Paper No An ASAE Meeting Presentation DAIRY CATTLE DRINKING BEHAVIOR AND STRAY VOLTAGE EXPOSURE. Steven D. LeMire Graduate Research Assistant

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1 Paper N An ASAE Meeting Presentatin DAIRY CATTLE DRINKING BEHAVIOR AND STRAY VOLTAGE EXPOSURE Steven D. LeMire Graduate Research Assistant Duglas J. Reinemann, Ph. D. Prfessr Department f Bilgical Systems Engineering University f Wiscnsin-Madisn, Milking Research and Instructin Lab Patrick J. Gaffney Graduate Student Department f Statistics University f Wiscnsin-Madisn Rger Kasper Research Crdinatr Rural Electric Pwer Services Wiscnsin Department f Agriculture Trade and Cnsumer Prtectin Written fr presentatin at the 1997 ASAE annual Internatinal Meeting Minneaplis Minnesta August 10-14, 1997 Summary: Eight stanchined lactating Hlstein cws (with individual water bwls) were used t determine the water bwl cntact time ver a 1 day perid. This wrk represents an ancillary questin frm an eperiment that was designed t study aversin t transient and steady state stray vltage applied t the water bwls. Data was cllected fr the number f cntacts and length f a water bwl cntact fr each cw. The average rate f arrival and average length f cntact was calculated. A Pissn prcess fr arrival was then assumed and Mnte Carl simulatins used t estimate the number f cws that wuld be epsed t a transient vltage fr herd sizes f 50, 100, and 200 cws. Keywrds: Stray Vltage, Stanchined Dairy Cws, Drinking Behavir, Transients The authr(s) is slely respnsible fr the cntent f this technical presentatin. The technical presentatin des nt necessarily reflect the fficial psitin f ASAE, and its printing and distributin des nt cnstitute an endrsement f views which may be epressed. Technical presentatins are nt subject t the frmal peer review prcess by ASAE editrial cmmittees; therefre, they are nt t be presented as refereed publicatins. Qutatin frm this wrk shuld state that it is frm a presentatin made by (name f authr) at the (listed) ASAE meeting. EXAMPLE C Frm Authr=s Last Name, Initials. "Title f Presentatin." Presented at the Date and Title f meeting, Paper N X. ASAE, 2950 Niles Rad, St. Jseph, MI USA. Fr infrmatin abut securing permissin t reprint r reprduce a technical presentatin, please address inquiries t ASAE. ASAE, 2950 Niles Rd., St. Jseph, MI USA Vice: FAX: DAIRY CATTLE DRINKING BEHAVIOR AND STRAY VOLTAGE EXPOSURE

2 INTRODUCTION Stray vltage epsure ccurs when an animal tuches surfaces with unequal vltage ptential and current flws thrugh the animal. There are many pssible surces f stray vltage [1]. In rder fr the epsure t ccur, the vltage must be present when the animal is tuching the cntact pints. Stray vltage can be categrized as either steady r transient. Steady vltages are nrmally caused by current being used t perate sme electrical device and are generally cnsidered t be present at the same r similar level fr several minutes t several hurs. Transient vltages are generally caused when an electrical device is started r stpped r by devices which perate intermittently such as an imprperly grunded fencer. Transient vltages may ccur as infrequently as nce per day r as frequently as nce per secnd (in the case f a faulty fencer). Animals have a high prbability f epsure when vltage ptentials are always present r present very frequently (nce per secnd) n devices which supply their nly direct surce f water. Hwever, if vltage ptentials are nt present at all watering lcatins r nt cntinuusly present, the prbability f epsure is reduced. Amng the mst cmmn epsure lcatins are between the water bwls and the cncrete flr f a barn. The purpse f this study was t assess epsure risks fr stanchined dairy cattle t intermittent vltage applied t the water line (water bwls). MATERIALS AND METHODS This study was mtivated by an ancillary questin frm an eperiment that studied drinking behavir f dairy cattle fr steady state and transient epsures [2]. This paper uses data frm eight cws fr tw days f backgrund data cllectin. The cws selected fr this study came frm the UW-Madisn herd. These cws had an average days-in-milk f 46 with a range frm 10 t 67. The average lactatin number was 3.3 with a range f 2 t 5. The diet cnsisted f 53 percent frage and 47 percent grain (dry matter basis). The frage was 45 t 48 percent dry matter. The grain was 90 percent dry matter. Each stall had its wn water bwl. The ttal water requirements fr dairy cws depend n a number f factrs [3]. Estimates f ttal water requirements can be made [4]. The water values recrded fr this wrk were frm the individual water bwls--the water cntent f the feed was nt used in these calculatins. On the first day f testing, there was n vltage placed n the water bwl. On the secnd day a 60 Hz steady vltage was placed n each water bwl that prduced 1 ma f current thrugh a 500 Ohm resistr using a standard stray vltage measurement cntact (4@ 4@ cpper plate with 250 lbs. pressure placed n a twel wetted with salt slutin). The current pathway fr the cws was frm muzzle t all fur hves. Tw data acquisitin units (Wave Riders) were used t recrd when each cw made cntact with the water bwl. As an artifact frm the main eperiment, the water was ff frm five a.m. t eight a.m. (three hurs) n bth days. The ttal water vlume cnsumed is fr a 24-hur perid. This was frm eight a.m. ne day t eight a.m. n the net. The cws were released frm their stalls fr milking at apprimately seven a.m.. As the cws finished milking, they were sent ut int an utside yard. Just prir t eight a.m. the cws were returned t the test stalls and manual water data cllectin began. On the secnd day f testing, the data acquisitin units were turned n at fifteen minutes after eight a.m.. A steady surce vltage f abut 20 VAC (RMS average) was placed in series with 19k-Ohm resistr, a 330-Ohm resistr, and the water bwl. A 100k-Ohm resister was placed between the 2

