Biomedical subjects

P H Hemsworth

Publications and source records attributed to P H Hemsworth.

At least 19 recordsLinked to original sources

PubMed2005

Susceptibility of reproduction in female pigs to impairment by stress or elevation of cortisol.

It is generally agreed that stress can impair reproduction. Furthermore, it is often thought that cortisol, which is secreted during stress as a result of activation of the hypothalamo-pituitary adrenal axis, is associated with this stress-induced impairment of reproduction. It has been hypothesized that reproduction in females is particularly susceptible to disruption by acute stress during the series of endocrine events that induce estrus and ovulation. Nevertheless, we found no support for this conjecture when we subjected female pigs to repeated acute stress or repeated acute elevation of cortisol during the period leading up to estrus and ovulation. Conversely, studies have demonstrated that prolonged stress and sustained elevation of cortisol can disrupt reproductive processes in female pigs. Nevertheless, in each study that demonstrated this effect, there were some animals subjected to the prolonged stressor or the sustained elevation of cortisol in which the reproductive parameters that were measured were not affected by the treatment. We propose that reproduction in female pigs is resistant to the effects of acute or repeated acute stress or acute or repeated acute elevation of cortisol even if these occur during the series of endocrine events that induce estrus and ovulation. Furthermore, while reproductive processes in some individuals are compromised, reproduction in a proportion of female pigs appears to be resistant to the effects of prolonged stress or sustained elevation of cortisol.

Animals↗

PubMed2005

Gender-specific effects of prenatal stress on emotional reactivity and stress physiology of goat kids.

The aims of this study were to investigate the effects of maternal stress during pregnancy on the emotional reactivity, the hypothalamo-pituitary-adrenocortical (HPA) axis, and the sympatho-adrenomedullary (SAM) system of goat offspring according to their gender, and to investigate the role of maternal cortisol in prenatal stress effects. Goats were exposed to ten transports in isolation or ten ACTH injections (0.125 IU/kg body weight) during the last third of pregnancy. Control goats remained undisturbed. No effect of repeated transport during the last third of pregnancy was found on basal cortisol concentrations of the offspring. However, an increase in phenylethanolamine N-methyl transferase activity in the adrenals was observed in prenatally stressed kids compared to control kids (P = 0.031). In the presence of novelty, prenatally stressed female kids were more active (P = 0.049) than control females; they also showed more signs of arousal (P = 0.039) and tended to explore more of their environment (P = 0.053) in reaction to a startling stimulus. On the contrary, prenatally stressed male kids tended to be less active (P = 0.051) than control male kids but showed more signs of distress (P = 0.047) in the presence of novelty. Intermediate effects were found on the emotional reactivity to novelty of kids born from dams given injections of ACTH. In conclusion, transport stress in pregnant goats affects the sympatho-adrenomedullary system and the emotional reactivity of their offspring in a gender-specific manner. Moreover, the effects of prenatal transport and ACTH injections showed some similarities but differed in some critical details.

Adrenocorticotropic Hormone↗

PubMed2003

Sources of sampling variation in saliva cortisol in dogs.

The main advantage of collecting saliva cortisol as opposed to plasma cortisol is that it is non-invasive and therefore it is now widely used in stress measurement studies on farm animals and dogs. Although a plasma cortisol response to handling associated with blood collection generally occurs at 3 min from the commencement of handling, there is no information in the literature on the time course of the response of salivary cortisol concentration to handling. The aims of these experiments were to (1). determine if there is a response to up to 4 min handling that affects cortisol concentration in saliva and (2). determine the main causes of variation in saliva cortisol in dogs over time. In experiment 1, saliva was collected from six Kelpies at 0 min then 2, 3 or 4 min after the commencement of restraint. There was no handling effect found in up to 4 min sampling time. In experiment 2, saliva was collected from six Labrador Retrievers five times in 2 h (14:00-16:00), three days a week for four weeks. Some of the sources of variation in saliva cortisol over time included between dog variation that varied over a period of days and variation between occasions that affected the group of dogs as a whole.

Animals↗

PubMed2003

Science and its application in assessing the welfare of laying hens in the egg industry.

