Influence of genetic factors on productive traits of firstcalf heifers

Abstract

The objects for the research were Holsteinized fi rst-calf heifers-daughters of sires with blood of 90 % or more of Holstein breed. In order to carry out the research three groups of first-calf heifers per 30 heads in each were formed. The 1st group included daughters of the sire Privelezh, the 2nd group included the daughters of the sire Alt Pilsner, and the 3rd group included the daughters of the sire Alt Tyson. The infl uence of sires on the productive traits of Holsteinized fi rst-calf heifers of Black-and-White breed was assessed under the conditions of the Petrovsky Agricultural Production Complex in the Bashmakovsky district of Penza region. It was revealed as a result of the research that the highest milk yield for 305 days of lactation was shown by the daughters of the sire Privelezh, which amounted to 9398 kg of milk and had a statistically signifi cant diff erence with the daughters of the sire Alt Pilsner – 3657 kg (Р > 0,999) and with the daughters of the sire Alt Tyson – 3542 kg (Р > 0,999). In terms of qualitative traits of milk productivity, the highest indicators were for fi rst-calf heifers of the 2nd and 3rd groups. For example, in terms of the mass fraction of fat the difference between cows of the 2nd and 1st groups was 0,16 abs.% (Р > 0,95). Diff erences were revealed between the 1st and 2nd groups by 0,04 abs.% (Р > 0,999). At the same time, due to higher milk yields animals of the 1st group exceeded their herdmates of the 2nd group in the yield of milk fat and protein by 127,92 kg (Р > 0,95) and 111,67 kg (Р > 0,999); 3rd group by 128,90 kg (Р > 0,999) and 109,08 kg (Р > 0,999), respectively. First-calf heifers of the 3rd group had the highest live weight (568,7 kg), the diff erence with their herdmates of the 1st group was 57,2 kg (Р > 0,999). Animals of the 2nd group exceeded the first group by 53,0 kg (Р > 0,999). The greatest variability in milk yield over 305 days of lactation was characterized by the 3rd group of cows (Cv=19,83 %) vice versa 17,45 and 18,92 % in the 1st and 2nd groups. First-calf heifers of the 1st group were distinguished by the greatest effi ciency and usefulness, although no significant differences were found between the groups. For example, per 1 kg of live weight, the Biological efficiency of a cow coefficient was 445,45 and the Cow biological f usefulness coefficient was 306,23.