Mutations in genes involved in oestrous cycle associated expression of oestrus

Association between somatotropic axis gene polymorphisms and reproductive efficiency of bovine females: a review

Abstract Reproductive characteristics directly reflect on productive performance, as they determine the number of calves born annually and the interval between generations, thereby affecting the selection intensity. This allows for the determination of the most important economic variables that directly affect the production system. The present study is a literature review of somatotropic axis gene polymorphisms that are associated with reproductive functions in heifers and cows (Bos taurus taurus and Bos taurus indicus). The following characteristics were analyzed from the various studies reviewed: number of services per pregnancy (Nº services/ pregnancy), age at first calving (AFC), calving interval (CI), and period of service calving conception interval (CCI). The research was conducted during the period from 2011 to 2021, and associations were found among all indicators of reproductive efficiency evaluated in heifers and cows, with 27 single nucleotide polymorphisms (SNPs): 18 in GHR, 5 in IGF-I, and 4 in STAT5A. This study revealed the relationships between SNPs and the reproductive efficiency indicators and demonstrated that molecular genetic techniques enhance the animal selection process, resulting in more profitable systems that are sustainable in the long term.

Associação entre polimorfismos de genes do eixo somatotrópico e eficiência reprodutiva de fêmeas bovinas: revisão de literatura

Resumo Características reprodutivas refletem diretamente no desempenho produtivo visto que são capazes de determinar o número de bezerros nascidos anualmente, além de afetar o intervalo entre gerações e, consequentemente, a intensidade de seleção, fazendo com o que tais atributos sejam apontados como variáveis econômicas das mais importantes que afetam diretamente o sistema de produção. O presente estudo propõe realizar uma revisão de literatura de polimorfismos de genes do eixo somatotrópico associados a funções reprodutivas em novilhas e vacas (Bos taurus taurus e Bos taurus indicus), indicadas pelos índices: número de serviços por gestação (Nº serviços/gestação), idade ao primeiro parto (IPP), intervalo de partos (IP) e período de serviço, como também denominado de intervalo parto-concepção (IPC). As pesquisas encontradas durante o período de 2011 a 2021 demonstraram associações entre todos os indicadores de eficiência reprodutiva analisados de novilhas e vacas com 27 polimorfismos de nucleotídeo único (SNPs), sendo 18 em GHR, 5 em IGF-I e 4 em STAT5A. Dessa forma, este estudo mostrou relação entre os SNPs e os indicadores de eficiência reprodutiva, demonstrando que técnicas de genética molecular potencializam o processo de seleção dos animais, resultando em sistemas mais lucrativos e que se sustentam a longo prazo.

Effect of expression of estrus and treatment with GnRH on pregnancies per AI in beef cattle synchronized with an estradiol/progesterone-based protocol

Three experiments evaluated the effects of expression of estrus and gonadotropin releasing hormone (GnRH) treatment on pregnancies per AI (P/AI) in beef cattle that were treated with an estradiol/progesterone (P4)-based protocol for fixed-time artificial insemination (FTAI). In Experiment 1, 20 non-lactating beef cows were treated with 2 mg estradiol benzoate (EB) and an intravaginal device containing 0.5 g of P4. Seven days later, P4 devices were removed and all cows received prostaglandin F2 alpha (PGF_2α) and 0.5 mg estradiol cypionate (ECP). Estrus was detected using tail paint and cows that did not show estrus by 48 h after P4 device removal were randomized to receive GnRH or no treatment. Ovulation, as determined by ultrasonography, occurred earlier in cows that showed estrus (68.0 ± 2.5 h) than in cows that did not (82.0 ± 2.1 h, P < 0.05). Furthermore, cows that received GnRH ovulated earlier (78.0 ± 2.6 h) than those that did not (86.0 ± 2.0, P < 0.05). Experiment 2 determined whether expression of estrus and the administration of GnRH to animals that did not show estrus increased P/AI. Non-lactating beef cows and heifers (n = 1356) were treated as in Experiment 1 (P4 device removal, PGF2α and ECP administration on Day 7) or extended until Day 8. All animals in estrus by 48 h after P4 device removal were inseminated and those not showing estrus received GnRH or no treatment and were FTAI 8 h later (i.e., at 56 h). P/AI were greater (P < 0.01) in animals that were observed in estrus by 48 h (56.4%) than in those that did not show estrus (46.5%). Likewise, animals that did not show estrus but were treated with GnRH had greater P/AI (53.8%, P < 0.04) than those that did not receive GnRH (37.9%). Experiment 3 was designed to determine the effect of delaying GnRH treatment to the time of FTAI (at 56 h) in cows not showing estrus by 48 h after P4 device removal. Suckled beef cows (n = 969) were treated as in Experiment 1, except that all cows also received 400 IU of eCG at the time of P4 device removal on Day 7. Cows that showed estrus by 48 h or 56 h had greater P/AI (62.3%, P < 0.05) than those did not show estrus (51.5%). Furthermore, when cows that did not show estrus by 48 h were analyzed separately, P/AI were greater (P < 0.05) in those that received GnRH at 48 h and were FTAI by 56 h (64.9%) than in those that received GnRH concurrent with FTAI by 56 h after device removal (54.6%). In summary, expression of estrus was associated with earlier ovulations and resulted in greater P/AI in cows and heifers treated with an estradiol/P4-based protocol for FTAI. Furthermore, GnRH treatment in animals that did not show estrus hastened the time of ovulation and increased P/AI.