3 water bwl and stall base (in parallel with the cw). A 500-Ohm shunt resistr was cnnected between the water bwl and a cpper cntact n the flr. The surce vltage was then adjusted s that 1 ma (RMS average) f current (+/- 10%) flwed thrugh the 500-Ohm shunt resistrs in all stalls. The shunt resistrs and flr cntacts were then remved and cws placed in the stalls. The data acquisitin unit was cnnected acrss the 330 Ohm Resistr and measured an elevated vltage signal when the cw made cntact with the water bwl. Tw filtering criteria were used n the raw data. One f these was magnitude f current flw. The 100k Ohm resistr was placed in parallel with the cw t eliminate nise prduced by pen circuit measurements. This resulted in a cntinuus small current flw thrugh the circuit (but nt the cw). The current flw thrugh the circuit and vltage measured acrss the 330-Ohm resistr increased when a cw cntacted the water bwl and reduced the ttal circuit resistance. A threshld f 0.18 ma thrugh the circuit (0.06V acrss the 330-Ohm resistr) was used t indicate cw cntact. This threshld level was cnfirmed with bth the 500-hm shunt resistr and by bservatin f cws drinking. A secnd filtering criteria was used t establish the definitin f an event. An event was defined t be any recrded cntact that was 1 secnd r mre apart frm any ther cntact. Fr eample, if a cw cntacted the water bwl cntinuusly fr 1.4 secnds, 100 cntact pints wuld be recrded. This was cnsidered a single event f 1.4 secnds duratin. If the cw stpped drinking fr 1.5 secnds and then tuched the water bwl again fr 0.5 secnds, a secnd event wuld have been recrded. The duratin between events wuld have been 1.5 secnds and the duratin f the secnd event wuld be 0.5 secnds. The drinking behavir f cws was assumed t be the same ver a prlnged perid. The best estimate fr mean cntact time is then the ttal cntact time fr all cws divided by the ttal number f cntacts. This is termed a weighted mean. The weighted mean was used fr the average cntact time and average time between cntacts. These values were used in a stchastic prcess t estimate the number f cws drinking at any given time, and later in the generatin f cw histries fr the Mnte Carl simulatins. Each Mnte Carl simulatin was run fr tw thusand iteratins n a Sun SPARCstatin 10 (taking up t 18 hurs f cmputer time each). In this wrk, the time between cntacts and the time spent in cntact with the water bwl were bth assumed t be epnentially distributed. This is a cmmnly used distributin fr time between events in many disciplines. A perfect epnential wuld have apprimately 63 percent f the bservatin belw the mean. Our distributins had almst 75 percent f the bservatins belw the mean fr the drinking time and apprimately 85 percent f the bservatins belw the mean fr time between drinks. This departure frm the ideal culd be caused by many pssible factrs. These include variatin between cws and change in the cntact rates with time f day. It is difficult t determine the true cause f the difference given that nly eight cws were mnitred with the data acquisitin unit fr ne day in this study. When imprved mdels fr drinking behavir-- under varying envirnmental and husing cnditins--becme available, they can readily be incrprated int the methdlgy presented here. RESULTS AND DISCUSSION The mean water cnsumptin increased 0.7 gallns n the secnd day f trial--this difference 3

