Responses of Lactating Holstein Cows to Chilled Drinking Water by syx19678

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									Responses of Lactating Holstein Cows to Chilled Drinking
Water in High Ambient Temperatures
 D. L. WILKS, C. E. COPPOCK, J. K. LANHAM, K. N. BROOKS, C. C. BAKER, and W. L. BRYSON
                                                               Department of Animal Science

                                                                                        R. G. ELMORE
                                                    Department of Large Animal Medicine and Surgery

                                                                                        R. A. STERMER
                                                                                            USDA-ARS
                                                                                Texas A&M University
                                                                                College Station 77843

                   ABSTRACT                              Chilled drinking water lowered respira-
                                                         tion rates and body temperatures and in-
      In Experiment 1, 12 lactating Holstein             creased feed intake and milk yield.
  cows were provided drinking water of                   (Key words: chilled drinking water,
  either 10.6 or 27.0'C for 24 hid in a                  stress hormones, lactating cows)
  changeover design to examine the effects
  of water temperature on feed intake, wa-
  ter intake, respiration rate, rectal tempera-                      INTROW C T l O N
  ture, plasma thyroid hormone concentra-               Upon initial exposure to high environmental
  tion, and milk yield. The 1st wk of each          temperatures, the lactating dairy cow may over-
  3-wktreatment period was for adjustment           compensate by drastically reducing feed intake
  and the next 2 wk were comparison                 in an attempt to lower internal metabolic heat
  periods. Least squares means for DM in-           production. At 40°C dietary intake may be
  take as a percentage of body weight were          reduced by as much as 40% (13). Not only does
  3.68 and 3.57 for 10.6 and 27.0'C treat-          reduced feed intake slow thyroid activity, but
  ment groups. Water intakes in liters per          heat stress also causes a decline in thyroid
  kilogram of dry feed consumed as a per-           activity (17). As high environmental tempera-
  centage of body weight were 21.3 and              tures depress secretion of thyroid hormones
  20.3. Respiration rates were 70.5 and             both directly by the stress itself and indirectly
   81.0 breaths per minute; rectal tempera-          by the reduction in feed intake, milk production
   tures were 39.7 and 39.9'C, Triiodothyro-         is ultimately depressed. Under some conditions,
   nine averaged .88 and .75 ng/ml; thyrox-          milk yield may decline 33% at 35'C and over
   ine, 42.4 and 39.2 ng/ml; cortisol, 3.03          50% at 40°C (13).
   and 2.06 ng/ml; and progesterone in milk,             Ingraham (9) noted a consistent positive ad-
   4.58 and 3.15 ng/ml for the 10.6 and              vantage of 1.09 kg of milk per head per day for
   27.0'C treatment groups. Milk yield aver-         cows provided chilled drinking water during
   aged 25.9 and 24.7 kg/d and FCM aver-             the summer in Mexico. In studies with beef
   aged 25.6 and 23.6 kg/d, respectively.            cattle, Lofgreen et al. (11) reported that beef
       In Experiment 2, 24 cows given a              cattle in a hot environment consumed more
   choice of chilled or warm water showed a          feed, gained more weight, and improved energy
   clear preference (about 98%) for the              use when they were given water cooled to
   warm water. If cows are given chilled              18.3'C than when they received water at
   water of 1O'C continuously, no warm                32.2'C. Cattle given cooled water also drank
    drinking water should be available.               less than those provided warm water. In a
                                                      3-yr study with feedlot steers, Hanis et al. (8)
                                                      provided two groups of steers either 29 or 18'C
   Received June 29,1989.                             drinking water and found no significant differ-
   Accepted November 1, 1989.                         ences in daily gains. In two studies with chilled

