Effects of Voltages on Cows over a Complete Lactation. 1. Milk Yield and Composition R. C. GOREWIT, D. J. ANESHANSLEY,1 and L. R. PRICE Department of Animal Science Cornell University Ithaca, NY 14853 ABSTRACT
INTRODUCTION
The effect of long-tenn voltage exposure on milk yield and composition was assessed. Forty cows in second to fifth lactation were used. Four groups of 10 Holstein cows were exposed to either 0, I, 2, or 4 V throughout an entire lactation. Each group was housed in a free-stall environment with bunk feed and water provided for ad libitum intake. Voltages (AC, 60 Hz) were applied between waterers and a metal grid. Cows could not drink without placing their front hooves on the metal grid. Individual records were maintained for milk weights, milk fat, protein, and somatic cell counts. Average actual (7312, 8527, 6938, and 7725 kg for groups exposed to 0, 1, 2, or 4 V, respectively) and mature equivalent (7802, 9281, 7303, and 8911 kg for groups exposed to 0, 1, 2, or 4 V, respectively) milk weights for 305 d showed no significant differences between groups exposed or unexposed to voltage. Average actual milk yields for 305 d in the previous lactations were 8016, 8163, 7679, and 7876 kg for groups exposed to 0, 1, 2, or 4 V, respectively. Somatic cell counts, milk fat, and protein showed no significant differences between groups exposed or unexposed to voltage. Feed and water intakes were not affected by voltage. (Key words: cows, voltages, milk yield)
Controlled research over the past decade has concentrated on short-tenn behavioral and physiological effects of neutral-to-earth voltage (stray voltage) (1, 2, 3, 4, 5, 6, 7, 8, 9). Accessibility to water is a key factor related directly to milk yield because water is a major component of milk. When water consumption decreases over time for a lactating cow, she yields less milk. Furthennore, her feed intake eventually decreases, which also compromises milk yield. Craine et al. (1) provided three water bowls, at 0, 3, or 6 V, to nonlactating heifers. Treatments were systematically switched such that each water bowl received each voltage for an equal time. Heifers could choose freely among the three water bowls. They drank from all three water bowls, but they drank 20% less at the 3-V water bowl and 68% less at the 6-V bowl. It was not clear whether all or only some heifers drank from the electrified water bowls or whether water consumption changed when two of the three water bowls were electrified. In a second experiment by Craine et al. (1), 30 nonlactating Holstein heifers were divided into control and treatment groups. The control group had access to a water bowl without voltage; the treatment group experienced a voltage regimen. In this regimen, voltage was increased from 0 to 8 V over a 5-wk period. Water consumption of the treatment group was compared with that of the control group. Although water consumption was very erratic, the treatment group did consume less water overall. At 8 V, the entire treatment group refused to drink for 8 h and drank sparingly over the next 16 h. The voltage treatment was then halted, and the heifers were monitored for the next 6 d. After 3 d, their water consumption was equal to that of the control group. More recently, a comprehensive study (2) focusing on the effects of voltages on isolated
Abbreviation key: T&R Center and Research Center.
= Teaching
Received September 16, 1991. Accepted June 15. 1992. lDepartrnent of Agricultural and Biological Engineering. 1992 J Dairy Sci 75:2719-2725
2719
2720
GOREWIT ET AL.
water bowls was performed on lactating cows. Milk yield, milk composition and quality, and cow health and reproductive function were monitored for 7 wk. Five groups of 3 fITst lactation cows and 3 multiple lactation cows were each exposed to 0, .5, I, 2, or 4 V for 3 wk following a 2-wk pretest and were monitored for 2 wk after voltage exposure. One cow and 1 heifer refused to drink from their water bowls for 36 h when bowls were electrified at 4 V. All other cows that were subjected to voltage on the water bowl drank after some delay during the first 24 h. The delay was directly proportional to the voltage level. However. within 48 h. those cows were consuming the same amount of water as during the pretest. Compared with the cows not receiving shocks from water bowls, cows that drank from the electrified water bowls showed no significant decrease in water consumption, feed intake, and milk yield over the 3-wk period in which they were subjected to voltages. Furthermore, no differences in cow health or reproductive function existed between cows that received voltage and those that did not. In another trial (2), 84 lactating cows were divided into four groups such that 20 cows were exposed to 3, 4, 5, or 6 V for 3 d and drank within 36 h. Four cows did not drink, 2 receiving 5 V and 2 receiving 6 V. Those experiments (2) were not carried out over prolonged periods representing a complete 305-d lactation. No controlled experimental trials have been carried out that assess the long-term (lactational cycle) yield effects of constant voltage applied to a specific point of contact with the cow. The objective of our study was to determine the effect of longterm voltage exposure on milk yield and milk composition of lactating Holstein cows. MATERIALS AND METHODS
Cows and Treatment Allocations
Forty cows in second to fifth lactation, never previously used in a stray voltage experiment, were selected for our full lactation trial from the Cornell University dairy herd Teaching and Research Center (T&R Center). Within 1 to 2 wk of calving, cows were rotated into one of four pens (0, I, 2, or 4 V; Journal of Dairy Science Vol. 75, No. 10, 1992
W
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Figure 1. Schematic drawing of one of four pens in which cows were housed. Comfort stall, waterer, bunk feed, and grain feeder are shown.
