCGR), and pappalysin 1 (PAPPA, previously known as pregnancy-associated plasma protein A, pappalysin 1) in granulosa cells from follicles of different sizes (experiment 2). Ovulatory capacity developed in follicles at 8.3 mm (50% ovulatory capacity) in noncarriers but at smaller sizes (5.5 mm) in Trio carriers. Similarly, in experiment 2, follicles of Trio carriers acquired a dominant phenotype, as determined by intrafollicular estradiol and CYP19A1, LHCGR, and PAPPA mRNA expression in granulosa cells, at significantly smaller sizes but at a similar time after wave emergence. Overall, dominance/ovulatory capacity was acquired when follicles of Trio carriers were ∼30% the size (volume basis) of follicles in noncarriers. In addition, follicles in Trio carriers appear to acquire dominance in a hierarchal manner, as demonstrated by the progressively greater number of follicles with a dominant phenotype between days 2 and 4 after wave emergence. Thus, results from this study provide further support for a physiological model in which selection of multiple follicles in Trio allele carriers is characterized by acquisition of dominance at a smaller follicle size but at a similar time in the follicular wave with multiple follicles acquiring dominance in a hierarchal sequence.

Luteal activity following follicular drainage of subordinate follicles for twin pregnancy prevention in bi-ovular dairy cows

Twin pregnancy is undesirable in dairy cattle. This study examines luteal activity following ultrasound-guided puncture and drainage of the smaller pre-ovulatory follicle at timed AI in cows with a pre-ovulatory follicle in each ovary. Luteal activity was determined through Doppler ultrasonography and plasma progesterone (P4) concentrations. The effects of GnRH treatment on Day 7 post-AI on subsequent luteal activity were also assessed. Two study groups were established: a control group of 29 cows and a follicular drainage (FD) group of 28 cows. After drainage, all cows developed a corpus luteum (CL) in the drained ovary. On Day 21 post-AI, drainage-induced CL and fellow CL were similar in terms of size and vascularization. According to a GLM repeated measures analysis of variance (P < 0.001), non-treated drained cows had lower P4 concentrations on Day 21 post-AI than non-treated non-drained cows, whereas GnRH treated cows, both drained and non-drained, showed the highest P4 concentrations at this time point. Twin pregnancy was recorded in 3 of the 8 pregnant control cows, whereas no twins were observed in the FD group. Our results indicate that luteal structures following follicular drainage were functional. As for the presence of an additional CL, this could suggest a reduced risk of pregnancy loss. In addition, luteal activity was significantly increased following GnRH treatment on Day 7 post-AI in drained cows.

Validation of SNP associations with bovine ovulation and twinning rate

Previous work identified SNP associations with twinning rate in the US Holstein population and developed a model for genomic prediction. The current study was conducted to assess the association of these SNPs with twinning rate and ovulation rate in a genetically diverse, outbred population selected for twinning and ovulation rate. A total of 18 SNPs that were components of a prediction equation for twinning rate in Holstein cattle were genotyped on 731 animals from the USDA Meat Animal Research Center production efficiency or twinning population. These 731 individuals were sires and dams well represented in the pedigrees of animals from the twinner population, and their genotypes were used in predicting genotypes for animals in the larger population (n = 16 035). Twinning rate and ovulation rate were analyzed in a two-trait repeated records analysis with marker associations analyzed individually as fixed effects. Criteria for marker validation were effect estimate with a sign consistent with previous estimates and significance at a nominal P < 0.01. Of the 14 SNPs passing quality control assessments, only one was validated. A SNP in the 5' flanking region of the IGF1 gene, discovered previously in a positional candidate gene analysis, was significantly associated with twinning rate in the USDA twinning population (P < 0.0002). This SNP may have utility in genomic prediction of twinning rate beyond the Holstein population.

Interrelationships among plasma metabolites, production, and ovarian follicular function in dairy cows

Associations of blood metabolites and production variables with ovarian function and parity, specifically, interval to first ovulation (IFO) and the incidence of ovarian cysts (OC) and multiple ovulation (MOV) at the first ovulation postpartum, were determined in lactating dairy cows. This retrospective study involved data on 169 Holstein cows from three studies on the same herd. Blood samples were taken weekly from week −1 to week 4, relative to calving, and transrectal ultrasonography was performed twice weekly from day 7 to day 60 postpartum. The overall IFO was 32.6 ± 1.9 d (mean ± SEM) and did not differ among lactations. Primiparous cows were at a greater risk of failing to ovulate before day 60 postpartum and cows in the third or greater lactation were at a higher risk for OC and MOV. Blood metabolites and production variables indicating a negative energy balance were associated with cows failing to ovulate before day 35 postpartum, but were not related with OC. Increased dry matter intake and milk yield, particularly in second lactation cows, were associated with a higher incidence of OC. While beta-hydroxybutyrate acid and insulin-like growth factor 1 were associated with MOV, the relationship was weak. Reducing negative energy balance is necessary to reduce IFO but may increase the incidence of MOV.

