Skewing Of Sex Ratio Research Articles

Dietary calcium and magnesium supplemented maternal diets on skewing of sex ratio and sexually dimorphic gene expression in Rabbit (Oryctolagus cuniculus) placenta

This study aimed to investigate the influence of calcium and magnesium supplementation on the skewing of sex ratio and placental genes expression in New Zealand White Rabbits. A total of 25 rabbits were allocated to 5 groups; each treatment group was supplemented with Ca and Mg; T1 (0.4% and 0.01%), T2 (0.6% and 0.02%), T3 (0.8% and 0.03%), and T4 (1.0% and 0.04%) respectively, while the C group was provided with regular feed and subjected to three breeding. The T3 group produced a female-biased litter and hence, the F1 female kits (n=12) of T3 and C group was provided same supplementation management. At 21 days of gestation, three animals from each group were sacrificed and placental samples were collected, the remaining animals were allowed for full-term delivery. The selected F1 produced female-biased litter with elevated serum Ca and Mg concentrations and reduced sodium and cholesterol levels. A total of 15 genes related to mineral absorption, placental development and immunity were selected to study the influence of diet on sex and placental gene expression. The expression of genes such as PEG10, SOD1, SLC30A, TLR4, AR, and TRPM6 was high in the treatment placenta compared to the control. RTL1, ESR2, CALM2, and TRPM6 upregulated in the treatment female placenta. The study concluded that the intake of 0.8% Ca and 0.03% Mg could lead to the production of more females and upregulation of some placental genes could serve as the molecular mechanism in response to intake of the minerals and fetal sex.

Molecular insights on skewing of sex ratio in rabbits (Oryctolagus cuniculus) supplemented with dietary calcium and magnesium.

The effect of dietary calcium (Ca) and magnesium (Mg) supplementation on serum biochemical parameters, steroid hormones, gene expression, and the sex ratio was investigated in female New Zealand white rabbits. A total of 25 rabbits were allocated into five treatment groups: The control group was fed with regular pellet feed, whereas, treatment groups were supplemented with Ca and Mg: T1 (0.40% and 0.01%), T2 (0.60% and 0.02%), T3 (0.80% and 0.03%) and T4 (1.00% and 0.04%), respectively. The rabbits were subjected to three breeding cycles. The T3 group skewed towards females (65.33%) from all three breeding. There was elevated Ca concentration in T3 (15.26 ± 0.77 mg dL-1) and T4 (15.61 ± 0.82 mg dL-1) groups compared to the control. The concentration of estradiol was significantly high in T3 and T4 groups at 0.5 days post-coitus (dpc) and T2, T3 and T4 groups at 21dpc. Testosterone was significantly high in T4 group at 0.50 dpc and T2 and T4 group at 21dpc. The expression of 13 genes was studied in the oviduct. Genes such as OVGP1, CCT4, ANXA2 and TLR4 were up-regulated and positively correlated with the female sex ratio. The molecular functions and pathways of up-regulated genes were suggestive of their role in fertilization such as sperm selection, sperm storage, immune regulation, implantation and early embryonic development. The variations in the serum electrolytes, steroid hormones and gene expression might have an impact on the skewing process.

Addressing stray animal population through alteration of sex ratio

Livestock plays a significant role in rural economy and livelihood by providing milk, meat, hide, drought power, etc. India’s livestock sector is one of the largest in the world with a holding of 11.6% of world livestock population. But due to economic reasons, dairy farmers have a strong preference for female calves for milk production and hence there is a very limited demand for male calves. Apart from that, there are several other reasons such as negligence of the indigenous populations and excessive focus on crossbreeding in the past few decades, increased mechanisation and the national policy to ban on cow slaughter have further added to the problem. In the common parlance, stray cattle include low-yield cows, bulls or calves that are abandoned and free to roam about in the open during the daytime because they are unproductive and creating traffic nuisance in cities, they also attack crops in villages. Therefore, techniques for gender selection and skewing of sex ratio towards female are demand of the hour. Flow cytometric sorting of spermatozoa is one of the best approaches to select the sexed semen for desire sex of calf, but its cost and patented technology is a definite disadvantage of this technology. In the present review, we will discuss in detail about the techniques available for skewing of sex ratio to address the stay animal population.

Maternal influence on the skewing of offspring sex ratio: a review

Sex pre-selection of the progeny to suit the livestock production system aids in greatly increasing the efficiency and profitability of the livestock enterprise to meet the demand for animal meat and dairy products. Individual animals can skew the sex ratio in response to various social and environmental stipulations. These social and environmental factors include the composition of the maternal diet, maternal hormonal levels, maternal stress, and the time of insemination. Hence, this present review focuses on these approaches and their success rate as premises for the alterations of offspring sex ratio in different animal species. Numerous studies have linked maternal nutrition and its influence on offspring sex ratio. A maternal diet rich in calcium and magnesium favoured the production of more females, while diets rich in sodium and potassium favoured more males. Furthermore, feeding animals with a particular type of fat diet, including omega-3, omega-6, or omega-9 fatty acids, assists in sex pre-selection. The circulating hormone level in females during conception is associated with the skewing of sex ratio. In addition, maternal stress during the conception period is also found to be associated with the skewing of the sex ratio in favour of female offspring. The timing of insemination relative to the ovulation period has been identified as a promising approach for the pre-selection of offspring sex; however, proper detection of oestrus is crucial. Among all the approaches reported, dietary manipulation could be regarded as the most affordable and stands a better chance of being optimised for commercial livestock production. Reduction in the cost of desired sex production by adopting sex pre-selection techniques will lead to the improvement of the economy and minimise the culling of the undesired sex. However, further research is necessary to focus on the understanding of the underlying molecular mechanisms for the production of animals of the desired sex.

