Lucas Luz Emerick

Effects of extender and equilibration time on post-thaw motility and membrane integrity of cryopreserved Gyr bull semen evaluated by CASA and flow cytometry

The objectives of the present study were to investigate the effects of three equilibration times (0, 2, and 4h) and two extenders (TRIS or Bioxcell) for cryopreservation of bull semen. Semen from 12 Gyr bulls was cryopreserved using an automated freezing machine. There were significant interactions between equilibration times and extenders for sperm motility and membrane integrity. The control treatment (0h equilibration) had the lowest values (P<0.05) for total (MOT) and progressive motilities (PROG), and percentage of sperm with intact plasma and acrosomal membranes (IPIA), with no significant differences between extenders. Extender TRIS had greater cryoprotective action than Bioxcell, with greater MOT, PROG, IPIA at 2 and 4h, as well as the lowest proportion of damaged plasma membrane (DPM, 72.2% vs. 85.8%) for all times. Equilibration for 4h yielded the most desirable (P<0.05) for MOT, PROG, and IPIA, and the least DPM percentage (86.5, 78.0, and 72.6% for 0, 2, and 4h, respectively). Overall, the combination of TRIS and 4h of equilibration was the most desirable semen cryopreservation method, with greatest MOT, PROG, and IPIA (TRIS-T4=26.8%; BIO-T4=18.3%) and the least DPM. In conclusion, based on objective analyses, equilibration during cryopreservation was essential for maintaining motility and integrity of sperm membranes; equilibration for 4h yielded the greatest sperm survival, independent of the extender used.

Correlações genéticas e fenotípicas entre características reprodutivas e produtivas de touros da raça Nelore

O objetivo deste trabalho foi estimar correlacoes geneticas e fenotipicas de caracteristicas reprodutivas e ponderais em 579 touros Nelore, em criacao extensiva. As caracteristicas reprodutivas estudadas foram: circunferencia escrotal, consistencia, volume e forma testiculares, comprimento dos testiculos esquerdo e direito, largura dos testiculos esquerdo e direito, motilidade e vigor espermaticos, defeitos espermaticos maiores, menores e totais e classificacao andrologica por pontos. As caracteristicas foram analisadas pelo metodo de maxima verossimilhanca restrita, com algoritmos livres de derivadas, sob modelo animal, com inclusao da matriz de numeradores dos coeficientes de parentesco entre os animais e seus ascendentes. As correlacoes geneticas entre circunferencia escrotal e as caracteristicas peso corporal, volume testicular, motilidade espermatica, vigor espermatico, defeitos espermaticos menores, defeitos espermaticos totais e classificacao andrologica por pontos foram, respectivamente, 0,72, 0,99, 0,72, 0,60, -0,67, -0,12 e 0,64. As maiores correlacoes fenotipicas encontradas entre peso e circunferencia escrotal, caracteristicas fisicas e morfologicas do semen, quando comparadas as correlacoes entre idade e as mesmas caracteristicas, sao indicativas de que o peso tem maior influencia na condicao reprodutiva. As correlacoes geneticas entre classificacao andrologica por pontos e as caracteristicas: peso, circunferencia escrotal, volume testicular, defeitos espermaticos maiores e defeitos espermaticos totais foram, respectivamente, 0,19, 0,64, 0,71, -0,47 e -0,58.

Carcass and meat traits of feedlot Nellore bulls fed different dietary energy sources

The objective of this experimental study was to evaluate the effects of different dietary energy sources on the carcass and meat traits of feedlot Nellore bulls. A total of 48 Nellore bulls at 32 months of age with 354.35±19.56 kg body weight were studied for 85 days. The bulls were allotted to four groups of 12 individuals: Whole corn grain - diet based on whole corn grain; Ground corn - diet based on ground corn grain; Citrus pulp - diet based on citrus pulp; and Steam-flaked corn - diet based on steam-flaked corn. Diets did not influence carcass quality or meat quality. Average values for fat depth, rib eye area, shear force, total cooking losses, and carcass yield were 4.97 mm, 74.71 cm2, 5.85 kgf, 26.82%, and 52.0%, respectively. Based on the quantitative and qualitative analysis of this study, there is no restriction for the adoption of any of the tested diets in feedlots with Nellore bulls and the evaluated energy sources may be used to replace ground corn grain.

Leptin and insulin in the seminal plasma of zebu bulls in peripuberty

In order to determine the profile of leptin and insulin values in seminal plasma and their correlations with sperm patterns during the peripuberty, a total of 16 crossbred Gyr dairy bulls were monitored from 60 days before to 60 days after puberty, separated into two groups, early and regular, according to the onset of puberty. Hormone values were determined by radioimmunoassay after gel filtration in fast performance liquid chromatography and semen patterns, according to the Brazilian College of Animal Reproduction. Insulin concentrations in seminal plasma did not differ between groups, nor between the ages, with the pooling of the data showing average of 35.15±16.93, 36.60±26.21, 26.82±09.81, and 43.56±31.71 32.24±16.71 U/mL for the pubertal period of -60, -30, 0, +30 and +60 days, respectively. These values were not correlated with sperm parameters, but differed in the group of animals with the highest percentage of major defects (31.08±18.58 U/mL) compared with those with lower percentage of these sperm defects (40.01±25.37 U/mL). Leptin was not correlated with sperm parameters and did not differ between groups or stage of sexual development, with concentrations of 23.10±10.43, 24.35±9.42, 22.41±9.90, 23.76±9.69 and 24.99±11.42 ng/mL for the periods of puberty aforementioned, respectively, after being grouped. These results demonstrated the binding of insulin to the structural quality of the sperm cell, and this hormone is indicated in andrologycal evaluation of future breeding soundness.