Dragan Stanojević

Involuntary reduction in vigour of calves born from sexed semen

The objective of this study was to compare the reproductive traits of heifers and the development characteristics of their calves following artificial insemination (AI) with sexed and non-sexed semen. The analysed characteristics included conception rate, gestation length, calf birth weight, calf vigour, stillbirth rate, and twinning rate. Data of 530 calves produced with sexed and 1,163 calves produced with non-sexed semen were analysed. The General Linear Model (GLM) was applied to assess the influence of semen type, farm, season of insemination, the calfs sex and the inseminating sire on gestation length and calf birth weight. With the exception of gestation length (P > 0.05), all other traits studied were significantly (P < 0.01) influenced by the type of semen. The conception rate was 55% for conventional and 44% for sexed semen, and the average gestation length was 274.6 and 274.9 days, respectively. The mean calf birth weight was 37.47 kg for non-sexed and 36.75 kg for sexed semen. The stillbirth rate was 6.19% for conventional and 7.54% for sexed semen, while the twinning rate was 3.78% for conventional and 1.13% for sexed semen. The calves produced with non-sexed and sexed semen differed significantly in viability (P < 0.001), the latter having a lower calf vigour score. The use of conventional semen did not affect the ratio of female and male calves (52.7:47.3%; P > 0.05); however, artificial insemination with X-sorted sexed semen significantly altered the sex ratio of calves (85.1:14.9%, P < 0.01). The results obtained in this investigation are in agreement with the majority of studies which compared the fertility traits, sex ratio and calf characteristics depending on the application of artificial insemination with sexed or conventional semen.

THE EFFECT OF THE LEVEL OF MILK YIELD ON THE REPRODUCTION TRAITS IN BLACK AND WHITE COWS

In this study a relationship between the milk yield and following reproduction traits: number of inseminations per conception (AIS), service period (SP), age at calving (AC), calving interval (CI) and birth weight (BW) is studied. The research involved dairy cows of European type of Black and White cattle which are being intensively improved by the genes of Holstein - Friesian breed. Mean values of general average for number of inseminations per conception, service period, age at calving, calving interval and birth weight are: 2.00; 98.78; 1088.08; 376.70 and 36.40, respectively. In general, the estimated phenotypic correlations (rp) between the milk yield over standard lactations and fertility traits were positive and unfavorable, and ranged from 0.24 for the relationship between milk yield and birth weight to 0.70 for relationship between milk yield and age at calving.

Elements of life satisfaction among young adults in Serbia

ABSTRACT Contemporary sociological studies argue that employment and personal life have diversified effects as determinants of life satisfaction (LS) of young adults. We have, therefore, decided to explore the three different aspects of general LS, satisfaction with personal (intimate) domain, satisfaction with family life and satisfaction with occupation (professional domain), by using the survey data on 1627 young adults aged from 19 to 35 from Serbia. The correlations between the three domains are significant, while the strongest tie is between satisfaction with intimate relations and satisfaction with family life. The analysis exposed that social variables (employment, education, housing autonomy and financial autonomy) and personal variables (partnership and parenthood) are in a diverse manner related to the three domains of LS, as well as that their effects are different for young men and women. Taking into account particularities of social context in Serbia, we have introduced functional autonomy (decision-making and acting independent of parents) as mediating variable. The results uncover that functional autonomy has little influence on satisfaction with occupation, while social variables have a strong effect, suggesting that agency in professional domain is significantly socially bound. Regression models reveal divergent and gender-specific relations of variables and three aspects of LS related to particular structural and cultural context in Serbia that sets limits to gender detraditionalization.