Figure 1); the fITSt cow went into the 0-V pen, the second cow to the I-V pen, the third cow to the 2-V pen, the fourth cow to the 4-V pen, and repeating with the fifth cow to the 0-V pen. It took approximately 5 mo to accumulate 10 experimental cows in each of the four pens. This helped to minimize seasonal effects. When a trial cow entered a pen, a herd cow came out. This method was also used when drying off the experimental cows; a herd cow would take the place of the dry cow in the pen. There were 10 cows in a pen at all times, which allowed us to examine short-term effects of voltage on many cows. For example, 41 herd cows were in the 4-V pen for as long as 202 d and as briefly as 4 d. Feed and Water Allocation
Cows were fed a TMR formulated to support a mature cow yielding 20 kg/d of milk. Later in lactation, the TMR was reduced to support 13 and then 9 kg/d of milk. The amount of bunk feed provided to each pen was adjusted, depending on the amount of feed that remained at the end of a day. Grain was fed individually through a system activated by an automated transponder (DeLaval Ration Master II, Kansas City, MO) to supplement the bunk mixture. Grain was adjusted to the cow's weekly milking performance and body weight. Water was provided only by waterers in the alley of each pen. Each waterer was equipped with an automatic heating system to prevent water from freezing in the winter months. A
2721
VOLTAGES AND MILK YIELD
metal-sided float was connected to the one opening in the waterer. Bars prevented more than a single cow from drinking at a time. Water consumption was monitored with an electromechanical water meter model C700 with type D pulser unit (Kent Meter Sales, Inc., Ocala, FL). The meter produced 200 switch cyclesl3.785 L of water. The meter also ha.d a visual. read-out that was mechanically dnven. The ViSUal read-out was read daily and recorded. A computer-based data acquisition system (4) was used to monitor water meters for each pen on a second by second basis. Water intake and currents delivered were recorded on the hard disk of the computer. At 0007 and 1900 h, the previous 12 h of data were transferred from the hard drive to a floppy disk. Milking
Cows were milked twice a day in a double10 herringbone parlor at a pulsation rate of 60 pulses/min and a 60:40 ratio with nonaltemating pulsation on the front and rear teats. Vacuum level was approximately 50 kPa. The milk system (DeLaval Jar MasterlParlor MasterlYield Master, Kansas City, MO) identified and milked the cows while it measured and recorded the amount of milk yielded by each cow at each milking. Weekly milk samples were taken from each cow by research personnel and analyzed for fat and protein by DHI; DHI records were also kept on all cows including the experimental cows and herd cows used in these experiments. DHI Records
The T&R Center participates in the DHI program. Milk weights and milk samples were collected by a DHI inspector once a month. Based on the milk yield data, DHI predicts the following yield estimates: 305-=
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VOLTAGE APPLIED TO WATERER Figure 3. Milk yield during experimental lactation (EXP. LACT.) as indicated by A) 305-d actual yield, B) 305-d mature equivalent (ME) yield, and C) total yield shown as a function of voltage treatment. Means (horizontal line) and standard errors of the mean (vertical bar) are indicated. These results are based on DHI records (= 10 cows per treatment).
