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OCR for page 39
Water Env~ronrnent
Interactions
Water, a nutrient, is essential for life, and intake is subject to marked inter-
action effects with environment. Little is known about actual requirements
for normal physiological functions within the TNZ or at thermal extremes.
Most estimates of water needs are based on free water consumed under ad
libitum offerings.
WATER SOURCES
The water needs of livestock are filled from three major sources: (1) free
drinking water, (2) water contained in feed, and (3) metabolic water pro-
duced by oxidation of organic nutrients. The catabolism of 1 kg of fat, car-
bohydrate, or protein produces 1190, 560, or 450 g of water, respectively.
Metabolic water is important to all animals, particularly those residing in dry
environments, such as the kangaroo rat (Church et al., 1974~. The first two
sources are of major concern in the management of livestock, although in
periods of negative energy balance, i.e., when depot fat and tissue protein
are being utilized, metabolic water would be important.
Water contained in or on the feed is extremely variable. It may range from
a low of 5 percent in dry grains to about 90 percent in young, fast-growing
grasses. In addition, the amount of dew or precipitation on the grass at the
time of grazing is subject to wide fluctuations. In the case of swine and poul-
try, diets are blended from dry ingredients and intake of water in a feed ac-
counts for about 10 percent of the total feed intake.
39
OCR for page 40
40
FARM ANIMALS AND THE ENVIRONMENT
WATER LOSSES
Water losses by animals are principally through: (1) urine, (2) feces, and
(3) evaporation from the body surface and respiratory tract, although under
severe stress cattle and other species may lose a significant amount through
drooling (McDowell and Weldy, 1967~. Unless animals are on a water re-
stricted diet, urinary excretion rate can usually be reduced without impairing
the ability of the kidneys to excrete body wastes (Church et al., 19744.
In ruminants the loss of water through feces is substantial, approximately
equal to urinary losses. The high-fiber nature of ruminant diets requires pro-
portionately more water to carry the ingesta through the gastrointestinal tract
than for nonruminants. Level of fiber is not, however, sufficient reason to
explain the level of fecal water, e.g., cattle feces contain 75-85 percent wa-
ter, while sheep and goat feces have 60~5 percent water. The ability to re-
absorb water in the lower gut and excrete drier fecal pellets instead of wet,
loose feces is presumably one mechanism of water conservation.
Water loss from the respiratory tract is extremely variable, depending on
relative humidity and respiration rate. Expired air is over 90 percent satu-
rated; hence, under conditions of low relative humidity, respiratory losses
are high. Conversely, losses are low when inspired air is near saturation.
When respiration rate increases in response to high temperatures or other be-
havioral stimulus, the rate of respiratory water loss is increased, e.g., cattle
may lose 23 ml/m2/h at 27°C and up to 50 ml/m2/h under severe heat stress
(Roubicek, 1969~.
Cutaneous evaporation of water is the major means of heat loss in cattle
and sheep at high temperatures (McDowell and Weldy, 1967; Robertshaw,
1966~. There are large differences among species in the importance of sweat-
ing with domestic livestock ranked in the descending order of horses, don-
keys, cattle, buffaloes, goats, sheep, and swine (McDowell, 1972~. The
threshold skin temperature for sweating varies among species with cattle re-
acting at about 25°C (McDowell et al., 19541. Zebu cattle may secrete up to
15 g/m2/min when heat stressed (McDowell, 1972), but during cold condi-
tions only 0.~1.0 g/m2/min are lost (Murray, 1966~.
Swine and poultry are examples of species that depend more on the respi-
ratory than cutaneous route for water loss. Total evaporative water loss in
poultry increases markedly with temperature rising from 10 to 40°C. As
noted in Table 5, cutaneous water loss plays a decreasing role in heat loss as
temperature rises and heat dissipation occurs predominantly through respira-
tory water loss.
