Porovnání mléčné užitkovosti genotypů českého strakatého a holštýnského skotu chovaných ve stejných podmínkách

The basic prerequisite to the economic prosperity of an agricultural company specializing in dairy cows is maximum production of milk and, by extension, dairy by-products at minimal production costs. In order to achieve that it is necessary to have dairy cows with the potential to reach optimal dairy production in the conditions of the given agricultural company. The objective of this paper is to assess the effect of genotype, lactation sequence, and age of the dairy cow at first calving on the parameters of her milk productivity. Our monitoring was conducted at a company named CIZ-AGRO, a. s., Cizkrajov. For our analysis, we used productivity data measured from October 2012 to February 2015, during which the cows ended at least one lactation period lasting 240 305 days. These input parameters were collected from a total of 495 dairy cows that had ended a total of 997 lactations. The compilation of lactations was subsequently sorted out by genotype and lactation sequence, and thereupon by genotype and age of the dairy cows at first calving. Thus classified groups were assessed by average milk production, dairy fat, milk protein per lactation, and percentage content of fat and protein in their milk. The obtained results were thereupon subjected to a statistical analysis. The highest average milk productivity per lactation (9283 liters) was achieved by dairy cows in the group H100 that calved first at the age of over 27 months; the lowest milk (6239.2 liters) was recorded with a C100 heifer. In the group classified by lactation sequence, the differences were not statistically significant, the groups classified by the age at first calving, the differences were less significant statistically (P<0.05). Evaluation of the percentage content of milk components as well as the overall production of milk components per lactation in the group of lactations classified by genotype and lactation sequence, there were no statistically significant differences between the individual groups identified. In the group of lactations classified by genotype and age at first calving, the result showed less significant differences (P<0.05) between the group evaluated by total milk fat productivity and milk protein content per lactation. Monitoring the percentage content of fat in the milk in relation to the genotype and age of the dairy cow at first calving recorded medium level of statistically significant differences between the groups (P