Milk lactoferrin and milk constituents in dairy Gyr heifers

Abstract The objective of this study was to describe the variation in bovine lactoferrin (LF) content in milk from dairy Gyr heifers during lactation and to evaluate its relationship with milk components. Milk samples were collected between August to October 2013 for performance test 1 (25 first lactation cows) and August to October 2014 for performance test 2 (20 first lactation cows), coordinated by the Brazilian Association of dairy Gyr Breeders (ABCGIL), in Uberaba, MG, Brazil. Milk yield (MY) of 45 primiparous cows was measured daily. The milk samples for analysis of LF concentration and of the other milk components such as somatic cell count and percentage of fat (F%), protein (P%), lactose (L%) and total solids (TS) were collected monthly. The somatic cell count (SCC) was transformed to a somatic cell score (SCS). Pearson correlation coefficients between LF and the other milk components were calculated. Analyses of variance were performed by mixed models including the fixed effects of test (1= calving 2013 and 2=calving 2014) year-season of sampling, lactation month and age of cow at calving as classificatory effects, and the effects of SCS and MY as covariates (linear effect). The effect of cow was analyzed as a random effect considering repeated measures over time. The mean LF concentration was 16.80 ± 12.41 μg/mL milk and the values showed variation across lactation indicating that the lactation month influences milk LF concentration. Lactoferrin content was correlated with SCS (0.64, P