1. Department Livestock—Ruminants and Technologies of Animal Products, Trakia University, 6000 Stara Zagora, Bulgaria
2. Scientific Center of Agriculture, Agricultural Academy, 8300 Sredets, Bulgaria
3. Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
4. Research Center of Stockbreeding and Agriculture, Agricultural Academy Bulgaria, 4700 Smolyan, Bulgaria