The waterer was electrically isolated from ground, and the metal frame of the waterer with mylar sheets was placed between the main frame of the waterer and the water bowl. The water bowl of each pen was attached to the main water supply with 1.5 m (50 ft) of plastic hose. This provided isolation of waterers from ground and from one another. The only part that could not be electrically isolated was the metal mat, which was not a problem because all other paths to electrical ground were adequately isolated. Data Analysis
Milk yields for the previous lactation of all experimental cows were based on DHI records. Milk yields for the experimental lactation were based on DHI records and daily records from Journal of Dairy Science Vol. 75, No. 10. 1992
the T&R Center's milking system. Milk fat and protein results were based on the analysis of weekly milk samples for each cow. Water consumption was based on daily readings of water meters; missing data were computed from the computer records of water intake. Average water intake per cow was computed by dividing the total water intake for a day by the number of cows in the pen. The number of cows in the pen was always IO except for those rare times when a cow was temporarily removed for mastitis or other health reasons. Currents were determined from the computer recordings of the analog outputs of each ammeter. Statistical Analysis
Statistical comparisons between experimental groups (0, 1, 2, or 4 V) during the experimental and previous lactations were performed using the general linear models procedure of SAS (10). The variables compared were DID predictions of 305-d actual yield, total yield, and 305-d mature equivalent yield; T&R Center's daily records of milk yield from which peak milk, days to peak milk, persistency, average daily yield, and total yield were computed; and analysis of weekly milk samples for percentages of protein and fat. The model that best fit the milk yield and composition data included voltage and lactation number as main effects and an interaction between both effects. Period was added as a main effect for the analysis of milk composition (percentages of fat and protein). Interactions of period with the other two main effects were also included for milk composition analyses. Periods were defined as three l5-wk blocks within each cow's lactation. Comparisons of the control pen with each experimental pen for differences in daily water intake per cow were made using a t test using pooled standard deviations (11). RESULTS
Currents delivered at each waterer were variable because of changes in environmental conditions at the metal mat and differences between cows and within cows over time. Maximum currents were determined when cows drank for more than 5 s. The averages
2723
VOLTAGES AND MILK YIELD TABLE 1. Average percentage of milk protein in weekly milk samples. l Lactation Current
wk 1 to 15
wk 16 to 30
(V)
(%)
0 1 2 4
3.2 3.1 3.2 3.2
3.3 3.3 3.3 3.3
wk 31 to 45
Average
(n)2
(%)
(n)
(%)
8
9
3.4 3.4 3.3 3.4
3.3 3.3 3.3 3.3
6 7
lAverage are broken into three 15-wk periods beginning at the start of lactation. 2n = 10 unless indicated otherwise.
(and ranges) of these currents for 2 d (randomly selected) were 3.1 rnA (4.5 to 1.5), 6.5 rnA (8.6 to 4.6), and 11.2 rnA (14.1 to 7.5) for the 1-, 2-, and 4-V pens, respectively. Based on the applied voltage and the range of delivered current, minimal animal resistances varied between 224 and 648 ohms. A comparison of 305-d actual yields in the previous lactation for the four groups of cows showed no significant differences among groups before the start of the voltage experiment (8016, 8163, 7679, and 7876 kg for the experimental groups receiving 0, 1, 2, or 4 V, respectively; F = .36, P > .78). The average number of lactations for the cows in the four groups during the experiment was also not significantly different among groups (3.0, 3.0, 3.1, and 2.8 lactations for the experimental groups receiving 0, 1,2, or 4 V; F = .17, P> .9). Comparisons between the control group (0 V) and each treatment group (1, 2, or 4 V) for any measure of milk yield during the experimental lactation showed no significant
difference. No differences were found in comparisons performed on DHI estimates of the 305-d actual yield (F = 1.3, P > .3; Figure 3A), 305-d mature equivalent yield (F = 1.3, P > .3, Figure 3B), and total yield (F = 1.2, P > .3; Figure 3C). No differences were found in comparisons performed on T&R Center's daily milk yield used to compute average daily yield (F = 1.9, P> .16; Figure 4A), peak milk (F 1.94, P> .15; Figure 4B), day to peak milk (F = 2.15, P> .12; Figure 4C), persistency (F = .79, P > .51; Figure 4D), total yield (F = 1.4, P > .27; Figure 4E), and days in milk (F = .76, P > .52; Figure 4F). Analysis of milk protein (Table I) and fat (Table 2) showed no significant differences between the control and the treatment groups (F = .36, P> .78 for protein; F = .18, P> .91 for fat). Water intake was measured daily for each pen, and the average daily intake per cow in the pen was computed. Therefore, these data include experimental and herd cows that were used to maintain the number of cows in each
=
TABLE 2. Average percentage of milk fat in weekly milk samples. l Lactation Current
wk 1 to 15
(V) 0 1 2
4
wk 16 to 30 (%)
3.6 3.5 3.7 3.6
3.8 3.7 3.8 3.7
wk 31 to 45
Average
(n)2
(%)
(n)
(%)
8
9
4.0 3.8 3.7 3.9
3.8 3.7 4.0 3.7
6 7
I Averages broken into three 15-wk periods beginning at the star! of lactation. 2n = 10 unless indicated otherwise.
Journal of Dairy Science Vol. 75. No. 10. 1992
2724
GOREWIT ET AL. 30 28 -
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Figure 4. Milk yield as indicated by A) average daily yield, B) peak milk, C) days to peak milk, D) persistency, E) total yield, and F) days in milk are shown as a function of voltage treatment. Means (horizontal line) and standard errors of the mean (vertical bar) are indicated. These results are based upon the Teaching and Research Center's daily milk yield data (n = 10 cows per treatment).