OBJECTIVE: To provide a rational framework for the scientific assessment of welfare and to use this framework to assess the welfare implications of issues relevant to the Australian egg industry. PROCEDURE: A well-accepted approach to the assessment of animal welfare, based on assessing how well the animal is adapting, is described. This approach is used to consider the welfare implications of issues such as space, perches, nest boxes, dust baths, abrasive strips and non-cage housing systems. CONCLUSIONS: The role of science in the welfare debate is to provide biological facts and thus it is important to separate welfare and ethics. The welfare of an animal in response to a housing system or husbandry procedure can be assessed by evaluating how much has to be done by the animal in order to cope and the extent to which the coping attempts are succeeding. Using this approach there is evidence for improved welfare from increasing space in cages, based on reduced aggression, corticosterone concentrations and mortalities and increased production, and for incorporating perches, based on the reduction in injuries at depopulation. Similar evidence for the inclusion of dust baths and nest boxes is lacking. The data on abrasive strips are equivocal with recommendations from overseas for their inclusion, whereas some local data have shown an increase in mortality can occur. Similarly, the data on non-cage systems are equivocal. The data on bone strength suggest improved fitness in non-cage systems, the data on stress suggest fitness may be better, similar or worse in non-cage systems, and the limited data on immunology suggest fitness may be worse in non-cage systems than in conventional cages.

Animal Welfare↗

PubMed2002

Susceptibility of reproduction in female pigs to impairment by stress and the role of the hypothalamo-pituitary-adrenal axis.

Although it is generally considered that stress can impair reproduction, we suggest that the impact of acute or repeated acute stress or acute or repeated acute elevations of cortisol are of little consequence in female pigs, even if these occur during the series of endocrine events that induce oestrus and ovulation. It is important to understand the impact of acute stress on reproduction because, in the intensive production of livestock, animals are often subjected to short-term challenges. There seems little doubt that reproduction in a proportion of female pigs is susceptible to impairment by severe and prolonged stress or the sustained elevation of cortisol but only when this continues for a substantial period. In female pigs, where reproduction is susceptible to impairment by severe prolonged stress, it is possible that the mediators of this suppression are cortisol, corticotrophin-releasing factor and vasopressin but, in pigs, there is evidence to suggest that adrenocorticotrophic hormone is not involved. Other substances secreted during stress may be involved but these are not considered in this review. It is possible that the mediators of stress act at any level of the hypothalamo-pituitary-ovarian axis. Although a variety of experimental manipulations have provided potential mediators and mechanisms for the stress-induced suppression of reproduction, these experimental manipulations rarely represented physiological circumstances so it is not clear if such mechanisms would be important in a physiological context. The precise mediators and mechanisms by which hormones released during stress may inhibit reproductive processes during severe prolonged stress are yet to be determined.

Adrenal Glands↗

PubMed2002

The effects of cognitive behavioral intervention on the attitude and behavior of stockpersons and the behavior and productivity of commercial dairy cows.

Two experiments, one involving 29 commercial farms and the other involving 94 commercial farms, were conducted to examine the effects of a training program targeting a number of attitudinal and behavioral variables in stockpeople. These stockperson variables had been previously shown to be related to fear of humans and productivity of commercial cows. In both experiments, two treatments were imposed: an Intervention treatment, consisting of a cognitive-behavioral intervention procedure designed to improve the attitude and behavior of stockpeople toward cows, and a Control treatment, in which no intervention was attempted. In Exp. 1, an analysis of covariance, using previous lactation variables as the covariate, revealed effects of the Intervention treatment on the attitude and behavior of the stockpeople and the behavior of cows. Stockpeople at Intervention farms showed more (P < 0.01) positive beliefs about handling cows and used a lower (P < 0.05) number and percentage of negative tactile interactions in handling cows than stockpeople at the Control farms. Cows at the Intervention farms showed a shorter (P < 0.05) flight distance to humans, indicating a lower level of fear of humans by these cows. However, 36% of the Intervention farms failed to show a reduction in average flight distance over the two lactations. Although there was no significant treatment effect on milk yield, the Intervention farms in which fear levels declined following the intervention had a higher (P < 0.05) milk yield than the other farms. In Exp. 2, a significant (P < 0.05) increase was found in the milk yield of cows following the Intervention treatment. Similar treatment effects were observed on both milk protein and milk fat. These results indicate that cognitive-behavioral interventions that successfully target the key attitudes and behavior of stockpeople that regulate the cow's fear of humans offer the industry good opportunities to improve the productivity of cows.

