Comparative histomorphometry of postnatal skin development of heifers of 4 breeds of base and initial genotypes
Abstract
The total thickness of the skin of the heifers of the four groups increased from 3 to 18 months of postnatal ontogenesis, depending on the breed, by 16–27 %. In the heifers of the base and original genotype breeds, different periods of completion of the growth of the skin thickness were established. In all four groups of heifers, there were fundamental differences in the dynamics of the growth of the thickness of the outer integument. The thickness of the epidermal layer of the skin reached maximum values in the early postnatal ontogeny of heifers. The thickness of the layers of the dermis of the heifers of the four groups increased with age, depending on the breed, by 33–43 % – papillary and 9–24 % – reticular. In the postnatal ontogenesis of the heifers of the four groups, the noticeable increase (more than 50 %) of the papillary layer of the dermis occurred in the early age period of 3–6 months, and the dynamics of changes in the thickness of the reticular layer depended on the breed of heifers. Structural transformations of its internal organization accompanied the postnatal development of the skin of the heifers of the four groups – the ratio of skin layers changed within 5–8 %, depending on the breed. In the dynamics of postnatal ontogenesis of heifers of the base and original genotype breeds, reliable differences in the thickness of the epidermis and the reticular (together with the subcutaneous base) skin layer was manifested, as well as the parameters of the growth ratio of the papillary/reticular layers of the dermis. The dependence of the parameters of the thickness of the epidermal barrier of the skin of heifers of the four groups on the period of the year and the seasonal differences in the growth of the papillary and reticular (together with the subcutaneous base) layers of the skin of heifers of the base and original genotype breeds indicate the probable corrective effect of environmental factors on the morphology of the skin of heifers and the difference in the manifestations of adaptation.
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