Chosen biotic factors influencing raw cow milk freezing point

Abstract

The milk freezing point depression (FPD) is important physical property. FPD is influenced by milk composition especially by components with osmotic pressure activity and by other physiological factors. There is possible to indicate a foreign (extraneous) water addition into milk by FPD. This is necessary to have a good estimated legislative FPD discrimination limit (FPD–L) for purpose of milk quality control. This paper was aimed at obtaining information to improve such estimation. Impacts factors as season variations, estimated state of dairy cow nutrition and some milk components and properties on milk FPD and their relations to FPD were quantified (n 11 540 – 72 607 bulk raw cow milk samples). The highest FPD was in Spring (−0.52097 ± 0.004877 °C), the lowest in Autumn (−0.52516 ± 0.005725 °C; P < 0.001). Correlation between FPD and lactose was 0.35 (P < 0.001). 12% and 5.4% of FPD variability is explainable by lactose and casein variability. Relationship between FPD and urea (U) was 0.26 (P < 0.001) in March. The worst FPD was in group with presupposed (according to milk urea and protein combination) nitrogen matter (NM) and energy (E) insufficiency (−0.51855 ± 0.007288 °C). The best FPD was in group with presupposed NM and E surplus in feeding ration (−0.52536 ± 0.004785 °C; P < 0.001). The FPD was worse in suspicion on E deficiency (on the basis of fat/crude protein ratio) as compared to presumption for balanced E nourishment of dairy herds (−0.52105 ± 0.006436 °C > −0.52244 ± 0.005367 °C; P < 0.001). Results can improve the estimation of objective FPD–L.

Keywords

• dairy cow
• bulk milk sample
• freezing point depression
• fat
• protein
• casein