 1990 J Dairy Sci 73:1091-1099                    1091
1092                                         WlLKS ET AL.

water offered for 10 midd water consumption          pens inside a barn. Each pen was open on the
declined as water temperature decreased (IO,         side to allow access to a dirt lot, which con-
1 ) Milam et al. (12) observed that chilled
  2.                                                 tained a portable shade. One adjustment week
         1')
water ( O C resulted in a greater cooling effect     for cows to become accustomed to the feeding
and increased DM feed intake and milk yield          system and to the water tanks preceded a
when compared with results in cows offered           7-d standardization period in which both groups
warm water (28'C).                                   were provided 30'C drinking water. No data
    In two experiments, Baker et al. (2) first       were collected during the adjustment week. The
offered 10°C drinking water to a group of six        first 7 d of each treatment period (21 d) were
cows for 8 h/d with 30'C water provided for          used as a time for adjustment to the drinking
the rest of the day. The treatment group had         water temperatures; the next 14 d were the
higher feed intakes (3.67 vs. 3.36 as a percent-     comparison periods. Daily ambient high and
age of body weight), but milk yields, rectal         low temperatures were recorded daily, and rela-
temperatures, and respiration rates were not         tive humidities were obtained from data ob-
affected significantly, although numerical dif-      tained with a sling psychrometer. Electronic
ferences indicated some resolution of heat           Calm feeding gates (American Calm. Inc.
stress. In the second experiment ( ) chilled
                                      2,             Northwood, NH) were used to measure feed
water (9.X)was offered for 48 h continuous-          consumption for individual cows. Cows were
ly. Cows in the treatment group drank more of        offered free choice once daily a complete ration
the chilled water than those in the control          composed of 45% concentrate, 15% whole cot-
group, which drank ambient water (30°C).The          tonseed, 10% coastal bermudagrass hay, and
treatment group had lower respiration rates and      30% corn silage on a dry basis. The ration was
body temperatures, which reflected the' greater       sampled three times per week, dried to a con-
heat-absorbing capacity of the water consumed.                               air
                                                      stant weight at 55"C, equilibrated to atmo-
This study is a continuation of the experiments       spheric moisture, and composited by week. The
by Baker et al. (2). Observations in our pre-        drinking water was supplied by the Texas
vious work (10, 2 indicated that cows did not
                  1)                                  A&M University water system and was sam-
 like chilled water and may drink less because        pled during each comparison period. The sam-
of their anticipation of the later availability of    ples were analyzed by the Texas Agricultural
 the preferred warm water. The objectives of          Extension Service, Soil Testing Laboratory
 Experiment 1 were to determine the effects of        (16). The water was chilled to 10°C with a
 providing continuously chilled drinking water        20,000 BTU, 208 to 230-V, three-phase refrig-
 to lactating Holstein cows in summer. In Ex-         eration unit with a storage capacity of 500 L.
 periment 2, we measured the preference of            This water was circulated between the cooler, a
 lactating Holstein cows for cold vs. warm wa-        1200-L storage tank,and the insulated drinking
 ter.                                                 water tank for the treatment group at a rate
                                                      sufficient to maintain the 10°C temperature.
           MATERIALS AND METHODS                      The water temperature was monitored by strate-
                                                      gically located and calibrated mercury and dial
                                                      thermometers. Both groups were offered water
Experiment 1
                                                      in 227.3-L insulated water tanks, and the tem-
   Eight multiparous and four primiparous             perature of the water in both tanks was re-
open lactating Holstein cows were used in a           corded twice daily. The cows in the treatment
changeover design of treatments of 10 or 30°C         group were exposed to 1 ° drinking water 24
                                                                                 0C
drinking water. All cows were ranked by FCM           h/d for 3 wk, but the cows in the control group
within parity and were assigned randomly to           received water at ambient temperatures of ap-
treatments and to periods. The average days in        proximately 3 ° except for twice daily trips to
                                                                     0C
milk for all cows at the beginning of the experi-     the milking parlor. The water temperatures
ment w s 108.8 d, and the average FCM from
       a                                               were reversed in the tanks at the end of treat-
the previous test day was 27.7 kg. Except when        ment period 1 Water intakes were monitored
                                                                      .
going to the milking parlor, both groups of           for both groups with meters read at 0800 and
cows had continuous access to feed and water           2000 h. Rectal temperatures and respiration
free choice, in enclosed 6.1- x 6.1-m adjacent         rates of individual cows were taken 3 d/wk at

