TECHNICAL BULLETIN 190 ISSN 0070-2315

FACTORS AFFECTING WATER CONSUMPTION OF DRY-PREGNANT

AND LACTATING COWS IN A MEDITERRANEAN ENVIRONMENT

S. Economides

",;[::,

AGRICULTURAL RESEARCH INSTITUTE

MINISTRY OF AGRIClTLTURE, NATURAL RESOURCES

AND THE ENVIRONMENT

NICOSIA CYPRUS

OCTOBER 1998

Editor - in Chief

Dr A.P. Mavrogenis, Agricultural Research Institute, Nicosia, Cyprus.

All responsibility for the information in this publication remains with the author(s). The use

of trade names does not imply endorsement of or discrimination against any product by the

Agricultural Research Institute.

2

FACTORS AFFECTING WATER CONSUMPTION OF DRY-PREGNANT AND LACTATING COWS IN A MEDITERRANEAN ENVIRONMENT

S. Economides

SUMMARY

Water consumption, dry matter intake and milk yield of a group of high yielding (HL) cows (milk yield ranging from 22 to 30 kg/cow/day), a group of low and medium yielding (LML) cows (milk yield ranging from 14 to 21 kg/cow/day) and a group of dry­pregnant (P) cows, were measured for a period of 12 months. During the same period, ambient temperature, humidity and rainfall were also recorded. Mean annual water con­sumption was 96, 80 and 58l/cow/day for HL, LML and P cows, respectively. Mean dai­ly water consumption (I/cow/day) during the summer months ranged from l09 to 132 1 in HL, 93 to 97 1in LML and 73 to 80 I in P cows, respectively. Mean annual water con­sumption O/kg dry matter intake) was higher in P than in HL and LML cows grouped to­gether (5.9 vs 5.5), but during the winter months more water was consumed by HL cows than P cows (4.2 to 4.5 vs 3.2 to 3.8). Positive and significant relationships were found between water consumption and temperature and negative relationships between water consumption and relative humidity or rainfall. Dry matter intake and milk yield were re­lated to water consumption when used in regression equations together with temperature and humidity. All regression equations could predict water consumption with high accu­racy. It is concluded that the water requirements of dairy cows, can be predicted with high accuracy from temperature, humidity, dry matter intake and milk yield.

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INTRODUCTION Thomas, 1975; Little and Shaw, 1978; ARC, 1980; Murphy et at., 1983; NRC, 1989; Hol­

Dairy cows require a plentiful supply of ter and Urban, 1992; Murphy, 1992). Equa­water, about 4 to 5 III of milk produced, and tions have been proposed to predict water this requirement is higher in dry hot areas consumption based on measures of these due to the need to facilitate heat dissipation variables. (ARC, 1980). Restricted water intake due to The main constraints to dairy cow pro­bad water quality or deficient supply would duction in Mediterranean climates are the be expected to affect primarily milk produc­ limited water supply, the low level of forage tion (NRC, 1989). Many factors such as dry production and the dry hot climate (Econo­matter intake, nature of the diet, physiologi­ mides, 1985). In many Mediterranean coun­cal state, milk yield, ambient temperature. tries, drinking water for dairy cows is provid­humidity and rainfall have been found to af­ ed mainly from wells or boreholes, and both fect water intake (Castle, 1972; Castle and its quantity and quality may not be adequate.

3

The objective of this study was to meas­ure water consumption of dry-pregnant and lactating cows and to examine relationships between water consumption and dry matter intake, milk yield, temperature, humidity and rainfall in a Mediterranean environment.

MATERIALS AND METHODS

Animals Data from 52 Friesian dairy cows (aver­

age daily number of cows) of the Agricultu­ral Research Institute's experimental dairy unit were used, from July 1993 to June 1994, to measure water consumption and factors affecting it. There were 12 dry-pregnant (P), 22 high yielding (HL) and 18 medium-and low-yielding cows (LML). Each group was kept separately, with separate feeding and water facilities in 0IJen sheds with adequate shade (about 10 m2/cow). The daily milk yield of cows is given in Table 1.

