Water nutrition in the dairy cow
Experiments were conducted to study two different aspects of water nutrition. First, the effect of ambient versus heated drinking water on the production responses of lactating Jersey and Holstein cows were evaluated. Second, the effects of supplementing the drinking water of transition dairy cattle with dextrose, on performance, energy and protein status were examined. The first experiment was replicated over four seasons with 18 cows randomly assigned to an ambient (7-15°C) or a continuously heated (30-33°C) drinking water treatment in a four week cross-over design. Free water intake was 3.40-5.95% greater for heated versus ambient drinking water treatment at 82.33, 79.62 (2.77 'P' < 0.05); 89.73, 86.09 (3.75 ' P' = 0.05); 91.22, 86.99 (2.21 'P' < 0.001); 93.00, 87.78 (1.59 'P' < 0.001) L/d for the heated and ambient water for the spring, summer, autumn and winter experiments, respectively with SEM and significance in brackets. Overall, water treatment had no effect on milk yield or feed intake. Cattle consumed 40% of their water intake within 2 h of milking and feeding times. In the second experiment, 24 multiparous Holstein dairy cows were randomly assigned to one of three treatments for an experimental period that extended from -7 d prepartum until 21 d postpartum. The treatments included a 0 (control), 1 and 2% dextrose solution metered into the drinking water. Postpartum DMI was greater for (' P' < 0.05) control versus 1 and 2% dextrose supplemented cows (16.27 ± 0.32; 13.30 ± 0.32; 13.41 ± 0.29 kg/d for treatments respectively). The NEL balance, milk yield and water intake was not affected by dextrose treatment. The rumen ammonia levels were reduced ('P' < 0.01) over the lactation period in the dextrose treated cows (8.87 ± 0.83; 5.38 ± 0.98; 5.32 ± 0.76, mg/dL for the control, 1 and 2% dextrose respectively) and the postpartum blood urea was reduced ('P' < 0.05) in a linear relationship to dextrose inclusion (5.59 ± 0.12; 4.76 ± 0.12; 4.04 ± 0.11 mmol/L for 0, 1 and 2% treatments), signaling a more effective use of dietary protein. The BW and BCS loss during the postpartum period was reduced in dextrose treated cows. The results demonstrate that cattle prefer warm water and the heating of dairy cattle drinking water may be more economical for colder environments and at specific times throughout the day. Additionally, water can be used as a vehicle for the transfer of energy substrates to transition cows which can increase dietary protein efficiency and minimize BCS loss.