Data from 34 yearling Hereford or Angus bulls were used to investigate relationships of testicular size, quantitative rates of sperm production, Sertoli cell numbers, numbers of germ cells supported per Sertoli cell, and the efficiency of spermatogenesis to daily sperm output and seminal quality. Two ejaculates were collected by electroejaculation from each bull on each of 2 days/week throughout the study. The percentage of progressively motile sperm and the percentage of morphologically normal sperm were determined from aliquots of fresh semen. Additional aliquots of semen were frozen in glass ampules or plastic straws and subsequently evaluated for postthaw motility and percentage of sperm with intact acrosomes. Sertoli cell numbers, the numbers of germcells per Sertoli cell, and the efficiency of spermatogenesis were unrelated to the quality of fresh or frozen semen (P greater than 0.05). In first ejaculates, the numbers of sperm and motile sperm were related (P less than 0.05) to testicular parenchymal weight (r = 0.38, and 0.50), daily sperm production (r = 0.45 and 0.53), and spermatids per gram of testicular parenchyma (r = 0.35 and 0.34). Testicular parenchymal weight and daily sperm production also were related to daily sperm output and to the average daily motile sperm output of these bulls (P less than 0.05), but could account for less than 25% of the variability in these end points among bulls.

Firfty serum and fifty semen samples collected from cattle and buffalo bulls were subjected to ELISA and gB gene based PCR, respectively to detect antibodies in serum and viral DNA in the semen against BHV 1. Out of 50 bulls, 15 (30%) serum samples were detected positive by ELISA while 21 (42%) semen samples were positive by gB gene based PCR. While correlating the results of ELISA and PCR, some seronegative bulls revealed presence of viral genome in semen whereas few seropositive bulls could not reveal viral genome in semen, thus, suggesting application of combined serological assay and PCR assay to detect the presence of BHV-1 infection in bulls.

The effect of two thawing temperatures (37°Cfor30 sec. and 60°Cfor 7 sec.)on sperm survivability and conception rate in buffaloes with frozen semen of Murrah bulls was compared. Thawing at 60°C resulted in statistically significant increase (P0.05) in sperm survivability (motility,live spermatozoa and intact acrosomes) compared with thawing at 37°c. In all, 161 buffaloes were inseminated with frozen semen thawed at 37°Cand 159buffaloeswith semen thawed at 60°Cbetween 2006-07 and 2009-10. Conception rate of 64.15% and 50.31% was obtained with semen thawed at 60°C and 37°C, respectively, and the difference was significant (P0.05). Artificial insemination of buffaloes with frozen semen thawed at 60°C for 7 sec. could be safely used to improve both sperm survivability and conception rate in buffaloes.

The objective of this experiment was to study wheather the administration of GnRH plus PGF2 alpha synchronizes the estrus in anestrus crossbred cows exposed to bull urine (BU) during the winter season (Nov to Feb). The results indicated that a greater proportion of BU-exposed cows (n=20) showed estrus as compared to control (n=8) (90 vs 37.5 % P0.05). The mean plasma progesterone concentration remained below 1ng/ml in all animals of each group during the treatment period. The overall conception rate was double in BU-exposed cows (66.7 vs 33.3 % P0.05). From this experiment it can be concluded that oro-nasal application of BU synchronizes the estrus in a greater proportion of anestrus cows treated with GnRH plus PGF2 alpha during winter season.

In the conditions of the Republic of Belarus there was determined the influence of experimental feed mixtures on the basis of humid preserved grain (conserved rolled grain of triticale; barley (Hordeum vulgare); oat (Avena sativa)) and protein, mineral and vitamin supplement (contains rape (Brassica napus) extraction cake; wheat bran; premix PKR-2; chalk; forage phosphate) on digestibility and metabolism of nutritive elements by young stock of cattle. There were presented recipes of the developed experimental feed mixtures and studied their influence on consumption and digestibility of nutritive elements of diets, metabolism of nitrogenous substances, calcium, phosphorous, as well as on hematological indexes. The proposed mixed fodders contained metabolizable energy; dry matter; crude protein; digestible protein; crude fat; fibre; starch; sugars; calcium; phosphorous; magnesium; potassium; sulphur; iron; copper; zinc; cobalt; manganese. In course of the study there was analyzed the consumption of the main nutritive elements; coefficients of their digestibility; nitrogen balance; balance of calcium and phosphorous; morphological and biochemical blood indexes.

Studying of efficiency of application of modified scheme of hyperimmunization of bull-producers with a designer salmonella polyantigenin in comparative analysis with the production scheme of hyperimmunization was realized in the conditions of the Republic of Belarus. Research results showed that engineered polyvalent antigen for hyperimmunization of producer bulls contained in their formula the following serovariants of salmonella in 1:1 ratio: S. typhimurium 371, S. dublin 373, S. choleraesuis 370, and S. enteritidis CB. The obtained antigen was sterile, harmless and had pH 7,3. Hyperimmunization of producer bulls in the experimental scheme revealed in increasing of leukocytes quantity on 57,3 %, banded neutrophils on 86,7 %, B-lymphocytes - on 42,2 %, content of total protein - on 25,6 %, content of Ig G - on 77,8 %, lg M - on 51,6%. After the fifth administration of antigen there was stated the lowering of agglutinating activity of blood serum on 25%, content of Ig G - on 54,4%, Ig M - on 14,6 %, that indicated to the inefficiency of antigen administration and became the basis for termination of hyperimmunization cycle. Immunobiological reaction of bull-producers which were hyperimmunized by the suggested scheme differed from reaction of animals which were hyperimmunized by the production scheme: content of total protein increased on 10,1%, protein content - on 27,3 %, content of lg G - on 24,8 %, lg M - in 23,7%