Abstract Letrozole comprises a non-steroid aromatase inhibitor that has been applied as a preventive for many uses, such as breast cancer prevention, treatment of hormonal dysfunction, and male infertility. Precisely in Northeast Brazil, ovine consist of the leading livestock produced, and their reproduction in captivity has been demonstrated difficult. Thus, we hypothesized whether the application of letrozole will improve male sheep reproduction. One group of 6 animals received a daily dosage of 0.5mg/Kg of letrozole for 60 days, while the other six animals were used as control. Samples were collected from control and treated animals after 30 and 60 days of the experiment. Blood samples were collected to measure the steroid hormone levels. Semen was collected from control and treated groups using an artificial vagina and cryopreserved for spermatozoa morphology and CASA analysis. The testicles were collected for histological analysis, gene expression, and immunohistochemistry of P450aromatase protein. Hormone levels demonstrate no differences in the estradiol/testosterone levels among the control and both treated groups. Immunohistochemistry analysis revealed the presence of P450aromatase protein in spermatogonia cells and Leydig cells in the control and treated groups in both periods analyzed. Moreover, there were no differences in the P450aromase gene expression in the control and treated group. Morphological analysis of the spermatozoa revealed that letrozole treatment did not affect mitochondrial activity or cause any deformities. In addition, motility parameters in the sperm from the treated group were not affected by letrozole treatment compared to the control group. Morphological analysis of the testis demonstrated that letrozole treatment increase the seminiferous tubule area but no signs of germ cell damage. Our results show that letrozole has a morphological effect on the testicles in the ovine model but no pathological or severe effect caused by hormone level imbalance. Overall, letrozole comprises a non-steroid aromatase inhibitor, which can be applied to ovine reproduction.

RESUMO: O objetivo deste estudo foi estimar componentes de variância e parâmetros genéticos para marmoreio na área de olho de lombo (MOL) e escore de condição corporal (ECC) usando Inferência Bayesiana por meio dos modelos animais linear misto e de limiar. Os dados foram obtidos em rebanhos de ovinos da raça Santa Inês criados no Meio-Norte do Brasil. As análises, considerando os métodos de Monte Carlo, foram realizadas com cadeias de Markov a partir de 500000 ciclos. Considerou-se burn-in inicial de 200000 ciclos com valores tomados a cada 250 ciclos, obtendo-se 1200 amostras. Os desvios do erro de Monte Carlo foram baixos para as herdabilidades médias em todas as cadeias, tanto pelo modelo linear quanto de limiar. As variâncias aditivas, estimadas pelo modelo de limiar, foram maiores que aquelas obtidas pelo modelo linear. O marmoreio na área de olho de lombo e o escore da condição corporal podem ser usados como critérios de seleção para obter progresso genético em ovinos da raça Santa Inês.

ABSTRACT: The aim of this study was to estimate the variance components and genetic parameters for marbling in the ribeye area (MRA) and body condition score (BCS) using Bayesian inference via mixed linear and threshold animal models. Data were obtained from Santa Ines breed sheep reared in the Brazilian Mid-North region. Analyses considering the Monte Carlo methods were performed with Markov chains from 500000 cycles onward. A 200000-cycle initial burn-in was considered with values taken at every 250 cycles, in a total of 1200 samples. The Monte Carlo Error deviations were low for the means heritability in all chains by both linear and threshold models. Additive variances estimated by threshold model were higher than those estimated by the linear model. Marble meat from the ribeye area and body condition score can be used as selection criteria to obtain genetic progress in Santa Inês sheep.

The objective of the present study was to evaluate the feeding behavior of feedlot Nellore bulls fed two levels of concentrate (650 and 710 g/kg dry matter) with or without the inclusion of 350 g babassu mesocarp meal/kg dry matter in the concentrate. Twenty-eight animals at 18 months of initial age and 356.66±19.25 kg initial body weight were used. A completely randomized design was used with treatments in a 2 × 2 factorial arrangement. Increase in concentrate level from 650 to 710 g/kg dry matter did not change the feeding time, of 194.41 and 189.64 minutes/day, respectively. The inclusion of 350 g babassu mesocarp meal/kg dry matter in the concentrate increased the feeding time from 173.92 to 210.12 minutes/day, ensuring similar energy intake in relation to the diets without this byproduct. Rumination time was not changed by increasing the concentrate level in diets with 350 g babassu mesocarp meal/kg dry matter in the concentrate, with average values of 420.48 and 398.09 minutes/day for the levels of 650 and 710 g concentrate/kg dry matter, respectively. However, in diets without babassu mesocarp meal, the rumination time was reduced by the concentrate level, with average values of 452.14 and 409.76 minutes/day for 650 and 710 g of concentrate/kg dry matter, respectively. Time spent on other activities increased from 810.23 to 860.00 minutes/day with increase in the concentrate level, which was not changed in the diets containing babassu mesocarp meal. The inclusion of babassu mesocarp meal in the diet altered the feeding behavior of feedlot cattle, due to the need to increase the feeding time to maintain the energy intake.