Animal behavior and animal welfare

The value of behavioral techniques in assessing animal welfare, and in particular assessing the psychological well being of animals, is reviewed. Using cats and horses as examples, 3 behavioral methods are presented: (1) comparison of behavior patterns and time budgets; (2) choice tests; and (3) operant conditioning. The behaviors of intact and declawed cats were compared in order to determine if declawing led to behavioral problems or to a change in personality. Apparently it did not. The behavior of free ranging horses was compared with that of stabled horses. Using two-choice preference tests, the preference of horses for visual contact with other horses and the preference for bedding were determined. Horses show no significant preference for locations from which they can make visual contact with other horses, but they do prefer bedding, especially when lying down. Horses will perform an operant response in order to obtain light in a darkened barn or heat in an outside shed. These same techniques can be used to answer a variety of questions about an animal's motivation for a particular attribute of its environment.     

Use of limited daily access to food in measuring the heat production associated with food intake in laying hens

1. Two experiments were carried out to determine the heat production associated with food intake in laying hens allowed access to food for one (experiment 2) or two hours (experiment 1) daily. 2. In experiment 1, heat production in the fed state was measured for two successive days after 46 h of food deprivation. The rate of heat production in the fasting state was measured from 47 to 69 h after feeding. 3. In experiment 2, heat production was measured at 4 fixed food intakes: 100, 70, 40 and 0 g/bird. Heat production associated with food intake, eating activity, net availability of ME and maintenance ME requirement was estimated. 4. Heat production after 46 h of food deprivation did not differ from that after 22 h of deprivation. In the hens receiving 100 g of food, heat production reached the pre-feeding level by 20 h after eating; the hens with lower food intakes reached the pre-feeding level more rapidly. It is suggested that the heat production associated with feeding had been eliminated by 22 h after eating. 5. Heat production associated with feeding was 16% of ME intake. Because the total energy cost of eating activity was only 0.8% of ME intake, the heat production associated with food intake in the limited-access hens came mainly from the effects of digestion, absorption and metabolism of the ingesta. 6. The net availability of ME was estimated to be 0.84. The estimated maintenance ME requirement was 569.6 kJ/kgW0.75 d.     

Influence of food restriction and of the presence of chicks on the reproductive system of the domestic hen

An experiment was conducted with 4 groups of hens: a control group of laying hens, a group subjected to food deprivation for 7 d, a group subjected to food deprivation for 7 d, then re-fed for 10 d and a group subjected to food deprivation for 7 d then re-fed for 10 d with two chicks per hen introduced during the last 7 d of refeeding. Food deprivation provoked the involution of the oviduct and ovarian regression, as well as a decrease in the plasma concentrations of luteinising hormone (LH) and sex steroids (progesterone, testosterone and oestradiol). After 3 d of re-feeding, there was a significant increase in the plasma concentrations of LH and steroid hormones. This phenomenon was even more marked after 10 d of re-feeding; most of the hens of the third group which were not given chicks, were at the point of lay. The presence of chicks resulted in the expression of maternal behaviour and suppressed a rapid return to laying. This was especially marked in hens showing typical maternal behaviour traits, for which the morphological and endocrine measurements indicated a decrease in the activity of the hypothalamo-hypophyseal-gonadal axis.     

Preference and motivation of laying hens to eat under different illuminances and the effect of illuminance on eating behaviour