 Journal of Dairy Science Vol. 73, No. 4, 1990
                             RESPONSES TO CHLLED DRINKING WATER                                      1093
0800, 1500, and 2000 h. Deep rectal tempera-            each day to diminish cue and position effects.
tures and respiration rates were used as indica-        Consumption was obtained by difference. On
tors of heat stress. During observation times,          Tuesday and Thursday of each week, respira-
cows were chained by a nylon neck collar to a           tion rates (an average of two 60-s counts) and
pipe fence within each pen. Respiration rates           deep rectal temperatures were taken at 1100 h
(number of breaths per minute) were observed            to indicate the degree of heat stress. Following
while cows were chained to the pipe fence               this trial, another 12 lactating Holstein cows
before rectal temperatures were taken. The av-          were subjected to the same 2-wk protocol.
erage of two successive 1-min counts taken by
two people was used as the respiration rate for                   RESULTS AND DISCUSSION
each observation time. Rectal temperatures
were taken using a digital thermometer and
                                                        Experiment 1
deep rectal probes 38 cm in length. Cows were
weighed every Friday during the experiment,                The weekly average maximum and mini-
and body weights were used to calculate feed            mum ambient temperatures and weekly average
intake as a percentage of body weight. Jugular          maximum and minimum humidities are
vein blood samples were obtained every Friday           graphed in Figure 1. In wk 4 and 6, the weekly
at 0800, 1500, and 2000 h, and plasma was               average temperatures were lower than the rest
analyzed for thyroxine (T4). triiodothyronine           of the weeks, which may have influenced the
 (T3), and cortisol with immuno 1251 kits (Pan-         observations for those weeks. However, wk 1
 tex, Santa Monica, CA). Both groups of cows            and 4 were adjustment weeks and data col-
 were milked twice daily at 2400 and 1300 h,            lected were not used in the statistical analysis.
 designated morning and evening milkings, re-              The mean temperatures of the chilled and
 spectively. Daily milk samples were taken at           ambient drinking water were 10.6 and 27.0"C,
 the morning milking to be analyzed for proges-         respectively. The temperature of the ambient
 terone by Ovusure Cowside Rapid Tube Kit               water was 3°C less than anticipated, but this
 (Elanco Products Company, Indianapolis. L )  N.        temperature was not controlled. Chemical com-
 Milk weights were obtained 3 d/wk at the               position of the water (Table 1 ) was typical of
 morning and evening milkings. At these times,          water from the Texas A&M University water
 samples of milk were taken for analysis of total       system. Daily drinking water intakes were aver-
 solids by drying at 100°C for 4 h, and for milk        aged for each week and are shown in Table 2.
 fat, milk protein, and SCC by the Texas DHIA           Cows tended to drink more of the chilled drink-
 laboratory. Data were analyzed using the Gen-          ing water (10.6"C) than the control water
 eral Linear Models procedure of SAS (3).               (27.0-C). Although the difference was not sig-
                                                        nificant. it differs from earlier work in which
Experiment 2

   Twelve lactating Holstein cows yielding
more than 27 kg of milk/d were used on Mon-
                                                      95
day through Friday of 2 consecutive wk. The
                                                      85
1st wk was an adjustment period and the 2nd
wk a comparison period. The cows were 8 7 5         ~




brought into the barn at 1020 h and tied in Z + 6 5
stalls without feed or water. At 1130 h, two 9 5 5       1
rectangular containers of water were offered to $ 4 5
each cow for a IO-min interval. The containers 2 35
were identical and contained similar amounts of I?    25 2
water-one with 10°C water, the other with wa-         I5

ter of about 30'C. The two containers were             5

placed side by side in place of the feed manger.         r/zz   r/z9   815  0112     8/19 0126  912   9/9
                                                          Ad)    Sld.   I     2       3    4     5     6
The amounts offered exceeded the amount
drunk in       cases. The positions Of the two         Figure 1. Weekly averages of daily ambient tempera-
containers (right side VS. left side) were rotated tures and of relative humidities.

                                                               Journal of Dairy Science Vol. 73, No. 4, 1990
1094                                              WlLKS ET AL.