Lack of association between genetic polymorphisms in IGF1 and IGFBP3 with twin births in a Brazilian population (Cândido Godói, Rio Grande do Sul)

Insulin-like growth factor (IGF-1) is an important peptide hormone involved in the reproduction and fetal development of mammals, and it is suggested that it may influence the human twinning rate. This study aimed to test such possible association, investigating the genetic polymorphisms IGF1 (CA)n and IGFBP3 rs2854744 in the population from Candido Godoi (CG), a small city located in the South of Brazil that has a high prevalence of twin births. A case-control study was performed comprising a total of 39 cases (representing about 40% of the mothers of twins who were born in CG after 1995) and 214 controls (mothers of non-twin children), 97 of whom were living in CG while 117 were living in Porto Alegre. DNA was extracted from blood leucocytes and genotyping was performed. According to the statistical analyses, there was no significant difference in the frequencies of both studied genetic polymorphisms when comparing case group with control group. Thus, our results pointed to a lack of association between IGF1 (CA)n and IGFBP3 rs2854744 polymorphisms and twin births in CG, but further investigations in other populations with different characteristics must be performed to confirm the role of IGF-I in human twinning.

The presence of two ovulatory follicles at timed artificial insemination influences the ovulatory response to GnRH in high-producing dairy cows

This study sought to examine the impact of the presence of two co-dominant (ovulatory) follicles at the time of artificial insemination (AI) on the ovulatory response to GnRH given in a fixed-time AI protocol. The study population comprised 622 lactating dairy cows: 306 (49.2%) with a single follicle, 198 (31.8%) with two bilateral follicles (one follicle per ovary) and 118 (19%) with two unilateral follicles (same ovary). Based on odds ratios, cows with two bilateral or unilateral follicles were less likely (by factors of 0.09 and 0.11, respectively) to undergo ovulation failure compared with cows with one follicle (P = 0.01 and P = 0.02, respectively); the likelihood of ovulation failure decreased 0.75 times with every one-mm increase in follicle diameter for cows with a single follicle, whereas individual follicle diameter was not related to ovulation failure in cows with two bilateral follicles (P = 0.001). The likelihood of double ovulation decreased 0.7 times with every one-mm diameter difference between the larger and smaller follicle for all cows with two follicles (P = 0.001), whereas cows with two unilateral follicles showed a higher (P < 0.05) double ovulation rate than cows with two bilateral follicles. In 116 (58.6%) of the cows with two bilateral follicles, only the larger follicle ovulated in 59.5% cows, whereas only the smaller one ovulated in the remaining 40.5% cows. In these cows, a one-mm size difference between the larger and the smaller follicle gave rise to a 1.12-fold increase in the ovulation failure rate for the larger follicles (P = 0.0001). Cows with two bilateral follicles were more likely (by a factor of 1.5) to conceive than cows with one follicle (P = 0.001). Significant right-left differences were not found in cows with two bilateral follicles, whereas the right ovary was more active than the left in the remaining cows. Our results indicate that cows with two co-dominant follicles at AI show different ovulation patterns to those with one dominant follicle. A higher rate of ovulation failure was observed among cows with one follicle than cows with two follicles, whereas the conception rate was higher for cows with two bilateral follicles than for the remaining cows. In cows with two follicles, double ovulations along with ovulation of the smaller follicle were related to the least size difference between the larger and smaller follicle.

Update on Multiple Ovulations in Dairy Cattle

This review updates the causal mechanisms and risk factors for multiple ovulations (MOV) in cattle. Clearly, MOV can lead to twin pregnancies, which negatively affects the health, production, and reproduction of cows. Therefore, a better understanding of the factors causing MOV may help to reduce twinning. Multiple ovulations occur after two or more follicles deviate and achieve codominance. The MOV rate is influenced by a complex network of hormones. For example, MOV is more common during periods of low progesterone (P4), that is, in anovulatory cattle or when luteolysis coincides with the selection of the future ovulatory follicle. There is also strong evidence for the luteinizing hormone (LH) being the primary factor leading to codominance, as high P4 concentrations suppress the transient LH surges and can reduce the ovulation rate in cattle or even inhibit deviation. Rates of MOV are increased in older and higher-producing dairy cows. Increased milk production and dry matter intake (DMI) increases hormone clearance, including P4; however, the association between milk yield and MOV has not been consistent. Additional risk factors for MOV include ovarian cysts, diet, season, and genetics.

Ovulation rate, antral follicle count, and circulating anti-Müllerian hormone in Trio allele carriers, a novel high fecundity bovine genotype