OCR for page 41
Water-Environment Interactions
TABLE 5 Heat Loss from White Leghorn Fowl by Respiratory and
Cutaneous Evaporative Heat Loss at Different Environmental
Temperaturesa
41
Heat Cutaneous Respiratory Total
Ambient Body Produced Evaporation Evaporation Evaporation
Temperature (°C) Weight (kg) (kcal/h) (kcal/h) (kcal/h) (kcal/h)
10 1.70 6.55 0.166 0.251 0.417
20 1.66 5.09 0.201 0.277 0.478
30 1.69 4.43 0.323 0.482 0.805
35 1.67 5.27 0.597 1.561 2.158
40 1.65 5.33 0.995 3.443 4.438
a Adapted from van Kampen, 1974.
FACTORS AFFECTING WATER INTAKE
There are numerous factors that influence the intake of free water, such as
animal species, physiological condition of the animal, level of dry matter in-
take, physical form of the diet, water availability, quality of water, tempera-
ture of the water offered, and ambient temperature.
Differences Among Species
Zebu cattle may have a lower intake of water than European breeds (Colditz
and Kellaway, 1972; Johnson et al., 1958; Ragsdale et al., 1950; Winchester
and Morris, 1956), but there is conjecture over whether observed values are
directly attributable to genotype (Figure 13) due to sampling variance, dif-
ferences in body size, or level of dry matter intake. When data from these
experiments are adjusted to a constant body size and dry matter intake, spe-
cies differences become negligible.
Water intake per kilogram of dry matter consumed may be as much as 40
percent less for sheep than cattle (ARC, 1965~. Over the temperature range
-17 to 27°C, the estimated requirements for cattle were 3.5 to 5.5 kg water/
kg DM, whereas in about the same temperature range sheep needed only 2.0
to 3.0 kg water/kg DM. The estimated water needs for swine are near that for
sheep, 2.~2.5 kg/kg DM.
Differences in water consumption among sheep, swine, poultry, and cattle
could be largely due to some of the factors already discussed, but further
testing will be required to discern potential species differences between Bos
indicus and Bos taurus and between cattle and buffalo.
OCR for page 42
42
FARM ANIMALS AND THE ENVIRONMENT
Physiological State
Young calves generally have higher intakes of water per kilogram of DM con-
sumed (S.() 7.0) than the 3.5 to 5.5 kg recommended for older cattle (ARC,
1965; Pettyjohn et al., 1963~. During the last 4 months of pregnancy, cows
may consume 30 percent more water than when dry and open (ARC, 1965)
and under barn feeding conditions the estimated intake of free water for lac-
tating cows is 0.87 kg water/kg milk produced (Winchester and Morris,
1956~.
The kg water/kg DM consumed by pregnant ewes increases from about 2.0
in the first month to 4.3 in the fifth month (Head, 1953~. Ewes carrying
twins will consume over twice the amount of water of nonpregnant ewes and
those carrying single lambs, 138 percent above nonpregnant ewes. When
corrected for water content of milk, lactating ewes consume 100 to 164 per-
cent more water than dry ewes (Forbes, 1968~.
Weanling pigs will consume approximately 20 kg water daily per 100 kg
of body weight, but those near market weight much less, 7 kg/100 kg of
FIGURE 13. Water intake of
two species of cattle as a func-
tion of environmental tempera-
ture (adapted from Winchester
and Morris, 1956).
16 _
a)
y
~ 12 _
._
-
A
-
z
o
~ 8 _
cat
an
it
o
cut
~ 4 _ ~
o
Bos to ; / if
~ Bos indices
, 1 1 1 1 1 1
10 15 20 25 30 35
AMBI ENT TEMPERATUR E (°C)
OCR for page 43
Water-Environment Interactions
43
body weight. Water intake for nonpregnant sows is estimated at 5 kg/day,
5-8 kg during pregnancy, and 15-20 kg while lactating (ARC, 1966).
Frequency of Watering
When cattle on grazing have water available free choice, they drink 2 to 5
times per 24 h (Castle et al., 1950; Hancock, 1953~. Cattle grazing pasture
with forage DM of 17.8 percent under cool conditions (13°C) will drink about
4 times daily with a rate of intake of 0.26 to 0.45 kg/second (Castle, 1972~.
