Changes in Freezing Point of Blood and Milk During Dehydration and Rehydration in Lactating Cows

Abstract

We studied the influence of short-term changes in water intake in 4 lactating Holstein cows on diurnal fluctuation of packed cell volume (PCV), freezing point of blood (FPblood), freezing point of milk (FPmilk), and the relationship between changes in FPblood and FPmilk. The experiment lasted 108 h and was divided into 3 periods: 1) control (38 h); 2) dehydration/rehydration with 4 consecutive 12-h sequences: 8 h without water, 0.5-h access to water, 1.5 h without water, and 2-h access to water; and (3) 22 h for reconstitution. Cows were milked at 12-h intervals. Blood was sampled from the jugular vein hourly throughout the experiment, and at 0, 15, 30, 60, 90, 120, 150, 180, 210, and 240 min after initiated rehydration following the 8-h dehydration sequences. Intakes of free water and water in feed were recorded every hour. The PCV was negatively affected by water intake within the hour before sampling. Dehydration lowered FPblood steadily, whereas FPblood increased by 0.024 degrees C within 30 min following a large water intake in the rehydration period. The FPblood was not significantly influenced by actual water intake, but was highly correlated with the available water pool at time of blood sampling. The FPmilk correlated positively with the FPblood collected 1 h before milk sampling, indicating a delay in the transfer of water from plasma to milk. In summary, FPblood and FPmilk decrease during dehydration and increase during rehydration. Rehydration following a long dehydration period caused an increase in FPmilk within 1 h, but not above the initial level for FPmilk of the cow.

The effect of season and production systems on qualitative and quantitative properties of milk produced in dairy farms of Yazd province

“…-0.565, p<0.01). Bjerg et al (2005) reported that the highest and lowest freezing point in storage tanks occurred in summer and winter respectively that matches with this study. According to the findings of present study, higher limits of temperature, sunshine hours and increase of consumed water through the longer days would be among the reasons that increased the freezing point of milk in the summer time.…”

“…Azad et al (2007) reported no significant differences for milk specific gravity in different months of the year in Bangladeshi cows (p>0.05) that is inconsistent with the findings of present study. Ozrenk and Selcuk Inci (2008) reported no significant seasonal effects on specific gravity of milk whereas at present study the highest and the lowest gravities were observed in February (1.0288g/cm 3 ) and October (1.0262g/cm 3 ) respectively (average 1.026g/cm 3 ). There was also a significant difference for microbial loads of the milk immediately stripped from udder in all seasons except autumn in both systems of traditional and industrial dairy farms at present study (table 2, p<0.01).…”

The freezing point of raw and heat treated sheep milk and its variation during lactation

“…The average value of FP in our study decreased in the summer, most probably as a result of high temperatures in the surrounding environment and short-term dehydration of the animals, as also reported by Bjerg et al (2005). Early in month 11 when the grazing season ended with reduced milk production, FP value was the lowest, corresponding to a higher content of solids also reported by Kuchtík et al (2008).…”

Freezing point of raw and heat-treated goat milk

“…The effect of high environmental temperatures and organism dehydration can also be the causes of this FP reduction. Bjerg et al (2005) reported a reduction in FP of milk due to short-term dehydration. In autumn, in months 9 and 10, the detected values were -0.5513 ± 0.0022°C and -0.5514 ± 0.0042°C.…”