High fecundity genotypes in sheep are a valuable model to study the physiological mechanisms underlying follicle selection and the control of ovulation rate. Similar genotypes in cattle had not been described until the recent identification of a major bovine allele, termed Trio, which had a large effect on ovulation rate. The present study was designed to evaluate ovulation rate, antral follicle count (AFC), circulating ant-müllerian hormone (AMH), and the association among these measures in unstimulated and superstimulated Trio carrier cattle. We hypothesized that AFC and AMH would be variable among individual cows but would be similar between Trio carriers and non-carrier control cows and that there would be no association between these measures of follicle numbers and ovulation rate. In experiment 1, ovulation rate was determined during 4 consecutive estrous cycles in Trio carriers (n = 34) and non-carrier controls (n = 27). Ovulation rate, on average, was greater (P < 0.01) in Trio carriers (3.5 ± 0.2) compared to non-carrier controls (1.1 ± 0.1) with ∼70% of carrier cycles (n = 136) having 3-4 ovulations while only ∼5% had single ovulations. In contrast, non-carrier cycles (n = 108) were mostly single ovulation (89%) with none having more than two ovulations. In experiment 2, AFC, determined at wave emergence, was not different (P = 0.54) between Trio carriers (24.5 ± 1.3; n = 45) and non-carrier controls (23.1 ± 0.9; n = 37), and no correlation was found between AFC and mean ovulation rate in either genotype (r = -0.009 and r = -0.07; P > 0.70, respectively). In Experiment 3, circulating AMH was also not different between genotypes (P = 0.65) while correlations were found between AFC and AMH in Trio carriers (r = 0.43; P = 0.05; n = 27) and non-carrier controls (r = 0.78; P < 0.01; n = 19). In experiment 4, AFC and AMH were determined in Trio-carriers (n = 9) in relation to a synchronized follicular wave which was unstimulated or stimulated with exogenous FSH. Stimulation with FSH increased ovulation rate, compared to unstimulated Trio carriers, however no association was found between AFC or AMH and ovulation rate regardless of whether superstimulation with exogenous FSH was used. In conclusion, the novel high fecundity bovine genotype Trio, results in consistent multiple ovulations despite having similar AFC and AMH. Therefore, our results suggest that differences in antral follicle numbers during the final stages of follicle development are not a key component of the mechanism underlying multiple ovulations in Trio carriers.

Follicular waves and hormonal profiles during the estrous cycle of carriers and non-carriers of the Trio allele, a major bovine gene for high ovulation and fecundity

A high fecundity bovine genotype has recently been discovered and genetic mapping indicates evidence for segregation of a major gene with influence on ovulation rate located on bovine chromosome 10. Cattle carrying the high fecundity allele, referred to as the Trio allele, have multiple ovulations while half-sibling, non-carriers generally have single ovulations. The present study was designed to evaluate follicle wave patterns and associated circulating hormones during the estrous cycle of Trio allele carriers (n = 7) and non-carrier half-sib controls (n = 5). We hypothesized that Trio allele carriers would exhibit multiple smaller dominant follicles and greater circulating FSH than non-carrier controls. The proportion of Trio carrier and non-carrier cows with 2 or 3-wave patterns was not different between genotypes with the majority (>70%) exhibiting 3-wave patterns. Trio carriers had greater (P < 0.01) number of ovulations (∼4 vs ∼1 ovulations) and smaller preovulatory follicles (8.9 vs. 14.9 mm; P < 0.01) than non-carrier controls. However, total luteal tissue volume and circulating progesterone, normalized to the initial ovulation or to the onset of luteolysis, were not different between genotypes (P > 0.10). Follicular waves were found to be associated with an FSH surge in both genotypes. Peak FSH concentration at each follicular wave (3-wave patterns) was not different (P > 0.05) between genotypes, but circulating FSH during the decline and nadir, encompassing the day of deviation, was greater (P < 0.05) in Trio carriers. Despite a difference (P = 0.032) in the length of the estrous cycle (23.0 vs. 25.2 d; Trio carrier and non-carriers respectively), the pattern of follicle growth, such as day of wave emergence, day of follicle deviation, and day of maximum diameter of the dominant follicle, when normalized to the FSH surge of each follicular wave were similar in Trio carriers compared to non-carriers although Trio carriers consistently had much smaller-sized follicles (P < 0.05). Thus, decreased follicle size and greater circulating FSH are key components of the mechanism that produces multiple ovulations in cattle that are carriers of the Trio high fecundity allele.

Development of a GnRH-PGF2α-progesterone-based synchronization protocol with eCG for inducing single and double ovulations in beef cattle

