PRODUCTION PERFORMANCES OF COWS OF DIFFERENT ORIGIN AND HOUSING METHOD

: In order to examine the variability of production performance traits (lactation duration, milk yield for the whole lactation, milk yield in standard lactation, milk fat content, milk fat yield in standard lactation, protein content and yield in standard lactation), 954 cows, domestic and imported Simmental populations, were included in the study, with a total of 3641 completed lactations. Cows were located in the area of Toplica district, reared on individual farming households (tied system) and on the farm with intensive farming (free system). Based on the rearing method and origin, animals were divided into four groups: Group 1 (domestic animals reared by individual agricultural producers on individual farming households); Group 2 (imported animals reared by individual agricultural producers on individual farming households); Group 3 (domestic animals reared on the farm) and Group 4 (imported animals reared on the farm). The fourth group of studied cows showed the highest yield and protein content, while the cows of the third group had the longest lactation and the highest milk fat content. All production performance traits varied highly significantly (p≤0.001) under the influence of the combined factor of housing/rearing method and origin.


Introduction
Milk production has biological and production significance. Together with reproduction, it is the material basis for the maintenance of the species. In terms of production, in addition to being the highest quality human food, it also provides the basis for meat production through rearing calves. Milk yield is the most important feature of milk performance and is determined for the whole lactation, as well as for the standard 305 day lactation. Milk production in standard lactations, i.e. 305 day lactation, enables the mutual comparison of lactations of different duration. Different genotypes of Simmental cows (domestic cows and Simmental cows imported from Germany and Slovenia), their production and reproductive traits, are examined by Perišić (1998,) in the region of upper flow of the Kolubara River. The study shows the average duration of the first three lactations of 307.18 days, in all animals insluded in the study, and the average milk yield for the duration of lactation of 4311.1 kg. The lowest milk yield is recorded in cows of Domestic spotted breed with production in the first three lactations of 3738.8 kg, 4033.4 kg and 4384.3 kg, respectively and the highest yield by cows of the German Simmental breed -4120.4 kg, 4669.2 kg and 5153.2 kg. The study shows the average milk fat content for the whole lactation of 3.83%, for all animals included in the study, an average milk fat yield of 165.06 kg and 4191.17 kg of 4% FCM.
In the study of the major milk performance traits of F 1 daughters of the same Simmental bulls in Germany and Serbia, Kučević et al. (2005) have established significantly greater absolute difference in the quantity of milk produced of 1057 kg in the F 1 generation in Germany, the difference at the level of significance (p ≤0.05). A statistically significant difference (p≤0.01) has been determined for milk fat and milk fat content, with daughters tested in Germany achieving higher production.
By comparing the three-year average of the best Simmental herd in our country and the average established for imported first calving heifers from Austria during 2004-2005, Medić et al. (2006 have determined the milk yield of 4472 kg for 305 days, for domestic animals, which is lower compared to imported animals by significant 1171 kg of milk. Austrian animals also had a significantly higher average milk fat content of + 0.49% and a total milk fat content of +73 kg. These differences of mean values are highly significant. Pantelić (2006) states that the average duration of lactation in first calving Simmental heifers in Serbia is 311.72 days, with a minimum duration of 241 and a maximum of 586 days.
In the study of the production potential of first calving Simmental heifers calving in the period 2007-2010 in the individual sector in Serbia, Nikšić et al. (2011) have recorded the average milk yield of 4348 kg, 3.93% milk fat content and milk fat yield of 171.1 kg. With the exception of 2009, the milk yield of first calving heifers has been steadily increasing on average by about 100 kg of milk per head per year.
In the analysis of the phenotypic variability of Simmental bull dams, Pantelić et al. (2013) have determined the milk yield of 5754.49 kg, with 3.98% and 230.24 kg of milk fat, i.e. 5755.47 kg of 4% FCM.
In the study of the effect of the import of breeding animals of the Simmental breed from Germany on the implementation of the breeding program on the territory of the city of Kragujevac, Kostic (2014) has obtained the following production results in his research: the imported animals in all three lactations have achieved higher milk yield (449.08 kg in I, 568.52 kg in II and 488.73 kg in III), milk fat (19.87 kg, 22.66 kg and 18.52 kg) and 4% fat corrected milk (477.64 kg; 567.26 kg and 473.36 kg). Domestic cows have recorded lower milk fat content in the first lactation by 0.05%, but the same trait in the second and third lactation has shown higher levels by 0.01% in each lactation.
The average production of all cows under control in Austria in 2012 (Genetic Austria) was 7073 kg of milk, 4.15% milk fat (293.53 kg), and 3.43% protein (242.60 kg), while the average production of first calving heifers was 6419 kg, with 4.13% milk fat (265.1 kg) and 3.40% protein (218.25 kg).

