Levels of insulin, insulin-like growth factor-I and thyroid hormones in relation to the body condition score changes in periparturient dairy cows

Abstract

The objective of this study was to determine the levels of insulin, insulin like growth factor I (IGF-I) and thyroid hormones in relation to the body condition score (BCS) of periparturient dairy cows. The study was carried out on twenty Holstein-Friesian dairy cows with average milk production of 7000 L/305 days in the previous lactation, parity ranging from 2-4. All cows were BCS scored during the early dry period, 7±3 days before and after parturition. Based on the BCS at the early dry period, cows were divided in two groups: cows with high BCS (3.75- 4.25, HBCS, n=10), and cows with moderate BCS (2.75-3.75, MBCS, n=10). Blood samples were taken at the time of BCS evaluation. Concentrations of insulin, IGF-I, triiodothyroinine (T3) and thyroxine (T4) were determined by radioimmunoassay (RIA, INEP-Zemun, Serbia). Statistical differences between mean values were determined using Student t-test (p lt 0.01). Mean BCS values at early dry period were significantly different compared to two other periods (p lt 0.01) within both groups, but BCS was similar in both groups at 7±3 days after calving (2.69±0.67:2.62± 0.27, p>0.05). IGF-I level in HBCS cows at days 7±3 before calving was significantly higher (16.28±3.07:11.76±2.28, p lt 0.01), with a reverse relationship after calving (3.77±1.64:8.46±2.37, p lt 0.01). Insulin level was significantly lower at 7±3 days before calving in HBCS cows (16.26±4.60:20.18±4.96mIU/L, p lt 0.05). Thyroid hormones levels were significantly lower in HBCS group et all examined periods.

Cilj ovog rada je bio da se odredi nivo insulina, insulinu sličnog faktora rasta IGF-I, trijodtironina (T3) i tiroksina (T4) u krvi u odnosu na promene telesne kondicije kod krava u peripartalnom periodu. Za ogled je odabrano 20 krava holštajn - frizijske rase između 2-4 laktacije i čija je proizvodnja mleka u predhodnoj laktaciji iznosila 7000 L za 305 dana. Telesna kondicija (OTK) je kod svih krava određivana na početku zasušenja, 7±3 dana pre i 7±3 posle teljenja. Na osnovu OTK na početku zasušenja, krave su bile podeljene u dve grupe: krave sa visokom OTK (3,75-4,25, n=10) i krave sa optimalnom OTK (2,75-3,75, n=10). Uzorci krvi su prikupljani u vreme određivanja OTK. Koncentracija insulina, IGF-I, trijodtironina (T3) i tiroksina (T4) određivana je RIA metodom (INEP-Zemun, Serbia). Statistička značajnost razlika između srednjih vrednosti procenjivana je Studentovim ttestom. Srednje vrednosti OTK u ranom periodu zasušenja bile su statistički značajno različite u odnosu na druga dva perioda (p lt 0,01) kod obe grupe, ali je OTK kod obe grupe bila slična 7±3 posle teljenja (2,69±0,67:2,62±0,27, p>0,05). Koncentracija IGF-I bila je statistički značajno viša kod krava sa visokom OTK, 7±3 dana pre teljenja (16,28±3,07:11,76±2,28, p lt 0,01), sa obrnutim odnosom 7±3 dana posle teljenja (3,77±1,64:8,46±2,37, p lt 0,01). Koncentracija insulina je bila značajno niža 7±3 dana pre teljenja kod krava sa visokom OTK (16,26±4,60:20,18±4,96 mIU/L, p lt 0,05). Nivo tireoidnih hormona je bio značajno niži kod krava sa visokom OTK u svim ispitivanim periodima.