Abstract
Exceptionally important aspect in cattle production, from the aspect of production and economy, is ensuring normal and regular fertility. Every cattle breeder wants to have high-yielding animals which at the same time have good fertility. In proper cattle breeding this means that from each cow during single year one healthy calf is obtained. Use of artificial insemination has enabled that one breeding male is used as sire for several tens of thousands of progeny, however, there is always the risk that sires could be carriers of lethal and semi-lethal genes, which can cause huge losses of calves. In order to bring these undesirable occurrences to a minimum, so called bilogical test is included in the breeding and selection activities, i.e. bulls are tested through their progeny for presence of difficult calving (dystocia) abd calf losses caused by genetic anomalies. In Republic of Serbia, this test is carried out on ehtire Simmental population in an exchange of data produced by primary breeding organizations. Per each tested bull, it is necessary to have data on minimum 50 randomly selected calves. Calves are examined visually 65 days after the birth, at the latest. In the present study, the results of the biological testing of 35 Simmental bulls, sires of total 3572 calves on the territory of Central Serbia, in the period 2008-2009, are used. The effect of sires on parameters of biological test were studied: body mass of calves at birth, calf score and calving score. Also, bulls were ranked based on said parameters, male/female calves ratio and percentage of twins and still-born calves for each bull individually were determined. After the rank of bulls was established, the correlation between the rank and studied fertility traits was determined. Correlations were expressed using the Spearman coefficient. Research results show that the effect of bulls was very high p<0,001 on all three parameters of the biological test, and also that the percentage of still born calves for all bulls was within limits, with the exception of bulls Zahlo (HB 1497) and Woz (HB 1433) where it was above 5.
Highlights
For present trends in modern production of milk and meat it is absolutely unacceptable to have one-sided selection for productive traits only, because it can greatly contribute to numerous metabolic disorders and shortening of productive life
In order to bring these undesirable occurences to a minimum, so called bilogical test is included in the breeding and selection activities, i.e. bulls are tested through their progeny for presence of difficult calving abd calf losses caused by genetic anomalies
Research results show that the effect of bulls was very high p
Summary
For present trends in modern production of milk and meat it is absolutely unacceptable to have one-sided selection for productive traits only, because it can greatly contribute to numerous metabolic disorders and shortening of productive life. Biological test provides the right information on breeding value of bulls in the progeny testing. It includes study of bulls in terms of inheritance of degenerative properties, potential incidence of calves with congenital deficiencies and defects, lethal and semi-lethal factors which ensures acurate insight of the quality of calves obtained from individual bull sire. With this test, practically, it is established if breeding male is carrier of lethal, semi-lethal or harmful genes, where:
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