TABLE I. Chemical composition of drinking water.1*2          periments with cattle (2. 11) in which a greater
Composition                           (WAG)
                                                             amount of heat was absorbed by chilled water
                                                             even though less was consumed.
Cations
 Calcium                                3.6                      Cattle with chilled drinking water ate more
 Magnesium                               1.o                 (P<.O6) feed than controls (Table 3), which is
 Potassium                              3.0                  consistent with other studies (2, 11, 12). Period
 sodium                               208.3                  effects were also significant ( P 4 0 3 ) ; cows
 Total cations                        215.9
                                                             consumed more feed as a percentage of body
Anions                                                       weight in the second half of the 6-wk experi-
 Carbonate                             59.8
 Bi-carbonak                          462.1                  ment. This may have been due to lower average
 Sulfate                               16.6                  ambient temperatures in the second treatment
 Chloride                              60.7                  period than in the first treatment period (Figure
 Total anions                         599.2                  1). In a study with beef cattle in a hot environ-
T t l solids
 oa                                   815.1                  ment (average maximum ambient temperature
DH                                      8.9
                                                             40.8'C), hfgreen et al. (11) found that cattle
     'Water w s f o the Texas A&M University water
                 rm                                          provided 18.3'C water 24 h/d ate more feed per
system.                                                      day and had a more efficient ratio of feed per
     ZAverage of k e e samples.                              unit of gun than cattle given 32.2"C water.
                                                             Similarly, Baker et al. (2) and Milam et al. (12)
                                                             observed an increase in feed intake when
                                                             chilled water (1O'C) was provided to lactating
cows consumed less chilled water than ambient                dairy cows for a portion of the day.
water (2, 5. 6, 10, 12, 15). The amount of heat                  Respiration rates flable 4) were 70.5 breaths
absorbed per cow per day from the chilled and                per minute for the treatment cows compared
ambient water was 2153.31 and 898.27 kcal.                   with 81.0 for the control cows (P<.OOOl). The
This value was calculated by taking the differ-              differences between respiration rates at the
ence between body temperature and drinking                   three observation times are also in Table 4.
water temperature and multiplying it by the                  Chilled drinking water had its greatest effect in
average liters of water consumed by each                     lowering respiration rates at 1500 h with a
group. Chilled drinking water absorbs more                   difference of 11.8 breaths per minute between
kilocalories of heat than ambient water, but                 the two treatments (P<.OoOl). The difference
there is an additional cooling effect for the                 between the chilled water treatment at 2000 h
treatment cows in this experiment, because they               and the controls at 2000 h was 1 1.1 breaths per
consumed more of the chilled water than the                   minute (Pc.OOO1). Chilled drinking water had
ambient water. This agrees with previous ex-                  the least effect at 0800 h with differences be-



TABLE 2. Effect of chilled drinking water on group water intake.
                                                         Dnnking water t m e a u e
                                                                        eprtr
                                           10.6.C                                      27.o.C
                                              ( W g DM intake                             (Ukg DM intake
Weeks                  (Ucow per d)           per 1 0 0 kg BW)         (Ucow per d)       per 100 kg BW)
'
1                   73.35                      22.78                   58.68              19.20
2                   79.23                      22.30                   62.63              18.25
3                   77.93                      21.99                   64.36              18.95
41                  72.17                      19.75                   79.76              21.72
5                   8 1.48                     20.95                   89.24              24.20
6                   75.17                      20.06                   74.89              19.85
Least sauazes means 78.45                      21.32                   72.78              20.11

     'Weeks of adaptation; not used in the statistical analysis.

Journal of Dairy Science Vol. 73, No. 4, 1990
                                    RESPONSES TO CHILLED DRINKING WATER                                               1095
TABLE 3. Effect of chilled drinkmg water on feed intake.
                                                               Drinking water temperature
                                             10.6'C                                            27.0'C
                          (DM intake/           (DM intake/                  (DM intake/            (DM intake/
We
 ek                       100 kg BW)            w75)                         1M) kg BW)             wt.75)
1                   3.22                        ,155                         2.87                   .I36
2                   3.55                        ,172                         3.43                   ,163
3                   3.54                        ,172                         3.40                   ,161
4                   3.65                        .I75                         3.67                   ,178
5                   3.89                        .I87                         3.69                   ,180
6                   3.75                        .I80                         3.77                   .184
Least squares means 3.68                        .I78                         3.57                   ,172
SE                   .04                        .002                          .04                   .002
         aP.M.