Experiments were designed to investigate the effect of different doses and timing of an eCG treatment given during GnRH-based synchronization protocols on follicular dynamics and fertility in cattle. In Exp. 1, Angus heifers (n = 50) received a 7-d Ovsynch + progesterone protocol (on d 0, GnRH and progesterone insert were administered; on d 7, progesterone insert was removed and PGF2α was injected; and on d 9.5, GnRH was injected 56 h after progesterone removal) with eCG (0, 300, 500, 700, or 1,000 IU) administered on d 7. In Exp. 2, Angus cows (n = 27) received the same protocol as Exp. 1 and were assigned randomly to receive 0 or 400 IU eCG i.m. on d 2 or 7. In Exp. 3, Angus cows (n = 18) received a 6-d Ovsynch + progesterone protocol and were randomly assigned to receive 0 or 800 IU eCG on d 3 of the protocol (Exp. 3a). A pilot field trial was also performed using the same treatments in suckled Angus-cross cows (n = 72; Exp. 3b). In Exp. 4, beef heifers (n = 200) were assigned randomly to the same treatments as in Exp. 3, but the second GnRH was not given, with Holstein bulls introduced on d 6. In Exp. 5, Angus cows (n = 12) received the same treatment as in Exp. 3, but were not inseminated. Progesterone concentrations were assessed in plasma collected during the estrous cycle following synchronization. Ultrasonography was used to monitor ovarian dynamics and to diagnose pregnancy. In Exp. 1, the mean number of ovulations was affected (P < 0.02) by the dose of eCG and the stage of follicular development when administered. Treatment with eCG on d 2 tended (P < 0.08) to extend the interval from PGF2α to ovulation, but was not successful in inducing double ovulations. In contrast, eCG on d 3 increased (P < 0.01) the number of cows with double ovulation when administered i.m. and increased (P < 0.04) pregnancy rate in single ovulating heifers after bull breeding (68.0 vs. 53.1%). This treatment also elevated progesterone concentrations during the estrous cycle following synchronization. Thus, the mechanism by which administration of eCG on d 3 of the synchronization increased pregnancy rates may be through supporting development of a healthy follicle and subsequent corpus luteum capable of secreting increased concentrations of progesterone during early pregnancy. In conclusion, strategic administration of eCG during a synchronization protocol can be used to improve reproductive performance through increased pregnancy rates in single ovulating animals as well as the induction of twin ovulations for twinning.

Involvement of PAPP-A and IGFR1 in Cystic Ovarian Disease in Cattle

Cystic ovarian disease (COD) is one of the main causes of infertility in dairy cattle. It has been shown that intra-ovarian factors, such as members of the insulin-like growth factor (IGF) system, may contribute to follicular persistence. The bioavailability of IGF to initiate its response by binding to specific receptors (IGFRs) depends on interactions with related compounds, such as pregnancy-associated plasma protein A (PAPP-A). The aim of this study was to determine IGFR1 and PAPP-A expression both in follicles at different stages of development and in cysts, to evaluate the roles in the etiopathogenesis of COD in cattle. The mRNA expression of PAPP-A was higher in granulosa cells of large tertiary follicles than in cysts, whereas the protein PAPP-A present in the follicular fluid from these follicles showed no differences. Although no PAPP-A mRNA expression was detected in smaller tertiary follicles, in their follicular fluid, this protease was detected in lesser concentration than in cysts. The mRNA expression of IGFR1 was lower in granulosa cells from cystic follicles than in those from tertiary ones. However, the protein expression of this receptor presented the highest levels in cystic structures, probably to increase the possibility of IGF response. The data obtained would indicate that animals with COD have an altered regulation of the IGF system in the ovary, which could be involved in the pathogenesis of this disease in cattle.

The effect of polymorphism in gene of insulin-like growth factor-I on the serum periparturient concentration in Holstein dairy cows

OBJECTIVE

To investigate the relationship between polymorphism within the 5'-untranslated region (5'-UTR) of IGF-I gene and its periparturient concentration in Iranian Holstein dairy cows.

METHODS

Blood samples (5 mL, n = 37) were collected by caudal venipuncture from each animal into sample tubes containing the EDTA and DNA was extracted from blood. In order to measure IGF-I concentration the collection of blood samples (n = 111) was also done at 14 d before calving (prepartum), 25 and 45 d postpartum.

RESULTS

We found evidence for a significant effect of C to T mutation in position 512 of IGF-I gene on its serum concentration in dairy cows in Iran. Cows with CC genotype had significantly higher concentration (Mean±SD) of IGF-I at 14 d prepartum (91.8±18.1) µg/L compared to those with TT genotype (73.3±14.4) µg/L (P=0.04). A significant trend (quadratic) was found for IGF-I concentration, as higher in CC cows compared to ones with TT genotype, during the 14 d before calving to 45 d postpartum (P=0.01).

CONCLUSIONS

We concluded that C/T transition in the promoter region of IGF-I gene can influence the serum concentration of IGF-I in periparturient dairy cows.

Altered theca and cumulus oocyte complex gene expression, follicular arrest and reduced fertility in cows with dominant follicle follicular fluid androgen excess

Aspiration of bovine follicles 12-36 hours after induced corpus luteum lysis serendipitously identified two populations of cows, one with High androstenedione (A4; >40 ng/ml; mean = 102) and another with Low A4 (<20 ng/ml; mean = 9) in follicular fluid. We hypothesized that the steroid excess in follicular fluid of dominant follicles in High A4 cows would result in reduced fertility through altered follicle development and oocyte maternal RNA abundance. To test this hypothesis, estrous cycles of cows were synchronized and ovariectomy was performed 36 hours later. HPLC MS/MS analysis of follicular fluid showed increased dehydroepiandrosterone (6-fold), A4 (158-fold) and testosterone (31-fold) in the dominant follicle of High A4 cows. However, estrone (3-fold) and estradiol (2-fold) concentrations were only slightly elevated, suggesting a possible inefficiency in androgen to estrogen conversion in High A4 cows. Theca cell mRNA expression of LHCGR, GATA6, CYP11A1, and CYP17A1 was greater in High A4 cows. Furthermore, abundance of ZAR1 was decreased 10-fold in cumulus oocyte complexes from High A4 cows, whereas NLRP5 abundance tended to be 19.8-fold greater (P = 0.07). There was a tendency for reduction in stage 4 follicles in ovarian cortex samples from High A4 cows suggesting that progression to antral stages were impaired. High A4 cows tended (P<0.07) to have a 17% reduction in calving rate compared with Low A4 cows suggesting reduced fertility in the High A4 population. These data suggest that the dominant follicle environment of High A4 cows including reduced estrogen conversion and androgen excess contributes to infertility in part through altered follicular and oocyte development.