In general, water intake, particularly of lactating cows, will depend upon
availability (Table 6~. Under extensive grazing systems in dry tropical areas,
water intake of sheep or cattle will decline as distance to water sources in-
creases. Water intake of sheep declined significantly, about 7.85 g/kg, when
distance between feed and water increased from 2.4 to 5.6 km (Daws and
Squires, 1974~.
Physical form of the diet influences water consumption (Table 7~. When
The same forage crop was made into both hay and silage, Holstein heifers on
the silage diet had higher total water intake (free + feed) and secreted more
urine than heifers on hay alone. Others have made similar observations
(Carder et all, 1964; Forbes, 1968~. Protein and salt levels in the diet will
also influence water consumption (ARC, 1965; Kwan et al., 1977; Pierce,
1962; Ritzman and Benedict, 1924; Sykes, 1955; Weeth and Haverland,
1961~.
Water Temperature
Findings on the effect of temperature on water intake are variable. When
Hereford cattle were kept in drylot where daily maximum temperature was
38°C, reducing the water temperature from 31.0 to 18.3°C caused a decline
in consumption of water, but daily gains increased (Ittner et al., 1951~.
However, at 31°C maximum daily temperature there was no effect of cooling
the water for finishing cattle (Harris et al., 1967~. When heated water
TABLE 6 The Effect of Water Availability
on Water Consumption by Lactating Grazing
COWS
Treatment
Water Consumed (kg)
Water in barn 2.8 in/day
Water in field 21.2 in/day
Both sources
0.1
5.3
5.5
a Adapted from Castle and Watson, 1973.
OCR for page 44
44
FARM ANIMALS AND THE ENVIRONMENT
TABLE 7 Effect of Some Diets on Water Intake of Holstein Heifersa
Experiment 1
Hay Pellets Hay-Grain Silage
Water consumed, kg/kg feed dry matter
Water in feed 0.14 0.14 0.14 1.40
Water drunk 3.57 3.10 3.16 2.84
Total water intake 3.71 3.24 3.30 4.24
Experiment 2
Hay
Ad lib. Maint.
Silage
Ad lib. Maint.
Water consumed, kg/kg feed dry matter
Water in feed 0.11 0.12 3.38 3.38
Water drunk 3.36 3.66 1.55 1.38
Total intake 3.48 3.79 4.93 4.76
Urine, kg/kg feed dry matter 0.93 1.14 1.85 1.68
a Data from Waldo et al., 1965.
(39.4°C) was presented to cows in a cold environment (-12°C), intake in-
creased, but at this low temperature, heating the water to 30°C did not influ-
ence consumption by sheep (Bailey et al., 19621.
Water temperature does not appear to alter rate of digestion. Under two
ambient temperatures, 3°C and 12°C, water temperatures of 1, 14, 27, and
39°C did not have a detectable effect on digestion of Holstein cows even
though ingestion of 21 kg of water at 1°C depressed lower, middle, and up-
per rumen temperatures by 13, 6, and 1°C within 10 min (Cunningham et
al., 19641.
Air Temperature
The concept that water intake of livestock is related to air temperature is well
recognized. Numerous experiments have shown significant positive correla-
tions between water intake and ambient temperature. Although water intake
may be related to ambient temperature, several other factors are important in
decision making on water needs.
Cattle Under controlled temperature conditions it has been demonstrated
that cattle tend to increase water intake as temperature rises (Figure 13 and
OCR for page 45
Water-Environment interactions
TABLE 8 Intake of Drinking Water and TDN of Brown Swiss, Holstein,
and Jersey Heifers Under Various Temperature Conditionsa
Air
Temperature kg Water/ kg TDN/ kg Water/
(°C) kg TDN Day Day
45
2 4.7 4.7 22.1
10 5.2 4.2 22.1
21 7.2 4.2 28.0
27 9.0 4.0 34.7
32 22.2 3.0 53.7
35 24.8 2.9 60.3
a Average body weight 361 kg (range 263~17 kg).
