Effects of intermittent electrical shock on responses related to milk ejection

Electric shock control of farmed animals: Welfare review and ethical critique

The available methods of electric shock control or containment of farmed animals are increasing and potentially include: (i) fixed and movable electric fencing; (ii) cattle trainers; (iii) prods or goads; (iv) wires in poultry barns; (v) dairy collecting yard backing gates; (vi) automated milking systems (milking robots); and (vii) collars linked to virtual fencing and containment systems. Since any electric shock is likely to cause a farmed animal pain, any such control or containment must, to be ethically justifiable, bring clear welfare benefits that cannot be practicably delivered in other ways. Associated areas of welfare concern with ethical implications include the displacement of stockpersons by technology, poor facility design, stray voltage, coercive behavioural change and indirect impacts on human society and values.

Stray voltage threshold is better determined under choice test conditions in sheep

Stray voltage (usually <10 V) can occur in farms. However, very little information is available related to sheep. In addition, little work has been carried out on the effects of the contextual conditions under which the animals are submitted to stray voltage. The aims of this study were (i) to determine the threshold voltage at which lambs start to express avoidance behaviour and (ii) to test if the contextual conditions (i.e. choice v. no-choice conditions) influence the determination of the threshold voltage inducing avoidance behaviour. Six-month-old female lambs fed ad libitum were trained to eat palatable pellets from one or two metallic feeders situated at the end of a 4-m long raceway. Voltage was then applied during a 2-min test to either the only feeder available (no-choice test, 1F, n = 13) or to the first of the two feeders in which the lamb started to eat (choice test, 2F, n = 13). The 1F lambs had to stop eating to avoid the voltage, whereas the 2F lambs were allowed to switch to the non-electrified feeder to carry on eating without any stray voltage. Stray voltage was applied every day, in steps of 0.5 V (AC, 50 Hz), from 0 up to 8 V. For voltages higher than 4.5 V, 2F lambs spent less time eating and ate less in the electrified feeder compared with the non-electrified feeder, and their latency to switch to the non-electrified feeder was shorter. In addition, a transient modification of behaviour was observed at 1.5 V. For 1F lambs, a decrease in the quantity of feed eaten was found for voltages higher than 5 V, although the time spent eating in the electrified feeder was not modified. Finally, 1F lambs urinated more during or just after the 2 min test than 2F lambs for voltages above 5 V. Although lambs with no choice experienced stray voltage as a negative event (increased occurrence of urination), they carried on eating in the electrified feeder whatever the voltage. Therefore, the contextual conditions in which animals are exposed to stray voltage influence their subsequent reactions: the first clear behavioural reaction threshold is easier to detect in choice than in no-choice conditions.

Medium-term effects of repeated exposure to stray voltage on activity, stress physiology, and milk production and composition in dairy cows

The medium-term effects of permanent or random exposure to stray voltage applied to the water trough were evaluated on milk production and stress physiology in lactating dairy cows. Seventy-four Holstein cows were assigned during two 8-wk experimental periods to 1 of 3 treatments. The treatments were permanent exposure to voltage (PERM, 1.8 V, n=23) applied to the water trough, random exposure to voltage (RAND, 1.8 V, 36 h/wk, n=25), and no exposure to voltage (control, n=26). On the first day of voltage exposure, PERM cows had higher activity levels than control cows (9.8+/-2.70 vs. -2.3+/-2.74 14-s periods of movement/h). During the eighth week of exposure, RAND cows had higher activity levels than control cows (4.2+/-3.64 vs. -7.7+/-3.54 14-s periods of movement/h) and higher milk cortisol concentration than PERM cows (0.21+/-0.024 vs. 0.14+/-0.020 ng/mL). No differences were observed between treatments for cortisol response after an ACTH challenge during the seventh week of exposure. No effects of voltage exposure were observed on production traits and daily water intake. There was a transient decrease in milk yield on the second day of exposure in PERM cows (-1.4+/-0.74 kg) and on the third day of exposure in RAND cows (-3.5+/-1.03 kg) compared with control cows. In dairy cows, permanent or random exposure to stray voltage (1.8 V; 3.6 mA) could induce a transient stress response. Moreover, unpredictable voltage exposure could be considered a mild stressor, with slight modifications in stress physiology and activity but no impairment in production in the medium term.