pen at 10. The average daily water intake per cow was 74.1, 76.2, 71.7, and 78.7 L for the 0-, 1-, 2-, and 4-V pens, respectively. No statistical differences existed among pens (t < 1.86; P > .05) except that cows in the pen with 4 V on the water drank significantly more water (t = 3.63; P < .001) than cows in the control pen. DISCUSSION
Cows drinking from waterers with voltage had current pass from their muzzles to their front hooves. Furthermore, currents were proportional to the voltage applied at the waterers. Cow impedances, calculated from the applied voltage and the measured current, were slightly lower than those previously reported for muzzles to front hooves (8). This reduced impedance may be explained by reduced contact impedance at the muzzle. Previous reports did not use water bowls as the contact point; Journal of Dairy Science Vol. 75, No. 10, 1992
thus, contact impedances may have been greater than those in the present study. All measures of milk yield and milk composition indicated that voltage at the waterer had no effect. Varialions among pens existed, but difference in milk yields or composition was not significant for any of the voltage treatments (1, 2, or 4 V) compared with those for the control group (0 V). Yields from previous lactations were not directly compared with yields during the experiment. The experimental cows were subjected to different conditions during their previous lactations, such as a different milking parlor, a tie-stall instead of a free-stall barn, or an especially cold winter; thus, comparison is inappropriate. CONCLUSIONS
Water intake was not significantly reduced with voltage treatment. Water intake was significantly greater for cows in the 4-V pen than
2725
VOLTAGES AND MILK YIELD
for cows in the control pen. The lack of significant decrease is not surprising; previous research (2) showed that cows that will drink will drink nonnal amounts of water within 2 d of the initial voltage exposure. This occurred for 3-wk exposures (2) and, in the present study, for full lactation exposures. As in previous research (2), some cows will not drink when 4 V are applied to a waterer. In our study, 1 first lactation cow, out of a total of 51 cows placed in the 4-V pen, had to be removed. This cow was a herd cow. Her milk yield decreased rapidly, and she was not consuming grain during her first 36 h in the pen. This was the only cow that had a water consumption problem. ACKNOWLEDGMENTS
The authors express their thanks to the personnel at the Cornell University T&R Center for their help in carrying out this work. Further appreciation is given to Bert Klei for his assistance on our statistical analyses of data. This study was financed by grants from the Empire State Electric Energy Research Corporation and the New York State Agricultural Experiment Station. This paper is dedicated to the memory of R. D. Appleman.
REFERENCES 1 Craine. L. B.• M. H. Ehlers, and K. K. Nelson. 1970. Electric potentials and domestic water supplies. Agric. Eng. 51:415. 2 Gorewit. R. C., D. J. Aneshansley. D. C. Ludington, R. A. Pellerin. and X. Zhao. 1989. AC voltages on water bowls: effects on lactating Holsteins. J. Dairy Sci. 72:2184. 3 Gorewit, R. C.• N. R. Scott, and C. S. Czarniecki. 1985. Responses of dairy cows to alternating electrical current administered semirandomly in a nonavoidance environment. 1. Dairy Sci. 68:718. 4 Henke Drenkard, D. V., R. C. Gorewit, N. R. Scott. and R. Sagi. 1985. Milk production, health, behavior. and endocrine responses of cows exposed to electrical currents during milking. J. Dairy Sci. 68:2694. 5 Lefcourt, A. 1982. Behavioral responses of dairy cows subjected to controlled voltages. J. Dairy Sci. 65:672. 6 Lefcourt, A. M.• and R. M. Akers. 1982. Endocrine responses of cows subjected to controlled voltage during milking. J. Dairy Sci. 65: 177. 7 Lefcourt. A. M.• R. M. Akers, R. H. Miller, and B. Weinland. 1985. Effects of intermittent electrical shock on responses related to milk ejection. 1. Dairy Sci. 68:391. 8 Majerius, O. L.. R. O. Martin, and R. A. Peterson. 1984. Stray voltage. Proc. Nat!. Stray Voltage Symp.• Am. Soc. Agric. Eng. Publ. 3-85. Am. Soc. Agric. Eng., St. Joseph. MI. 9 Norell, R. J.• R. J. Gustafson. R. D. Appleman, and J. B. Ovennier. 1983. Behavioral studies of dairy cattle sensitivity to electrical currents. Trans. Am. Soc. Agric. Eng. 26:1506. 10 SAS@ User's Guide: Statistics. 1982. SAS Inst., Inc.• Cary, NC. 11 Snedecor, G. W.• and W. G. Cochran. 1967. Statistical Method. 6th ed. Iowa State Univ. Press, Ames.