4 was nt statistically significant. Fur cws cnsumed less water n the secnd day and fur cws cnsumed mre water. The p-value fr the difference between these days was fr a tw-tailed paired t-test. There was 80 percent pwer t find a 2.6 galln (r abut 10%) difference between the tw test days. The data fr ttal water cnsumed is shwn in Table 1. All the cws drank within 15 minutes f the start f the trial n bth days. Table 1. Water cnsumptin fr 24 hurs fr the n current day and the 1 milliamp day (Gallns). N Current Day 1 Milliamp Day Difference Stall Stall Stall Stall Stall Stall Stall Stall mean Standard Deviatin Since there was n significant change in ttal water vlume and n indicatin frm visual bservatin that cws were affected, it is assumed that the cws were nt affected by the presence f the vltage n the water bwl used t autmatically recrd drinking behavir. This result was epected as the reactin level fr these cws was well abve 1 ma. The mean reactin level was 8.2 milliamps when 10 cycles f a 60 Hz signal was applied every 2 secnds [5]. The number f times a cw tuched the water bwl and the average cntact time recrded electrnically are shwn in Table 2. The nn-weighted mean cntact time was 9.2 secnds with a nn-weighted mean time between cntacts f secnds. The weighted average mean cntact time was 7.8 secnds and the weighted mean time between cntacts was secnds. The weighted (verall means) were used fr the distributins in the epsure estimates in tables 4, 5 and 6. Table 2. Cw water bwl cntact time Summary Results. Stall Number 4

5 Cw Number Ttal Cntact Time (Secnds) Mean Cntact Time (Secnds) Mean Time Between Cntacts (Secnds) Percent Cntact time Number f Cntacts Days in Milk Lactatin Risk f Epsure Mdeling The generatin f summary statistics, as in Table 2, aids in the understanding f typical (r average) cw behavir. That data can be used t determine the percentage f time that a individual cw is in cntact with the water bwl, and thus ptentially epsed t transient vltages n the water bwl. A simple, stchastic, drinking-state mdel was used t estimate the number f cws that culd be in cntact with the water bwl at any given time, and hence the risk f epsure t a transient vltage n the water bwls [6]. Mnte Carl simulatins were then used t estimate the number f epsures that a cw culd receive ver perids f 1 and 30 days. The Mnte Carl simulatins take int accunt the back-ff time, which is a measure f the reluctance f a cw t return t the bwl after a shck. Stchastic Prcesses Stchastic prcesses can be used t mdel the epsure risks fr stanchined dairy cws where each cw has its wn water bwl. Fr eample, if there were 100 cws in a barn, the number f cws drinking at any given time can range between 0 and 100. Therefre, there are 101 drinking states in the mdel (Figure 1). Suppse we are in state 2 (2 cws drinking), we can mve nly t state 1 (when ne cw stps drinking) r t state 3 (if anther cw starts drinking befre any f the tw stp). The directed lines (arcs) between states dente the pssible changes (transitins) that can ccur. The number n each arc specifies hw fast we mve frm ne state t the net. Figure 1. Drinking (cntact) state mdel diagram fr stanchined dairy cws with individual water bwls that are cnnected by ne water line. A cw cmes t the bwl at the Arrival Rate (AR), r every 1/AR secnds n average. This cw 5