Effects of handling aids on calf behavior

Effects of three different handling aids on calf behavior were determined. Group 1 calves were intensively-reared intact Holstein males (mean 180 days old); Group 2, extensively-reared beef-breed females (mean 230 days); Group 3, extensively-reared castrated beef-breed males (mean 253 days). Calves in each group were assigned to one of three handling aid treatments (n=5 per treatment subgroup; total n=45): electric prod (Prod), oar with rattles (Oar), manual urging (Manual). Treatments were applied only as needed to encourage forward movement of calves through the length of a solid-sided semicircular chute system. Number of treatment applications, length of time required to move through the entire chute system, and behavior during movement through the chute were recorded. An approach test was conducted 1 day before and 1 day and 1 week after chute tests to evaluate changes in behavior due to handling aid application. During chute tests, Group 1 Prod calves required the fewest treatment applications (4.9) vs. 23.5 (Oar) or 13.5 (Manual), ran most often (1.40 times) vs. 0.20 times (Manual) or 0.33 times (Oar), and made contact with chute sides most often (1.8 times vs. 0.2 times (Manual) or 0.7 times (Oar), respectively (all P<0.05). Similar trends were observed for calves in Groups 2 and 3. There were no significant differences between behaviors observed during the approach tests conducted before and after handling aid treatments had been imposed. Regardless of treatment, intensively-reared Group 1 calves appeared markedly less fearful of handlers during approach tests compared to extensively-reared calves in Groups 2 and 3, which demonstrated overt attempts to escape from the test facilities. One week after chute tests, 13 of 15 Prod calves from all three groups walked, rushed, or backed >1 m away from the handler when the prod was buzzed but not applied, suggesting that the buzzing sound alone may have sufficed to encourage movement by calves that had previously experienced both the sensation and sound associated with electric prodding.

Oxytocin release and milk removal in ruminants

Before milking, less than 20% of the milk yielded by dairy cows is stored within the cistern, where it is immediately available for removal. Most of the milk is available for the milking machine only after milk ejection, which occurs in response to tactile teat stimulation and oxytocin release. For complete milk removal, milk ejection is necessary throughout the entire milking process. The continuation of stimulatory effect of the milking machine until the end of milking is, therefore, essential. Premilking teat stimulation causes induction of alveolar milk ejection before the start of milking. Thus, bimodal milk flow curves (i.e., interruption of milk flow after removal of the cisternal milk) are avoided. Continual ejection of milk is dependent on the presence of elevated oxytocin concentrations during the entire milking. Any interruption of the milk ejection process can disturb milk removal. Disruption of milk removal can be caused by peripheral inhibition of oxytocin effects on the mammary gland or by inhibition of oxytocin release by the central nervous system. Peripheral inhibition is induced by elevated concentrations of catecholamines through stimulation of alpha-adrenergic receptors in the mammary gland, likely via changes in ductal resistance. Inhibition of oxytocin release by the central nervous system has been observed in primiparous cows immediately after parturition, during peak estrus, and during milking in unfamiliar surroundings; concentrations of beta-endorphin and cortisol are elevated in this situation. However, the role of endogenous opioid peptides in the inhibition of oxytocin release in cows remains unclear. In conclusion, during machine-milking, the physiological requirements of the cows need to be considered, and, most importantly, stressors must be minimized.

Effect of suckling during early lactation and changeover to machine milking on plasma oxytocin and cortisol levels and milking characteristics in Holstein cows

Plasma concentrations of oxytocin and cortisol, and milk yield and flow rates, were compared in three primiparous cows and two cows in their second lactation during suckling and subsequent machine milking. After calving, cows suckled their calves for 3-4 weeks and then the experiment was carried out over 4 d. Blood samples were taken prior to, during and after suckling or evening machine milking (EMM) on day 1 of the experiment (the last day of suckling), day 2 (first EMM) and day 4 (third EMM). After weaning and rehousing, cows were machine milked twice daily. During the first EMM, average milk yield and flow rate in the second minute of milking were significantly lower (P < 0.05) than corresponding values for the other 2 d. Plasma oxytocin concentrations were lower during the first than during the third EMM (P < 0.001) and suckling (P < 0.001), and more oxytocin was released during the third EMM than during suckling (P < 0.01). Cortisol concentrations were higher during and after the first EMM than during the third EMM. Thus in cows sucked for several weeks after calving and then separated from their calves and rehoused we found a transient decrease in oxytocin release, milk yield and flow rates during the first machine milking.