1. In experiment 1, 10 laying hens were given the choice to eat food pellets from any of 4 food bowls illuminated by overhead, incandescent luminaires at <1, 6, 20 or 200 lux. During a trial hens were allowed to eat for 5 min. After each minute had elapsed (from the start of eating) the light sources were extinguished and the illuminances re-assigned to the food bowls in a random manner. Each hen received two trials, one where the food was freely available and another where it was hidden in a sand and gravel mix. 2. The hens chose to eat for most time in the brightest (200 lux) and least in the dimmest (<1 lux) environments for both free and hidden food (free: 5.9, 10.5, 10.4, 15.7s for increasing illuminance; Hidden: 5.5, 9.8, 9.1 and 15.7s. 3. In experiment 2, 9 hens were trained to peck at either an illuminated or unilluminated panel to access a food reward behind a guillotine door for 3 s. Five hens were trained to peck the illuminated panel to access food brightly lit (200 lux) or the unilluminated panel to access food dimly lit (<1 lux); 4 hens were trained vice versa. The flock was then divided into three groups of three, and three treatments imposed on each group in a Latin-square arrangement. In treatment 1, one peck at either panel allowed access to the chosen light environment (F1:F1). In treatment 2, 5 pecks were required to access food brightly lit on a variable ratio, but only one to access food dimly lit (ratio V5:F1). In treatment 3, the variable ratio was increased to V10:F1 to access food in the light. 4. Over 40 trials for each hen, the mean number of attempts to eat food in the light (where the panel which allowed access to food brightly lit was pecked at least once) was 34.5 for F1:F1, 12.1 for V5:F1 and 8.5 for V10:F1. The mean number of food rewards taken in bright light was 34.5, 3.1 and 1.8, respectively. For both variables, the difference between F1:F1 and V5:F1 was significant but not between V5:F1 and V10:F1. By interpolation of the 'attempts' data, it was estimated that hens would work 2.3 times harder to gain access to food brightly lit than for food dimly lit. 5. In experiment 3, the influence of the same illuminances applied over a food bowl as in experiment 1 (<1, 6, 20 or 200 lux) on the number of pecks/min, food consumed/min, food consumed/peck and the force of pecks was examined. 6. The amount of food consumed was lowest in the dimmest environment (3.1 vs 7.5, 7.4 and 7.1 g/ min for increasing illuminance, respectively); as was the number of pecks (35.6 vs. 125.0, 123.1, and 125.4 pecks/min respectively for increasing illuminance). The amount consumed per peck did not vary significantly with illuminance. The mean peck force showed a trend to be lowest in the dimmest environment (5.3 vs. 6.6, 7.0 and 6.6 N respectively, for increasing illuminance). 7. Overall, the hens showed a preference and appeared motivated to eat in bright as opposed to dim light. The hens were unwilling to eat at low illuminances although the 'efficiency' of eating (g/peck) was not impaired significantly. These data may have implications for novel lighting systems and those where hens are required to eat in the dark or in very dim light.     

Behavioural differences between laying hen populations selected for high and low efficiency of food utilisation

1. The effects on behaviour of selecting light-hybrid laying hens for high and low efficiency of food utilisation were investigated. Efficiency of food utilisation was measured as the proportional deviation of observed food consumption from expected food consumption. 2. Videograms of the day-time behaviour of 48 to 53-week-old individually caged hens from the F3 generation were analysed by instantaneous sampling. 3. Low-efficiency hens spent more time food-pecking, walking, pacing, and showing escape and aggressive behaviour than did high-efficiency hens. High-efficiency hens spent more than twice as much time resting and sleeping, and were never observed pacing prior to laying. 4. These differences were larger during the 2 h before laying than at other times of day. 5. Low-efficiency hens had poorer plumage, especially on the neck and the breast, and the poorer the plumage the more agitation they showed. 6. Time spent food-pecking was negatively correlated with laying frequency. 7. Differences in the occurrence of specific behaviour patterns, particularly those symptomatic of pre-laying frustration, partly explained differences in efficiency of food utilisation. Selection for higher efficiency of food utilisation might eliminate hens which are most frustrated prior to laying in cages.     

Induction of a pause in laying by corticosterone infusion or dietary alterations: effects on the reproductive system, food consumption and body weight

A pause in laying was induced in hens by infusing 30 micrograms corticosterone/h, feeding diets deficient in calcium or sodium and by food and water withdrawal. In hens infused with corticosterone, food consumption remained high and body weight was unchanged, although liver weight doubled. The other treatments were associated with a decline in food consumption and a loss of body weight but liver weight was unchanged. The weight of the ovary was reduced most severely in hens infused with 30 micrograms corticosterone/h, but the number of follicles weighing more than 12 mg was not altered by any of the treatments. A decrease in the number of large, yolk-filled follicles was matched by an increase in the numbers of small follicles. All treatments resulted in an increase in the number of atretic follicles. All treatments produced an elevation of plasma corticosterone concentrations within the normal physiological range, and a decrease in plasma LH concentrations. These features may constitute part of the physiological mechanism causing regression of the ovary and the cessation of egg-laying, but they do not prevent recruitment of small follicles to the stage which precedes entry into the hierarchy of large, yolky follicles.     