Journal of Dairy Science Vo!. 75. No. 10, 1992
INTRODUCTION
The effect of long-tenn voltage exposure on milk yield and composition was assessed. Forty cows in second to fifth lactation were used. Four groups of 10 Holstein cows were exposed to either 0, I, 2, or 4 V throughout an entire lactation. Each group was housed in a free-stall environment with bunk feed and water provided for ad libitum intake. Voltages (AC, 60 Hz) were applied between waterers and a metal grid. Cows could not drink without placing their front hooves on the metal grid. Individual records were maintained for milk weights, milk fat, protein, and somatic cell counts. Average actual (7312, 8527, 6938, and 7725 kg for groups exposed to 0, 1, 2, or 4 V, respectively) and mature equivalent (7802, 9281, 7303, and 8911 kg for groups exposed to 0, 1, 2, or 4 V, respectively) milk weights for 305 d showed no significant differences between groups exposed or unexposed to voltage. Average actual milk yields for 305 d in the previous lactations were 8016, 8163, 7679, and 7876 kg for groups exposed to 0, 1, 2, or 4 V, respectively. Somatic cell counts, milk fat, and protein showed no significant differences between groups exposed or unexposed to voltage. Feed and water intakes were not affected by voltage. (Key words: cows, voltages, milk yield)
Controlled research over the past decade has concentrated on short-tenn behavioral and physiological effects of neutral-to-earth voltage (stray voltage) (1, 2, 3, 4, 5, 6, 7, 8, 9). Accessibility to water is a key factor related directly to milk yield because water is a major component of milk. When water consumption decreases over time for a lactating cow, she yields less milk. Furthennore, her feed intake eventually decreases, which also compromises milk yield. Craine et al. (1) provided three water bowls, at 0, 3, or 6 V, to nonlactating heifers. Treatments were systematically switched such that each water bowl received each voltage for an equal time. Heifers could choose freely among the three water bowls. They drank from all three water bowls, but they drank 20% less at the 3-V water bowl and 68% less at the 6-V bowl. It was not clear whether all or only some heifers drank from the electrified water bowls or whether water consumption changed when two of the three water bowls were electrified. In a second experiment by Craine et al. (1), 30 nonlactating Holstein heifers were divided into control and treatment groups. The control group had access to a water bowl without voltage; the treatment group experienced a voltage regimen. In this regimen, voltage was increased from 0 to 8 V over a 5-wk period. Water consumption of the treatment group was compared with that of the control group. Although water consumption was very erratic, the treatment group did consume less water overall. At 8 V, the entire treatment group refused to drink for 8 h and drank sparingly over the next 16 h. The voltage treatment was then halted, and the heifers were monitored for the next 6 d. After 3 d, their water consumption was equal to that of the control group. More recently, a comprehensive study (2) focusing on the effects of voltages on isolated
Abbreviation key: T&R Center and Research Center.
= Teaching
Received September 16, 1991. Accepted June 15. 1992. lDepartrnent of Agricultural and Biological Engineering. 1992 J Dairy Sci 75:2719-2725
2719
2720
GOREWIT ET AL.
water bowls was performed on lactating cows. Milk yield, milk composition and quality, and cow health and reproductive function were monitored for 7 wk. Five groups of 3 fITst lactation cows and 3 multiple lactation cows were each exposed to 0, .5, I, 2, or 4 V for 3 wk following a 2-wk pretest and were monitored for 2 wk after voltage exposure. One cow and 1 heifer refused to drink from their water bowls for 36 h when bowls were electrified at 4 V. All other cows that were subjected to voltage on the water bowl drank after some delay during the first 24 h. The delay was directly proportional to the voltage level. However. within 48 h. those cows were consuming the same amount of water as during the pretest. Compared with the cows not receiving shocks from water bowls, cows that drank from the electrified water bowls showed no significant decrease in water consumption, feed intake, and milk yield over the 3-wk period in which they were subjected to voltages. Furthermore, no differences in cow health or reproductive function existed between cows that received voltage and those that did not. In another trial (2), 84 lactating cows were divided into four groups such that 20 cows were exposed to 3, 4, 5, or 6 V for 3 d and drank within 36 h. Four cows did not drink, 2 receiving 5 V and 2 receiving 6 V. Those experiments (2) were not carried out over prolonged periods representing a complete 305-d lactation. No controlled experimental trials have been carried out that assess the long-term (lactational cycle) yield effects of constant voltage applied to a specific point of contact with the cow. The objective of our study was to determine the effect of longterm voltage exposure on milk yield and milk composition of lactating Holstein cows. MATERIALS AND METHODS
Cows and Treatment Allocations
Forty cows in second to fifth lactation, never previously used in a stray voltage experiment, were selected for our full lactation trial from the Cornell University dairy herd Teaching and Research Center (T&R Center). Within 1 to 2 wk of calving, cows were rotated into one of four pens (0, I, 2, or 4 V; Journal of Dairy Science Vol. 75, No. 10, 1992
W
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W l-
CJ
CJ
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Figure 1. Schematic drawing of one of four pens in which cows were housed. Comfort stall, waterer, bunk feed, and grain feeder are shown.
