Short communication: Genetic parameters for feed intake, production, and extent of negative energy balance in Nordic Red dairy cattle

The aim of this paper was to study the genetic parameters for feed intake, milk production, and energy balance in Nordic Red dairy cattle from an experimental data set. The data were collected at the MTT Agrifood Research Finland Rehtijarvi experimental farm in 4 feeding trials between 1998 and 2008, and included lactation wk 2 to 30 for 291 Nordic Red nucleus heifers descending from 72 different sires. The studied traits included weekly averages for energy-corrected milk yield (ECM, kg/d), dry matter intake (kg/d), body weight (BW, kg), body condition score (BCS, score 1 to 5), and energy balance (EB, MJ of metabolizable energy/d). The data were analyzed with both fixed and random regression models. The heritabilities of ECM and BCS were moderate to high and remained fairly constant over the entire lactation period, whereas the heritabilities of BW and EB were the highest in early lactation (0.47 and 0.37, respectively) and declined later on. The heritabilities of DMI were highest (0.33) around lactation wk 5 and again at lactation wk 30, and were somewhat lower at the beginning of the lactation and in the middle period. The genetic correlations between the traits differed considerably between early and later lactation periods, especially for the trait pairs ECM-dry matter intake, ECM-EB, BW-EB, and BCS-EB, being negative or close to zero in lactation wk 2 to 5 but turning moderate to strong and positive by lactation wk 10. The results suggest that the lactating cows express their genetic potential for feed intake and energy utilization most clearly between lactation wk 2 to 10. The best candidate trait for selection might be EB in lactation wk 2 to 5 because it has a moderate heritability and is not genetically correlated with BW or BCS in that period.