Influence of lactation stage, delivery order of calving and genetic group on milk quality

Abstract

Milk production and quality are influenced by environmental factors such as nutrition, genetic factors such as breed and physiological. The aim of the present study was to evaluate the influence of lactation stage, delivery order and genetic group on the quality of milk from crossbred cows 3/4 Gyr, 7/8 Gyr and 15/16 Gyr. Fresh milk samples were collected from crossbred cows. Fat, protein, lactose, non fat dry extract (NDE) and somatic cell count (SCC) of milk according to lactation stage, delivery order of calving and genetic groups were evaluated. The experimental design was completely randomized. Tukey test at 5% probability was used. Animals at the final third of lactation (201 to 305 days) showed higher fat, protein, NDE and SCC levels when compared to animals of other lactation stages. First delivery animals produced milk with higher content of solids compared to animals with 2 deliveries and above three deliveries. First calving the animals produced milk with higher solids content compared to animals with two calving and above three calving. Fat, protein and NDE results of fresh milk were consistent with limits established by the Brazilian legislation for milk quality, regardless of lactation stage, delivery order of calving and genetic group. Milk SCC was higher in cows in advanced lactation stage, The results were however below limits required by law. 3/4 crossbred Gyr cows showed higher SCC, with average values above limit established by current legislation.