Influencia de dos métodos de reproducción artificial sobre el peso al nacimiento y al destete de terneras gyrolando

Abstract

In order to obtain a high yield dairy production, it is necessary that females present genetic quality and stability in their breeding and lactation functions so, they must be in conditions of good management practices and animal welfare. The famous Gyr, Indian milk zebu of Gyr Hills and the Kathiawar Forest, is a livestock adapted to the conditions of tropics hot and very resistant to ectoparasites, while Holstein, dairy cattle widely spread internationally, are animals adapted at cold temperatures and are very susceptible to diseases caused by ectoparasites; the product of the crossing of both is the Gyrolando rustic and very productive race for environmental conditions in hot climate. The present investigation, non-experimental, observational, descriptive, retrospective and transversal type, was conducted in a farm in Santo Domingo province with average environmental conditions of 21ºC- 32ºC of temperature and 86.9% of relative humidity. The objective was to evaluate the influence of two methods of artificial reproduction on the weight at birth and weaning of Gyrolando calves using the data from the control books and through the physical taking of the weights. The database, sample size, was 414 calves’ product of embryo transfer (TE) and 269 product of artificial insemination (AI). The information obtained was organized and tabulated in Microsoft Excel sheets based on the different variables studied; Student t tests were applied for independent samples, after fulfilling the requirements of the parametric tests such as normality and independence of data and homogeneity of variances and Mann Whitney U test in case of non-compliance with any requirement. The results are presents in bar and line graphs which allow a better understanding of the information collected. For the processing of the data, the statistical program SPSS version 22 for Windows was used and a reliability of 95%, that is, a level of significance of 5%. The results show that at birth, artificial insemination (AI) weighed less (29,96 kg) than embryo transfer (TE) (32,31 kg), statistically different values. The management and weaning of suckling calves influenced the daily weight gain that was higher for herds of both embryo transfer (1,10 kg), the highest one and for those born by artificial insemination (1,07 kg) while the smallest increase was for transfer of embryos that remained with their mothers (0,62 kg), due to the effects of racial quality and feeding system. The females of the age group 2-4 years gave birth of calves of greater weight at birth at both season of year while those of the group 4-6 and more than 8 years gave birth to calves of lower weight in the summer, corresponding to the age group 4- 6 years to show that females delivery calved with lesser weight in winter. It is concluded that calves of better weights at birth and at weaning are born by TE.