Effects of the Crop-Livestock-Forest System (iCLF) on the reproductive features and puberty of Nelore and Canchim bulls

Abstract

One of the key-points to raising the yield of livestock production systems is the increase in reproductive efficiency, which can be achieved, among other factors, by reducing the age of entry of animals in reproduction. For this, an adequate environment is crucial for sexual development and maximum expression of the animals' genetic potential. It is known that animals subjected to heat stress become more susceptible to changes in their physiological functions, which can impair their development and onset of reproductive activity. In a tropical environment, the Crop-Livestock-Forest (iCLF) systems, which are rich in shaded areas, have been shown to be efficient in increasing the ambience and performance of cattle. In this sense, the present project will aim to evaluate the endocrine, physiological and reproductive characteristics and the puberty of Nelore (Bos indicus) and Canchim bulls (5/8 Bos taurus x 3/8 Bos indicus) kept in pasture under different microclimate conditions in a tropical environment, when the iCLF is adopted as a management strategy for the production of young bulls. Twenty contemporary Nelore and 20 Canchim young bulls, 7-8 months old and 220-230 kg live weight, will be monitored for 10 months after weaning. The experimental design provides for the allocation of 10 Nelore and 10 Canchim bulls in non-shaded pastures (Control Group) and 10 Nelore and 10 Canchim bulls in shaded pasture areas of the iCLF system (iCLF Group). In the study, the effects of system of production, breed and age on the responses of weight, temperament, scrotal thermoregulation, biometry and testicular consistency will be considered, in addition to the echotexture of the testicular parenchyma, and their respective interactions. Semen collections will be carried out for the computerized assessment of motility (CASA) and sperm morphology, in addition to conducting analyzes of the functionality of the plasma and mitochondrial membrane by the tests of osmotic and ultracytochemical resistance, respectively. Blood glucose, testosterone, cortisol and electrolytes of interest will be measured to determine the endocrine-physiological profile of the animals. Statistical analyzes will be carried out using the SAS MIXED procedure (version 9.4). The level of significance previously adopted will be 5%. (AU)