Behaviour and hormone concentrationsin nest deprived and renesting hens

1. Nest and egg deprivation is a procedure traditionally used to disrupt incubation behaviour expression in commercial flocks. The aim of this study was to establish how nest deprivation affects the subsequent changes in behaviour and hormone secretion and whether readiness to renest is related to hormone concentration before and during nest deprivation. 2. Incubating broiler breeder hens were deprived of their nest either in their familiar environment, by blocking the nest entrance in the home cage or in an unfamiliar environment, by transfer in a different cage. After 3 days of nest deprivation, next access was allowed and readiness to incubate tested. 3. Both methods of nest deprivation resulted in the expression of similar behaviours associated with the disruption of incubation, and similar increases in plasma LH and oestradiol and decreases in plasma prolactin. The percentage (70%) of hens which renested after either method of nest deprivation did not differ significantly. 4. Readiness to renest was not related to the concentrations of plasma prolactin measured before or during the 3 days of nest deprivation. However, hens which would later renest could be identified by using behavioural criteria. They emitted more avoidance trills before, and sat on the wire floor for longer periods during, the nest deprivation period than the others.     

Ability of heifers to discriminate between familiar herdmates and members of an unfamiliar group: preference test and operant conditioning test

Using a preference test and operant conditioning in a Y-maze, this experiment examined the ability of heifers to discriminate between their own familiar herdmates and member(s) of an unfamiliar group. Sixteen Danish Friesian heifers, eight older animals (360.6 ± 24.2 days of age) and eight younger ones (190.1 ± 14.1 days of age) were used. Each age group was further divided into two experimental groups. Members of each of these groups were housed together in small pens before the experiments began. In experiment 1, each of the 16 animals was allowed to approach either a familiar or an unfamiliar individual in the Y-maze. The test was repeated 12 times, with a different unfamiliar subject for each test. In experiment 2, eight heifers were individually tested in a conditioning experiment to examine whether they could learn to discriminate between a group of their three herdmates and a group of three unfamiliar heifers. Test animals were rewarded when they chose their own group. In experiment 1, heifers did not show a preference between familiar and unfamiliar individuals. Interestingly the younger stimulus heifers but not the test animals showed an ability to discriminate between unfamiliar animals by vocalizing. In experiment 2, four of the eight test animals achieved the criterion for successful discrimination between the familiar and unfamiliar group ( P  < 0.003: binomial law). There was no age group difference in the ability to discriminate between familiar and unfamiliar animals. In conclusion, heifers did not show a preference toward familiar or unfamiliar individuals; but after conditioning, some heifers could learn to discriminate between familiar and unfamiliar groups.     

Influence of sudden changes in management program on physiological and behavioral parameters in hens