Figure 1); the fITSt cow went into the 0-V pen, the second cow to the I-V pen, the third cow to the 2-V pen, the fourth cow to the 4-V pen, and repeating with the fifth cow to the 0-V pen. It took approximately 5 mo to accumulate 10 experimental cows in each of the four pens. This helped to minimize seasonal effects. When a trial cow entered a pen, a herd cow came out. This method was also used when drying off the experimental cows; a herd cow would take the place of the dry cow in the pen. There were 10 cows in a pen at all times, which allowed us to examine short-term effects of voltage on many cows. For example, 41 herd cows were in the 4-V pen for as long as 202 d and as briefly as 4 d. Feed and Water Allocation
Cows were fed a TMR formulated to support a mature cow yielding 20 kg/d of milk. Later in lactation, the TMR was reduced to support 13 and then 9 kg/d of milk. The amount of bunk feed provided to each pen was adjusted, depending on the amount of feed that remained at the end of a day. Grain was fed individually through a system activated by an automated transponder (DeLaval Ration Master II, Kansas City, MO) to supplement the bunk mixture. Grain was adjusted to the cow's weekly milking performance and body weight. Water was provided only by waterers in the alley of each pen. Each waterer was equipped with an automatic heating system to prevent water from freezing in the winter months. A
2721
VOLTAGES AND MILK YIELD
metal-sided float was connected to the one opening in the waterer. Bars prevented more than a single cow from drinking at a time. Water consumption was monitored with an electromechanical water meter model C700 with type D pulser unit (Kent Meter Sales, Inc., Ocala, FL). The meter produced 200 switch cyclesl3.785 L of water. The meter also ha.d a visual. read-out that was mechanically dnven. The ViSUal read-out was read daily and recorded. A computer-based data acquisition system (4) was used to monitor water meters for each pen on a second by second basis. Water intake and currents delivered were recorded on the hard disk of the computer. At 0007 and 1900 h, the previous 12 h of data were transferred from the hard drive to a floppy disk. Milking
Cows were milked twice a day in a double10 herringbone parlor at a pulsation rate of 60 pulses/min and a 60:40 ratio with nonaltemating pulsation on the front and rear teats. Vacuum level was approximately 50 kPa. The milk system (DeLaval Jar MasterlParlor MasterlYield Master, Kansas City, MO) identified and milked the cows while it measured and recorded the amount of milk yielded by each cow at each milking. Weekly milk samples were taken from each cow by research personnel and analyzed for fat and protein by DHI; DHI records were also kept on all cows including the experimental cows and herd cows used in these experiments. DHI Records
The T&R Center participates in the DHI program. Milk weights and milk samples were collected by a DHI inspector once a month. Based on the milk yield data, DHI predicts the following yield estimates: 305-=
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7.4 6.8
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4
VOLTAGE APPLIED TO WATERER Figure 3. Milk yield during experimental lactation (EXP. LACT.) as indicated by A) 305-d actual yield, B) 305-d mature equivalent (ME) yield, and C) total yield shown as a function of voltage treatment. Means (horizontal line) and standard errors of the mean (vertical bar) are indicated. These results are based on DHI records (= 10 cows per treatment).
The waterer was electrically isolated from ground, and the metal frame of the waterer with mylar sheets was placed between the main frame of the waterer and the water bowl. The water bowl of each pen was attached to the main water supply with 1.5 m (50 ft) of plastic hose. This provided isolation of waterers from ground and from one another. The only part that could not be electrically isolated was the metal mat, which was not a problem because all other paths to electrical ground were adequately isolated. Data Analysis
Milk yields for the previous lactation of all experimental cows were based on DHI records. Milk yields for the experimental lactation were based on DHI records and daily records from Journal of Dairy Science Vol. 75, No. 10. 1992
the T&R Center's milking system. Milk fat and protein results were based on the analysis of weekly milk samples for each cow. Water consumption was based on daily readings of water meters; missing data were computed from the computer records of water intake. Average water intake per cow was computed by dividing the total water intake for a day by the number of cows in the pen. The number of cows in the pen was always IO except for those rare times when a cow was temporarily removed for mastitis or other health reasons. Currents were determined from the computer recordings of the analog outputs of each ammeter. Statistical Analysis
Statistical comparisons between experimental groups (0, 1, 2, or 4 V) during the experimental and previous lactations were performed using the general linear models procedure of SAS (10). The variables compared were DID predictions of 305-d actual yield, total yield, and 305-d mature equivalent yield; T&R Center's daily records of milk yield from which peak milk, days to peak milk, persistency, average daily yield, and total yield were computed; and analysis of weekly milk samples for percentages of protein and fat. The model that best fit the milk yield and composition data included voltage and lactation number as main effects and an interaction between both effects. Period was added as a main effect for the analysis of milk composition (percentages of fat and protein). Interactions of period with the other two main effects were also included for milk composition analyses. Periods were defined as three l5-wk blocks within each cow's lactation. Comparisons of the control pen with each experimental pen for differences in daily water intake per cow were made using a t test using pooled standard deviations (11). RESULTS
Currents delivered at each waterer were variable because of changes in environmental conditions at the metal mat and differences between cows and within cows over time. Maximum currents were determined when cows drank for more than 5 s. The averages
2723
VOLTAGES AND MILK YIELD TABLE 1. Average percentage of milk protein in weekly milk samples. l Lactation Current
wk 1 to 15
wk 16 to 30
(V)
(%)
0 1 2 4
3.2 3.1 3.2 3.2
3.3 3.3 3.3 3.3
wk 31 to 45
Average
(n)2
(%)
(n)
(%)
8
9
3.4 3.4 3.3 3.4
3.3 3.3 3.3 3.3
6 7
lAverage are broken into three 15-wk periods beginning at the start of lactation. 2n = 10 unless indicated otherwise.
