Thyroid and metabolic status of simmental cows during different periods of lactation

Cilj ove disertacije je da se doprinese razjašnjenju uticaja tireoidnih hormona na proizvodne sposobnosti i zdravlje visokomliječnih krava rase simentalac, praćenjem parametara endokrinog i metaboličkog statusa istih jedinki, kao i organskih sastojaka mlijeka, ali u različitim fiziološkim odnosno proizvodnim periodima u toku 2. laktacije. U cilju pojašnjenja značaja redosljeda laktacije u 3. laktaciji se određivala koncentracije biohemijskih sastojaka krvi koji mogu biti indikatori energetskog statusa, kao i količina i organski sastojci mlijeka, dok će u 4. laktaciji energetski status životinja biti određivan samo ispitivanjem organskih sastojaka mlijeka. Ispitivanja su sprovedena na farmi goveda u Gradišci, Republika Srpska-BiH, ukupno 30 krava rase simentalac. Sve odabrane krave su ujednačene po tjelesnoj kondiciji, klinički zdrave, sa eutokijom, iz objekata vezanog sistema držanja, i pod veterinarskim nadzorom. Krave su podeljene u tri grupe. Prva grupa (n=10) u 2. laktaciji, druga grupa (n=10) u 3., i treća grupa (n=10) u 4. laktaciji. Uzorci krvi, kravama prve grupe su se uzimali punkcijom vena coccigea, u različitim proizvodnim ciklusima, odnosno nedelju dana pred partus, i poslije teljenja 21., 60., i 90. dana, odnosno na kraju tranzicionog perioda ili u ranoj laktaciji, kao i u vrijeme srednje i pune laktacije. U uzorcima krvi, nakon spontane koagulacije, centrifugiranja i odvajanja seruma, određivane su koncentracije trijodtironina (T3) i tiroksina (T4), radioimunološkom metodom (RIA) korišćenjem komercijalnih test paketa, i koncentracije biohemijskih sastojaka krvi: glukoza, ukupni proteini, albumini, urea, ukupni bilirubin, kalcijum, fosfor, magnezijum i aktivnost AST. Kravama druge grupe u 3. laktaciji su uzimani uzorci krvi 30., 60. i 90. dana laktacije, a u punoj krvi su određivane koncentracije glukoze i BHBA na licu mesta, a u krvnom serumu aktivnost AST, i koncentracije ukupnih proteina, albumina, ukupnog bilirubina, uree i NEFA. Kravama treće grupe u 4. laktaciji određivani su 30., 60. i 90. dana laktacije samo količina i kvalitet mlijeka. Mliječnost krava je određivana kod prve grupe krava 21., 60., i 90. dana laktacije, a kod druge i treće grupe 30., 60. i 90. dana laktacije...The aim of this thesis is to contribute to the clarification of the influence of thyroid hormones on the production capabilities and health of the high Simmental cow breed, monitoring parameters of the endocrine and metabolic status, and components of milk of the cows in different physiological and production periods during the 2nd lactation. In order to clarify the order of importance of lactation during the 3rd lactation, biochemical constituents of blood concentrations will be monitored as they may be indicators of energy status, as well as of the amount of organic components of milk, while during the 4th lactation, the energy status of the animal will be determined only by examining organic milk constituents. Tests were carried out on cattle farms in Gradiška, the Republic of Srpska – B&H, on a total of 30 Simmental breed cows. All selected cows were matched for body fitness - they were clinically healthy, with normal calving - from the facilities where they were kept on a leash, under veterinary supervision. The cows were divided into three groups. The first experimental group (n=10) pertained to the 2nd lactation; the second group (n=10) pertained to the 3rd, and the third group (n=10) to the 4th lactation period. Blood samples of the first group of cows were taken by puncture of the vena coccigea in different production cycles the week before calving and 21, 60, and 90 days after calving, and at the end of the transition period in early lactation, as well as during medium and full lactation. In the blood samples after spontaneous coagulation and centrifugation and serum separation, concentrations of triiodothyronine (T3) and thyroxine (T4) were measured and determined by radioimmunoassay RIA using commercial test packages, as well as the concentration of the biochemical constituents of blood: glucose, total protein, albumin, urea, total bilirubin, concentrations of calcium, phosphorus and magnesium, and AST activity. Blood samples were taken from cows in the second group during the 3rd lactation on the 30th, 60th and 90th days of lactation. Blood glucose and BHB concentrations were determined on the spot. In the blood serum AST activity and total protein, albumin, bilirubin, urea and NEFA were measured. With reference to the third group of cows during the 4th lactation, on the 30th, 60th and 90th days of lactation, only the quantity and quality of milk was determined..