that fluid and tissue loss during freshening can equal the weight of the calf and she now has an immediate demand to produce milk. This rapid loss in volume leaves an internal void, potentially allowing the rumen to move, resulting in a DA (Displaced Abomasum). Immediate water consumption not only rehydrates the cow, but also helps to add weight to the rumen, stabilising it. Figure 1 shows the variation in milk yield when the cow is dehydrated vs. rehydrated. Water con- tent is about 65% of the dairy cow’s body weight and 87% of fluid milk output. When calculating replacement fluids, it’s important to consider maintenance requirements, environ- ment, production needs, and fluid losses due to calving, heat stress, sweat, sickness or other challenges. By way of exam- ple, to maintain normal cellular functions a 680 kg cow re- quires 68 litres of water daily during thermal neutral condi- tions. Some of this water comes from their feed ration (10-30%) and the balance from daily water volume intake (usually 8 to 9% of their total body weight). For a lactating cow, each 38 litres of milk produced requires an additional 3.8 litre of water over maintenance requirements. The rumen serves as a reservoir that releases consumed water to the body fluid compartments via osmotic pressure. As cells re- quire fluid for metabolism, electrolytes and other nutrients exert osmotic pressure in order to continuously supply the cells with fluid for normal functions. If the body does not have enough fluids, then the amount of nutrients transferred to the cells (for metabolism etc.) is greatly reduced. Therefore, managing the water content in the rumen is important for maintaining both normal rumen fluid volume as well as other body fluid reserves.


Osmolytes Dehydration is problematic as fluid loss associated with fresh- ening can be equivalent up to what she would normally drink


in an entire day, and most cows do not drink well in the hours pre-freshening. Osmolytes are compounds that affect cellular water holding capacity and fluid regulation. Osmolytes func- tion to help maintain cell volume and fluid balance thereby improving Cellular Energetics (assist transport of electro- lytes). They also help cells maintain protein synthesis and cell division and help maintain gut integrity.


Economic impact A successful transition period is accomplished by a well-or- chestrated nutrient repartitioning. However, any miscues sur- rounding the transition cow can cost the dairy producer hun- dreds if not thousands of dollars in either health related issues or long-term production losses. In fact, 70-80% of vet- erinary costs are incurred one to three weeks post-freshening and it is estimated that any incident that decreases milk pro- duction by little less than half a litre at the peak of lactation will decrease milk production by 227-454 kg throughout lac- tation. Additionally, any incident that decreases milk produc- tion by 0.91 -2.27 kg at the peak of lactation will have a pro- portional greater decrease in milk production throughout lactation. The transition period should be the dominant area of focus for a dairy producer. With proper understanding of the relationship between transition cow physiology and proper nutrition, a dairy can realise big savings on treatment interventions, culling or lost production. Getting post-fresh- ening cows back on feed quickly is important to recovery, optimising lactation potential and warding off many meta- bolic issues. Bottom line – physiology of the fresh cow changes dramatically at freshening and calcium alone doesn’t answer all the nutrient demands that these changes dictate. To optimise recovery outcomes, producers need to be sure to meet all the physiology demands with more nutrients than commonly discussed.


▶DAIRY GLOBAL | Volume 6, No. 2, 2019 17


Delayed or inadequate post-freshening recovery can cost the dairy producer significantly.


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