Prediction of milk, fat and protein yields in first lactation from serum beta-lactoglobulin concentrations during gestation in Italian Brown heifers

The Authors report the results of a study carried out on 23 pregnant Italian Brown heifers, with the aim to determine the relationships between blood serum β-lactoglobulin (β -LG) concentrations during first gestation and subsequent milk production and quality in first lactation, in order to obtain an improved selection method for replacement heifers. At weeks 20, 26 and 32 of gestation, β-LG concentrations (±SE) were 706±78, 753±66 and 772±63 ng/ml, respectively (P>0.05). High and significant (P≤0.05) correlation coefficients were observed only between β-LG content at week 32 and total milk and protein yields in first lactation. Prediction equations of milk, fat and protein production in first lactation from log10 β-LG content at week 32 of gestation, from parent average genetic indexes and from both were calculated by means of multiple regression analysis. When the contribution of both β-LG content and predicted genetic indexes were considered, the regression equations gave generally a better estimate of the production parameters in first lactation (higher R2, lower SE of estimate) than the above mentioned parameters alone. These results suggest that it is valuable to pre-estimate milk, fat and protein production in Italian Brown first lactating cows by means of the analysis of serum β-LG content during gestation.