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Sex ratio of equine offspring is affected by the ages of the mare and stallion.
Abstract: The aim of this study was to determine the influence of parental age on the sex ratio of offspring in horses. Two trials were performed. In the first trial, the data from a randomly obtained population with a 1:1 sex ratio of 59,950 Mangalarga Marchador horses born in Brazil from 1990 to 2011 were analyzed. The sex ratios of the offspring were compared among groups according to the mare and the stallion ages (from 3 to 25 years). In the first step of the analysis, the mares and stallions were grouped according to age in 5-year intervals. In the second step, the groups were based on the parental age gap at conception. In the third step, the group of the mares and stallions with similar ages from the second step was subdivided, and the different parental age subgroups that were divided into 5-year intervals were compared. In the fourth step, the sex ratio of the offspring was determined according to the ages of the mares and the stallions at conception. The second trial was based on the data from 253 horses of several breeds that were born after natural gestation into a herd from 1989 to 2010, and the offspring of groups that were younger or older than 15 years were compared. The data from both trials were analyzed using a chi-square test (P ≤ 0.01 for the first trial; and P ≤ 0.05 for the second trial) for the comparisons of the sex ratios. In the first trial, the Spearman test (P ≤ 0.01) was used to verify the correlations between the parental age and the offspring sex ratio. In the first trial, the offspring sex ratio decreased as the mare or stallion age increased, and the decrease was more marked for the mares than for the stallions. In the second trial, the mares older than 15 years had more fillies than the younger mares, but the stallion age had no effect on the sex of the offspring. The first trial, with a large number of horses, revealed the pattern of the distribution of the sex ratios of offspring according to the parental age in horses, whereas the second trial, with a more restricted number of horses, confirmed the influence of the age of the mare on the offspring sex ratio. We concluded that the parental age affected the offspring sex ratio in horses and that this effect was stronger for the mares than for the stallions.
Copyright © 2015 Elsevier Inc. All rights reserved.
Publication Date: 2015-07-09 PubMed ID: 26234461DOI: 10.1016/j.theriogenology.2015.07.001Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research investigates the influence of the age of mares and stallions on the sex ratio of their offspring, with the findings indicating that as the parents’ age increases, the offspring sex ratio decreases, particularly in mares than in stallions.
Research Context and Purpose
- The research was primarily aimed at understanding the impact of parental age on the sex ratio of offspring in horses. This understanding could provide insights into better management and planning practices in equine breeding.
Research Methodology
- Two trials were conducted in the study. The initial trial involved the analysis of data from a randomly obtained population with a 1:1 sex ratio of 59,950 Mangalarga Marchador horses born in Brazil from 1990 to 2011. The second trial utilized data from 253 horses of different breeds born after natural gestation between 1989 and 2010.
- In both trials, the sex ratios of offspring were compared among various groups based on the mare and stallion ages ranging from 3 to 25 years.
- Additionally, the researchers analyzed the sex ratio based on parental age gap at conception, and subdivided groups of mares and stallions according to their similar ages to form different parental age subgroups categorized in 5-year intervals.
- The researchers also determined the offspring’s sex ratio according to the specific ages of mares and stallions at conception.
- Data from both trials were analyzed using a chi-square test, with set probability values considered significant. The initial trial also utilized the Spearman test to verify the correlations between the parental age and the offspring sex ratio.
Research Findings
- In the first trial, a decrease in the offspring sex ratio was observed as the mare or stallion age increased. The extent of decrease was observed to be more marked for the mares than the stallions.
- In the second trial, it was found that mares older than 15 years gave birth to more fillies than younger mares did; however, the age of the stallion did not show a noticeable impact on the sex of the offspring.
- The initial trial, which used a large sample size, revealed the distribution pattern of the sex ratios of offspring in relation to the age of the parents in horses. The second trial, even though it used a smaller sample size, confirmed the influence of the age of the mare on the sex ratio of offspring.
Research Conclusion
- The research concluded that the age of the parents affected the offspring sex ratio in horses specifically, the effect was much stronger in mares than in stallions.
Cite This Article
APA
Santos MM, Maia LL, Nobre DM, Oliveira Neto JF, Garcia TR, Lage MC, de Melo MI, Viana WS, Palhares MS, da Silva Filho JM, Santos RL, Valle GR.
(2015).
Sex ratio of equine offspring is affected by the ages of the mare and stallion.
Theriogenology, 84(7), 1238-1245.
https://doi.org/10.1016/j.theriogenology.2015.07.001 Publication
Researcher Affiliations
- Departamento de Medicina Veterinária, Pontifícia Universidade Católica de Minas Gerais, Betim, Minas Gerais, Brazil.
- Departamento de Medicina Veterinária, Pontifícia Universidade Católica de Minas Gerais, Betim, Minas Gerais, Brazil.
- Escola de Medicina, Universidade Federal de Ouro Preto, Ouro Preto, Minas Gerais, Brazil.
- Associação Brasileira dos Criadores do Cavalo Mangalarga Marchador, Belo Horizonte, Minas Gerais, Brazil.
- Associação Brasileira dos Criadores do Cavalo Mangalarga Marchador, Belo Horizonte, Minas Gerais, Brazil.
- Departamento de Medicina Veterinária, Pontifícia Universidade Católica de Minas Gerais, Betim, Minas Gerais, Brazil.
- Departamento de Medicina Veterinária, Pontifícia Universidade Católica de Minas Gerais, Betim, Minas Gerais, Brazil.
- Regimento de Cavalaria Alferes Tiradentes, Polícia Militar do Estado de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
- Departamento de Clínica e Cirurgia Veterinária, Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
- Departamento de Clínica e Cirurgia Veterinária, Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
- Departamento de Clínica e Cirurgia Veterinária, Escola de Veterinária, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
- Departamento de Medicina Veterinária, Pontifícia Universidade Católica de Minas Gerais, Betim, Minas Gerais, Brazil. Electronic address: guilhermerv@pucminas.br.
MeSH Terms
- Aging / physiology
- Animals
- Brazil
- Female
- Horses
- Male
- Maternal Age
- Paternal Age
- Pregnancy
- Sex Ratio
Citations
This article has been cited 4 times.- Todd ET, Hamilton NA, Velie BD, Thomson PC. The effects of inbreeding on covering success, gestation length and foal sex ratio in Australian thoroughbred horses. BMC Genet 2020 Apr 8;21(1):41.
- Chiang C, Lewis LR, Borkowski G, Flaws JA. Late-life consequences of short-term exposure to di(2-ethylhexyl) phthalate and diisononyl phthalate during adulthood in female mice. Reprod Toxicol 2020 Apr;93:28-42.
- Flores JG, Bueno VC, Bastos HBA, Rechsteiner SMDEF. Foal sex in Thoroughbred horses: related factors. Anim Reprod 2024;21(3):e20230073.
- Firman RC, Ellis CM, Thorn S, Mawson PR. Parental effects on offspring sex ratio in the Numbat (Myrmecobius fasciatus): does captivity influence paternal sex allocation?. J Mammal 2023 Oct;104(5):1036-1046.
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