Animal Husbandry↗

PubMed2000

Human factors affecting the behaviour and productivity of commercial broiler chickens.

1. The purpose of this study was to examine the relationship between stockperson attitude and behaviour; bird behaviour and productivity in the chicken meat industry. 2. No relationship between stockperson attitude and behaviour was observed, which is in contrast to studies in the pig and dairy industries. 3. Evidence is provided for the existence of sequential relationships between stockperson behaviour, bird fear levels and productivity in the broiler farms examined. 4. The mechanism(s) responsible for the negative relationships between fear levels and production is unclear. It is hypothesised that chronic stress or a series of acute stress responses may be the mechanism through which fear affects productivity. 5. The relationship between human behaviour, bird fear levels and productivity indicates the potential that exists to improve productivity and perhaps welfare of commercial broilers by reducing fear levels in broiler chickens.

Agriculture↗

PubMed2000

EEG changes in 4-week-old lambs in response to castration, tail docking and mulesing.

OBJECTIVE: To interpret changes in EEG in relation to perceived pain of castration, mulesing and docking in lambs. DESIGN: Analysis of covariance (randomised block design) to determine the effects of treatment on eight bandwidths of the EEG frequency spectrum. PROCEDURE: Ninety-eight, 3- to 4-week-old lambs were subjected to one of seven treatments: castration, tail docking, mulesing, ear tagging, sham shearing, formalin injection (to induce lameness) and handling. EEG was recorded for 15 min before treatment, during treatment, and for 15 min after treatment. RESULTS: Consistently lower mean power values across all bandwidths of the EEG were found at the time of mulesing and docking than at handling and shearing (P < 0.01). Formalin injection resulted in lower power values than handling and shearing (P < 0.01). Castration had lower power values than handling and shearing. Similarly, for 15 min after treatment, mulesing and formalin injection had significantly lower power values than handling, shearing, ear tagging and castration (P < 0.05). CONCLUSION: The consistent effects associated with mulesing, docking and castration compared to handling, shearing and ear tagging suggest that mulesing at both the time of treatment and during 15 min after treatment results in a response that is similar to that of induced lameness. Docking and castration result in a response at the time of treatment that is similar to induced lameness and mulesing, but during 15 min after treatment is similar to the non-noxious control treatments. However, the depressing effects on the mean power values are the reverse of that anticipated from a previously developed pain model, highlighting the need for further research to develop this technology to evaluate pain associated with husbandry procedures.

Animal Husbandry↗

PubMed2000

Relationships between human-animal interactions and productivity of commercial dairy cows.

This study examined the relationships between a number of stockperson and cow variables at 66 commercial dairy farms. Variables such as the attitudes and behavior of stockpeople toward their cows and the behavioral response to humans and productivity of cows were studied over one lactation. There were consistent and significant correlations between some of these stockperson and cow variables. For example, a positive attitude by stockpeople toward the behavior of dairy cows was negatively correlated with the number of forceful, negative, tactile interactions used by stockpeople in handling cows (r = -0.27, df = 127, P < 0.01). Furthermore, based on farm averages, the number of forceful, negative, tactile interactions used by stockpeople was negatively correlated with the percentage of cows approaching within 1 m of an experimenter in a standard test (r = -0.27, df= 64, P< 0.05). Although not confirming a fear-productivity relationship, a moderate but nonsignificant correlation was found between flight distance of cows to an experimenter in a standard test and milk yield (r = -0.27, df = 33, P > 0.05). Support for the existence of a negative fear-productivity relationship was the finding that the use of negative interactions by stockpeople was significantly and negatively correlated with milk yield, protein, and fat at the farm (r = -0.36, -0.35 and -0.33, respectively, df = 64, P < 0.01) and was significantly and positively correlated with milk cortisol concentrations at the farm (r = 0.34, df= 64, P < 0.01). Furthermore, the percentage of cows approaching within 3 m of an experimenter in a standard test was positively correlated with conception rate to the first insemination (r = 0.38, df = 46, P < 0.01). The significant correlations found in the present study between stockperson attitudes and behavior and cow behavior and productivity, although not evidence of causal relationships, indicate the possibility of targeting these human characteristics to reduce fear responses of dairy cows to humans and improve the cows' productivity.