Management and feeding All cows were fed and managed indoors,

and no grazing was practiced. Newly-calved cows were assigned to the first group (high yielding cows, HL) until approximately 4 months post partum. The cows were subse­quently moved to the second group (LML) until late lactation. Approximately two months before the expected calving, they were dried off and were moved to the third group of dry-pregnant cows (P). Cows in the HL group were offered 2.0 kg of alfalfa hay and 4 to 5 kg of barley hay (cut at the milk stage) per head daily and a concentrate mix-

Table 1. Mean daily milk yield of high (HL) and low (LML) yielding cows

Milk yield (kg/day)

HL LML

January 23.3±O.58 14.5± 1.31 February 23.6±O.39 14.0±O.07 March 24.9±O.36 14.6±1.22 April 23.6±1.43 14.8±2.03 May 24.9±O.98 14.1±1.l8 June 25.4±0.47 14.9±1.64 July 28.6±O.83 15.7±O.61 August 29.8±O.66 15.9±O.35 September 27.0±l.l4 17.1±2.27 October 23.6±I.06 21.2±1.47 November 22.0±2.58 20.8±2.19 December 23.9±O.IO 15.7±l.l8

ture containing 18% crude protein on as fed basis. Cows in the LML group were offered 3.5 to 4.5 kg of barley hay and 3.0 to 2.0 kg of barley straw/head daily and a concentrate mixture containing 16% crude protein on as fed basis. Pregnant cows were offered 2.5 to 3.0 kg of barley hay and 3.0 to 2.5 kg of bar­ley strawlhead daily and a concentrate mix­ture containing 16% crude protein on as fed basis. Occasionally, cows were offered small quantities of green alfalfa, green maize or green barley replacing an equivalent part of cereal hay.

The ingredients of the two concentrate mixtures fed to cows, and containing either 18 or 16% crude protein were the following (kg/t finished feed). The concentrate mixture with 18% crude protein contained 613 barley grain, 100 corn grain, 236 soybean meal, 25 wheat bran, 2.5 dicalcium phosphate, 18 limestone, 3.5 salt and 2.0 vitamins and trace elements. The concentrate mixture with 16% crude protein contained 758 barley grain, 170 soybean meal, 50 wheat bran, 2.5 dical­cium phosphate, 14 limestone, 3.5 salt and 2.0 vitamins and trace elements. The vita­mins and trace element mixture provided 8000 LD. vitamin A, 600 LD. Vitamin D, 15 LD. Vitamin E, 25 mg Mn, 30 mg Fe, 1.5 mg I, 1.5 mg Co, 45 mg Zn and 60 mg Mgl kg concentrate feed.

The dry matter (DM) and neutral deter­gent fiber (NDF) contents of the two concen­trate mixtures were 89.0 and 20.Wlo (DM ba­sis), respectively, while the crude protein content (CP) was 20.4 and 18.2%, respec­tively (DM basis). The DM, CP and NDF contents were 88.0, 21.2 and 40.5 for alfalfa hay, 88.0, 9.4 and 56.6 for barley hay and 90.0,3.8 and 75.0% for cereal straw, respec­tively. The average sodium content of the concentrates, including the NaCl supple­ment, was 1.6 glkg and of roughages 1.8 to 2.0 glkg as fed. The average potassium (K) content was 18 to 20 glkg for roughages and 4.5 glkg for concentrates on as fed basis.

The daily allowance of metabolisable en­ergy (ME) intake for each cow was adjusted every two weeks based on liveweight, parity and the energy secreted in milk (NRC, 1989). The average daily ME intake derived from roughage was subtracted from the rec­ommended ME intake, and the daily allow­ance of concentrates was calculated from

4

published values of the ME content of feeds (Hadjipanayiotou et aI., 1983; NRC, 1989). Cereal hay and alfalfa hay were group fed at 07:00 h and straw was fed at 13:00 h. The daily allowance of the concentrate mixture was offered individually in 5 meals (08:00, 12:00, 16:00, 20:00 and 24:00 h) for lactat­ing cows and in two meals (08:00 and 16:00 h) for pregnant cows using an electronic management system (NEDAP POIESZ, Hen­gelo, Holland). Any concentrate residues were offered as 6th or 3rd meal at 04:00 h for lactating and pregnant cows, respective­ly. Milk yield was recorded twice daily. The weekly milk yield of each cow was used to calculate the mean daily milk per cow in each group.

Measurement of water consumption The quality of drinking water was con­

stant (Table 2), although the Na content was slightly higher during the summer months (range 450 to 480 ppm). Metered water was available from open water troughs, one for each group of cows. The daily records of wa­ter consumption were corrected for the daily direct evaporation from the water trough. This was considered to be equivalent to the evaporation measured with the USWB Class A Pan Evaporimeter at the experimental site (Metochis, 1979). Correction for any rainfall was also made.