SOURCE: Adapted from Johnson and Yeck, 1964.
Table 8), with 27°C being the temperature where marked changes in intake
by lactating cows is noted (Table 81. Below that point water consumption is
considered largely a function of dry matter intake (Bianca, 1970; Brody et
al., 1954; McDowell and Weldy, 1967; McDowell et al., 1969; Ragsdale et
al., 1949, 1950, 1951; Winchester and Morris, 1956~.
Under controlled environmental conditions no appreciable effect has been
shown by changing rate of . ir movement from 0.64 to 12.9 kph on water
consumption at -8, 10, 18, and 27°C. Changing the radiation level from
0.02 to 0.84 cal/cm2/min had no effect on the intake of water at 7°C but had
significant effects at 21 or 27°C (Brody et al., 1954; Thompson et al.,
1954).
The correlation of water consumption of cattle and ambient temperature
under field conditions is less clear because of confounding factors. However,
at ambient temperatures from-37 to 7°C, water intake of Herefords in feed-
lots was positively correlated with air temperature on the same day (r =
0.27) and with feed intake the previous day (r = 0.25) (Williams, 19591.
The correlations were statistically significant with the conclusion that obser-
vations on water intake made at low constant temperatures were only in gen-
eral related to intakes under low fluctuating temperatures.
For average daily temperatures around 8°C in Britain, water intake of lac-
tating cows was significantly correlated with daily milk yield and dry matter
content of the forage but was not significantly related to either air tempera-
ture or relative humidity. Average intake was 3.70 kg/kg DM consumed after
adjustment for water in the milk (Castle and Macdaid, 19751. When maxi-
mum daily temperatures for grazing cattle are in the range of 13 to 28°C, wa-
ter consumption is positively correlated with maximum temperature, forage
DM and daily hours of sunshine but negatively correlated with rainfall and
OCR for page 46
46
FARM ANIMALS AND THE ENVIRONMENT
TABLE 9 Correlation Coefficients Between Intake of Drinking Water and
Various Climatic and Production Variables for Lactating Holstein Cowsa
Variable Correlation Coefficient Significance (P value)
Maximum air temperature +0.57 <0.05
Rainfall - 0.57 <0.05
Relative humidity - 0.82 <0.01
Sunshine + 0.86 <0.01
Forage DM +0.52 n.s.
Milk yield +0.36 n.s.
a Adapted from Cowan et al., 1978.
relative humidity as illustrated in Table 9. Even though the correlation be-
tween water and intake was not significant, it is similar to the correlation for
maximum air temperature and water.
When maximum daily temperature exceeds 30°C, free water intake tends
to rise more rapidly than from 25 to 30°C, but variation among individuals
increases markedly. It is, therefore, difficult to characterize water needs be-
cause of confounding with changes in animal behavior and the possibility
that animals may use high water intake to maintain a sensation of fill that
may result in lowered feed intake (McDowell, 19724. The data in Table 8 il-
lustrate the point. The kg water/kg TDN consumed rose very rapidly above
27°C and so did total water intake, but kg TDN had decreased by 30 percent.
The marked decline in TDN intake per day is not likely to occur under field
conditions, thus the estimates of water based on this experiment and that in
Figure 13 appear abnormally high for general recommendations.
Figure 14 shows that "previous temperature exposure" of the animals will
markedly affect level of water intake. The Shorthorn heifers switched from a
cold environment in January (6°C) to a 32°C control room had a more rapid
rise in water intake than similar heifers changed from outside to a 32°C con-
tinuous temperature in August. After both groups had become adjusted to the
32°C (approximately 10 weeks), water intake became steady at a level of 1.8
times the level of the control group under cool conditions. After the third
week of exposure, feed intake was at the preexposure level, but rate of live-
weight gain was 12.5 percent less than for the control group (0.81 kg/day).
