The Effect of the Use of Sexed Semen on Reproductive Traits and Sex Ratio of Black and White Calves

Sperm sexing is a relatively new biotechnological procedure which offers us the possibility to choose the offspring sex. This method is widely used today in the insemination of the dairy cattle breeds and it is based on the difference in total DNA quantity between X and Y chromosome spermatozoa. In this research paper we have analysed the fertility, sex ratio and characteristics of female Black and White breed calves inseminated by the sexed sperm produced by 6 bulls on 6 commercial farms of the PK Belgrade. Conception rate was 44% with average gestation length of 274.9 days. Average calf birth weight was 36.75 kg. The stillbirths and twinning rates were 7.16 and 1.13%, respectively. Artificial insemination by sexed sperm assessed by c2 test highly significantly (P0.05) gestation length. Regardless the low conception rate, the application of sexed sperm in dairy cattle breeding is very significant since it enables the breeders to use the best replacement female animals what may result in the improvement of genetic basis of breeding stock

PHENOTYPIC VARIABILITY OF FERTILITY AND MILK TRAITS IN OFFSPRING OBTAINED BY INSEMINATION BY SEXED AND CONVENTIONAL SEMEN OF HOLSTEIN BREED BULLS

The objective of this paper was to compare heifers reproductive traits and characteristics of their calves after artificial insemination performed by conventional (non-sexed) and sexed sperm on 6 commercial farms in Serbia. Conception rate was 55% and 44% for conventional and sexed semen, an average gestation length being 274.6 and 274.9 days, respectively. Average body mass at birth was 37.47 and 36.75 kg for non-sexed and sexed semen, respectively. The rate of stillbirths and twinning was 6.19 and 3.78% for conventional and 7.54 and 1.13% for sexed semen, respectively. The use of conventional semen exerted no statistically significant (P>0.05) effect on female: male calves relationship (51.96 : 48.04) while artificial insemination by sexed semen highly significantly (P<0.01) changed calf sex-ratio (85.10 : 14.90). First-calf heifers originating from sires whose sperm was obtained in conventional way produced 7880 kg milk with 269 kg milk fat and 242 kg protein in standard lactation, while first-calf heifers originating from sires whose sperm was sex-sorted produced 8184 kg milk with 251 kg milk fat and 242.3 kg protein. Type of insemination (conventional and sexed semen) did not significantly affect the studied milk yield traits (P>0.05)

Correlation analysis of milk production traits across three generations of Simmental cows

The relationship between milk production traits over whole lactations was evaluated across three generations of Simmental cows (between daughters, dams and granddams) by a corelation analysis with whole lactation traits in the daughter generation being used as the dependent variables (x<sub>1</sub>), and those in the dam and granddam generations being used as the independent variables (x<sub>2</sub> and  x<sub>3</sub>). The results were obtained from a sample of 1170 daughters and as many dams and  granddams. The correlation of whole lactation milk production traits between daughters, dams and  granddams, as calculated by simple, partial and multiple correlation coefficients was very weak or  non-existent. All of the calculated simple and partial correlation coefficients were positive and mostly  statistically very significant (P<0.01). The calculated coefficients of multiple correlation (R1.23) between  lactation length, milk fat content, milk yield, milk fat yield and 4% FCM yield with the expression of the traits in the daughters being used as the dependent variable and that in the dams and granddams as the independent variable were statistically very significant (P<0.01), amounting to 0.091, 0.251, 0.180, 0.133 and 0.153, respectively.Key words: Simmental breed, production traits, generation, coefficient of partial correlation, coefficient of multiple correlation

Uticaj paragenetskih faktora na intenzitet plodnosti kod krava simentalske rase

In scientific literature, fertility is generally assessed through age at first conception, gestation length, length of service period, calving interval, and calf birth weight. Determination of the effect of particular non-genetic factors on the above traits is a vital step in cattle breeding and reproduction. Length of calving interval is largely governed by the effect of non-genetic factors, viz. fixed effects generally including the effect of breeding region, season of birth, calving season, year of birth, calf sex and their interactions, and continuous or regression effects including age at first conception or age at calving. The effect of fixed and continuous non-genetic factors on length of calving period was analysed in 245 Simmental cows (907 calving interval) in three breeding regions, with the effect of season of birth as a fixed factor and cow age at first conception as a continuous factor being highly significant (P 0.05).U literaturi plodnost se najčešće posmatra preko uzrasta pri prvoj oplodnji, trajanja bremenitosti, servis perioda, intervala između telenja i mase teladi pri rođenju. Determinisanje uticaja pojedinih sistematskih faktora na pomenute osobine od velike je važnosti u procesu odgajivanja i reprodukcije goveda. Dužina intervala između telenja definisana je najvećim delom dejstvom paragenetskih faktora, od kojih kao fiksni uticaji najčešće se pominju uticaj odgajivačkog područja, sezone rođenja i telenja, godine rođenja, pola teladi i njihove interakcije, a od kontinuelnih ili regresijskih uzrast krava pri prvoj oplodnji ili telenju. Analiza uticaja fiksnih i kontinuiranih negenetskih faktora na dužinu odnosno trajanje intervala između telenja izvršena je kod 245 krava (907 međutelidbenih intervala) simentalske rase raspoređenih na tri odgajivačka područja pri čemu je uticaj sezone rođenja kao fiksnog i uzrasta krava pri prvoj oplodnji kao kontinuiranog faktora bio visoko značajan (P0.05)

Base Characteristics, Preservation Methods, and Assessment of the Genetic Diversity of Autochthonous Breeds of Cattle, Sheep and Pigs in Serbia: A Review

Preserving local autochthonous domestic animal populations and the products derived from them is a crucial aspect of managing human utilization of the biosphere. This management approach aims to ensure sustainable benefits for both present and future generations. The diversity of autochthonous domestic animal populations plays a vital role in the functionality and sustainability of the food production system. It encompasses both productive and non-productive aspects, contributing significantly to the overall health, nutrition, and food security of the landscape by providing a wide range of animal-derived food resources. Based on the data contained in the Draft Program of Rural Development, a significant presence of more than 44 autochthonous and local breeds of domestic animals has been noted in Serbia. In order to enable the sustainable preservation of local domestic animals, the competent Ministry of Agriculture of the Republic of Serbia has, through a number of projects, implemented models for the preservation of local breeds on farms (in situ), as well as provided technical assistance to small farms that keep animal collections. It also helps the local population to procure animals, conducts product quality research, and provides opportunities to integrate conservation programs through tourism. Given that molecular characterization is a key factor for the preservation of autochthonous breeds, in the Republic of Serbia, DNA markers are used for identification and to investigate the belonging to a specific breeds or strain. All the mentioned activities led to an immediate increase in the number of animals, which is especially true for the autochthonous breeds of cattle (Busha), sheep (Sjenicka, Svrljiska, and Vlach-vitohorn) and pigs (Mangalitsa, Moravka, and Resavka) that are discussed in this paper. In addition to the significant measures undertaken to preserve animal genetic resources (AnGR), it is necessary to continue to work primarily on ex situ conservation in order to prevent the loss of their gene pools. However, regardless of the evident effort that has been made to preserve autochthonous genetic resources in Serbia, we believe that there is still a lot of room for further improvement. This primarily refers to advanced technologies that have not been applied so far, mostly related to the identification of genomic regions associated with economic traits, resistance to diseases, and adaptability to emerging climate changes. In this way, the production capacity and functional characteristics of autochthonous species and breeds of domestic animals in Serbia will be improved