6 drinks fr a perid f time and then leaves its bwl at the Leaving Rate (LR), r spends 1/LR secnds drinking (in cntact with the water bwl) n average. Nte that when tw cws are drinking, the rate f mving t the 1-cw-drinking state is 2LR because either f the tw cws culd be the net t finish. Similarly, the rate f mving t three cws drinking is 98AR because any f the 98 nn-drinking cws culd be the net t cme t the bwl. The dds, fr eample, that less than three cws are drinking at a given time (in particular, at the time f a randmly ccurring transient), can be calculated using this mdeling apprach. Assuming that bth the time between drinks and the time spent drinking are epnentially distributed, the prbability that n cws are drinking (P n ) at any time is given by the fllwing frmula. [7] where P n M! AR = P ^ n ( M n)! n! LR P n : Prbability f n cws drinking at a given time. P: Prbability f n cws drinking at a given time. AR P = 1 + ^ n LR AR: Arrival rate t the water bwl (1/ average time between drinks). LR: Leaving rate r average time t drink (1/average length f drinks). M: Number f cws in the barn. n: Number f cws drinking at any given time. Clearly this depends n the number f cws in the barn M and the rati f arrival rate divided by leaving rate. If this rati gets bigger (either cws arrive faster r leave slwer), then the cws are spending a larger percentage f their day at the bwl. Hence their risk f epsure t a transient vltage increases, and the dds are that mre cws will be shcked by a transient. Similarly if the number f cws increase, we are als likely t see mre cws epsed. Fr eample, with an average drinking time f 7.8 secnds and an average time between drinks f secnds, the prbability f 3 cws being epsed at any instant t ne transient in a herd f 50 is 3.5 percent whereas in a herd f 200 it is 22.5 percent. Figure 2 shws the prbability f n cws drinking at any given time fr barns with 50, 100,and 200 cws with a average cntact time f 7.8 secnds and an average time between cntact f secnds. As we can see frm Figure 2, the mre cws we have in the barn, the higher the prbability that mre cws are drinking at any given time. 6

7 Prbability f n Cws Drinking w Prbability w w w w 50 cws 100 cws 200 cws w w w w w w Number f Cws Drinking Figure 2. Plt f the prbability that n number f cws are drinking at any time fr 50, 100, and 200 cw barns where cws are stanchined with individual water bwls. Mnte Carl Simulatins The stchastic mdel develped in the previus sectin estimates the number f cws drinking at any pint in time. Hwever, it cannt be easily etended t take int accunt the behavir ver a fied perid f time. Mnte Carl simulatin can prvide an estimate fr the number f cws epsed fr a given rate f transients. In additin, it can prvide slutins fr a wider range f mdels. The mdel assumes that cws will drink at least nce a day, and further, that cws back ff frm the bwl after a shck and take lnger t return. Transients were randmly generated at a specified rate and assumed t be instantaneus. Cw drinking histries were generated fr each individual cw in the herd, based n the weighted average arrival rates and cntact times. If a transient epsure ccurs during a cw's drinking perid, the cw backs ff and will return later t the bwl. The average time t return t the water bwl was assumed t be ten times lnger when epsure ccurred than when it did nt. The time t return t drinking after a shck was cnstrained t nt eceed 24 hurs. One-day and 30-day perids with herd sizes f 50, 100 and 200 cws and ccurrence f transients f 1, 10 and 100 per day were simulated. The parameters used in the simulatin wrk are shwn in Table 3. A value f 4976 secnds was chsen (r ten times the average time between drinks) fr the average cw back-ff time. This reflects an assumptin that a cw wuld be mre reticent t return t the bwl after a shck. The results are nt sensitive t ur chice fr this parameter value, at a mderate rate fr transient ccurrence, since the number f shcks a cw receives is small relative t the number f times at the bwl. Fr eample, the mst shcked cw receives an average f shcks during ne day, in a herd f 100 cws, with transients ccurring at a rate 7

8 f 10 per day. We verified the afre-mentined by running simulatins fr mderate transient rates, with an average back-ff time equal t the mean time between drinks, and fund negligible difference in the results. Table 3. Parameters used in the Mnte Carl Simulatins t generate Tables 4, 5, and 6. Average time spent drinking (1/DR) Average time between drinks (1/AR) Average cw back ff time after receiving a shck Maimum time withut drinking 7.8 secnds secnds 4976 secnds Table 4 shws the epected number f epsures fr a 30-day perid. Fr eample, it wuld be epected that abut 37 percent f the herd wuld receive between 1 and 5 shcks if n average ne transient was ccurring each day fr 30 days. S if there were 100 cws, it wuld be epected that 37 f them wuld receive between 1 and 5 shcks. If there were 120 cws, it is epected that apprimately 45 f the cws wuld receive 1 t 5 shcks. 1 day Table 4. Epected percent f the herd that is epsed t 0, 1 t 5, r greater than 5 shcks ver a 30 day perid. Number f Epsures >5 1 Transient per day 62.8 % 37.2 % Transients per day 1.0 % 67.9 % 31.1 % 100 Transients per day % Table 5 shws the average number f epsures that a cw wuld receive ver 1 and 30 days. Fr eample, a given cw wuld be epsed n average 4.6 times if there were 10 transients per day fr 30 days. Alternatively, in a herd f 100 cws, the epected ttal number f shcks wuld be 460 in the same time perid. Table 5. Epected number f epsures fr a given cw and the standard errr f the estimate. 1 Day 30 Days 1 Transient per day (0.000) 10 Transients per day (0.001) 100 Transients per day (0.004) (0.002) (0.008) (0.021) 8