Animals↗

PubMed1999

Sustained but not repeated acute elevation of cortisol impaired the luteinizing hormone surge, estrus, and ovulation in gilts.

We tested the hypothesis that sustained and repeated acute elevation of cortisol would impair the LH surge, estrus, and ovulation in gilts. Cortisol was injected intramuscularly, to achieve a sustained elevation of plasma concentrations of cortisol, or intravenously, to achieve an acute elevation of plasma concentrations of cortisol. Control gilts received i.m. injections of oil and i.v. injections of saline. These treatments were administered to gilts (n = 6 per treatment) at 12-h intervals from Days 7 to 11 of the estrous cycle until after estrus ceased or until Day 27 or 28 of the estrous cycle, whichever came first. The repeated acute elevation of cortisol had no effect on the LH surge, estrus, or ovulation. In contrast, when the elevation of cortisol was sustained, the LH surge, estrus, and ovulation were inhibited. We conclude that cortisol is capable of direct actions to impair reproductive processes in female pigs but that plasma concentrations of cortisol need to be elevated for a substantial period for this to occur.

Animals↗

PubMed1999

Tail docking and beliefs about the practice in the Victorian dairy industry.

OBJECTIVE: To determine the occurrence of tail docking and beliefs about the practice in the Victorian dairy industry. DESIGN: Survey responses were analysed using chi-square tests and by correlation and regression analyses to determine associations between husbandry practices and beliefs and to identify possible predictive variables in relation to docking. PROCEDURE: A survey of the occurrence of docking and beliefs about the practice was conducted in 1997 using face-to-face interviews of 313 respondents at 234 Victorian dairy farms. RESULTS: On average, 35% of dairy farms routinely docked cattle. The practice varied from 11 to 63% in different regions and 12% of stud farms docked their cows. Rubber rings were used on 75% of farms and the average age of the cow at docking was 18 months. Twenty-two percent of cows were docked at a level above the top of the udder and 54% were docked level with the top of the udder. Respondents that docked believed that milking was finished quicker, the risks of leptospirosis for the operator and mastitis for the cow were reduced, the cows were easier to handle, fly numbers were reduced and milk quality was improved. There was a general belief that intact tails could cause significant discomfort to the operator and that docking resulted in acute but not chronic pain. CONCLUSIONS: Docking is an entrenched practice in the Victorian dairy industry. Those farmers who docked generally believed that it was a highly desirable farming practice with particular benefits for the operator.

Animal Welfare↗

PubMed1999

Inhibition of the secretion of LH in ovariectomised pigs by sustained but not repeated acute elevation of cortisol in the absence but not the presence of oestradiol.

Prolonged stress is known to impair reproduction. It has been proposed that reproduction will also be impaired when a severe acute stress occurs during a period of elevated plasma concentrations of oestradiol, such as during the follicular phase of the oestrous cycle. In this experiment, we hypothesised that repeated acute and sustained elevation of cortisol would suppress the secretion of LH in ovariectomised pigs and that these effects would be enhanced in the presence of oestradiol negative feedback. Cortisol (or vehicle) was administered 12 hourly to ovariectomised pigs (n=6/treatment) for 8 days in the absence of oestradiol treatment and for a further 8 days during treatment with oestradiol. Vehicle was administered to 'control' pigs, 10 or 20 mg cortisol was administered i.v. to pigs to produce 'repeated acute' elevation of cortisol and 250 mg cortisol was administered i.m. to pigs to give a 'sustained' elevation of cortisol. Both before and during treatment with oestradiol, plasma concentrations of LH were monitored on the day before treatment, on the 4th and 8th days of treatment and following an i.v. injection of GnRH at the end of the 8th day of treatment. The repeated acute elevation of cortisol did not impair any parameters of LH secretion (i.e. mean plasma concentrations of LH, pulse amplitude or frequency, pre-LH pulse nadir or the LH response to GnRH) in the absence or in the presence of oestradiol. In contrast, when the elevation of cortisol was sustained, the mean plasma concentrations of LH and the pre-LH pulse nadir were significantly (P<0.05) lower on the 8th day of treatment than on the day before treatment and on the 4th day of treatment. Nevertheless, no other parameters of LH secretion were affected and these effects only occurred in the absence (not in the presence) of oestradiol. In conclusion, cortisol needed to be elevated for more than 4 days to impair the secretion of LH, and oestradiol did not enhance the impact of cortisol on LH secretion in ovariectomised pigs.