Effect of COQ9 and STAT5A polymorphisms on reproductive performance in a Holstein cow herd in Mexico

Coenzyme Q9 (COQ9), a coenzyme Q (CoQ) precursor, is an essential component of the mitochondrial electron transport chain that drives adenosine triphosphate production. COQ9 polymorphism 18:25527339 is characterized by substitution of guanine (allele G) for adenine (allele A), which modifies the function of the protein encoded by the gene. In Holsteins, allele A has been associated with better reproductive performance in terms of the conception rate, number of services per conception (SPC) and days open (DO). The signal transducer and activator of transcription (STAT) protein is a transcription factor activated in the presence of cytokines and growth factors. STAT5A polymorphism 19:42407732 in exon 8 has been associated with higher fertility and embryonic survival rates. The objective of this study was to determine the relationship of COQ9 and STAT5A polymorphisms with reproductive parameters [calving to first heat interval (CFHI), DO and SPC]. Blood samples were taken from 112 lactating Holstein from a herd in México for allele genotyping by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). To estimate the association between reproductive parameters and genotypes, a linear mixed-effect model was performed. The COQ9 AG genotype was associated significantly with lower SPC (P<0.05) but not with DO or CFHI. No significant association with any reproductive parameter was found for STAT5A. Our findings suggest that the COQ9 18:25527339 polymorphism is a useful molecular marker for improvement of reproductive performance in dairy herds.

Sire effect on early and late embryonic death in French Holstein cattle

We investigated the effect of maternal sire on early pregnancy failure (between D0, day of insemination and D90) in their progeny during the first and second lactations (n=3508) in the Holstein breed. The estimated breeding value (EBV) for cow fertility of 12 bulls (reliability⩾0.95) was used to create the following three groups: low, medium and high EBV (EBV from -0.7 to 1 expressed as genetic standard deviation relative to the mean of the breed). In their daughters (93 to 516 per bull), progesterone measurement was carried out on the day of artificial insemination (AI; D0) to check whether the cows were in the follicular phase and on D18 to 25 to assess non-fertilisation-early embryonic mortality (NF-EEM). Late embryonic mortality (LEM) and early foetal death (FD) were determined by ultrasonography on D45 and D90 and by the return to oestrus after the first AI. Frequencies of NF-EEM, LEM, FD and pregnancy were 33.3%, 11.7%, 1.4% and 48.5% and incidences were 35.1, 19.0, 2.7 and 51.1, respectively. Sire EBV was significantly related to the incidences of pregnancy failure between D0 and D90, fertilisation failure-early embryonic mortality (FF-EEM) and LEM but not to the incidence of FD between D45 and D90 of pregnancy. The relative risk (RR) of FF-EEM was significantly higher (RR=1.2; P<0.05) for the progeny group of low EBV bulls when compared with high EBV bulls. The same effect was observed when comparing LEM of the progeny groups from the low EBV bulls to those from moderate and high EBV bulls (RR, respectively, of 1.3 and 1.4; P<005). The incidence of FF-EEM was significantly higher when cows were inseminated before 80 days postpartum compared with later, and for the extreme values of the difference between milk fat and protein content measured during the first 3 months of lactation. FF-EEM was also significantly related to the year of observation. The incidence of LEM was higher for the highest producing cows and was influenced by interaction between milk yield×lactation rank and milk yield×milk protein content. In conclusion, this study showed large differences in early pregnancy failure between progeny groups and highlights the interest of accurate characterisation of embryonic death in order to identify potential candidate genes for female fertility.

Using UHF proximity loggers to quantify male-female interactions: a scoping study of estrous activity in cattle

Reproductive efficiency is an important determinant of profitable cattle breeding systems and the success of assisted reproductive techniques (ART) in wildlife conservation programs. Methods of estrous detection used in intensive beef and dairy cattle systems lack accuracy and remain the single biggest issue for improvement of reproductive rates and such methods are not practical for either large-scale extensive beef cattle enterprises or free-living mammalian species. Recent developments in UHF (ultra high frequency) proximity logger telemetry devices have been used to provide a continuous pair-wise measure of associations between individual animals for both livestock and wildlife. The objective of this study was to explore the potential of using UHF telemetry to identify the reproductive cycle phenotype in terms of intensity and duration of estrus. The study was conducted using Belmont Red (interbred Africander Brahman Hereford-Shorthorn) cattle grazing irrigated pasture on Belmont Research Station, northeastern Australia. The cow-bull associations from three groups of cows each with one bull were recorded over a 7-week breeding season and the stage of estrus was identified using ultrasonography. Telemetry data from bull and cows, collected over 4 8-day logger deployments, were log transformed and analyzed by ANOVA. Both the number and duration of bull-cow affiliations were significantly (P<0.001) greater in estrous cows compared to anestrus cows. These results support the development of the UHF technology as a hands-off and noninvasive means of gathering socio-sexual information on both wildlife and livestock for reproductive management.