Possible role of IGF2 receptors in regulating selection of 2 dominant follicles in cattle selected for twin ovulations and births

Abundance of IGF-2 receptor (IGF2R), FSH receptor (FSHR), and LH receptor (LHCGR) mRNA in granulosa cells (GCs) or theca cells (TCs) or both cells as well as estradiol (E2), progesterone (P4), and androstenedione concentrations in follicular fluid were compared in cows genetically selected (Twinner) or not selected (control) for multiple ovulations and twin births. Cows were slaughtered at day 3 to 4 (day 3) and day 5 to 6 (day 5) of an estrous cycle, and ovaries, follicular fluid, GCs, and TCs were collected. The two largest (F1 and F2) E2-active (EA) and E2-inactive (EI) follicles were selected according to their E2-to-P4 ratio and diameter. Androstenedione levels in EA F1 and F2 follicles were 5-fold greater (P < 0.05) in Twinner cows than in control cows on day 3 but did not differ on day 5. Twinner cows also had greater (P < 0.05) E2 and P4 concentrations, whereas steroid levels in EI follicles did not differ (P > 0.10) between genotypes. In EA F2 follicles, IGF2R levels in GCs were greater (P < 0.05) in control cows than in Twinner cows on day 3 and day 5, whereas IGF2R mRNA in TCs did not differ (P > 0.10). On day 3, FSHR mRNA levels were greater (P < 0.05) in GCs of EA F1 and EI F2 follicles of control cows than of Twinner cows. LH receptor mRNA expression was less in GCs and greater in TCs of EA F2 follicles in control cows than in Twinner cows (P < 0.05). We hypothesize that reduced GC IGF2R expression in F2 follicles of Twinner cows may play a role in the development of 2 or more dominant follicles.

Incorporation of genetic technologies associated with applied reproductive technologies to enhance world food production

Animal breeding and reproductive physiology have been closely related throughout the history of animal production science. Artificial insemination provides the best method of increasing the influence of sires with superior genetics to improve production traits. Multiple ovulation embryo transfer (MOET) provides some ability to increase the genetic influence of the maternal line as well. The addition of genetic technologies to this paradigm allows for improved methods of selecting sires and dams carrying the best genes for production and yield of edible products and resistance to diseases and parasites. However, decreasing the number of influential parents within a population also increases the risk of propagating a recessive gene that could negatively impact the species (Reprod Domest Anim 44:792-796, 2009; BMC Genomics 11:337, 2010). Furthermore, antagonistic genotypic relationships between production traits and fertility (Anim Prod Sci 49:399-412, 2009; Anim Genet 43:442-446, 2012) suggest that care must be taken to ensure that increasing the frequency of genes with a positive influence on production does not negatively impact the fertility of the replacement females entering the herd.

Effects in cattle of genetic variation within the IGF1R gene on the superovulation performance and pregnancy rates after embryo transfer

The insulin-like growth factor 1 receptor (IGF1R) is a membrane glycoprotein mediating most biological actions of IGF1 and IGF2, and has an important effect on ovulation, pre-implantation embryo development and pregnancy rate. The objectives of this study were to detect IGF1R gene polymorphisms of cattle and analyze the relationship with superovulation performance and pregnancy rates after embryo transfer (ET), as well as the hormone concentrations at the day of ET. One reported SNP of IGF1R G404T and a novel SNP of IGF1R G399A were analyzed in 170 Chinese Holstein donor cows and 118 Luxi recipients cattle. Statistical analysis revealed that the G404T mutation was associated (p=0.019) with increased ovulation rate and females with this mutation had enhanced performance in producing transferable embryos. For the polymorphic locus G399A, recipients with g.399 GG and g.399 GA genotypes had greater pregnancy rates after ET than that of g.399 AA genotype. Furthermore, the same tendency was observed that the genotype groups with greater pregnancy rates had greater progesterone and lesser estrogen concentrations, but these did not reach statistical significance. Results of the present study showed, for the first time, that the polymorphism in IGF1R is associated with superovulation traits, and indicated that the IGFIR gene can be used as a potential marker for donor selection.