Animals↗

PubMed1998

The effect of repeated boar exposure on cortisol secretion and reproduction in gilts.

It has been proposed that short-term activation of the hypothalamo-pituitary adrenal axis, with a consequent increase in the secretion of cortisol, amy disrupt the endocrine events prior to ovulation and thereby impair reproduction in females. We investigated this concept in gilts in which oestrus was detected by introduction to boars, where intense physical contact is possible, or by applying pressure to the back of gilts (back-pressure test) during fence-line exposure to boars, where intense physical contact is prohibited. We expected that there would be a greater release of cortisol and that reproduction would be inhibited in gilts introduced to boars compared to gilts in which the back-pressure test was used. As expected, introduction of gilts to boars resulted in a significant transient increase in plasma concentrations of cortisol while there was no significant effect of using the back-pressure test on plasma cortisol. Nevertheless, introduction of gilts to boars did not impair reproduction and there was no effect of method of detecting oestrus on duration of oestrus, sexual receptivity, fertility or fecundity. The length of the oestrous cycle was decreased and ovulation rate increased in gilts that were introduced to boars compared to gilts that underwent the back-pressure test, indicating that introduction of gilts to boars may have stimulated these aspects of reproduction. These stimulatory effects may have been due to an increased exposure of gilts to sexual behaviour and stimuli from boars when introduced to boars and/or to stimulatory effects of the hypothalamo-pituitary adrenal axis on some aspects of reproduction.

Adrenal Glands↗

PubMed1998

Repeated acute activation of the hypothalamo-pituitary adrenal axis prior to and during estrus did not affect reproductive performance in gilts.

We investigated the effects of repeated acute activation of the hypothalamo-pituitary adrenal axis, prior to and during estrus, on reproduction in gilts. Individual gilts (n = 24 per treatment) either served as controls or were subjected to daily acute stress ("negative handling," brief electric shock with a battery-operated prodder during confinement with the experimenter) commencing, on average, 8 days prior to estrus. Gilts subjected to negative handling had a significant elevation in plasma concentrations of cortisol that lasted at least 3-4 h, and these gilts were slower than control gilts to approach and interact with the experimenter in a standard test. Nevertheless, reproductive performance--as measured by sexual receptivity and proceptivity, ovulation, the percentage of gilts that became pregnant, the number of embryos 20-21 days after insemination, and the weight of embryos--was not affected by repeated acute activation of the hypothalamo-pituitary adrenal axis. Our results suggest that repeated acute activation of the hypothalamo-pituitary adrenal axis prior to and during estrus does not affect the factors that control estrus and ovulation in gilts.

Adrenal Glands↗

PubMed1997

Behavioural and EEG changes in sheep in response to painful acute electrical stimuli.

OBJECTIVE: To measure acute pain in sheep, based on a human pain model, and examined changes in both electroencephalogram frequency spectrum and behavioural responses to increased electrical stimulation in sheep. DESIGN: Analysis of variance (treatment and animal effects) for stimulus intensity where each animal received each electric shock treatment given in the order 0, 5, 10 and 20 mA. PROCEDURE: Eight sheep with electrodes implanted over the surface of the brain were examined for escape-avoidance and electroencephalogram responses to four levels of electrical stimulation from 0-20 mA. RESULTS: With increasing stimulus intensity at the time of feeding, the sheep were more hesitant to return to the feeder or remain near the feeder following stimulation. There was little difference between the 0 and 5 mA stimuli for any of the behaviour variables (P > 0.05). However, there were marked increases in the time taken to re-approach the feeder after receiving an electric shock of 5 mA and of 20 mA (P < 0.05; mean values 3 and 119 s, respectively) and remaining near the feeder for 5 s (P < 0.001; mean values 10 and 167 s, respectively). Following the stimulus, there was an overall increase in the electroencephalogram power spectrum in the first four seconds, which then rapidly returned to normal. In particular, the 20 mA stimulus resulted in higher absolute power values than in the control (0 mA) treatment for delta 2 (P < 0.001), theta 1 (P < 0.05), theta 2 (P < 0.05), alpha 1 (P < 0.001), alpha 2 (P < 0.001) and beta 1 (P < 0.01), bandwidths. Similarly, for the 10 mA stimulus, the absolute power values were greater than the control treatment for delta 2 (P < 0.05), alpha 1 (P < 0.01), alpha 2 (P < 0.001) and beta 1 (P < 0.01) bandwidths. CONCLUSION: The experiment suggests that a human acute pain model is applicable to sheep and that these electroencephalogram changes may provide a good measure of acute pain in sheep

