Utjecaj bikova očeva holštajn pasmine na mliječnu proizvodnju njihovih kćeri u prvoj laktaciji

The current production of the dairy farms in the Federation of BiH uses deep frozen sperm of the Holstein breed. However, the sperm usually comes without any information on progeny test of the bulls or production value indexes enclosed. On the other hand, the farms do not examine or register all the characteristics relevant to the future generations. This paper only examines the effects pertaining to the standard and absolute lactation milk yield for individual bulls. The quantity of milk in the first standard lactation was taken as a basis for our analysis. It was found that the average quantity of milk in the first standard lactation for 410 first-calf cows was 5,515 kg, with the variations ranging from 2,658 to 8,728 kg, with standard deviation of 1,013 kg and the large relative coefficient of the variability (18.3%). In the period from 1998 to 2005, the sperm from 101 bulls was used at the farm, out of which only 11 bulls had 10 and more daughters. For this reason, the system of Contemporary Comparison was applied on these individual bulls, in order to examine relative upbringing value – RUV. It was found that only five bulls had RUV higher than 100%, where the positive difference between the average values of these daughters and contemporary cows with the same age ranged from 1,228 to 635 kg. The negative RUV for six bulls ranged from 136 to 725 kg, which means that the father bulls of these first-calf cows really reduced the produced milk quantity in the first standard lactation. If the farm’s management was aware of this, they would not permit to have their sperm used at the farm, and also of the bulls whose number of doses was too small, so it was not possible to determine their RUF effect. One of the characteristics of this farm is that the cows were milked for too long. Only 107 cows, or 26.22%, were milked up to 356 days. This means that the majority of the first – calf cows, a total of 303 heads or 69.51%, had the lactation period longer than one year. An average duration of the absolute lactation was 432.5 days. Due to the reason of prolonged lactation, daily milk quantities were reduced during the final stage; likewise, the number of calves was reduced, as well as the utilization of increased lactation during the first three lactations which, in case of Holstein breed, represent the highest lactation quotas in the overall lactation sequence.