Andrew D. Fisher

The effects of feed restriction and lying deprivation on pituitary–adrenal axis regulation in lactating cows

Abstract In order to examine the effects of moderate feed restriction and periodic lying deprivation on pituitary–adrenal axis function in lactating dairy cows, 32 non-pregnant Jersey cows were allocated to two levels of feeding (4% vs. 3% of body weight of dry matter daily) and lying restriction (free lying vs. prevention of lying from 15:00 to 06:45 h daily) in a 2×2 factorial plan for 7 days. There were no feeding×lying interactions, and feeding level did not affect plasma cortisol concentrations, adrenocorticotrophic hormone (ACTH) and cortisol responses to challenge with 15 μg corticotrophin-releasing hormone (CRH), or ACTH and cortisol responses to CRH following the administration of 0.3 mg dexamethasone. Compared with free-lying animals, lying-restricted cows had increased basal plasma cortisol concentrations, and reduced ACTH and cortisol responses following CRH challenge relative to pre-challenge baselines. Lying-restricted cows also had an increased plasma cortisol/ACTH ratio for the total area under the hormone response curves following CRH. Dexamethasone administration prior to CRH challenge produced a similar result to CRH challenge alone, indicating that there were no differences between lying-restricted and free-lying cows in negative feedback sensitivity of the pituitary to glucocorticoids. In conclusion, 7 days of moderate feed restriction did not appear to alter pituitary–adrenal axis function, whereas periodic lying deprivation reduced pituitary responsiveness to CRH and increased plasma cortisol/ACTH ratio following CRH challenge.

Measuring judgement bias and emotional reactivity in sheep following long-term exposure to unpredictable and aversive events

Animal welfare research is now starting to measure the cognitive component of affective states in an effort to improve welfare assessments of animals. Twenty-six Romane ewe lambs were trained to a spatial location task previously demonstrated to test for judgement bias in sheep. This required a go/no-go response according to the location of a bucket in a pen, with one location being positively reinforced (with a feed reward) and the other negatively reinforced (with a fan-forced blower). While training in the judgement bias arena continued, half of the sheep (n=13) were subjected to a chronic, intermittent treatment that consisted of stressful events common to production systems. After 3 weeks of treatment, all sheep were tested for biases in judgement by placing the bucket in ambiguous locations between the two learnt reference locations. The emotional reactivity, as characterised by behavioural and physiological responses, of all sheep to events that were unexpected, novel or sudden was then tested. A significant treatment × bucket location interaction was seen on day 3 with Stressed sheep approaching the bucket locations less than Control sheep (p=0.007). This may reflect a bias in judgement, however it is also possibly a treatment-induced difference in learning. Cardiac data did not indicate treatment differences, however the RMSSD of Control sheep in novel and unfamiliar situations was always higher than the Stressed animals. No meaningful treatment differences in emotional reactivity behaviours were evident. This paper provides further evidence that affective states exist and can be measured in animals.

The effect of repeated testing on judgement biases in sheep.

Testing judgement biases of animals may provide insight into their affective states; however important questions about methodologies need to be answered. This experiment investigated the effect of repeated testing using unreinforced, ambiguous cues on the response of sheep to a go/no-go judgement bias test. Fifteen sheep were trained to differentiate between two locations, reinforced respectively with feed (positive) or with the presentation of a dog (negative). The responses to nine ambiguous locations, positioned between the positively and negatively reinforced locations, were tested repeatedly over 3 weeks. Sheep exhibited a symmetrical gradation in response to ambiguous locations between the positive and negative reinforcers. There was a significant decline (P=0.001) in the total number of approaches to the ambiguous positions over time (weeks). This effect of time suggests that sheep learnt that the ambiguous locations were unrewarded. This result supplies evidence of a limitation identified in current judgement bias methodology, due to repeated testing, which has the potential to provide misleading results.