Relationships between water consumption and different factors

In order to investigate the relationships between water consumption and climatic fac­tors, milk yield or dry matter intake/cow/day, simple or multiple regression equations were

Table 2. Quality characteristics+ of the drinking water

pH 7.58 Conductivity* 2.89 Boron . 0.57 Ca 62 ~g 67 Na 470 K 14 Bicarbonate 290 Carbonate 0 Sulphate 513 Chloride 524

+~inerals in ppm; * mmho/cm at 25°C.

used. Water consumption (Y), expressed in l/cow/day, was regressed on temperature, humidity, milk yield or dry matter intake. The group daily water intakes divided by the daily number of cows in the group were used as individual observations. The regression equations were calculated either for dry­pregnant or lactating cows separately, or dry-pregnant and lactating cows together. The independent variables tested were the following: • Dry matter intake (DMI) in kg per cow per

day. Records of group daily feed intake (dry matter) divided by the number of cows in the group were used as individual observations. Feed intake was constant for two weeks, and was corrected daily for concentrate residues.

• Milk yield (MY) in kg per cow per day. The weekly total milk yield of each group was divided by the number of cows in each group and by 7 to calculate mean daily milk yield per cow in each group. These values were used as individual observa­tions.

•The daily values for minimum temperature, (MINT) average temperature (AVET) and maximum (MAXT) temperature, and rela­tive humidity at 08:00 h (RH8) and at 13:00 h (RH13) were used as individual observations.

Meteorological data Temperature, relative humidity and rain­

fall were recorded at a Meteorological Sta­tion 800 m away from the cow sheds.

Statistical analysis The data were analysed by one-way anal­

ysis of variance (Steel and Torrie, 1960), and differences among means were tested by Duncan's new multiple range test. The mean daily intakes of dry matter and water per cow in each group, and water consumption per kg dry matter intake were used as indi­vidual observations (Blaxter et al., 1961). Simple or multiple linear regression equa­tions were used to study relationships be­tween water consumption (dependent vari­able) and dry matter intake, milk yield, temperature or humidity.

RESULTS

Mean daily water consumption, dry mat­ter intake, sodium intake from the drinking

5

--- - -- - ----- - ------ --------

- --------- --- - - - - --------

___ - -

Table 3. Mean daily intake of water, dry matter and sodium

Water consumption (lIcow) Dry matter intake (kg/cow) Sodium intake from water (g/cow) Total sodium intake (g/cow) Water consumption (I/cow/kg DMI)

HL LML p SD

96.0a 79.7b 58.0c 19.8 17.2a 14.9b 10.lc 1.10 43.2a 35.9b 26.2c 8.92 74.3a 62.6b 44.3c 9.13

5.6b 5Ab 5.9a 1.58

Means in the same line with different letters are significantly different (P<OJ)J).

water and total sodium intake during the whole year of the HL and LML cows were significantly higher (P<O.O I) than those of P cows (Table 3). However, water consump­tion (per kg dry matter intake) of P cows was significantly higher (P<O.OI) than that of HL and LML cows (Table 3).

Mean daily water consumption (Table 4) and total sodium intake (Table 4) per month of HL cows were significantly higher (P<O.O I) than that of LML and P cows. and of LML cows significantly higher (P<O.O I) than that of P cows. Similarly. mean daily dry matter intake and sodium intake from drinking water of HL cows were significant­ly higher (P<O.Ol) than those of LML and P cows. and of LML cows significantly higher (P<O.O I) than that of P cows. Monthly changes of water consumption and milk yield of HL and LML cows are shown in Figure 1.

However, water consumption (liters per kg dry matter intake) differed significantly

between HL, LML and P cows, depending on the month of the year (Table 4). Water consumption per kg dry matter intake of HL cows was significantly higher (P<O.O]) than that of P cows in December, January, Febru­ary and March, it was similar in April, and significantly lower in the other months (Ta­ble 4). In P cows, water consumption per kg dry matter was lower than that of LML cows in January. it was similar in February. March, April and December. and higher in the other months (Table 4).