Figure 15 portrays the estimated water intake of nonlactating cattle ex-
pressed as kg water/kg DM intake. From -10 to 20°C there is a slight pro-
gressive rise. Above 25°C consumption rises more sharply due to the initia-
tion of sweating and increased respiration rate. At 35°C or higher it is
virtually impossible to keep feed intake up. The estimated physiological
needs are 10 kg/kg DM at 40°C, but usually the cattle are so distressed that
behavior becomes variable, in which case water intake may rise markedly
OCR for page 47
Water-Environment Interactions
12
en
-
a, 1 0
en
-
_
0 2 4 6 8
Summer-September
Winter-January
.
47
\
Sammy
Inter
Control
10 12 14
WEEKS
January
April
FIGURE 14. Intake of drinking water of Shorthorn heifers kept in an open barn January-Apr~l
(control), or changed from outside to 32°C in January (winter), or to 32°C in September (sum-
mer) (adapted from Bond and McDowell, 1972).
(B.) or even decline (By. Seldom does the stress level suggested at above
35°C occur throughout the day; hence, the major concern is below 35°C on a
daily basis. The extreme rise of water consumption in Figure 13 and Table 8
appears as much a function of reduced DM intake as the direct effects of
stress. When temperature falls below -10°C, physiological needs may de-
cline slightly (Point P. Figure 15), but due to the high degree of stress behav-
ior may vary as indicated by Point B. Figure 15.
Sheep The relation of drinking water intake to ambient temperature for
sheep appears to parallel that for cattle. From O to 15°C water intake of gro-
wing and fattening sheep is 2.0 kg/kg DM consumed, increased to 2.5 kg at
15-20°C and 3.0 kg above 20°C (ARC, 19651. Up to approximately 38°C
daily maximum temperature, water intake appears positively related to tem-
perature, but at 40°C or higher, water intake may decline or rise rapidly, as
in Figure 15 for cattle (Daws and Squires, 19741. When temperature declines
to-12°C, the temperature of the rumen, rectum, and subcutaneous tissues
decreases, resulting in a decline of about 50 percent in water intake from the
15°C level (Bailey et al., 19624.
OCR for page 48
48
FARM ANIMALS AND THE ENVIRONMENT
25
20
lL
by
Zen
- a,
UJ ~
- .~ 15
UJ Y
~- 10
_ ~
2 ~
an En 5
UJ _
O'
1
I
l
B 1
, p
~-B2
j B ~I ~I I I
-20 -10 0 10 20 30 40
-10 0
TEMPERATURE ( C)
FIGURE 15. Estimated ad libitum water intakes for nonlactating cattle over the temperature
range -10 to 35°C; solid line with extensions "P" at high and low denoting "physiological
needs"; "B." and "B2" indicate behavior patterns at extreme temperature.
In tropical Australia and other areas a number of tests have been made on
the influence of drought and temperature on the tolerance of various types of
sheep to dehydration. Merino sheep seem to have a higher tolerance than Eu-
ropean breeds to water deprivation (Macfarlane et al., 1958~. It has also been
suggested that type of body covering may influence water needs with hair
sheep having the least need, followed by coarse wool sheep and fine wool
sheep (Hafez, 1968~.
Swine Experiments under controlled temperature conditions have shown
an inconsistent relation between ambient temperature and water intake. At 7,
12, 20, and 30°C, water intakes were 2.88, 2.76, 2.74, and 4.28 kg/kg of
DM. The corresponding values, when measured as kilograms of water con-
sumed daily per kilogram of body weight, were 0.136, 0.122, 0.123, and
0.181 (Close et al., 19711. The major increase in water consumption be-
tween 20 and 30°C, when expressed as a function of DM intake, is primarily a
function of the reduced DM intake with increasing temperature above 25°C
(Fuller, 19654. Presently, the needs for water at temperatures lower than
10°C are not identified, mainly because of the current production environ
ments.