tween the two treatments at this time of 8.7                       whereas control cows averaged 39.9-C
breaths per minute (P<.02). Within each treat-                     (P<.OOOl). Chilled drinking water had its great-
ment, differences in respiration rates between                     est effect in lowering rectal temperatures at
the observation times were also significant ex-                    2000 h with a difference of .4"C between the
cept between 0800 and 2000 h (P<.OOOl). Res-                       two treatments (P<.OoOl). The difference be-
piration rates for both groups tended to be                        tween the chilled water treatment at 1500 h and
lower in wk 4 and 6 compared to wk 1,2, and                        the control treatment at 1500 h was .3'C
3. This trend may be due to a decline in the                       (P<.0001).Chilled drinking water had its least
average weekly temperatures in wk 4 and 6                          effect at 0800 h with differences between the
(Figure 1).                                                        two treatments .1"C (fk.02).Within each treat-
   Rectal temperatures (Table 5) for the treat-                    ment, differences between the three times were
ment cows across all times was 39.7'C,                             significant (Pc.OOO1). Similar to respiration



TABLE 4. Effect of chilled drinking water on respiration rates (breawmin)
                                                       Drinking water temperature and observauon time
                                                      10.6-c                                     27.0'C
We
 ek                             0800 h        1500 h            2000 h          0800 h       1500 h          2000 h


1'                              79.4          91.0              74.0            83.2         100.5           87.8
2                               68.3          89.0              72.3            82.5          97.7           86.3
3                               74.0          90.3              72.3             84.1        100.9           84.0
41                              62.6          64.7              53.7            58.3          74.7           60.7
5                               60.0          67.0              61.6            63.5          83.0           70.1
6                               52.9          73.8              65.1            59.8          85.5           75.1
 eky
W e l least
    squares means               64.6d         7 8.
                                                 gbgC           68.3d            73.3c        90.4a          79.4b
SE                               1.8           2.3               1.5              1.8          2.3            1.5
Least square means
All timese                                                  70.5                                             81.0
SE                                                            .79                                              .SO
     ~                                           ~~              ~                  _           _
         a*b,c7dMeansih different superscripts differ (P<.05)
                    wt
         eP<.OOO 1.
         ' e k of adaptation, not u e in siaustical analysis.
           Wes                     sd

                                                                           Journal of Dairy Science Vol. 73, No. 4, 1990
1096                                                 WILKS ET AL.

TABLE 5. Effect of chilled drinking water on rectal lernperature('C).

                                                         -
                                                   Drinkine water ternmature and observation time
                                               10.6'c                                       27.0'C
Weck                        0800 h         1500 h            2000 h        0800 h        1500 h      W         h


11                           39.5         40.4               40.1          39.8         40.7         40.6
2                            39.1         40.3               39.9          39.5         40.7         40.6
3                            39.5         40.6               40.2          39.8         40.8         40.5
4'                           38.9         39.1               38.8          38.5         39.1         38.7
5                            39.0         39.8               39.4          39.0         39.9         39.5
6                            39.0         39.8               39.5          38.9         40.1         39.9
Weekly least
 squares means               39.3e         40.0b             39.7c         39.4d         40.3a       40.1a.b
SE                             .7
                                0             I
                                             .n                .os            .M           .M            .05
Least squares means
NItimesf                                                     39.7                                    39.9

     asb,c*deMeans
                 with different superscripts differ (P<.05)
     fP<.rnI.
     'Weeks of adaptation; not u e in statistical analysis.
                                sd