Dry matter intake was not related to wa­ter consumption in P, HL and LML cows separately. However, there was a significant relationship when all lactating cows were

1 <­

considered together (R-=O.l I, P<O.Ol) or when all cows were considered together (R2= 0.33, P<O.O I) (fable 5). Similarly, milk yield used as a single independent vari­able had no relationship with water con­sumption. There were highly significant (P<O.O 1) relationships between water con-

Table 4. Daily consumption of water ii/cow/day). sodium+ (g!cow/day) and water consumptIon relative to dry matter intake (I/kg/DMI) of Friesian cows

-- ------ --- ---- --- .---- - - - _... _- - --- - - - - .. - ~--- - ­

January Fehruary March April May June July August September October November December -- ------- - _.- - ­

Daily \vater consumption - . - - - ­

HL LML P SO -- --_._- - --- -- ­

75a* 53b 37c III 71a 56b 35c 9.6 69a 53b 35c lOA

lOla 79b 57c 12.0 J03a S5b 70c \0.8 109a 93b 76c 11A \l8a 93b SOc 7A 132a 97b 73c 8.9 lIla 94b 6Sc 6A 99a 93b 72c ) 1.6 87a Slb 54c 9.2 80a 65b 44c 7.\

HL

M.Sa* 62.3a 59.6a 74.6a 76Aa 79Aa S4.6a 905a 82.1a 76.9a 71.2a 68Aa

- --- ------- --- -- .. _- ------ - - -- -- ­

Sodium intake

LML P - . ----- ­

51.0b 37.1 c SI.2b 33 ..1c 4SAb 32.3c 60.9b 44.lc 65.0b 5").:k 67.8b 51.Sc 66.% 53.0c 68.3b 49.2c 69.9b 48.6c 7l.8b 50.0c 66.% 42.9c 57Ab 40.3c

- -­ -- ­

Relative waler intake

SO HL LML P

4.9 4Aa 3.7b 3.2c 4.4 4.2a 3.9ab 3.Sb 5.2 4Aa 4.0ah 3% 5.3 6.2a 5.8a 6Jla 4.7 6.3b S.6c 7.3a 5.1 6.5b 6.6b 7.7a 3.6 6.7b 6.6b SAa 4.1 7.6b 7.0c S.Oa 2.9 6.2b 6.1b 7.0a 5.4 5.5b 5.5b 7.3a 4.1 4.6b 4.8b 5.3a 3.1 4.5a 4.lb 3.Sb

---- --- ----- - 0_-- ---- -­

+Sodium intake from feed and water: *N.S. Non significant. Means in the same line with different letters differ SIgnificantly (P<O.OI).

SO

O.S 0.7 0.9 0.9 1.0 O.S u.s 0.7 0.5 O.S 07 (J.G

6

-o-HL cows

-+-LML cows

-o-HL cows

~LMLcows

140140

120120

>­.. 100 "0 100 j 0 >­..

"0a 80 80 C.

ll: ~

"0a;E ':;':::I 60.. 60

~ l: = 0<> ;:;: - 40~ 40 ~

20j.~20 o -- I I ---,-----------.----------.--,------ ! --,- --------,-----~ 0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Figure 1. Daily water consumption and milk yield of high yielding cows (HL), and low and medium yielding cows (LML).

The inclusion of DMI as a third indepen­sumption and temperature (MINT, AVET, dent variable in any of the combinations ofMAXT), or relative humidity (RH8, RH13), temperature and humidity, improved R2 con­with P, HL and LML cows separately, with siderably when dry-pregnant and lactatingHL and LML cows together or all cows to­

weregether (Table 5). The relationships between cows considered together. The equa­water consumption and the combination of tion best describing this relationship was the either AVET or MAXT with RH8 or RH 13 following: were significant, but they did not improve the accuracy of prediction of water consump­ Y=-27.9 + 4.6 DMI + 1.78 MAXT - 0.18 RH13 tion compared with the relationship of (R2=0.82, P<O.OI)MAXT alone as an independent variable.

Table 5. Regression equations of water consumption (l/cow/day) on DMI, maximum temperature, and relative humidity

Group of cows* DMI (Xl) MAXT (X2) RHl3 (X3)

P (12) Y=6.3+1.94 X2 Y=91.8-0.84 X3 R2=0.76 R2=0.61

HL (22) Y=33.3+2.30 X2 Y=131.7-0.93 X3 R2=0.76 R2=0.52

LML (18) Y=29.6+1.82 X2 Y=110.9-0.82 X3 R2=0.68 R2=0.57

HL+LML (40) Y=15.0+4.55Xl Y=31.1+2.00 X2 Y=121A-0.87 X3 R2=0.11 R2=0.61 R2=OA6

All cows (52) Y=13.6+4.60XI Y=21A+2.08 X2 Y=112.9+0.9 X3 R2=0.33 R2=OA8 R2=0.38

* For explanation of variables see Materials and Methods. All R2 values were significant at P<O.OI; Figures in parentheses indicate the number of observations used.

