Water has been coined the “forgotten nutrient,” probably because it doesn’t carry a price tag like milk replacer — or whole milk and calf starter — that dairy producers feed their calves. But when water consumption isn’t where it should be it can be costly indeed in terms of reduced calf growth and performance.
Hugh Chester-Jones, dairy and beef systems production specialist at the University of Minnesota’s Southern Research and Outreach Center in Waseca, deals with 1,100 calves a year — mostly Holstein — that come through the center for research projects. He calls water the “essential nutrient.”
“Water has an important influence on the intake level of calf starter,” he said. “Water goes directly into the rumen and creates an aqueous environment needed by rumen bacteria, whereas milk or milk replacer goes directly to the abomasum because the rumen of the calf has not been developed yet.”
After helping the center’s calves survive another winter, Chester-Jones is looking forward to spring and summer months. But he said it’s often more challenging to maintain good calf growth and health in the summer than in the winter months.
Contributing to the challenge is high heat and humidity — making availability of fresh clean water all the more important. The upper critical temperature for calves is 78 degrees or greater. But heat stress is also impacted by humidity. Chester-Jones said calves can generally tolerate a higher temperature-humidity index than cows.
Conditions for a temperature-humidity index of 76, which will stress cows but is still tolerated fairly well by calves:
76 degrees, 100 percent relative humidity;
78 degrees, 80 percent humidity;
80 degrees, 70 percent humidity;
84 degrees, 45 percent humidity; and
88 degrees, 45 percent humidity.
But producers need to pay close attention to those calves at that temperature-humidity index. A calf that’s breathing faster and heavier, with increased body temperature, poor appetite and general malaise is showing signs of heat stress. It’s suggested heat stress increases calf energy needs because panting and standing more both expend energy. Feed intake drops and maintenance energy is estimated to increase 20 percent to 30 percent.
“In addition, as calves attempt to maintain body temperature in the summer months, increased respiration and sweating results in water losses which have to be replaced,” Chester-Jones cautioned.
Hot weather can impair the calf’s immune function and promote bacterial growth, which results in more infectious disease and secondary dehydration. According to research at the center, calves born between late May and August have the most depressed performance.
Maternal factors influence heat stress in calves. Heat-stressed cows will have depressed intakes. Often premature and light-birth-weight calves result. Heat stress during late gestation can also reduce colostrums quality, causing calves to be smaller and less vigorous.
“Water intake should be increased to prevent dehydration and perhaps increase starter intake,” Chester-Jones advised.
To prevent calves from slopping water into their starter buckets, solid dividers between buckets is suggested, or spacing buckets about 5 inches apart, which also prevents the calves from dripping water into their starter buckets. The other alternative is replacing soiled water and soggy starter frequently.
Farmers well know that water intake is closely related to starter intake, which, in turn, drives rumen development. However, Chester-Jones said that water intake may increase independent of starter intake when weather conditions are at the upper critical temperature for calves.
Research has shown that the amount of liquid in milk replacer also affects the amount of water consumed. And water temperature can also affect water intake. It’s a good idea to offer warmer water for calves, especially in colder weather.
How do pre-weaned calves respond to milk and starter feeding without additional water offered? Chester-Jones cited research from 20-some years ago in which calves were offered free-choice water, or no water, when fed 4.2 pounds of milk replacer — 11.4 percent solids — twice a day for three weeks and then once a day in week four prior to weaning. There were no differences in daily gain for the first three weeks, but greater gain in week four for calves offered water. Starter intake was higher for calves given water from week two onward, with the biggest differences in weeks three and four. Water intake made no impact on the incidence of scours, though. The authors emphasized the importance of free-choice water to support good starter intake and calf growth.
Recently, the center revisited this work by offering restricted or free-choice water to pre-weaned calves during the summer months. Calves either received free-choice water, or were offered no water for 35 days, then five pounds daily from day 36 to weaning at 42 days. Both groups got water free-choice after weaning.
Calves were individually fed a 20:20 milk replacer — 12.5 percent solids — twice a day for 35 days, and then once a day from day 36 to weaning at 42 days. An 18-percent texturized calf starter was fed free-choice from day one to day 56.
“Water intake and dry-matter intake increased in both groups from day 35,” Chester-Jones said. “Contrary to the previous work, there were no differences in dry-matter intake and calf performance pre- and post-weaning. There were no differences in scouring days and health costs.”
An even newer study at the center conducted April to July last year evaluated water and dry-matter intake when calves were fed a 24:20 milk replacer at 0.62 pound in 4.25 pounds of water, or 1.56 pounds in 5.3 pounds of water, twice daily for 35 days and then once daily from day 36 to weaning at 42 days. In the first group, the 24:20 milk replacer was fed at 1.25 pounds per day, while the second group of calves got 24.:20 milk replacer at 1.5 pounds per day. Both milk replacers were fed with 14.7 percent solids. An 18-percent texturized calf starter was offered free choice from days one to 56.
“Water intake increased as dry-matter intake increased, especially from day 35 onward,” Chester-Jones said. “Calves fed higher milk replacer levels had lower starter intakes. Calves gained well and had good frame growth. Number of scouring days was lower than in previous summer studies.”
Chester-Jones said milk-replacer intake averaged 1.13 pounds and 1.39 pounds of dry matter, respectively, for the two milk-replacer regimens noted above. Starter intake from the study averaged 2.05 and 1.92 pounds per day, respectively. Daily gains from day one to day 56 were 2.05 and 1.92 pounds, respectively. None of these differences was statistically different.
Water intake was higher for the second group, perhaps due to higher solids intake from the milk replacer. But even post-weaning, the second group of calves were still drinking more water.
Total water intakes for the two groups, respectively, were: one to 42 days – just over 2.1 quarts versus just over 2.3 quarts; days 43 to 56 – 8.3 quarts versus 8.6 quarts; one to 56 days, on average – just under 3.7 quarts versus almost 3.9 quarts.
“Water availability is important for calf health and does impact feed intake and growth, especially when milk feeding is reduced or the calves are weaned,” he gave as his take-home message.