Materials and Methods
Basic data on production traits, as well as data on the origin of all the studied cows, were collected in collaboration with the "Lazar" Blace farm, which housed part of the cattle included in this study. For the animals that were reared on the households/farms of individual agricultural producers, data on the above performance traits were collected in cooperation with the breeding organizations, which are responsible for the implementation of the breeding program in the area of Toplica district. This study identified differences in the production traits of imported cows reared on the "Lazar" Blace farm and by individual agricultural producers, then differences in the milk performance traits between the imported and cattle of domestic origin on the farm, but also with individual agricultural producers of Simmental breed cows in the same area.
The total number of animals and their completed lactations is divided into four groups, with each group having approximately the same percentage of cows of different lactations by order, as follows: Group 1: Domestic animals reared by individual agricultural producers on individual farming households (n = 1526); Group 2: Imported animals reared by individual agricultural producers on individual farming households (n = 234); Group 3: Domestic animals reared on the farm (n = 1100); Group 4: Imported animals reared on the farm (n = 781). When examining the impact of the unified factor of housing/rearing and origin, the model with fixed unified factor of housing/rearing and origin (NP) was used: Yij = µ + NPi + eij Yij: trait studied, µ: population average for a given trait, NPi: fixed unified effect of housing/rearing and origin (i = 1,2,3,4) eij: random error Dragan Nikšić et al. 420 The analyzed factors are combined/merged due to their interaction, because to the greatest extent their impact is reflected through the interaction of these two factors. Subsequent to the variance analysis and determining the basic parameters of descriptive statistics by using the test of least significant differences (LSD), the differences between the groups were determined individually for all observed traits.
SPSS Statistics software for Windows, Version 23.0 was used for the statistical data processing and application of the said model.