(and ranges) of these currents for 2 d (randomly selected) were 3.1 rnA (4.5 to 1.5), 6.5 rnA (8.6 to 4.6), and 11.2 rnA (14.1 to 7.5) for the 1-, 2-, and 4-V pens, respectively. Based on the applied voltage and the range of delivered current, minimal animal resistances varied between 224 and 648 ohms. A comparison of 305-d actual yields in the previous lactation for the four groups of cows showed no significant differences among groups before the start of the voltage experiment (8016, 8163, 7679, and 7876 kg for the experimental groups receiving 0, 1, 2, or 4 V, respectively; F = .36, P > .78). The average number of lactations for the cows in the four groups during the experiment was also not significantly different among groups (3.0, 3.0, 3.1, and 2.8 lactations for the experimental groups receiving 0, 1,2, or 4 V; F = .17, P> .9). Comparisons between the control group (0 V) and each treatment group (1, 2, or 4 V) for any measure of milk yield during the experimental lactation showed no significant
difference. No differences were found in comparisons performed on DHI estimates of the 305-d actual yield (F = 1.3, P > .3; Figure 3A), 305-d mature equivalent yield (F = 1.3, P > .3, Figure 3B), and total yield (F = 1.2, P > .3; Figure 3C). No differences were found in comparisons performed on T&R Center's daily milk yield used to compute average daily yield (F = 1.9, P> .16; Figure 4A), peak milk (F 1.94, P> .15; Figure 4B), day to peak milk (F = 2.15, P> .12; Figure 4C), persistency (F = .79, P > .51; Figure 4D), total yield (F = 1.4, P > .27; Figure 4E), and days in milk (F = .76, P > .52; Figure 4F). Analysis of milk protein (Table I) and fat (Table 2) showed no significant differences between the control and the treatment groups (F = .36, P> .78 for protein; F = .18, P> .91 for fat). Water intake was measured daily for each pen, and the average daily intake per cow in the pen was computed. Therefore, these data include experimental and herd cows that were used to maintain the number of cows in each
=
TABLE 2. Average percentage of milk fat in weekly milk samples. l Lactation Current
wk 1 to 15
(V) 0 1 2
4
wk 16 to 30 (%)
3.6 3.5 3.7 3.6
3.8 3.7 3.8 3.7
wk 31 to 45
Average
(n)2
(%)
(n)
(%)
8
9
4.0 3.8 3.7 3.9
3.8 3.7 4.0 3.7
6 7
I Averages broken into three 15-wk periods beginning at the star! of lactation. 2n = 10 unless indicated otherwise.
Journal of Dairy Science Vol. 75. No. 10. 1992
2724
GOREWIT ET AL. 30 28 -
.16
DAILY YIELD.
A
26 -
'6'
C
-
20
W :;:
~
:E
2
B
-t-
4644 -
t
o 50
-
40
-
35
-
30
-
25
2
c -t-
-I-
o
..~
g
g W ~
9.0 -
7.8 7.2
_
-t4
VOL TAGE APPLIED TO WATERER
-I-
4
TOTAL MILK (T&R)
tt
6.6
2
0
4
350 330 :§:310-
~ i=
290 270 -
250 2
-t-
2
~ 6.0
DA YS TO PEAK MILK
o
E
:iii
4
-t-
o
8.4
t
""""NCV
t t t
-
4
42 40 ......._ , -_ _...,..._ _--,-_ _-.,_-J
45
o
.11
60 . . , - - - - - - - - - - - - - - , PEAK MILK YIELD
48-
-
.12
o
...J
-
.14
~ .13 -
24 22
.15
F
-Io
-t-
DAYS IN MILK
t t 2
4
VOLTAGE APPLIED TO WATERER
Figure 4. Milk yield as indicated by A) average daily yield, B) peak milk, C) days to peak milk, D) persistency, E) total yield, and F) days in milk are shown as a function of voltage treatment. Means (horizontal line) and standard errors of the mean (vertical bar) are indicated. These results are based upon the Teaching and Research Center's daily milk yield data (n = 10 cows per treatment).