Endocrine-disrupting effect of the ultraviolet filter benzophenone-3 in zebrafish, Danio rerio.

The chemical ultraviolet (UV) filter benzophenone-3 (BP-3) is suspected to be an endocrine disruptor based on results from in vitro and in vivo testing. However, studies including endpoints of endocrine adversity are lacking. The present study investigated the potential endocrine-disrupting effects of BP-3 in zebrafish (Danio rerio) in the Fish Sexual Development Test (Organisation for Economic Co-operation and Development TG 234) and a 12-d adult male zebrafish study. In TG 234, exposure from 0 d to 60 d posthatch caused a monotone dose-dependent skewing of the phenotypic sex ratio toward fewer males and more female zebrafish (no observed effect concentration [NOEC]: 191 μg/L, lowest observed effect concentration [LOEC]: 388 μg/L). Besides, gonad maturation was affected in both female fish (NOEC 191 μg/L, LOEC 388 μg/L) and male fish (NOEC 388 μg/L, LOEC 470 μg/L). Exposure to BP-3 did not affect the vitellogenin concentration in TG 234. After 12 d exposure of adult male zebrafish, a slight yet significant increase in the vitellogenin concentration was observed at 268 μg/L but not at 63 μg/L and 437 μg/L BP-3. Skewing of the sex ratio is a marker of an endocrine-mediated mechanism as well as a marker of adversity, and therefore the conclusion of the present study is that BP-3 is an endocrine-disrupting chemical in accordance with the World Health Organization's definition.

Usage of X‐ and Y‐chromosome fluorescent in situ hybridization to determine whether the murine oocytes selectively attract one class of spermatozoa over another

While gender in mammals is determined by heterogametic male germ cells, controversy exists whether female reproductive tract selectively permits one class of sperm to reach the oocyte. Additionally, the oocyte itself might be able to attract or selectively bind to X- or Y-bearing sperm, but disagreement exists on this subject. In a recent study, investigators employed PCR analysis with sex chromosome specific primers and demonstrated that bovine oocytes were fertilized with equal frequency by X- or Y-bearing sperm (Zuccotti et al. 2005). However, this study permitted each oocyte to be fertilized by more than one spermatozoa. Tthese results might not mirror normal physiological conditions. Another study demonstrated no skewing of sex ratio in bovine oocytes in vitro fertilized with sorted or mixed sperm populations (Bermejo-Alvarez et al. 2008). To address this question in rodents, we sought to establish a fluorescent in situ hybridization (FISH) method for determining relative oocyte-associated X and Y sperm numbers in control mice. While our laboratory and many others have employed FISH-based-approaches to distinguish epididymal X- and Y-bearing spermatozoa, such existing procedures have not been successful to label oocyte-associated sperm. We describe a FISH method that maintains the integrity of this association and differentiates oocyte-associated X- versus Y-bearing sperm. Cumulus oocyte complexes (COCs) were collected from NIH Swiss females on a control diet. Spermatozoa were obtained from caudal epididymis of male mice, capacitated, and used to inseminate COCs under standard culture conditions. We analyzed the epididymal sperm (n=3961) beforehand, and 50.25 ± 3.6% (n=1987) were Y-sperm and 49.75 ± 3.6% (n=1974) were X-sperm, which are not different from 1:1 ratio. A total of 20 oocytes with 1539 bound sperm were analyzed by a modified XY FISH, as described previously (Whyte et al. 2007), which included incubating slides in 0.01% pepsin/ 0.01N HCl solution for 20 min at 37°C to digest the zona pellucidae and thereby permit the probes to penetrate and bind to sperm DNA. We were able to determine total number of sperm bound to each oocyte and sex chromosome each harbored (Figure 1). The average numbers of X and Y spermatozoa per oocyte were 40.7 ± 4.2 and 36.3 ± 3.8, respectively. These values were not statistically different from 1:1. An average of 77.0 ± 7.8 total sperm associated with each oocyte. This FISH procedure provides a valid and effective way to assess ratios of X and Y sperm associated with murine oocytes. Additionally, as no difference in X to Y sperm ratios was observed, the data dispute the hypothesis that murine oocytes selectively attract one class of sperm over the other in normal mice. It is plausible though that maternal diet or other factors alters expression of zona pellucida proteins or chemoattractants that the oocyte might produce to govern which class of sperm bind and fertilize it. This modified XY FISH procedure provides the groundwork for our future studies to analyze whether contrasting maternal diets with varying fat content alters ability of oocytes to recruit and bind one class of sperm over another. Figure 1a and b Representative images of X- and Y-sperm associated with oocytes (dotted circles) after 5 h in vitro fertilization. X-sperm are stained in green and Y-sperm are stained in red, and the nuclei are in blue (DAPI)