Analysis of Variance↗

PubMed1997

Pain-related cerebral potentials in response to acute painful electrical stimulation in sheep.

OBJECTIVE: To examine associations between late event-related cerebral potential amplitudes and behavioural responses to noxious electrical stimulation as an indicator of acute pain in sheep. DESIGN: Analysis of variance for the effects of stimulus intensity on the behaviour and event-related cerebral potential variables. PROCEDURE: Ninety-six brief constant current electrical pulse trains were presented to the front left leg of eight sheep at four intensities (2.5 to 10 mA) in a randomised order. An event-related cerebral potential and a graded flinch response were recorded for each stimulus and the 24 event-related cerebral potentials at each intensity were averaged to produce a mean waveform. Various components of this waveform were analysed and changes in these measures and the sheep's flinch response, as stimulus intensity increased, were determined. RESULTS: Both the flinch response and some event-related cerebral potential components, that is, peak amplitudes 114 [N1], 187 [P1], 318 [P2] and 230 [Pm] ms after stimulus onset, were significantly affected as stimulus intensity increased. CONCLUSION: These corresponding behavioural and event-related cerebral potential changes indicate the usefulness of using changes in the event-related cerebral potential to measure acute pain in sheep.

Analysis of Variance↗

PubMed1996

Repeated matings with individual ewes by rams differing in sexual performance.

Twenty-four sexually mature rams were individually exposed to 10 estrous ewes on three occasions to determine the relationship between levels of sexual performance (ejaculation rate or serving capacity) and the incidence of repeated matings (ejaculations) with individual ewes. Rams that attained six ejaculations in a relatively short period of time (HP rams) mated fewer times with individual ewes than low-performing (LP) rams (P < .01). As a consequence, HP rams tended to mate with a greater number of different ewes than did LP rams (P < .06). In addition, time required to attain six ejaculations was inversely correlated with the number of different ewes mated (P < .03). The HP rams did not differ from LP rams in the number of different ewes investigated and courted. These findings highlight the value of using rams with relatively rapid ejaculation rates when breeding large groups of naturally cycling or synchronized ewes.

Animal Husbandry↗

PubMed1995

The effect of breeding facility and sexual stimulation on plasma cortisol in boars.

Nine boars were used to evaluate effects of breeding facility design and sexual activity on plasma cortisol concentrations . In one breeding facility (conventional), boars were housed individually in small pens, and female pigs were mated in those boar pens. In another breeding facility (Detection-Mating Area [DMA] system), boars were housed individually in stalls, and female pigs were mated in a specific mating pen adjacent to the front of stalls where boars were housed. After 51 d of housing treatment, a catheter was surgically implanted in the cephalic vein for collection of blood samples. Daytime profiles (hourly collections from 0900 to 1700) of cortisol did not differ among boars in the two treatment groups. Cortisol was greater (P < .01) in the morning than in the afternoon. Administration of ACTH increased (P < .001) plasma cortisol in boars, but breeding facility did not affect the ACTH-induced changes in cortisol concentrations. There was a treatment x time interaction (P < .02) for cortisol after sexual stimulation, and the magnitude and duration of increase in cortisol were greater (P < .05) in the DMA treatment group. Cortisol was greater (P < .001) after than before mating for both treatment groups. An acute increase in plasma cortisol concentration in boars seems to be a normal biological response to sexual activity. However, magnitude and duration of the increase in cortisol may be influenced by breeding facility design and mating procedure. There is no evidence, based on physiological data, that housing boars in stalls in the DMA system has any adverse effects on their welfare.

Adrenocorticotropic Hormone↗