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.
Subject(s)
Horses , Maternal Age , Paternal Age , Sex Ratio , Aging/physiology , Animals , Brazil , Female , Male , PregnancyABSTRACT
Este trabalho foi realizado com o objetivo de estudar a fertilidade de éguas cobertas após a ovulação, segundo um manejo de palpação retal a cada 24 (P1) ou 12 horas (P2), e cobertas por dois garanhões (G1 e G2). O estudo utilizou 84 ciclos estrais de 50 éguas mestiças do tipo militar, distribuídos ao acaso, segundo um esquema fatorial 2 x 2. A taxa de gestação para o primeiro, segundo e terceiro ciclos estrais foram de: 29,41 por cento (5/17) e 50 por cento (4/8) para o grupo P1G1; 25 por cento (5/20), 54,54 por cento (6/11) e 100 por cento (2/2) para o grupo P2G1; 41,66 por cento (5/12) e 50 por cento (2/4) para o grupo P1G2; e de 60 por cento (6/10) para o grupo P2G2, respectivamente. A taxa de gestação total/ciclo, para cada um dos quatro tratamentos, foi de 36 por cento (9/25), 39,40 por cento (13/33), 43,75 por cento (7/16) e 60 por cento (6/10), respectivamente. A taxa de concepção por ciclo estral não diferiu (p>0,05), pelo teste Exato de Fisher. Assim, os dados foram reagrupados levando-se apenas em consideração a freqüência de palpação retal, e obteve-se 39,02 por cento (16/41) e 44,19 por cento (19/43) de taxa de concepção/ciclo e 55,20 por cento (16/29) e 63,30 por cento (19/30) de taxa de concepção total para os intervalos de palpação de 24 e 12 horas, respectivamente.
The objective of the experiment was to study the fertility of mares bred after ovulation, detected by rectal palpation every 24 (P1) or 12 hours (P2), using two stallions (G1 and G2). This study was done with 84 estrus cycles of 50 military crossbred mares, randomly assigned to four treatments. The conception rate for first, second and third estrus cycles were 29.41 percent (5/17) and 50.00 percent (4/8) for group P1G1; 25.00 percent (5/20), 54.54 percent (6/11) and 100.00 percent (2/2) for group P2G1; 41.66 percent (5/12) and 50.00 percent (2/4) for group P1G2; and 60.00 percent (6/10) for group P2G2, respectively. The conception rate for each treatment were 36.00 percent (9/25), 39.40 percent (13/33), 43.75 percent (7/16) and 60.00 percent (6/10). The conception rate by estrus cycle did not differ (p>0.05) by Fisher Test. The data obtained were regrouped considering only the rectal palpation frequency and it was obtained 39.02 (16/41) and 44.19 percent (19/43) for conception rate by estrus cycle and 55.20 percent (16/29) and 63.30 percent (19/30) for total conception rate for 24 and 12 to rectal palpation intervals, respectively.
Subject(s)
Female , Animals , Horses , Ovulation Detection/veterinary , Fertilization , Palpation/veterinary , Pregnancy Rate , Reproductive Techniques/veterinaryABSTRACT
Este trabalho foi realizado com o objetivo de estudar a fertilidade de éguas cobertas após a ovulação, segundo um manejo de palpação retal a cada 24 (P1) ou 12 horas (P2), e cobertas por dois garanhões (G1 e G2). O estudo utilizou 84 ciclos estrais de 50 éguas mestiças do tipo militar, distribuídos ao acaso, segundo um esquema fatorial 2 x 2. A taxa de gestação para o primeiro, segundo e terceiro ciclos estrais foram de: 29,41 por cento (5/17) e 50 por cento (4/8) para o grupo P1G1; 25 por cento (5/20), 54,54 por cento (6/11) e 100 por cento (2/2) para o grupo P2G1; 41,66 por cento (5/12) e 50 por cento (2/4) para o grupo P1G2; e de 60 por cento (6/10) para o grupo P2G2, respectivamente. A taxa de gestação total/ciclo, para cada um dos quatro tratamentos, foi de 36 por cento (9/25), 39,40 por cento (13/33), 43,75 por cento (7/16) e 60 por cento (6/10), respectivamente. A taxa de concepção por ciclo estral não diferiu (p>0,05), pelo teste Exato de Fisher. Assim, os dados foram reagrupados levando-se apenas em consideração a freqüência de palpação retal, e obteve-se 39,02 por cento (16/41) e 44,19 por cento (19/43) de taxa de concepção/ciclo e 55,20 por cento (16/29) e 63,30 por cento (19/30) de taxa de concepção total para os intervalos de palpação de 24 e 12 horas, respectivamente.
The objective of the experiment was to study the fertility of mares bred after ovulation, detected by rectal palpation every 24 (P1) or 12 hours (P2), using two stallions (G1 and G2). This study was done with 84 estrus cycles of 50 military crossbred mares, randomly assigned to four treatments. The conception rate for first, second and third estrus cycles were 29.41 percent (5/17) and 50.00 percent (4/8) for group P1G1; 25.00 percent (5/20), 54.54 percent (6/11) and 100.00 percent (2/2) for group P2G1; 41.66 percent (5/12) and 50.00 percent (2/4) for group P1G2; and 60.00 percent (6/10) for group P2G2, respectively. The conception rate for each treatment were 36.00 percent (9/25), 39.40 percent (13/33), 43.75 percent (7/16) and 60.00 percent (6/10). The conception rate by estrus cycle did not differ (p>0.05) by Fisher Test. The data obtained were regrouped considering only the rectal palpation frequency and it was obtained 39.02 (16/41) and 44.19 percent (19/43) for conception rate by estrus cycle and 55.20 percent (16/29) and 63.30 percent (19/30) for total conception rate for 24 and 12 to rectal palpation intervals, respectively.