9 The epected number f epsures fr the cw receiving the greatest number f epsures is shwn in Table 6. Fr eample, if there were 100 randmly ccurring transients in ne day, it wuld be epected that at least ne cw wuld receive abut 5 shcks. Table 6. Epected number f epsures fr the mst epsed cw and the standard errr f the estimate. 1 Day 30 Days 50 Cws 100 Cws 200 Cws 50 Cws 100 Cws 200 Cws 1 Transient per day (0.011) (0.012) (0.012) (0.015) (0.015) (0.015) 10 Transients per day (0.012) (0.013) (0.012) (0.031) (0.030) (0.028) 100 Transients per day (0.017) (0.018) (0.017) (0.071) (0.067) (0.064) SUMMARY AND CONCLUSIONS This study demnstrates a methd fr estimating the prbability f dairy cw epsure t transient vltages. Estimates f the epsure risks and the factrs affecting these prbabilities have been presented. The drinking behavir data used t estimate the prbability f epsure were frm stanchined dairy cattle with individual water bwls in each stall as the nly direct surce f water fr each cw. The applicability f these results depends n similarity f drinking behavir and validity f the underlying distributinal assumptins. On average, the eight Hlstein cws used in this study drank abut 29 gallns f water in 24 hurs. Different amunts f water cnsumptin wuld presumably result in different cntact times and epsure risk. The epsure estimates in Table 4,5, and 6 are based n a back ff time that is ten times greater than the mean arrival time. If a cw was nt shcked n the net drink, it then went back t its nrmal drinking behavir. The severity f the epsure and individual sensitivity f the cw epsed wuld influence these behavirs. The behavir f cws that share waterers r are hused in free-stall barns will be different. The ccurrence f transients were assumed t be randmly distributed ver the day. Depending n the surce f transient vltages, this may nt be the case. The methd presented culd be used t adjust epsure estimates fr drinking behavir f cws under varying envirnmental and husing cnditins. Further wrk needs t be dne t better understand the nature f the distributins f cw cntact times fr varius envirnmental cnditins. 9

10 REFERENCES 1 Ludingtn, D., Surce f Stray Vltage/Current. Effects f Electrical Vltage/Current n Farm Animals. United States Department f Agriculture Handbk Number Reinemann, D.J., L.E. Stetsn, S.D. LeMire, and J.W. Patch, Cmparisn f Dairy Cw Aversin t Cntinuus and Intermittent Current. Paper N , Written fr presentatin at the 1997 Internatinal Meeting spnsred by ASAE: the Sciety fr Engineering in Agriculture, Fd and Bilgical Systems, Minneaplis, MN, August Winchester, C.F., and M. J. Mrris, Water intake rates f cattle. J. Anim. Sci. 15: Rberts, J., Getting a Water Meter T Wrk Fr Yu. Wiscnsin Department f Agriculture, Trade and Cnsumer Prtectin: Rural Electric Pwer Services, P.O. B 8911; Madisn, WI Reinemann, D.J., L.E. Stetsn, N. Laughlin, Effects f Frequency and Duratin n the Sensitivity f Dairy Cws t Transient Vltages. Paper N , Written fr presentatin at the 1994 Internatinal Winter Meeting spnsred by the American Sciety f Agricultural Engineers, Atlanta, Gergia,, December 13-16, Hel, P. G., S. C. Prt, C. J. Stne, Intrductin t Stchastic Prcesses. Hughtn Mifflin Cmpany, Bstn. 7 Trivedi, S. K., Prbability and Statistics with Reliability, Queuing, and Cmputer Science Applicatins. The authrs wuld like t gratefully acknwledge cntinued funding frm the Wiscnsin Dept. Of Agriculture, Trade and Cnsumer Prtectin. D:\SDL\STRYVOLT\97WORK\wavewrk\paper\ASAE\ASAE.FINAL.PAPER_COR wpd 10

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