Effects of selection for blood serum IGF-I concentration on reproductive performance of female Angus beef cattle

Reproductive performance of animals affects lifetime productivity. However, improvement of reproductive traits via direct selection is generally slow due to low heritability. Therefore, identification of indicator traits for reproductive performance may enhance genetic response. Previous studies showed that serum IGF-I concentration is a candidate indicator for growth and reproductive traits. The objective of our study was to estimate the variances or covariances of IGF-I concentration with reproductive traits. Data were collected from a divergent selection experiment for serum IGF-I concentration at the Eastern Agricultural Research Station owned by The Ohio State University. The study included a total of 2,662 calves in the 1989 to 2005 calf crops. Variance or covariance components were estimated for direct and maternal genetic effects, maternal environment effects, environment effects, and phenotypic effects using an animal model in a multiple-trait, derivative-free, restricted maximum likelihood (MTDFREML, Boldman et al., 1995) computer program. Direct additive genetic correlations suggest that selection for greater IGF-I concentration (heritability = 0.50 ± 0.07) could lead to increased conception rate (heritability = 0.11 ± 0.06, r = 0.32, P < 0.001) and calving rate (heritability = 0.13 ± 0.06, r = 0.43, P < 0.001) and decreased age at first calving in heifers (heritability = 0.35 ± 0.20, r = -0.40, P < 0.001).

Variation in sequences and mRNA expression levels of growth hormone (GH), insulin-like growth factor I (IGF-I) and II (IGF-II) genes between prolific Lezhi black goat and non-prolific Tibetan goat (Capra hircus)

Growth hormone (GH), insulin-like growth factor-I (IGF-I), and II (IGF-II) play a key role in the development of preantral to preovulatory follicles in some species. To better understand the role of these genes in controlling follicular development and fecundity in goats, in the present study, we first cloned the cDNA encoding GH, IGF-I and IGF-II from prolific Lezhi black goat and non-prolific Tibetan goat (Capra hircus), and their mRNA expression between the two breeds were compared. By reverse transcriptase-polymerase chain reaction (RT-PCR) strategy, we obtained full-length 688-bp GH, 493-bp IGF-I, and 566-bp IGF-II cDNAs, encoding for 217 amino acid (aa) GH, 154 aa IGF-I, and 179 aa IGF-II putative proteins. Analysis of their nucleotide and amino acid sequences revealed a high degree of identity between the two breeds, although one base change in GH resulted in one amino acid substitution in the translated proteins. However, two base changes in IGF-I and IGF-II did not lead to any amino acid changes. Real-time PCR analyses revealed that in the middle of estrus, GH, IGF-I and IGF-II genes were expressed, albeit at different levels, in all three tissues (anterior pituitary, endometrium and ovary) examined. GH was most highly expressed in ovary (P<0.01) and its expression was greater in all three tissues examined in Lezhi black goat than in Tibetan goat (P<0.05). IGF-I and IGF-II genes were expressed at a higher (P<0.05) level in anterior pituitary of Lezhi black goat than that in Tibetan goat, but they had a similar expression pattern in endometrium and ovary. These results provide the foundation of information required for future studies of these gene effects on goat fecundity.

Follicular characteristics and luteal development after follicle-stimulating hormone induced multiple ovulations in heifers

A protocol based on small doses of FSH was examined for the induction of double or triple (multiple) ovulations in cattle. Ovulation rate, follicular characteristics, and luteal responses were determined. In Exp. 1, three groups of estrous-synchronized, cyclic Holstein heifers were treated once daily, on d 3 to 6 of the cycle, with a FSH product (Folltropin-V): large FSH dose (total of 150 mg; n=18), medium FSH dose (total of 130 mg, n=12), and small FSH dose (total of 80 mg; n=7). Controls received saline (n=6). Prostaglandin F(2α) was injected on d 6, ultrasound-guided aspiration of surplus follicles (if needed) was performed on d 7, and GnRH was injected on d 8 to induce ovulation. The large FSH dose induced growth of more (2.6±0.3, P<0.05) large follicles than controls on d 8; medium and small FSH doses insufficiently stimulated growth of <2 large follicles. Ovulation rates were determined in subgroups of heifers (n=10, 13, 4, and 6, respectively). The large FSH dose induced greater rates (P<0.01) of mostly double and triple ovulations (90% multiple ovulations, 70% double ovulations), most of which (89%) were bilateral, with only 2 out of 10 heifers requiring aspiration of surplus follicles. Medium and small FSH doses induced fewer multiple ovulations (38% and 25%, respectively). Estradiol concentrations on d 8 did not differ among treatments, but the concentration per large follicle in controls was greater (P<0.05) than in FSH treatments. Mean corpus luteum (CL) volume in single-ovulation controls was greater (P<0.05) than that of multiple ovulations in the large FSH group and total CL volume and progesterone concentrations were numerically greater in multiple ovulations. In Exp. 2, the characteristics of follicles aspirated on d 7 from large FSH (n=11) and control heifers (n=10) were compared. Based on estradiol-to-progesterone ratio, 57% of the large FSH-treated follicles were classified as codominant/healthy follicles and 43% as subordinate/early atretic. Although concentrations of estradiol and androstenedione in FSH-treated codominant follicles were less (P<0.05) than in controls, estradiol-to-progesterone ratio indicated that those follicles were steroidogenically active. Finely tuned small doses of FSH administered during the first follicular wave can induce a large incidence of double/triple, mainly bilateral, ovulations in cattle, which may serve as a basis for treatment aimed at promoting twinning in beef cattle.

