Linking first lactation survival to milk yield and components and lactation persistency in Tunisian Holstein cows

摘要: Abstract. Genetic parameters were estimated for first lactation survival defined as a binary trait (alive or dead to second calving) and the curve shape traits of milk yield, fat protein percentages using information from 25 981 primiparous Tunisian Holsteins. For each trait, shape curves (i.e. peak lactation, persistency), level production adjusted 305 days in milk (DIMs) total yield (TMY), average fat (TF %) protein (TP %) percentages defined. Variance components with a linear random regression model under three bivariate animal models. Production modelled by fixed herd  ×  test-day (TD) interaction effects, classes 25 DIMs   age of calving   season calving interaction of pregnancy, environment effects additive genetic effects. Survival was  year interaction effects age calving  effects, random permanent effects. Heritability ( h2 ) estimates 0.03 ( ±0.01 ) for survival and 0.23 ( ), 0.31 ( ) and TMY, TF % TP %, respectively. correlations between and TMY, TF % TP % 0.26 ( ±0.08 −0.24  ( ±0.06 and −0.13 survival and persistency were  −0.35 ±0.09 ) and  −0.19 Cows that had higher persistencies for more likely not survive.