Indoor space allowance: effects on growth, behaviour, adrenal and immune responses of finishing beef heifers

AbstractThe objective was to determine the daily live-weight gain, behaviour, adrenal and immune responses of finishing beef heifers housed at two different space allowances. Heifers (no. = 32) with a mean live weight of466 (s.e. 3·6) kg were assigned to either 1·5 or 3·0 m2 average individual space allowance in four slatted-floor pens (two per treatment) for a period of 104 days. On days 5, 40, 68 and 96, heifers (no. = eight per treatment, four per pen) were challenged with 1·98 i.u. ACTH per kg M0·75, and serial blood samples were analysed for plasma cortisol concentrations. The other 16 heifers were immunized against keyhole limpet haemocyanin (KLH) on day 28, and blood samples collected on days 28, 42, 56, 70, 84 and 98 were analysed for anti-KLH immunoglobulin (Ig) concentrations. All heifers were blood sampled on days 0, 14, 56 and 98, and red and white blood cell numbers, packed cell volume (PCV) and plasma concentrations of creatine kinase (CK), non-esterified fatty acids (NEFA) and urea were determined. Behavioural observations were conducted on days 8, 43, 71 and 99 by scan sampling for 24 h (10-min intervals), and continuous 4-h observations were conducted on days 100 and 101.Heifers at 1·5 m2 space allowance had a lower daily live-weight gain compared with those at 3·0 m2 (0·60 v. 0·87 (s.e. 0·04) kg; P 0·05). Heifers at 1·5 m2 had lower plasma NEFA concentrations (P 0·05). The time spent lying down was lower for heifers at 1·5 m2 (10·0 v. 21·1 h/day; P < 0·05). Social interactions were fewer (P < 0·05), and incidence of head-resting behaviour was higher (P < 0·05) among heifers at 1·5 m2 compared with 3·0 m2 space allowance. In conclusion, the restricted space allowance resulted in a substantial decrease in daily live-weight gain, and changes in adrenal response and behaviour.

Growth, behaviour, adrenal and immune responses of finishing beef heifers housed on slatted floors at 1.5, 2.0, 2.5 or 3.0 m2 space allowance

Overcrowding of housed cattle can be detrimental to animal performance and welfare. The objective of this study was to measure the production, behaviour, adrenal and immune responses of finishing beef heifers at four space allowances on slatted floors. Simmental crossbred heifers (n = 96; 468 (s.e. 3.2) kg initial bodyweight) were assigned to treatments of 1.5, 2.0, 2.5 or 3.0 m2 average individual space allowance, with three pens of eight heifers per treatment, for 140 days. On days 13, 69 and 132, heifers (9 per treatment) were challenged with 1.98 i.u. adrenocorticotrophic hormone (ACTH)/kg bodyweight0.75 and blood samples were collected for cortisol determination. All other heifers (15 per treatment) were immunised against keyhole limpet haemocyanin (KLH) on day 84. Behavioural observations of all animals were conducted to record lying, eating and ruminating times, and aggressive and social behaviour. Heifers at the 1.5 m2 space allowance had lower (P < 0.01) average daily gains than heifers at 2.0, 2.5 and 3.0 m2 space allowances (0.52, 0.65, 0.70 and 0.69 (pooled s.e. 0.031) kg, respectively). Daily lying time was reduced (P < 0.001) for heifers at 1.5 m2 compared with 2.0, 2.5 and 3.0 m2 space allowances (10.3, 11.8, 12.0 and 11.7 (pooled s.e. 0.26) h, respectively). There were no effects of treatment on aggressive or social behaviour, basal or ACTH-induced cortisol and anti-KLH IgG1 or IgG2 antibody responses. It was concluded that the 1.5-m2 space allowance was detrimental to animal growth and comfort compared with the other three space allowances.

