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Breed features of inheritance of pedigree value of mass part of fat in milk of dairy cows
In the dairy cattle breeding an important selection breeding sign is mass part of fat in milk, that is one of the indexes of milk quality.
The feature of inheritance of pedigree value of mass part of fat in milk is absence of such form, as over dominance, that is possible to explain by low changeability of this sign (CV = 2,4–5,1 %).
The main form of inheritance of mass part of fat in milk is intermediate that in the cows of Holstein breed presents 70,7 % and in the cows of the Ukrainian Black – and White dairy breed – 52,6 %. Characteristic feature of inheritance of pedigree value of mass part of fat in milk is that at all forms of inheritance indexes of pedigree value for daughters are with a minus meaning. It should be noted that for all four forms of inheritance of pedigree value daughters are characterized by the best indexes that inherited pedigree value of an intermediate form. Their advantage above Holstein breed cows of the same age where regression were shown is 0,67 % (Р<0,001), above the cows of the same age with dominance of mother on 0,23 % (Р<0,01) and above the cows of the same age with dominance of father on 0,18% (P<0,001).
There is analogous appropriateness for the cows of the Ukrainian Black-and-White dairy breed. Daughters with the intermediate form of inheritance are also characterized by the best pedigree value of mass part of fat in milk, comparatively with other forms. So, comparatively with regression advantage presents 0,37 % (Р<0,001), with dominance of father 0,47 % (Р<0,001) and with dominance of mother 0,17 % (Р<0,01).
Thus, selection among the population of dams and sires on mass part of fat in milk will assist the improvement of this sign in breeds mostly at the intermediate form of inheritance. At the same time, among cows of Holstein and the Ukrainian Black-and-White dairy breed regression is appeared that presents respectively 13,5% and 37,3% and pedigree value of daughters is at the level – 0,7 and – 0,5 %. In both breeds paternal features of daughters, in that regression was shown had not high, but positive pedigree value though.
To our opinion it can be explained by unsuccessful combination of genotypes of paternal features, that is impossible to foresee if it is predicted only on the indexes of pedigree value of paternal features. In fact the phenomenon to the crossing-over provides genetic changeability of every new combination. Obviously, such genetic secrets can be exposed with introduction of genome estimation of animals already after birth of descendants and to determine the grade of concrete animal on the genotype. Amount of structural areas of DNA, so-called SNP, where the information is coded about the level of development of selection sign, testifies the genetic grade of animal.
Inheritance of pedigree value on mass part of fat in milk at dominance of father and mother in both breeds appeared negative. At dominance of father a pedigree value for daughters of Holstein breed presents –0,21 % and for daughters of the Ukrainian Black-and-White dairy breed –0,5 %. At dominance of mother –0,26 % and –0,2 % respectively. Pedigree value of parents in both breeds at their dominance appeared with minus meaning that testifies unsuccessful selection of sires to the concrete dams, that is why in this case it is possible to talk not about dominance of father, but about regression of pedigree value of daughters to the genotype of parents. For the forms of inheritance dominance of mother we have an example of regression of pedigree value of daughters on a genotype of mothers.
The best absolute indexes and pedigree value on mass part of fat in milk are educed for the cows of Holstein and Ukrainian Black-and White dairy breeds at dominance of father and intermediate inheritance, mainly at the terms of reliable advantages of pedigree value of fathers above mothers. The main form of inheritance of pedigree value on mass part of fat in milk for the cows of both breeds is intermediate and it’s frequency presents (52,6–70,7 %). Other forms of inheritance present: dominance of mother is (4,4–5,8 %); regression – (13,5–37,3 %) and dominance of father – (4,3–11,3 %). The most desirable form of inheritance of pedigree value on mass part of fat in milk, over dominance is absent in the cows of Holstein and Ukrainian Black-and-White dairy breeds.
Key words: Ukrainian Black-and-White dairy breeds, Holstein breeds, pedigree value, mass part of fat, forms of inheritance: intermediate, dominance of mother, dominance of father, over dominance, regression.