Season of birth influences life span of Mediterranean fruit flies, rats and mice

-

A Study on the Dynamics of the Development of Red Steppe Cows and Their Ayrshire and Holstein Crossbreeds

When purchasing animals from abroad, agricultural enterprises often underestimate their demand for feed quality and feeding standards for ensuring genetically determined milk productivity. Therefore, increasing attention should be paid to raising local breeds. During the creation of new production relations, it is very important to preserve achievements of scientists and breeders. The widespread use of red steppe cows is due to good feed payment, unpretentiousness, and their adaptability to the steppe zone with its arid climate. There was a real threat of extinction of purebred red steppe cattle: with the intensification of dairy cattle breeding, as well as low milk productivity, these animals are inferior to the best dairy breeds by productivity, but they are better by endurance, resistance to diseases, and adaptability to extreme environmental conditions. Therefore, scientific research is needed on improving the productive and technological qualities of this breed using the best global gene pool of dairy cattle. This article presents the results of a study on the development of heifers of purebred red steppe cows and their Ayrshire and red-motley Holstein crossbreeds. Differences in the live weight indicators of the purebred and crossbred heifers were due to the effect of crossbreeding and intensive growing technology, which made it possible to maximize the genetic potential of the crossbred animals. Keywords: breed, steppe red, Holstein, Ayrshire, live weight, feed costs, die

Stressors and antistressors: how do they influence life span in HER-2/neu transgenic mice?

The purpose of this study is to investigate possible influences of different stressors (saline injections, light deprivation and constant light regimen) and geroprotectors (Epitalon and melatonin) on survivals of female HER-2/neu transgenic mice. We propose a semi-parametric model of heterogeneous mortality (frailty model) for the analysis of the experimental data. In this model, we assume that treatment influences parameters of both frailty distribution and baseline hazard. The unique design of the experiments makes it possible to compare the effects on survival produced by different treatments in terms of changes in population heterogeneity and underlying hazard. Parameters of the model help to describe the possible influences of various stressors, geroprotectors, and their dosage on the life span of laboratory animals. The proposed model helps to advance our understanding of the effects-such as debilitation, longevity hormesis and incomplete hormesis-which occur in the population as a result of different treatments

Stress resistance declines with age: analysis of data from a survival experiment with Drosophila melanogaster

An approach towards analyzing survivorship data is proposed for the study of changes in stress resistance with age in the population of Drosophila melanogaster. This is based on the model of heterogeneous mortality (frailty model). Results of the data analysis show that observed populations of flies are heterogeneous and the accelerated selection, debilitative effect and changes in individual frailties are the aftermath of stress. These results also reveal that debilitative effect and accelerated selection are much better pronounced in survivals of flies that are stressed at an older age. Mild stress, when applied at both ages, produced a reduction in frailty variance. Stress of greater magnitude produced higher frailty variance in the young-treated flies. Among the old-treated insects, stress of longer duration led to a reduction of both the mean and the variance of frailty distribution. Population of young-treated flies became more heterogeneous, population of old-treated flies became less heterogeneous, and both populations became more robust in average after stress