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------ ----------- -------- - --- ------

Table 6. Water consumption of cows on rainy and non rainy days

Water consumption (I/cow/dayl

ilL LML P

No at rainy Rainfall Rainy Non rainy Rainy Non rainy Rainy Non rainy Month days (mm) days days days days

January 15 140.2 73 77 February 14 64.6 69 73 March 6 35.3 64 70 April 3 19.0 99 101 May 4 8.0 95 104 June 0 0 (lOY) July 0 0 (118) August 0 0 (132) September 0 0 (111l Octoher 1 13 60 100 Novemher 4 27.4 75 88 Decemher 3 6.7 73 81 Total 50 314.2 608 694 Mean 76 87 c/r 87.3 100.0

._._-------­

For the lactating groups together, the in­clusion of milk yield as a third variable in any of the combinations of temperature and humidity improved the accuracy of predic­tion of water consumption. The equation best describing this relationship was the follow­mg:

y= 1.04+ 1.89MAXT-0.Ol RHl3 + I.77 MY

(R2= 0.80, P<O.OI)

Water consumption of cows was signifi­cantly reduced on rainy days (Table 6). There were 50 rainy days and a total of 314 mm of rainfall in the year. Water consump­tion of HL cows was reduced on rainy days by 12.7%, of LML by 16.5 % and of P cows by 20.8%.

DISCUSSION

The high milk yields of the HL cows dur­ing the summer months can be partly ex­plained by calving season and the proper nu­trition and management practices (adequate shades, the feeding of high energy density diets and the supply of plentiful drinking wa­ter at all times). With good management practices, even when temperature rises above the thermal comfort zone, high milk produc­tion can be kept at acceptable levels (Wier­sma, 1978; Solomon et al., 1995).

The higher dry matter intake, the physio­logical state of the cows and the level of

42 59 52 60 37 57 70 80 74 87

(93) (93) (97) (94)

74 93 77 81 61 65

487 582 61 73

83.5 100.0

milk production caused sumption of lactating

days Jays

35 30 21 54 50

51 53 39

333 42

79.2

38 39 38 64 73

(76) (80) (73) (68)

73 54 44

423 53

100.0 - -------- ­ ------------ ­

higher water con­compared to dry­

pregnant cows (ARC, 1980; NRC, 1989). The present results are also in agreement with those of Holter and Urban (1992) who found that water consumption in lactating cows was curvilinear with highest water in­take in summer (late June) and lowest in winter. Moreover, water consumption of lac­tating cows increased when air temperature increased (NRC, 1989; Bahman et al., 1993; Solomon et al., 1995). McDowell et al. (1969) found that water consumption in­creased by 28% when cows were exposed to 32 °C compared to 15 to 24 oC. Increased water consumption during the warmer months serves as the major tool for heat dis­sipation by evaporation (Flamenbaum et al., 1986).

The daily sodium intake from water over the whole year was 58, 57 and 59% of the total daily sodium intake of HL, LML and P cows, respectively. However, the proportion of the daily sodium intake from water was much higher in summer than in winter, as a result of the higher water consumption. Dur­ing the summer months, the daily sodium in­take from water ranged from 62 to 68tJc of the total sodium intake. The total daily sodi­um intake/cow in the three groups of cows (Table 4) was above the recommended al­lowances by NRC (1989), because the sodi­um requirements were calculated to be met

8

from the basal diets and the supplement (NRC, 1989), without considering any sodi­um intake from the drinking water.

During the summer months, daily water consumption (per kg dry matter intake) was higher (range 6.5 to 8.4 ) than the daily water consumption during the winter months (range 3.2 to 4.5 ). Over the whole year, P cows consumed more water per kg DMI than lactating cows and also from May until No­vember, whereas lactating cows consumed more water/kg DMI during the winter months. Higher water consumption of dairy cows/kg DMI was also reported by Lacetera et al. (1995). Estimated water requirements for cattle range from 3.5 to 5.3 kg of water/ kg of dry matter intake, with temperatures from -17 to 27 °C (NRC, 1981), while ARC (1980) estimated water requirements for pregnant cows to be 5.2 kg/kg OMI at tem­peratures from -17 to 10°C and 7.0 kg/kg OMI at temperatures from 21 to 25°C. The higher water intake/kg OMI of dry-pregnant cows may be attributed to the increased total body water of pregnant cattle in foetal tis­sues and associated embryonic fluids (ARC, 1980). Moreover, it is possible that the low efficiency of conversion of metabolisable en­ergy during late pregnancy (13%), and con­sequently the higher heat increment may in­crease water consumption, required for the higher heat dissipation by evaporation in the warmer months.