Cow sensitivity to electricity during milking

Alternating currents were delivered to lactating cattle through the milk during milking. Electrodes were placed at the top of each short milk tube and jointed for one electrical contact. A metal grid on which the cows' rear hooves stood during milking was the second contact. Constant voltages (0 to 16 V) applied to contacts showed first lactation cows to be more sensitive than multiple lactation cows. First lactation cows kicked milking machines at 8 V (currents greater than 5 mA), and multiple lactation cows kicked at 16 V (currents greater than 8 mA). At lower voltages, there were no consistent significant differences in milking duration, milk yield, or composition for primary or residual milk. Application of constant currents of 5 mA for first lactation cows and 8 mA for multiple lactation cows produced no undesired behaviors but did result in some differences in production variables. Milking duration decreased during application of constant current to first lactation cows. Blood cortisol monitored in the multiple lactation cows during trial 2 showed a significant increase during milking but was equivalent or less during application of current. This study demonstrates that currents of 5 mA or less, delivered through the milk line, did not produce any direct economic effect. To produce this current, voltages on the milk pipe line would have to be in excess of 125 V (obvious human safety hazard) or in excess of 5 V on the claw of the milking cluster.

Effects of voltages on cows over a complete lactation. 1. Milk yield and composition

The effect of long-term 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, 1, 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, 7308, 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.

The detection and measurement of stray electrical leakages on dairy farms: effects on performance

Sources of stray electrical leakage from Power Supply Authority alternating current (AC), fence energiser pulses and randomly generated pulses and spikes on 55 dairy farms in the Waikato area were identified between December 1986 and March 1988. The electrical measurements were made using a specifically designed voltmeter able to detect voltages between 0.1V and 1500V, from single voltage spikes of two microseconds or greater duration from direct current (DC) as well as 50 Hz AC. Ninety-five sources of stray voltage were identified, and 53 per cent of properties had more than one source of >0.5V. The major source was from electric fence energisers. Rotary platform parlours were among the commonest sources of random or transient voltage spikes. Leakage of AC into one or other of the components of the milk transport system such as vat, plate cooler, milk lift pump and milk line was common. Owners acknowledged the improvements in milk production, reproductive performance and growth rate of calves after reduction of the exposure of dairy cattle to stray electrical leakage. A representative summary of five case records helps define the range of improvements that may possibly be achieved.

Catecholamines, oxytocin and milk removal in dairy cows

Experiments were designed to study the effects of catecholamines on oxytocin responses and milk removal in dairy cows. Adrenalin, noradrenalin, dopamine, isoproterenol (a beta-adrenoceptor agonist), phentolamine (an alpha-adrenergic blocker) and propranolol (a beta-adrenergic blocker) were infused intravenously. In addition, adrenalin was infused together with phentolamine and/or propranolol. Infusions started 8 min before milking and lasted until the end of milking. In some cases electroshocks (for 5 s) were applied immediately before milking in the absence and presence of phentolamine and propranolol. Adrenalin, noradrenalin and dopamine reduced milk removal, but only if administered in supraphysiological amounts. The effect of adrenalin and electroshocks on milk removal could be inhibited only partly by phentolamine. Inhibition of milk removal was not mediated by reduced oxytocin responses. Enhanced local release of catecholamines from sympathetic nerves was presumably responsible for lowered milk removal in response to electroshocks. Milk removal was facilitated during alpha-adrenergic blockade and during beta-adrenoceptor stimulation.

Effect of exogenous prolactin administration on lactational performance of dairy cows

Eight Holstein cows were utilized to examine the effect of prolactin on lactational performance prior to peak milk production (day 21-34 postpartum) and after peak milk production (day 60-73 postpartum). During each 14 day period, cows received daily intramuscular injections of pituitary-derived bovine prolactin (120 mg; 13.0 IU/mg protein) or excipient. Cows were housed in a controlled environment at 18.1C, 47.8% relative humidity and a 15 hr light: 9 hr dark cycle. In cows administered exogenous prolactin, circulating prolactin concentrations increased within one-half hr post injection, peaked within 2 to 6 hours and declined through the remainder of the day. Average prolactin concentration in the plasma was increased 2 to 5 fold over the 24 hr period in response to prolactin treatment. Yields of milk and milk components (fat, lactose and protein) were not affected by prolactin treatment in either period but the concentration of alpha-lactalbumin in milk was significantly increased (P less than .10) in both periods. Circulating concentrations of somatotropin, triiodothyronine, thyroxine, glucagon, nonesterified fatty acids and glucose were not altered. In prolactin-treated cows, the milking-stimulated prolactin release was decreased at both the PM milking, when circulating concentrations of prolactin were high, and the AM milking, when prolactin concentrations had returned to baseline. Concentration of prolactin in milk tended to increase but was not significantly altered by administration of exogenous prolactin. However, prolactin concentrations in plasma were correlated (r = .56) with milk concentrations. It is clear that postpartum administration of exogenous prolactin during the period of lactation prior to peak milk yield or after peak milk yield does not alter lactational performance in high producing dairy cows.

