THE CHANGES OF MILK PRODUCTIVITY AND QUALITY OF LATVIAN LOCAL BREED DAIRY COWS
Dairy cow milk productivity can be affected by series of factors that could be influenced by environment or cows’ physiological condition. One of the best factors for characterization of the rearing conditions and cow potential is the age at first calving (AFC) and the live weight at the beginning of first lactation. The aim of our study was to determine the effect of AFC and live weight at first lactation on the local breed cow milk productivity, composition and quality. In the study were included 25 Latvian Brown (LBGR) and 25 Latvian Blue (LZ) breed cows in the genetic resource conservation program and analysed in VPP AgroBioRes project. Cows were located in different regions of Latvia and in different farms (in average 2.8 cows per farm). Cows were distributed in 4 groups depending on their AFC and live weight in the beginning of first lactation.. The average milk productivity in first lactation the highest were in year 2017 for LBGR breed cows (5250.1 kg), in the same time LZ breed cows characterized with 5164.5 kg milk. The AFC not only significantly (p<0.05) impacted the milk productivity, but also showed effect on analysed cow lifespan as LBGR breed cows in the group with AFC >30 months did not live past third lactation. The significantly higher LBGR cow milk productivity in the third lactation were in cow group with live weight at first lactation 451 – 500 kg, but in LZ breed group - >550 kg (accordingly 5342.5±231.35 and 5493.0±522.69 kg milk).