Cattle fattening, first of all, should be beneficial for a farmer, therefore, in Latvia more suitable are such average intense fattening methods as fattening with grass fodder. In the world, demand for beef, produced in an environmentally friendly manner, ensuring the appropriate animal welfare conditions, is growing. The aim of the study was to find out the fattening results of Hereford (HE) and Aberdinanguss (AB) pure-bred bulls and their crosses when fed with grass fodder. The study was conducted in 2015 and 2016 within the framework of the project ‘Baltic Grassland Beef’. AB crossbreed bulls were slaughtered when they were 519 ± 16.6 days old, but HE pure-bred bulls − 584 ± 7.3 days old (p ≤ 0.05). The biggest live weight and slaughter weight showed HE crossbreed group bulls – 557 ± 19.4 kg and 293 ± 12.2 kg, respectively, but the biggest live weight daily gain from birth to slaughter was observed to AB pure–bred group bulls – 952 ± 24.7. Carcass conformation score in muscle development was the highest for AB pure–bred group bulls. Their average conformation score was 3.2 ± 0.08 points. In terms of fat score development, carcass with the best quality was obtained from HE crossbreed group bulls, the resulting fat score – 2.4 ± 0.10. The obtained results prove that pure-bred and crossbreed bulls used in this research are suitable for fattening with grass in the conditions of Latvia

The quality of forage grass mostly depends on the harvesting time. In early vegetation stages, grasses have a high protein and energy content and high dry matter digestibility. The data on the protein content and energy value of different grasses gives a possibility to choose the best conservation method. Changes in the chemical composition of perennial grasses during the vegetation were investigated at the Laboratory of Biochemistry of the LUA Research Centre "Sigra". The dynamics of the content of amino acids was evaluated.