Administration of serotonin inhibitor p-Chlorophenylalanine induces pessimistic-like judgement bias in sheep

Judgement bias has potential as a measure of affective state in animals. The serotonergic system may be one mechanism involved with the formation of negative judgement biases. It was hypothesised that depletion of brain serotonin would induce negative judgement biases in sheep. A dose response trial established that 40 mg/kg of p-Chlorophenylalanine (pCPA) administered to sheep for 3 days did not affect feeding motivation or locomotion required for testing judgement biases. Thirty Merino ewes (10 months old) were trained to an operant task for 3 weeks. Sheep learnt to approach a bucket when it was placed in one corner of the testing facility to receive a feed reward (go response), and not approach it when in the alternate corner (no-go response) to avoid a negative reinforcer (exposure to a dog). Following training, 15 sheep were treated with pCPA (40 mg/kg daily) for an extended duration (5 days). Treated and control sheep were tested for judgement bias following 3 and 5 days of treatment, and again 5 days after cessation of treatment. Testing involved the bucket being presented in ambiguous locations between the two learnt locations, and the response of the sheep (go/no-go) measured their judgement of the bucket locations. Following 5 days of treatment, pCPA-treated sheep approached the most positive ambiguous location significantly less than control sheep, suggesting a pessimistic-like bias (treatment × bucket location interaction F(1,124.6)=49.97, p=0.011). A trend towards a significant interaction was still evident 5 days after the cessation of pCPA treatment (p=0.068), however no significant interaction was seen on day 3 of testing (p=0.867). These results support the suggestion that judgement bias is a cognitive measure of affective state, and that the serotonergic pathway may be involved.

Evaluation of a new approach for the estimation of the time of the LH surge in dairy cows using vaginal temperature and electrodeless conductivity measurements

The objective of the study was to test the effectiveness of a new type of conductivity sensor, along with vaginal temperature, at identifying the LH peak associated with estrus in dairy cows. Twelve mature non-lactating Holstein-Friesian cows had their estrous cycles synchronized on two occasions, and then data were collected for the following spontaneous cycles. An indwelling electrodeless plastic-coated toroidal conductivity sensor, which also recorded temperature, was placed in the vagina throughout the cycle. Blood samples were collected for LH measurement, and ultrasound scanning used to confirm ovulation. Although there was a relationship between vaginal mucus conductivity measured by the toroidal sensor and the timing of the LH surge, it was not sufficiently robust in individual cows to be able to identify the time of the LH surge. The mean increase in vaginal temperature at estrus was 0.48 degrees C. An algorithm was developed which used the detected individual cow temperature peak to test the relationship with the LH peak. In 16 out of 21 cases where ovulation was confirmed and data existed, the estimated individual peak was within 4h of the LH surge, in three cases it was +/-6h, and in two instances it was early. In conclusion, the temperature algorithm was able to identify the time of the LH surge and thus predict time of ovulation in a way that would allow effective AI, although this result needs to be tested in lactating cows. However, the toroidal conductivity sensing method was not able to produce data of sufficient quality to develop a predictive relationship in individual cows.

The effects of 12, 30, or 48 hours of road transport on the physiological and behavioral responses of sheep.

To identify long-distance transport durations compatible with acceptable animal welfare, the aim of this study was to determine the responses of healthy sheep to road transport under good conditions for 12, 30, or 48 h. Merino ewes (n = 120; 46.9 +/- 0.39 kg) were allocated to road transport treatments of 12, 30, or 48 h, with 2 replicates per treatment. Blood and urine samples and BW were taken pretransport and at 0, 24, 48, and 72 h posttransport. Lying time was measured using data loggers. Increasing transport durations resulted in reduced (P < 0.001) BW and increased (P < 0.05) hemoconcentration, but these effects did not exceed clinically normal ranges for any transport duration, and sheep generally recovered to pretransport values within 72 h posttransport. Sheep transported for 30 and 48 h had less BW on arrival than sheep transported for 12 h (P < 0.001). There were no differences (P > 0.05) between the 12- and 30-h treatments in sheep BW at 24, 48, or 72 h after arrival. Sheep transported for 30 and 48 h had greater total plasma protein concentrations on arrival than sheep transported for 12 h (P < 0.001). Although the white cell count and neutrophil:lymphocyte ratio increased with transport, there were no consistent effects of transport duration. There were also no effects (P = 0.10) of transport duration on plasma cortisol concentrations. There were no treatment differences (P > 0.05) in lying times during the first 18 h after arrival. Sheep transported for 30 or 48 h lay down less (P < 0.05) than sheep transported for 12 h between 18 and 24 h after arrival, but there were no other differences over 72 h. These findings indicate that healthy adult sheep, transported under good conditions, can tolerate transport durations of up to 48 h without undue compromise to their welfare.