rates, rectal temperatures for both groups de-                  ml) (Table 6). There were also no significant
clined in wk 4. Lanham et al. (10) and Milam                    effects of treatment on time between the two
et al. (12) reported differences in rectal temper-              groups. However, the 1500 h concentration of
atures taken 10 min after providing chilled                     both groups tended to be lower than the con-
water in a moderate environment, but the re-                    centrations of T4 during the cooler times of the
duction in body temperature was transient. Ba-                  day. Within the treatment group, the 1500 h T4
ker et al. (2) also noted a trend for cows                      concentration was 14.4 ndml lower than the
consuming chilled water to have lower body                      2000 h concentration (fc.001).There were no
temperatures. Because chilled water is effective                other treatment by time effects within each
in cooling t e body, cows are not required to
              h                                                 group. These results agree with h t t and Wet-
increase respiration rates as high in order to                  temann (14), in which the concentrations of T4
keep body temperatures lower. This indicates                    and T 3 tended to decrease in steers exposed to
that cows consuming chilled water in a hot                      32'C compared with concentrations in s'mrs at
environment may have lower maintenance re-                      4°C. The main secretory product of the thyroid
quirements than those consuming ambient wa-                     gland is T4, followed by T3. Both increase the
ter.                                                            energy metabolism of most tissues in the body.
    Cows given chilled drinking water had                       This may explain the lower plasma concentra-
higher plasma T3 concentrations (Table 6)                       tions of these hormones during the hotter times
 across all times than controls ( 3 8 ng/ml)                    of the day and the higher plasma concentrations
 (fc.008).The difference between treatment and                  in cows provided chilled vs. ambient drinking
 control cows at 1500 h, the hottest time of the                water in hot environments. Similar to feed in-
 day, was .16 ng/ml (k.05).There were no                        take, the thyroid gland may be attempting to
 other significant effects of treatment on time                 lower body heat production, thereby enabling
 between the two groups, but the 1500 h plasma                  the animals to compensate for the greater envi-
 concentration of T3 tended to be lower for both                ronmental heat load. However, thyroid hor-
 groups compared to the cooler times of the day.                mone secretion is also related to factors other
 Chilled drinking water did not significantly af-               than environmental temperature. Thyroid hor-
 fect T4 across times, but it tended to be higher                mone secretion is reduced when feed intake is
 in the treatment cows (42.4 ng/ml vs. 39.2 ng/                  lower (17). Thyroid hormone secretion in-

 Journal of Diy Science Vol. 73, No. 4, 1990
             ar
                                 RESPONSES TO CHILLED DRINKING WATER                                              1097
TABLE 6. Effect of chilled drinking water on plasma concentrations of uiiodothyronine (T3). thyroxine (Tk),
                                                                                                          cortisol, and
milk progesterone (P4).
                                           Drinking water temperature and observation time
                                       10.6-c                                               27.0.C
                OSOOh            1500 h          UXX)h               0800 h           1500 h          2000 h
                                                                Wml)
Hormone
 T3               .87'             .84'            .93'                .81'vb          .68b              .77',b
 T4            42.4a.b*C         35.2c           49.6a               36.4b.C         37.2b*c          43.9aSb
 Cortisol        1.84"-b          3.56'           3.7P                2.52'~~         2.32'~~           1.34b
 p4'            ...              ...             ...                 ...              ...             ...
Means, all times and periods
 T3                                .88'                                                 .75b
 SE                                .03                                                  .03
 T4                              42.4                                                 39.2
 SE                               1.6                                                  1.6
 Cortisol                         3.03                                                 2.06
 SE                                .44                                                  .44
 p4                               4.58                                                 3.15
 SE                                .56                                                  S6
   a7b-cMeansi same row w t different superscripts differ (Pe.05).
             n            ih
   'Milk P4 was measured twice daily and averaged on a weekly basis.




creases from the first (1.96 ng/ml) to the third             plasma cortisol may also suggest that the body
(2.99 ng/ml) trimester of lactation, and Hol-                is attempting to lessen metabolic heat produc-
steins have lower T 4 secretion rate than Guern-             tion by reducing the thermogenic actions of this
seys.                                                        hormone.
    Cortisol was not significantly affected by                   As shown in Table 6, cattle provided chilled
chilled drinking water across all times, but the             drinking water had higher milk progesterone
treatment cows tended to have higher plasma                  concentrations than controls (4.58 vs. 3.15 ng/
cortisol concentrations than controls (3.03 vs.              ml) (R.08). cows were open during the
                                                                            All
2.06 ng/ml) (Table 6). However, the                          entire experiment. Three cows expressed signs
2000-h concentration of cortisol in the treat-               of standing estrus during the 8-wk experiment
ment group was 2.45 ng/ml higher than the                    and were bred, but none conceived. At the time
2000-h concentration in the control group                    of their breeding, two of the cows were in the
(k.03). The elevated cortisol in wk 5 may be                 control group and one was in the treatment
the result of the lower temperatures in wk 4.                group. The absence of signs of estrus and the
Other studies that measured plasma cortisol                  tendency toward lower milk progesterone in the
concentrations in hot weather probably refer to              control group may indicate that cows were in
long-term vs. short-term effects (1, 4). Christi-            metestrum or proestrum most of the time. How-
son and Johnson (4) exposed cows to moderate                 ever, the majority of the treatment cows appar-
heat stress (35°C) for 20 min and observed a                 ently never came into estrus. This indicates that
rise in plasma cortisol concentrations. Howev-                there may be other factors that affect reproduc-
er, aftcr cows were exposed to 7 to 10 wk of                  tive efficiency of cows in the summer. Similar
chronic mild heat stress ( 5 C , plasma cortisol
                           3')                                to this study, Folman et al. (7) showed an
 was depressed (4). Abilay et al. (1) also noted a            increase in summer plasma progesterone con-
depression in plasma cortisol in cows exposed                 centrations in cattle that were cooled by forced
 to a 33.5'C environment. These authors (1) also              ventilation and related reduced fertility in the
 suggested that depressed cortisol in heat-ex-                summer to lower progesterone concentrations.
 posed cows may reflect the inactivity of a      n                Cows receiving chilled drinking water pro-
 enzyme in the adrenal cortex which synthesizes               duced more milk (25.9 vs. 24.7 kg/d) (P<.02),
 cortisol from progesterone. The depression in                as shown in Table 7. Milk fat percentage also