The hedgehog system in ovarian follicles of cattle selected for twin ovulations and births: evidence of a link between the IGF and hedgehog systems

Hedgehog signaling is involved in regulation of ovarian function in Drosophila, but its role in regulating mammalian ovarian folliculogenesis is less clear. Therefore, gene expression of Indian hedgehog (IHH) and its type 1 receptor, patched 1 (PTCH1), were quantified in bovine granulosa (GC) or theca (TC) cells of small (1-5 mm) antral follicles by in situ hybridization and of larger (5-17 mm) antral follicles by real-time RT-PCR from ovaries of cyclic cows genetically selected (Twinner) or not selected (control) for twin ovulations. Expression of IHH mRNA was localized to GC and cumulus cells, whereas PTCH1 mRNA was greater in TC than in GC. Estrogen-active (E-A; follicular fluid concentration of estradiol > progesterone) versus estrogen-inactive follicles had a greater abundance of mRNA for IHH in GC and PTCH1 in TC. Abundance of IHH mRNA in GC was not affected by cow genotype, whereas TC PTCH1 mRNA was less in large E-A follicles of Twinners than in controls. In vitro, estradiol and wingless-type (WNT) 3A increased IHH mRNA in IGF1-treated GC. IGF1 and BMP4 treatments decreased PTCH1 mRNA in small TC. Estradiol and LH increased PTCH1 mRNA in IGF1-treated TC from large and small follicles, respectively. In summary, functional status of ovarian follicles was associated with differences in hedgehog signaling in GC and TC. We hypothesize that as follicles grow and develop, increased free IGF1 may suppress expression of IHH mRNA by GC and PTCH1 mRNA by TC, and these effects are regulated in a paracrine way by estradiol and other intra- and extragonadal factors.

Genetic control of multiple births in low ovulating mammalian species

In mammals, litter size is a highly variable trait. Some species such as humans or cattle are monotocous, with one or sometimes two newborns per birth, whereas others, the polytocous species such as mice or pigs, are highly prolific and often produce a dozen newborns at each farrowing. In monotocous species, however, two or three newborns per birth may sometime be unwanted. In more polytocous species such as sheep or pigs, litter size is studied in order to increase livestock prolificacy. By contrast, twinning rates in humans or cattle may increase birth difficulties and health problems in the newborns. In this context, the aim of our review was to provide a clearer understanding of the genetic and physiological factors that control multiple births in low-ovulating mammalian species, with particular focus on three species: sheep, cattle, and humans, where knowledge of the ovulation rate in one may enlighten findings in the others. This article therefore reviews the phenotypic and genetic variability observed with respect to ovulation and twinning rates. It then presents the QTL and major genes that have been identified in each species. Finally, we draw a picture of the diversity of the physiological mechanisms underlying multiple ovulation. Although several major genes have been discovered in sheep, QTL detection methods in humans or cattle have suggested that the determinism of litter size is complex and probably involves several genes in order to explain variations in the number of ovulations.

Polymorphism of insulin-like growth factor 1 gene and its association with litter size in Small Tail Han sheep

The insulin-like growth factor 1 (IGF1) gene was studied as a candidate gene for high prolificacy in sheep. Polymorphisms of 5' regulatory region and all four exons of IGF1 gene were detected in Small Tail Han (n = 277), Hu (n = 58), Texel (n = 48) and Dorset (n = 46) sheep by PCR-RFLP and PCR-SSCP analysis. A microsatellite polymorphic site and a restriction fragment length polymorphism were shown in the 5' regulatory region of IGF1 gene. The ewes with genotype 123/123 bp had 0.81 (P < 0.05) or 1.03 (P < 0.01) lambs more than those with genotype 125/125 bp or 125/127 bp, the ewes with genotype 123/125 bp had 0.46 (P < 0.05) or 0.68 (P < 0.01) lambs more than those with genotype 125/125 bp or 125/127 bp. In addition, there were two mutations (C1511G and A1513G) in 5' regulatory region of IGF1 gene. The ewes with genotype BB or AB had 0.96 (P < 0.05) or 0.38 (P < 0.05) lambs more than those with genotype AA, but there were no significant differences between BB and AB genotypes (P > 0.05) in Small Tail Han sheep. These results preliminarily indicated that these polymorphisms of IGF1 gene could be used in molecular marker-assisted selection for sheep breeding programs.

Increased abundance of aromatase and follicle stimulating hormone receptor mRNA and decreased insulin-like growth factor-2 receptor mRNA in small ovarian follicles of cattle selected for twin births