pen at 10. The average daily water intake per cow was 74.1, 76.2, 71.7, and 78.7 L for the 0-, 1-, 2-, and 4-V pens, respectively. No statistical differences existed among pens (t < 1.86; P > .05) except that cows in the pen with 4 V on the water drank significantly more water (t = 3.63; P < .001) than cows in the control pen. DISCUSSION
Cows drinking from waterers with voltage had current pass from their muzzles to their front hooves. Furthermore, currents were proportional to the voltage applied at the waterers. Cow impedances, calculated from the applied voltage and the measured current, were slightly lower than those previously reported for muzzles to front hooves (8). This reduced impedance may be explained by reduced contact impedance at the muzzle. Previous reports did not use water bowls as the contact point; Journal of Dairy Science Vol. 75, No. 10, 1992
thus, contact impedances may have been greater than those in the present study. All measures of milk yield and milk composition indicated that voltage at the waterer had no effect. Varialions among pens existed, but difference in milk yields or composition was not significant for any of the voltage treatments (1, 2, or 4 V) compared with those for the control group (0 V). Yields from previous lactations were not directly compared with yields during the experiment. The experimental cows were subjected to different conditions during their previous lactations, such as a different milking parlor, a tie-stall instead of a free-stall barn, or an especially cold winter; thus, comparison is inappropriate. CONCLUSIONS
Water intake was not significantly reduced with voltage treatment. Water intake was significantly greater for cows in the 4-V pen than
2725
VOLTAGES AND MILK YIELD
for cows in the control pen. The lack of significant decrease is not surprising; previous research (2) showed that cows that will drink will drink nonnal amounts of water within 2 d of the initial voltage exposure. This occurred for 3-wk exposures (2) and, in the present study, for full lactation exposures. As in previous research (2), some cows will not drink when 4 V are applied to a waterer. In our study, 1 first lactation cow, out of a total of 51 cows placed in the 4-V pen, had to be removed. This cow was a herd cow. Her milk yield decreased rapidly, and she was not consuming grain during her first 36 h in the pen. This was the only cow that had a water consumption problem. ACKNOWLEDGMENTS
The authors express their thanks to the personnel at the Cornell University T&R Center for their help in carrying out this work. Further appreciation is given to Bert Klei for his assistance on our statistical analyses of data. This study was financed by grants from the Empire State Electric Energy Research Corporation and the New York State Agricultural Experiment Station. This paper is dedicated to the memory of R. D. Appleman.
REFERENCES 1 Craine. L. B.• M. H. Ehlers, and K. K. Nelson. 1970. Electric potentials and domestic water supplies. Agric. Eng. 51:415. 2 Gorewit. R. C., D. J. Aneshansley. D. C. Ludington, R. A. Pellerin. and X. Zhao. 1989. AC voltages on water bowls: effects on lactating Holsteins. J. Dairy Sci. 72:2184. 3 Gorewit, R. C.• N. R. Scott, and C. S. Czarniecki. 1985. Responses of dairy cows to alternating electrical current administered semirandomly in a nonavoidance environment. 1. Dairy Sci. 68:718. 4 Henke Drenkard, D. V., R. C. Gorewit, N. R. Scott. and R. Sagi. 1985. Milk production, health, behavior. and endocrine responses of cows exposed to electrical currents during milking. J. Dairy Sci. 68:2694. 5 Lefcourt, A. 1982. Behavioral responses of dairy cows subjected to controlled voltages. J. Dairy Sci. 65:672. 6 Lefcourt, A. M.• and R. M. Akers. 1982. Endocrine responses of cows subjected to controlled voltage during milking. J. Dairy Sci. 65: 177. 7 Lefcourt. A. M.• R. M. Akers, R. H. Miller, and B. Weinland. 1985. Effects of intermittent electrical shock on responses related to milk ejection. 1. Dairy Sci. 68:391. 8 Majerius, O. L.. R. O. Martin, and R. A. Peterson. 1984. Stray voltage. Proc. Nat!. Stray Voltage Symp.• Am. Soc. Agric. Eng. Publ. 3-85. Am. Soc. Agric. Eng., St. Joseph. MI. 9 Norell, R. J.• R. J. Gustafson. R. D. Appleman, and J. B. Ovennier. 1983. Behavioral studies of dairy cattle sensitivity to electrical currents. Trans. Am. Soc. Agric. Eng. 26:1506. 10 SAS@ User's Guide: Statistics. 1982. SAS Inst., Inc.• Cary, NC. 11 Snedecor, G. W.• and W. G. Cochran. 1967. Statistical Method. 6th ed. Iowa State Univ. Press, Ames.
Journal of Dairy Science Vo!. 75. No. 10, 1992