                                                                      Jou~~al Dairy Science Vol. 73, No. 4. 1990
                                                                           of
1098                                                  WKKS ET AL.

TABLE 7. Effect of chilled drinking water on milk yield     ing water that we did not measure. An alterna-
and components.                                             tive for dauy farmers with cold well water is to
                                    Drinking water          use insulated water tanks to keep the water
                                     temwrature             cool.
Component                  10.6.C           27.0’C

Milk yielda                25.9
                                        (kgld)
                                             24.7
                                                 - Experiment 2
                                                               After the adjustment weeks, all 24 cows
SE                           .35               .34
3.5% F C M ~               25.5              23.6           clearly preferred ambient water. The first 12
SE                            .35              .34          cows drank an average of 97.2% ambient water
                                         (%)                with a range of 87.4 to 100%. Seven cows
Fat                         3.43               3.31         drank only warm water. The second set of 12
SE                           .06                .06         COWS averaged 99.3% ambient water with a
Protein                     3.07               3.07         range of 94.5 to 100%. Ten cows drank only
SE                            .2
                               0                .02         the warm water. Corresponding respiration
ShT                          8.17              8.29
SE                            .08               .08
                                                            rates and deep rectal temperatures for the corre-
Total solids                11.59             11.60         sponding groups during the comparison weeks
SE                            .09               .09         were 80.5 and 39.6”C and 97.5 breaths per
                                       (X   io3) -          minute and 40.5’C. Clearly, these cows had
                                                            elevated respiration rates and body tempera-
SCC                        84.7              133.1
SE                         42.6               42.6          tures, which reflected the July conditions.
     aP<.02.
                                                            Chilled water averaged 1O’C; line water aver-
                                                            aged 29.6”C during the wk 1 of comparison and
     bP<.0003.
                                                            31.0’C during the wk 2. Preference for warm
                                                            water does not prove that cows would “wait”
                                                            for the preferred water, but this appeared to
                                                            occur in our earlier studies (12), in which cows
tended to be higher in the treatment cows;                  given chilled water before milking were seen to
therefore, FCM was also different (25.5 vs.                 go immediately to the warm water trough after
23.6 kg) (P<.0003).Milam et al. (12) also                   leaving the milking parlor. These findings sug-
observed increased milk yields in cows pro-                 gest that if chilled water were offered continu-
vided with chilled drinking water.                          ously, cows might drink from the wash rack
    Treatment cows consumed 3.08% more feed                 sprinklers, or any other warm water source that
than the control cows, and the concentration                was available to them.
(by calculation) of NE) in the diet was 1.69
Mcalkg DM. This resulted in an additional .65                      ACKNOWLEDGMENTS
kg of feed consumed/d by the treatment cows,
which is equivalent to an additional 1.10 Mcal/     We express appreciation to the Texas Dairy
d. The treatment cows also produced 1.2 kg Herd Improvement Association for the milk
more milk/d, which required an additional 1.72 analyses. We thank Barbara Perkins for help in
Mcal NEl/d. These results indicate that the the preparation of the manuscript.
cows fed chilled water produced more milk
even though they did not consume enough ad-                             REFERENCES
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