OCR for page 49
Water-Environment Interactions
49
Poultry Laying hens deprived of water survive 8 days at an ambient tem-
perature of 14°C, but only 6 days when the temperature is 29°C (Bierer et
al., 1966~. At 35°C White Leghorn fowl lose, by respiratory evaporation,
2.6 g of water per hour as compared to 0.5 g/h at 20°C (van Kampen, 19741.
Thus, rising ambient temperatures increase the need for water. Water is lost
from poultry as a fluid (excretory water loss through urinary and digestive
systems or as a vapor (respiratory water loss). Another major route of water
loss for laying poultry is eggs. About two-thirds of the egg is water.
Poultry derive water from three sources: feed, which contains about 10
percent water by weight; metabolism of proteins, carbohydrates, and fats
(metabolic water); free water consumption. The latter is the primary source
of water, comprising about 74 percent of the total daily intake (Table 10~.
The secondary source of water is metabolic water, at only 18 percent of
the total intake. There is a close correlation between metabolic water and cal-
ories produced: 0.135 g H2O per converted kcal (Kerstens, 19641. Therefore,
a hen consuming 100 g of feed per day that has a caloric value of 3 kcal/g
produces about 40 g of metabolic water per day. The hen drinks water at a
ratio of 2 to 3 g of water per gram of diet. So, the intake of water is, at tem-
peratures of 21-22°C, typically 250 g water per 100 g feed during egg pro-
duction. Laying hens consume more water on days when an egg is formed
and laid than on nonlaying days, 225 g versus 115 g, respectively (Howard,
1975).
As ambient temperatures rise, chickens consume increasing amounts of
water; intake is 2.0-fold at 32°C, and 2.5-fold at 37°C greater than intake at
21°C.
Water availability for poultry is important for survival under heat stress.
Hens allowed ample drinking water in containers large enough for their
TABLE 10 Water Intake by Broiler Chickensa
Percent of Total
Total H2O
Age Ambient Intake H2O in Metabolic Drinking
(weeks) Temperature (°C) (g/bird) feed H2O H2O
1 31 16 9 19 72
3 25 32 1 1 23 66
5 22 91 7 14 79
7 20 140 6 16 78
9 20 163 6 16 78
Mean 8 18 74
a Adapted from Kerstens, 1964.
OCR for page 50
so
FARM ANIMALS AND THE ENVIRONMENT
heads to be dunked survive longer during hot stressful conditions (Vo and
Boone, 1978~. Thus, the water serves as a coolant for external evaporation or
to absorb heat from the head during drinking positions. In corroboration of
these observations, hens were noted to withstand high ambient temperatures
when allowed unlimited access to water, as compared to those given equiva-
lent amounts by syringe directly in the crop (Lee et al., 1945~. The connota-
tion of these data is that water presumed to be drunk during heat stress may
actually have been lost to the surroundings when shaken off the head. The
impact of such losses on total water intake is not known.
Because of the many factors that may influence the needs for drinking wa-
ter, the real needs for water are difficult to characterize. That a positive rela-
tion exists between temperature and the amount of water consumed by ani-
mals when water is available free choice is undisputed. On the other hand, it
is very unlikely that real water needs rise by 400 to 500 percent at 30°C or
above. Most likely, the quick rise in water consumption at high temperature
is used by animals as a stopgap measure to maintain heat balance until physi-
ological processes can adjust to the new environment. No doubt ingested wa-
ter is used as a heat sink in the rumen and may also be used by animals under
acute thermal stress to replace feed at least on a temporary basis. In addition,
what is sometimes measured as water consumption, because water disap-
peared from a container, may have been lost by animals immersing part of
their body in response to heat or from evaporation.
In general, drinking water intake per unit DM intake remains nearly con-
stant up to about 27°C. At that point, water intake seems to rise rather rap-
idly in response to stress, but after an acclimation period of perhaps several
weeks, intake may decline to near the lower temperature level. When making
estimates of water requirements under different environmental conditions,
one should remember that animals on farms rarely encounter constant ther-
mal stress throughout a 24-h period.
Representative terms from entire chapter:
water consumption
