Bioenergetic and ethological features of the first-calf heifers of different genotypes

The aim of this work was to study bioenergetic and ethological indicators in crossbred first-calf heifers compared to purebred first-calf heifers. The research was conducted on the first-calf heifers of Ukrainian Black-Pied dairy breed and first-generation crossbreeds obtained as a result of crossing with Brown Swiss breed, as well as, on the first-calf heifers of Ukrainian Red-Pied dairy breed and first-generation crossbreeds obtained as a result of crossing Ukrainian Red-Pied dairy with Montbéliarde breed. The purebred Black-and Red-Pied first-calf heifers prevailed over crossbreed first-calf heifers on the indicator of milk yield for 305 days of lactation by 106.45 and 218.36 kg, respectively. Accordingly, the indicators of average daily milk yield were also higher by 0.35 and 0.72 kg and the indicators of average daily milk yield adjusted by 4 % fat content per 0.15 and 0.16 kg. At the same time, the indicator of average fat content in milk prevailed in crossbreeds of Black-Pied and Brown Swiss breed by 0.08 % compared to purebred Black-Pied breeds, and in Red-Pied crossbreeds with Montbéliarde breed by 0.16 % compared to purebred Red-Pied breeds. The purebred Black-Pied first-calf heifers had an advantage by 2.04 MJ compared to crossbreeds, while the Red-Pied first-calf heifers had a slight advantage by 0.06 MJ compared to crossbreed first-calf heifers on the indicator of daily cost of exchange energy (EE). The purebred Black-and Red-Pied first-calf heifers had higher cost of exchange energy allocated with milk compared to crossbreed first-calf heifers by 0.42 and 0.82 MJ. They also had higher cost of exchange energy rates for heat products by 0.79 and 0.25 MJ. According to the energy index indicator, purebred Black - and Red-Pied first-calf heifers prevailed over crossbreeds first-calf heifers by 0.16 and 0.07 %, respectively. The same trend was observed in relation to the productive index indicator. The purebred Black-and Red-Pied first-calf heifers had a slight advantage by 0.001 and 0.002 kg adjusted by 4 % of milk fat content per 1 MJ. According to the indicators of daily behavioral reactions, no special differences between a purebred and crossbreed were found.