Cardiovascular responses of cows given electrical current during milking

Six Holstein cows in late lactation were used to determine effects of 4-mA square wave alternating current on mammary gland blood flow rate, heart rate, and blood pressure. Current to the lumbar-sacral region of the cows' back was applied 10 s prior to udder massage and throughout milking. Heart rate was measured from systolic pulses (beats/min) off strip chart recordings. Blood pressure determinations were made from carotid arterial cannulae. A single rise in blood flow rate occurred during milkings without current. Mammary blood flow increased (30% with respect to rest) without 40 s of milking. Heart rate and blood pressure did not change significantly. An abrupt increase in mammary blood flow rate, heart rate, and blood pressure was seen immediately upon current application prior to milking. Mammary blood flow rate increased 50%, heart rate 25 beats/min, and blood pressure 33 mm Hg. The response latency was approximately 60 s. A second rise in mammary blood flow (31%) was milking induced, occurring within 42 s of milking machine attachment. Milk yield was not influenced by current. Our data suggest that 4-mA of alternating current, applied prior to and throughout milking, causes an immediate elevation in mammary blood flow rate, heart rate, and blood pressure of cows. Cardiovascular responses are short-lived. Current given throughout milking does not influence normal physiological changes in mammary blood flow during milking.

Correlation of indices of stress with intensity of electrical shock for cows

Electrical shock is commonly used as a paradigm of stress. Cows have a higher tolerance to electrical shock than other species. To test this tolerance, seven lactating cows were shocked biweekly for 10 s: 0, 2.5, 5.0, 7.5, 10.0, then 12.5 mA, 60 Hz. At lower mA, cows became tense and showed limited movement. As mA increased, cows became more agitated. The experiment was terminated because of the severity of behavioral responses. Heart rate immediately after shock increased with mA and was significantly different from baseline at 10 mA (+17 beats/min) and 12.5 mA (+30 beats/min). Prolactin and glucocorticoids were unaffected by shock; however, both increased pronouncedly following a single recannulation prior to blood sampling. Norepinephrine was unaffected by shock or recannulation. Epinephrine doubled in two exceptional cows at 10 mA. The two exceptional cows showed consistent glucocorticoid responses, had consistently elevated baseline heart rates and prolactin, and were the only cows not shocked at 12.5 mA due to severe behavioral responses. The dramatic behavioral responses displayed by cows subjected to electrical shock were not correlated with significant or prolonged physiological responses. This dichotomy, although probably exaggerated in cows, suggests that electrical shock may not be a good paradigm of "stress".

Source of stray voltage and effect on cow health and performance

In dairy cows, two distinct and important aspects of the interrelationship between stray voltage problems on the farm and dairy cow productivity can be identified. One is behavioral modification that increases in intensity when currents associated with neutral-to-earth voltages above .7 V find a pathway through the cow. The other is immediate endocrine response. Results of research are less clear on the current necessary for the latter to occur; it may require 8 mA or more. This implies, depending on the pathway and the cow's pathway resistance, that voltage difference between two cow contact points must exceed 3 V. Resistance of different cow pathways range from 350 to 1700 omega. Milk production is more likely to be affected adversely when cows are subjected to shock patterns both intermittent and irregular. Less than 10% of the dairy cow population are thought to perceive any electrical currents upon contact with conductive grounding equipment provided voltages on the farm electrical neutral system remain below .35 V. This paper also identifies various sources of stray voltage problems and discusses appropriate procedures for correction.

Small electric currents affecting farm animals and man: a review with special reference to stray voltage. II. Physiological effects and the concept of stress

The literature on the influence of small, steady electric currents on animal health, especially cardiovascular and endocrinological functions and milk let-down, and the effects on milk production is reviewed, with special reference to the problem of stray voltage. Direct physiological effects in cows may occur above 4 mA. How the long-term effects may contrast with the acute effects is not known. Habituation may occur. The altered behaviour and physiological changes due to exposure to stray voltage may be termed a stress response. The type of stress most likely to be encountered is chronic. Whether or not stress occurs depends on the timing and context of exposure and on individual cognition. Hence stray voltage may threaten farm animal health and production wherever modern animal housing is applied.