Estimation of genetic parameters for predicted nitrogen use efficiency and losses in early lactation of Holstein cows

The objective of this study was to estimate genetic parameters predicted N use efficiency (PNUE) and losses (PNL) as proxies loss for Holstein cows. Furthermore, we have assessed approximate correlations between PNUE, PNL, dairy production, health, longevity, conformation traits. These traits are considered important in many countries currently evaluated by the International Bull Evaluation Service (Interbull). values PNUE PNL were obtained using combined milk mid-infrared (MIR) spectrum, parity, yield–based prediction equations on test-day MIR records with days (DIM) 5 50 d. After editing, final data set comprised 46,163 21,462 cows from 154 farms countries. Each trait divided into primiparous multiparous (including second fifth parity) groups. Genetic breeding estimated a multitrait (2-trait, 2-parity classes) repeatability model. Herd-year-season calving, DIM, age parity used fixed effects. Random effects defined (within-parity permanent environment), nongenetic cow (across-parity additive animal, residual heritability first later 0.13, 0.12, 0.14, 0.49, 0.40, 0.55, 0.43, respectively. negative high (from −0.89 −0.53), whereas phenotypic also but relatively low −0.45 −0.11). At level reliability more than 0.30 all novel traits, total 504 bulls born after 1995 had publishable Interbull multiple-trait across-country (EBV). other 30 interest, corrected EBV bulls, ranged −0.46 (udder depth) 0.47 (milk yield). Obtained results showed complex relationship efficiency, traits: instance, efficient seem give milk, which is linked deeper udders, lower fertility, longevity. Additionally, representing less N, −0.32 (angularity) 0.57 (direct calving ease). Even if further research needed, our provided preliminary evidence that could be included improvement programs help their management.