Abstract
This study covered 737 controlled first calving Simmental cows with, lactations concluded within one year. All first calving animals were on the farms of individual farmers in the municipalities of Kragujevac and Mladenovac. The research included the influence of bull sires, year and season of calving on milk yield and fertility. Least squares method was used to determine the average duration of lactation of 323.74 days. For a period of 305 days, heifers produced 3701.67 kg of milk, or 3644.58 kg of 4% FCM. The average production of milk fat was 144.26 kg and milk fat content was 3.88%. The interval from calving to first insemination lasted in average 124.19 days, and the animals were first calved at the age of 789.95 days. The bull sires had a highly significant effect (P<0.01) on the duration of lactation, milk yield and 4% FCM, milk fat yield and content and age of cows at first calving. The duration of service period was not under significant effect (P>0.05) of bull sires. Year of calving had a significant effect (P<0.01) on the duration of lactation, production of milk, milk fat and 4% FCM. Milk fat content, service period and age at first calving did not show significant variation due to the impact of different years of calving (P>0.05). Season of calving of cows demonstrated highly significant effect (P<0.01) on the production of milk and 4% FCM, and significant (P>0.05) on the production of milk fat, however it had no effect (P>0.05) on the milk fat content, duration of lactation and service period and age at calving.
Highlights
Milk production is important from the biological aspect as well as from the aspect of production
In order to more precisely determine the effects of different non-genetic factors, all first calving cows included in this study were classified into four groups according to the season, and three groups according to year of calving
Season of calving of cows demonstrated highly significant effect (P0.05) on the production of milk fat and the milk fat content, but it had no effect on the duration of lactation and service period, and age at calving (P>0.05)
Summary
Milk production is important from the biological aspect as well as from the aspect of production. Nikšić et al(2011) have investigated the production potential of first calving Simmental cows calved in the period 2007-2010 in the individual sector in Serbia, and found the average milk production level of 4.348 kg of milk with 3.93% milk fat content and milk fat yield of 171.1 kg. Analysing the production and reproductive performance of Simmental bull dams in our country, Pantelić et al(2005) have found the average age at first conception of 517.61 days, and the duration of the service period of 108.98 days. Pantelić et al(2013) list some of the indicators of milk production and fertility of Simmental cattle population: the duration of lactation - 311.45 days, milk yield - 5754.49 kg, milk fat percentage - 3.98% and milk fat quantity -230.24 kg, and 5755.47 kg – yield of 4 % FCM. The average duration of gestation of studied animals is 286.31 days, 110.37 days of service period, and calving interval of 398.44 days
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