About physiological and morphological processes in poultry at natural and induced molting

Abstract

Plumage is a characteristic feature of birds. Feathering as a cutaneous derivative is a complex structure with specific mechanism of formation. Functions of plumage are thermal regulation, mechanical protection of bird's body and flight. Color and form of feathers in different parts of the bird's body could also serve as sexual characteristics. Molting in adult birds depends on season of a year, age of birds and management conditions as well. The process of molting is closely associated with reproductive function. A change in management conditions can induce full or partial molting in chicken, ducks, geese, turkeys, and Guinea fowl. Stress factors can also induce molting thus affecting the productive cycle in poultry. Molting is a complex biological process. The change of feathering occurs as a result of altered interactions between endocrine glands of the body including pituitary, thyroid and sex glands. An influence of the hormones released by these glands on the molting-related metabolic processes is mediated by central nervous system (I.C. Dunn et al., 2009). The resulting morphological and physiological alterations allow a manipulation of the reproductive function to optimize timing and intensity of lay in females and sperm production in males. The data are presented to specify the processes in meat-type hens and cocks exposed to molt-inducing factors (A.P. Konopleva et al., 1976; Sh.A Imangulov et al., 2000; P.F. Surai et al., 2012). The molting was induced by technological, chemical or hormonal factors. On days 7, 30 and 60 after the exposure to a moltinducing factor the condition of pituitary and thyroid gland body heat production, Ca and thyroxin levels in serum were recorded. Molting related alterations substantially influenced digestibility of dietary nutrients, fat deposition in body and egg productivity in laying hens. Stressed cocks responded to stress factors rather with significantly lowered sperm production than with molting. The result is a 3-5 % decrease in egg fertility in the second productive period. The layers ceased the lay and started the second productive period in 45-60 days. The intensity of lay in this second period reached 60 %, its duration was 6 months. The chicks hatched from molted layers were found to be more livable if compared to the first productive period. The comparison of different methods of molting induction showed the technological approach to be more effective if compared to chemical or hormonal factors. The alterations disclosed during artificially induced molting in modern meat-type chicken strains were found similar to those in less productive poultry reported in special literature earlier.