Influence of [beta]-carotene and vitamin A supplementation on the ovarian activity of dairy cows with chronic fertility impairment/Utjecaj [beta]-karotena i vitamina A na aktivnost jajnika mlijecnih krava s kronicnim funkcionalnim sterilitetom

The aim of this study was to determine the influence of supplemented [beta]-carotene and vitamin A on the ovarian activity during the periovulatory period in dairy cows with chronic fertility impairment. A total of 46 non pregnant Holstein cows with fertility impairment, at the age of 5-7 years, were selected for this study. The animals in three experimental groups were supplemented with either a combination of [beta]-carotene and vitamin A, [beta]-carotene only or vitamin A only. Non supplemented animals served as controls. All animals included in the survey were gynecologically examined; the estrus was synchronized and inseminated. Initial blood levels of [beta]-carotene as well as the levels at the time of insemination and in the luteal phase as well as the ovarian structures during ovulation and formation of corpus luteum and [P.sub.4] and conception rate, were monitored. Significant increases in follicular size as well as luteal tissue growth were found in animals supplemented with [beta]-carotene and vitamin A combination and vitamin Aonly. Positive correlation between the serum concentrations of [beta]-carotene at insemination and at day 7 of the luteal phase and the concentrations of progesterone and the conception rate, lead to a conclusion that periovulatory [beta]-carotene and and vitamin A supplementation could improve follicular growth and development of the corpora lutea in cows with fertility impairement. Key words: [beta]-carotene, vitamin A, infertility, dairy cows Cilj ovog istrazivanja bio je utvrditi utjecaj dodanog [beta]-karotena i vitamina A na ovarijalnu aktivnost tijekom peri ovul at ornog razdoblja u mlijecnih krava s kronicnim funkcionalnim sterilitetom. Za ovo istrazivanje odabrano je 46 negravidnih krava holstajnske pasmine s funkcionalnim sterilitetom, u dobi od 5 do 7 godina. Zivotinje su podijeljene u tri pokusne skupine, s kombinacijom P-karotena i vitamina A, samo [beta]-karotena i samo vitamina A. Kontrolna skupina bile su krave bez dopunske terapije. Svim zivotinjama na pocetku istrazivanja izvrsen je ginekoloski pregled, sinkronizacija estrusa i umjetno osjemenjivanje. Mjerena je pocetna razina [beta]-karotena u krvi, razina u vrijeme oplodnje i tijekom luteinske faze, zatim corpus luteum i razina P4, kao i postotak koncepcije. Znacajan porast folikula kao i luteinskog tkiva zabiljezen je kod zivotinja kojima smo dali kombinaciju [beta]-karotena i vitamina A i samo vitamin A. Pozitivna korelacija izmedu serumske koncent