Results and Discussion
In this study, the following milk performance traits were analyzed: lactation duration, whole and standard lactation milk yield, milk fat content and yield, and protein content and yield. Table 1 shows the lactation duration of the observed cows divided into four groups. The shortest duration of lactation was recorded in cows of domestic origin reared by individual agricultural producers, 304.12 days. The imported cows reared by individual agricultural producers had an average lactation duration of 313.67 days, while slightly longer lactation time was recorded in cows of domestic origin reared on the farm, 323.96 days, and slightly longer in imported animals, 314.13 days. The results obtained are higher than the average lactation duration reported by Perišić (1998) andPantelić (2006), except for the first group of cows, where the duration of lactation is shorter compared to values obtained by these two authors. The combined housing/rearing and origin factor showed statistically very highly significant (p≤0.001) effect on the observed four groups of cows for the trait tested. If the milk yield values for the whole and standard lactation by groups are observed, as shown in Table 1, the lowest values were recorded in cows of domestic origin housed/reared on individual agricultural households/farms, slightly higher values were recorded in the second and third group of cows, and the highest in imported cows reared on the farm (Group 4). Milk yield values for the whole and standard lactation varied statistically very highly (p≤0.001) under the unified factor of housing/rearing method and origin of the animal. The obtained values for milk yield in all four groups were significantly higher than the values for first calving heifers in Serbia, as reported by Nikšić et al. (2011). Groups of imported animals (3 and 4) achieved higher production than animals originating from Germany in the research of Perišić (1998) and bull dams in Serbia, cited in their research by Pantelić (2013). Observing by groups (Table 1), the highest milk fat content was recorded in cows of domestic origin reared on the farm -3.94%, 3.92% of milk fat content was recorded in imported animals reared on the farm and by individual agricultural producers, while the lowest content of milk fat was recorded in domestic cows reared by individual agricultural producers (3.89%). The values obtained are in the concordance with those obtained by Nikšić et al. (2011), slightly lower than the milk fat content of bull dams in Serbia reported by Pantelić et al. (2013), and by 0.10% higher in relation to the values obtained by Perišić (1998). The influence of the factors of the housing/rearing method and the origin of the animals had statistically very high (p≤0.001) impact on the milk fat content of the four observed groups. Table 1 also see shows the realized milk fat yields by groups based on origin and method of housing/rearing. The highest yields were obtained from imported cows on the farm (252.56 kg), followed by cows of domestic origin also on the farm (231.11 kg), imported cows reared by individual agricultural producers originating (192.46 kg), and the lowest yields were achieved by domestic cows reared by individual producers (187.22 kg). All four groups of cows achieved significantly higher milk fat production than those cited by Perišić (1998) and Nikšić et al. (2011), while the milk fat production of bull dams cited by Pantelić et al. (2013) is the same as the third group of cows. The influence of these factors on the variability of milk fat yield of the observed population by groups was statistically very high (p≤0.001).
Looking at the population by groups, it can be concluded that the animals reared by individual agricultural producers had the same protein content (3.15%), regardless of their origin. Slightly higher values for protein content were obtained from farm-raised animals (3.16%), while a significantly higher percentage was obtained from farm-raised imported animals (3.24%). Protein content values obtained are significantly lower than the results reported in Austria for the entire examined population of cows and first calving heifers in their 2012 annual report. The effect of these two combined factors on the observed trait of the four groups of cows was statistically very highly significant (p≤0.001). Table 1 also lists the milk protein yield values in the observed population divided into four groups. The lowest yield was achieved by cows of domestic origin reared by individual producers, 151.44 kg, which is 3.26 kg less than the yield of cows originating from import reared under the same conditions. The farm reared domestic animals had a protein yield of 185.81 kg, while under the same conditions the imported animals realized a yield of 208.57 kg. As for the protein content, the protein quantity was significantly lower than the results reported in Austria for the whole examined population of cows and first calving heifers in their 2012 annual report. Protein yield varied statistically very high significantly (p≤0.001) under the influence of the unified factor of rearing method and origin.  Based on the test of the least significant difference (LSD, Table 2) it can be stated that the difference between the groups was statistically significant at different levels of significance (p≤0.001 *** to p≤0.005 *), in all examined traits, except between groups 1 and 4 for the trait lactation duration, 1 and 2 for the trait milk production in standard lactation, 2 and 4 for the milk fat content, 1 and 2 and 2 and 3 for the protein content, and 1 and 2 for the trait of protein yield, where no statistically significant differences were established (p> 0.05 nz).

Conclusions
Farm-reared cows (domestic and imported) achieved by 1614.34 kg higher yield than cows reared on individual agricultural households (domestic and imported), while imported animals (farm-reared and reared on individual agricultural households) produced by 1261.50 kg more milk compared to animals of domestic origin (farm-reared and reared on individual agricultural households).
All observed production performance traits varied very significantly (p≤0.001) under the influence of the combined factor of the rearing methid and the origin of animals. Based on the results obtained for production performance traits, it can be concluded that the yield of milk, milk fat and protein in the observed population was above the average of the whole population of cows of the Simmental breed in the Republic of Serbia.