The objective of this study was to estimate coefficients of variability heritability, genetic and phenotypic correlations between indicators of milk productivity in relation to milk yield and fat content, butter fat and protein content in milk. The foremost quality of 21st century Holstein cow is efficiency (Beaulieu, 1993). She must continue to increase both life production and production per year, preserving the quality. Due to the use of optimum breeding programs the rates of the genetic improvement of milk production have increased nearly twice in the 1990 as compared to those in the 1970 according to Aleksiev et.al. (1991), Vankov (1978), Vankov et.al. (1982) and Kennedy,(1991). A primary objective of this study was to determine coefficients of variability, heritability, genetic and phenotypic correlation between indicators of milk productivity in relation to milk yield and fat content, butter fat and protein content in milk. Heritability, genetic and phenotype correlation of milk productivity and protein content in milk of Bulgarian Black and White cows White were estimated, using the linear statistical model (Harvey 1977).
We?ve studied different modified types of herringbone milking parlor - 2x3 2x4 and 2x5 with single or double milking apparatus. The purpose of this investigation was to establish some limiting factors in selection of different types of herringbone milking parlor. Basic criterion for this selection was that the herringbone-milking parlor was to be controlled by one milker. The time needed for different milking operations was measured by chronometer and chronography on the farm of the Institute of Animal Breeding in Stara Zagora, Bulgaria. We have established that:- The main factor for selection of the herringbone-milking parlor with single milking apparatus is continuity of the process of milking for all herds, including the organization of work.- The main factor for selection of the herringbone-milking parlor with double milking apparatus is the duration of machine milking of the cows.
The ethological research took part on the farm of the Institute of Animal Breeding in Stara Zagora, Bulgaria with three groups consisting of five cows each, leveled by the method of the analogues in regard to the breed, age lactation, and milk yield. The purpose of this investigation was to determine the influence - changing of the permanent places of cows, change of the sequence of milking and changing of the neighbors bilateral under the main behavior reactions (standing, lying, feeding, moving) and milk production of lactating cows bred tied with milking performed by milk duct. During this research we made visual observations of main reactions of behavior (standing and lying) by the method of group chronometer measuring after 5 min, a day before and 2 days after the change. A control was done under an average daily milk yield and continuing of the milking of each cow from the three groups. We found that the complex change in the investigated factors registered impermanent changes in the built stereotype of animals shown with the changing of main behavior reactions and increase of average daily milk yield.
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