Faculty of Veterinary Medicine University of Zagreb
Abstract
The objective of this study was to evaluate three synchronization fix timed-AI protocols throughout the year on one commercial dairy farm in a semi-arid zone. Mean temperature-humidity indices (THI) were 77.5, 84.9, 70.8 and 58.8 in spring, summer, autumn and winter, respectively. Insemination was synchronized in 3 groups of healthy Holstein Friesian dairy cows (Body Condition Score 2.25-3; scale 1-5) using controlled intravaginal drug release (CIDR) +E2 (n = 99), CIDR+GnRH (n = 38), or Select-Ovsynch (n = 181). Pregnancy
diagnosis was done by rectal palpation 45-50 days after one AI. Pregnancy rate did not differ between the three methods, but was lower (P0.05), but rates were lower in spring than in winter (P0,05), ali je u proljeće postotak bio niži nego zimi (P<0,05). U navedenoj polusušnoj zoni visoki THI ima negativan učinak na plodnost muznih krava te se nijedan od triju primijenjenih protokola nije pokazao dobrim za plodnost u ljetnom razdoblju. Prema tome, trebalo bi uvesti sezonsko planiranje teljenja u kojem bi životinje bile osjemenjivane u hladnije doba godine