Effects of meloxicam or tolfenamic acid administration on the pain and stress responses of Merino lambs to mulesing

OBJECTIVE To determine the effectiveness of two long-acting non-steroidal anti-inflammatory drugs (NSAIDs) at reducing the pain and stress responses to mulesing in lambs. PROCEDURES Merino lambs (n = 60) were allocated at 5 weeks of age to six treatment groups: (1) sham mules; (2) mules; (3) tolfenamic acid-sham mules; (4) tolfenamic acid administered 45 min before mulesing; (5) tolfenamic acid at the time of mulesing; (6) meloxicam at the time of mulesing. Plasma cortisol was measured at -0.75, -0.25, 0, 0.5, 1, 3, 6, 12, 24, 48 and 72 h relative to mulesing. Beta-endorphin concentrations in plasma were determined at 0, 0.5, 1, 6, 12, 24, and 48 h. Haematology was performed on blood samples taken at -0.75, 0, 24, 48 and 72 h. Plasma haptoglobin was measured at 0, 12, 24, 48 and 72 h. Rate of wound healing was determined 72 h post mulesing, and animal behaviour, including posture, was measured for 6 h after mulesing. RESULTS The mulesed lambs exhibited large increases in plasma concentrations of cortisol, beta-endorphin and haptoglobin. All mulesed animals lost weight significantly in the week after mulesing, regardless of analgesic administration, but the difference in weight between mulesed and unmulesed lambs was less at the final measurement, 2 weeks after mulesing. Mulesed lambs spent significantly less time lying ventrally than control lambs. All lambs that were mulesed, including those administered NSAIDs, spent more time standing with a hunched posture and less time walking normally than control lambs. CONCLUSIONS The NSAID treatments applied 45 min before or at the time of mulesing at the dose levels used in this study were not effective in reducing the acute response of lambs to mulesing.

The effects of temperature elevation and water deprivation on lamb physiology, welfare, and meat quality

Romney-cross ewe lambs (n = 27) were subjected to controlled environmental conditions to induce acute heat stress. The goals of the study were to: (1) determine appropriate physiological indicators of acute heat stress, (2) determine threshold rectal temperatures (Tr) for catecholamine and cortisol release, (3) determine effects on meat quality, and (4) assess the effect of dehydration on the above measures. There were 3 treatments: control (ambient temperature and humidity), heat stress (33°C, and 85-100% humidity), and heat stress combined with water deprivation. The duration of the treatment period was 12 h. Respiration rate (Rf) and rectal temperature (Tr) were highly correlated with increasing temperature humidity index (THI) (r > 0.75, P < 0.001), whereas heart rate was less responsive to THI (r = 0.30, P < 0.05). The welfare of these lambs was at risk at Tr greater than 40.5°C, a point at which respiration rate was maximal and unable to prevent further increases in Tr. Plasma cortisol concentrations were increased in heat-stressed lambs after Tr reached approximately 40.7°C. Plasma catecholamines were only elevated in lambs when Tr was greater than 42°C. The majority of lambs subjected to heat stress had a Tr less than 42°C, and there were no significant effects on meat quality. Despite exhibiting increases in plasma protein concentrations, there were no indications that dehydrated lambs were under additional stress during heat challenge in comparison with hydrated lambs. Additional keywords: heat stress, hyperthermia, dehydration, catecholamines, cortisol. A le wa ri c T.