No relationship was found in the present work between DMI and water consumption in any treatment group separately, when OMI was regressed as a single variable on water consumption. When DMI was includ­ed in the regression equations with more var­iables the equation that best predicted water consumption of dry-pregnant and lactating cows together was the combination of DMI with MAXT and RH13 R2=0.82. Positive re­lationships between DMI and water con­sumption were also reported in other studies (Paquay et al., 1970; Little and Shaw, 1978; Stockdale and King, 1983).

Water consumption in all groups of cows was positively and significantly related with MINT, AVET or MAXT temperatures when used as single variables (Table 5). However, MAXT temperature had the highest accuracy in predicting water consumption. Murphy et al. (1983) suggested that temperature meas­ures (minimum, average and maximum)

were highly correlated, which justified the use of only one measure to predict water consumption. Positive relationships between water consumption and air temperature were also reported by Castle and Macdaid (1975), Castle and Watson, (1973), and ARC (1980), while others found no relationship (Castle and Thomas, 1975; Little and Shaw, 1978).

Relative humidity at 08:00 or 13:00 h was inversely related with water consump­tion. Humidity at 13 :00 h was a better pre­dictor of water consumption. A negative re­lationship between water intake and humidity was also reported by Castle and Macdaid (1975), while NRC(l981) suggests that cows consume less water under condi­tions of high humidity than at low levels of humidity. However, Castle and Thomas (1975) found no relationship between water consumption and humidity.

The combination of MAXT or AVET with humidity was also positively related with water consumption. The prediction, however, of water consumption was always better with MAXT alone. Although Stock­dale and King (1983) found no relationship between water consumption and average or maximum temperature, a positive relation­ship was found between water consumption and maximum temperature after removing the effect of rainfall. Moreover, Castle (1972) suggested that temperature per se was not a major factor influencing water consumption and relative humidity and rain­fall were of greater significance. It is reason­able to assume that in countries with lower temperatures, higher humidity and higher rainfall, water consumption of grazing ani­mals is less influenced by air temperature.

There was no relationship between water consumption and milk yield, when milk yield was used either as a single variable or together with either temperature or humidity. However, there was a positive relationship between water consumption and milk yield as a third variable together with temperature and humidity. Some workers found positive relationships between water consumption and milk yield (Castle, 1972; Castle and Thomas, 1975; Little and Shaw, 1978; Mur­phy et aI., 1983), while others found no sig­nificant relation between water consumption and milk yield (Paquay et aI., 1970; Castle and Macdaid, 1975).

9

Water consumption was reduced on rai ny days. The reduction was higher for dry­pregnant cows (20.8%), intermedi;He for LML cows (16.5%) and lower for HL cows (12.7o/c). During rainy days OMI was nol re­duced. The lower water consumption may be related to a fall in ambient temperature.

To concl ude, water consumption was higher in lactating than dry-pregnant cows, but water consumption per kg dry matter in­take was higher in dry-pregnant cows. Water consumption was positively related with temperature and negatively related with hu­midity and rainfall. When dry matter intake, maximum temperature and relative humidity are used in the same equation they can pre­dict water consumption with high accuracy. Similarly, milk yield together with maximum temperature and relative humidity can also predict quite accurately waler consumption of dairy cows.

ACKNOWLEDGEMENTS

The author is grateful to Mr G. Kypria­nou, Mr Ch. Vanezis and Mrs M. Thcodori­dou for skilled technical assistance.

REFERENCES

ARC, 1980. Agricultural Research Council. The Nutrient Requirements of' Ruminullt Liwstock. Commonwealth Agricultural Bureaux, Farnham Royal. England.

Bahman, A.M., lA. Rooke. and lH. Topps. 1993. The performance of dairy cows offered drinking water of low or high salinity in <I hot arid climate. Animol ProdliCTioll 57 :23-28.

Blaxter. K.L.. FW. Wainman, and R.S. Wilson. 1961. The regulation of food intake by sheep. Allimal ProdUCTion 3:51-61.

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