Vladan Bogdanovic

Simmental cattle breed in different production systems

The paper gives the analysis on the state in population of Simmental cattle reared in Europe with a special review on the state in Simmental cattle in our country which makes about 80 % total cattle fund in Serbia, and is characterized by a negative trend in the number of cattle, as well as by a low average milk production per cow. The most important results obtained by both domestic and foreign authors by means of various methods of improving Simmental breed and its raising in different systems have been shown. The directions for improving Simmental cattle according to the productive directions have been analyzed. Possible methods of improving the Simmental cattle in our country have been pointed out, which should be in accordance with already existing genetic potential of each actual population, its purpose (registered breeding stock, production breeding stock), as well as with the market needs for cow milk, milk products and meat (primarily beef meat, for export). A special emphasis has been given to the importance of organizing the production of meat in the cow-calf system in which Simmental breed, following the model of many European countries, should have good performance also in our country, if the same production should be organized in deserted hilly and mountainous regions. In this way we could contribute to more significant increase in overall beef production, and to reactivate unused natural resources as well.

The state in the sector of milk production in European Union and in our country

The paper gives an analysis of the state in milk production from the aspect of total produced quantities of milk and total purchased quantites of milk by the diaries in EU. The number of farms engaged in cattle production has been analysed, along with the farms engaged in milk production. Trend in development of cattle breeding in EU is going in the direction of decreasing the number of farms raising the breeding stocks of dairy cows and to the simultaneous increase in the number of cows per farm for milk production with constant increase of the quantity of milk produced per cow. In 2008 the number of cows per farm in EU27 was on average 9.8 cows, in EU25 on average 16.6 cows, with great variation among member countries observed. Average milk yield in total cow population in 2008 in EU15 was 6646 kg, in EU25: 6357 kg and in EU27: 6133kg. In Serbia the average milk yield in registered cows of Simmental breed is about 4500 kg, and in Holstein Friesian breed around 8700 kg. It is important to emphasize that in Serbia there is a far less number of cows under controlled milk yield (around 5.5% Simmental cows in total number), and that there is a decline observed in the number of cattle in Serbia in the last decade per average rate of 2-3 % annualy.

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.

EFFECT OF NON-GENETIC FACTORS ON STANDARD LACTATION MILK PERFORMANCE TRAITS IN SIMMENTAL COWS* *

Abstract The effect of systematic and continuous environmental factors on milk performance traits over standard lactations in 2805 Simmental cows was evaluated using the general linear model. The systematic factors included the effect of farm or breeding area, calving season, year of birth, season of birth, lactation group and their interactions. The continuous factor analysed was the effect of age at first conception. The effect of farm, lactation group and calving season on standard lactation milk performance was found to be highly significant (P<0.01), excepting the effect of calving season on milk fat percent in standard lactations which showed statistical significance (P<0.05). The interactions between year and season of birth, farm and calving season, and farm and lactation group had a highly significant effect (P<0.01) on all performance traits studied. Age at first conception, as a continuous factor, had a highly significant effect (P<0.01) on milk yield and milk fat percent, and a non-significant effect on milk fat yield. The model used to correct the performance traits over standard lactations for the effect of systematic factors was highly significant (P<0.01). The variance of the model accounted for 20.06 and 37.31% of the total variance of milk fat yield and milk fat percent, respectively. The resulting coefficients of determination (R2) ranged from 0.20 for milk fat yield to 0.37 for milk fat percent.

Regression analysis of milk production traits in Simmental cows.

The relationship between milk production traits over whole lactations was evaluated across three generations of Simmental cows, i.e. between daughters, dams and grand dams, by a phenotypic regression analysis with whole lactation traits in the daughter generation being used as the dependent variables (x1), and those in the dam and grand dam generations being used as the independent variables (x2 and x3). The results were obtained from a sample of 1170 daughters and as many dams and grand dams. The significance of the partial regression coefficients b2 and b3 was separately evaluated by a t-test. An analysis of variance was used to estimate the significance of the simultaneous effect of the production traits of dams and grand dams on the milk production achieved in the daughter generation. The calculated value of the partial regression coefficients for the whole lactation production traits across three generations (grand dams, dams and daughters) and their statistical significances determined by the t and F tests, as well as the regression equations used, suggested that the effect of the grand dam generation on the milk production traits in granddaughters was substantially lower than the effect of dams. The calculated partial regression coefficients (b2 and b3) were positive and statistically very significant (P<0.01), excepting the regression coefficients b3 for lactation length and b2 for milk fat content that were not statistically significant (P>0.05). A very significant change (P<0.01) was observed in all production traits in the daughter generation as simultaneously affected by the traits in the dam and grand dam generations.