Cattle genetically selected for twin ovulations and births (Twinner) exhibit increased ovarian follicular development, increased ovulation rate, and greater blood and follicular fluid IGF-1 concentrations compared with contemporary cattle not selected for twins (Control). Experimental objectives were to 1) assess relationships among aromatase (CYP19A1), IGF-1 (IGF1), IGF-2 receptor (IGF2R), and FSH receptor (FSHR) mRNA expression in small (≤5 mm) antral follicles and 2) determine their association with increased numbers of developing follicles in ovaries of Twinner females. Ovaries were collected from mature, cyclic (d 3 to 6) Twinner (n = 11), and Control (n = 12) cows at slaughter and pieces of cortical tissue were fixed and embedded in paraffin. Expression of mRNA was evaluated by in situ hybridization using (35)S-UTP-labeled antisense and sense probes for CYP19A1, FSHR, IGF1, and IGF2R mRNA. Silver grain density was quantified within the granulosa and theca cells of individual follicles (2 to 7 follicles/cow) by Bioquant image analysis. Follicles of Twinners tended to be smaller in diameter than Controls (1.9 ± 0.1 vs. 2.3 ± 0.1 mm; P = 0.08), but thickness of granulosa layer did not differ (P > 0.1) by genotype. Relative abundance of CYP19A1 (P < 0.01) and FSHR (P < 0.05) mRNA was greater in granulosa cells of Twinners vs. Controls, respectively, whereas IGF2R mRNA expression was less in both granulosa (P < 0.01) and theca (P < 0.05) cells in follicles of Twinners vs. Controls, respectively. Abundance of CYP19A1 mRNA in granulosa cells was correlated negatively with IGF2R mRNA expression in both granulosa (r = -0.33; P < 0.01) and theca (r = -0.21; P = 0.05) cells. Expression of IGF1 mRNA was primarily in granulosa cells, including cumulus cells, and its expression did not differ between Twinners vs. Controls (P > 0.10). Detected increases in CYP19A1 and FSHR, but not IGF1, mRNA expression along with decreases in IGF2R mRNA expression in individual follicles of Twinners support the hypothesis that increased follicular development and steroidogenesis in Twinner females result from increased extra-ovarian IGF-1 production. Furthermore, a reduction in follicular IGF2R mRNA expression accompanied by a reduction in receptor numbers would increase availability of free IGF-2 and its stimulation of follicular development in Twinners.

Single Nucleotide Polymorphisms in the Insulin-Like Growth Factor 1 (IGF-1) Gene are Associated with Performance in Holstein-Friesian Dairy Cattle

Insulin-like growth factor 1 (IGF-1) has been shown to be associated with fertility, growth, and development in cattle. The aim of this study was to (1) identify novel single nucleotide polymorphisms (SNPs) in the bovine IGF-1 gene and alongside previously identified SNPs (2) determine their association with traits of economic importance in Holstein-Friesian dairy cattle. Nine novel SNPs were identified across a panel of 22 beef and dairy cattle by sequence analysis of the 5′ promoter, intronic, and 3′ regulatory regions, encompassing ~5 kb of IGF-1. Genotyping and associations with daughter performance for milk production, fertility, survival, and measures of body size were undertaken on 848 Holstein-Friesian AI sires. Using multiple regression analysis nominal associations (P < 0.05) were identified between six SNPs (four novel and two previously identified) and milk composition, survival, body condition score, and body size. The C allele of AF017143 a previously published SNP (C-512T) in the promoter region of IGF-1 predicted to introduce binding sites for transcription factors HSF1 and ZNF217 was associated (P < 0.05) with increased cow carcass weight (i.e., an indicator of mature cow size). Novel SNPs were identified in the 3′ region of IGF-1 were associated (P < 0.05) with functional survival and chest width. The remaining four SNPs, all located within introns of IGF-1 were associated (P < 0.05) with milk protein yield, milk fat yield, milk fat concentration, somatic cell score, carcass conformation, and carcass fat. Results of this study further demonstrate the multifaceted influences of IGF-1 on milk production and growth related traits in cattle.

Roles of hCG in Advancing Follicular Growth to Ovulation after Concurrent Injections of PGF(2α) and GnRH in Postpubertal Holstein Heifers Bearing a CL

A study was conducted to test the hypothesis that injecting Gonadotropin-releasing hormone (GnRH) concurrently with Prostaglandin F2 alpha (PGF(2α)) followed by an injection of human Chorionic Gonadotropin (hCG), would advance follicular growth to ovulation in Holstein heifers bearing a corpus luteum (CL). After manual examination of the CL, group 1 (PGF; n = 12) received an injection of PGF(2α) (25 mg, im). Group 2 (PGF + GnRH; n = 13) received an injection of GnRH (100 μg, im) immediately after an injection of PGF(2α). Group 3 (PGF + GnRH + hCG; n = 12) received concurrent injections of PGF(2α) and GnRH followed with hCG (1500 IU, im) two days later. Follicular size and day of ovulation were monitored by daily ultrasonographic examination from days 1 to 10. Blood was collected on days-7, 0 (PGF(2α) administration), 2, and 7. Progesterone was not different (P > .05) on days-7, 0, and 2 between the experimental groups. However, it was higher (P < .005) in the PGF + GnRH + hCG group on day 7 compared to PGF + GnRH heifers, but not significantly higher than the PGF. Additionally, heifers in the PGF + GnRH + hCG group ovulated earlier (P < .05) than heifers in the PGF + GnRH and the PGF group. This data indicates that hCG advances follicular growth to ovulation in spite of high levels of progesterone when injected 48 h after concurrent treatments of GnRH and PGF(2α) on heifers bearing a CL.