The present study was designed to test the effects of sudden changes of food access and light duration on the physiological and behavioral parameters of hens. The physiological parameters investigated were heart rate (HR), body temperature (BT), and locomotor activity (LA) using a radiotelemetry system. After implantation of the telemetry transmitters, six hens were housed individually in cages under constant environmental conditions for 10 days with a photoperiod of 15 h light (04.00–19.00 hours), and food was available ad libitum at all times. After that, the same hens were subjected to a feed withdrawal trial, from 12.00 to 08.30 hours, followed by a lighting hour reduction trial by changing the time of lights‐off from 19.00 to 14.00 hours. The physiological and behavioral data were recorded for 2 days before each trial, as control data. With the feed withdrawal trial, during the light and dark periods, HR and BT were significantly lower in the hens without food access than in the control. Whereas, LA was significantly lower only during the light period in the hens without food access than in the control. Further, the time spent resting increased significantly, but the time spent feeding decreased significantly in the hens without food access than in the control. Also, the number of times the cage was pecked and pecking of the feeder occured at a significantly higher level, while the number of times beaks were wiped occured at a significantly lower level in the hens without food access than in the control. With the lighting hour reduction trial, during the light period, HR and BT were significantly higher, whereas LA was significantly lower in the ’sudden light‐off’ treated hens than in the control. In addition, during the dark period, HR, BT and LA were significantly higher in the sudden light‐off treated hens than in the control. Moreover, in the sudden light‐off treated hens, the time spent preening and feeding decreased significantly, but the time spent resting increased significantly than in the control. It is concluded that sudden changes in a management program might result in many significant differences as were found in the physiological and behavioral parameters of hens in the present study.     

Conditioned fear-related ultrasonic vocalizations are emitted as an emotional response

Ultrasonic vocalizations (USVs) are observed along with freezing behavior when rats are placed under fearful situation. Coping style with stress is categorized into two forms, namely passive and emotional avoidance and active operant avoidance. In this study, fear-induced USV was compared between two conditioning protocols. Two groups of male Wistar rats were contextually conditioned for 10 days by exposing to the shock box. One group was shock-unavoidable and the other shock-avoidable by operant control of emitting the USVs. They were then proceeded to the extinction phase. As the results, the shock-unavoidable group emitted greater USV in both conditioning and extinction phases. The extinction burst, commonly seen in active learned responses, was not observed in either group. The duration of freezing was also longer in shock-unavoidable conditioned rats. These results suggest that under the shock-unavoidable condition, rats receive more stress and thus emit more USV. It is therefore concluded that fear-induced USV is an emotional and passive response to the stress, rather than being controlled in an operant-way.     

Dustbathing Behaviour of Uropygial Gland Extirpated Domestic Hens: Effects of Dust Deprivation

Dustbathing behaviour of uropygial gland extirpated and intact White Leghorn hens was studied after 27 and 75 h of deprivation of dust. Thereafter the hens were given access to dust (litter) and latency and duration of their first dustbathing bout were recorded. A short latency and/or a long duration were taken to indicate a strong urge to perform dustbathing. Judged by either of these criteria the gland extirpated birds showed a higher dustbathing tendency than the intact birds and in both groups the dustbathing tendency increased from 27 to 75 h of deprivation. Because of these findings the present study failed to support the “lipid regulation theory”: that the amount of lipid in the plumage should regulate the dustbathing tendency. Rank in the social hierarchy significantly influenced latency and duration of dustbathing but there was no simple correlation. After two weeks with constant access to litter no differences in the amount of feather lipids could be found between gland-extirpated and intact birds.     

The effect of egg formation and laying on the food and water intake of brown leghorn hens

Food and water intakes of four caged Brown Leghorn hens were studied on a daily and hourly basis in relation to egg formation. In addition the food intake of two similar hens was studied using a Skinner box which provided a more detailed record of ingestive behaviour in a non‐social situation in which social interactions might not mask the relationship between food intake and physiological needs. Food intake was greater on days on which ovulation occurred than on days during which there was neither ovulation nor oviposition. Water intake was greater on days during which ovulation occurred than on days with oviposition but no ovulation. On this latter type of day (laying day) food intake was greater than on days without ovulation and oviposition (resting day). Both food and water intakes were depressed for 1 to 2 h before oviposition, but ingestion increased during the hour of laying and remained high for 1 to 2 h.     

Response of laying hens to asymmetrical interrupted lighting regimens: physiological aspects

1. There were no significant differences in the mean time of oviposition, distribution of ovipositions over the 24 h or proportion of eggs laid in the modal 8 h when conventionally-lit hens were compared with hens which received interrupted lighting with the same apparent daylength. 2. Intermittently-lit hens performed 25% less feeding activity than conventionally-lit hens, but without a significant reduction in mean food intake. There were genetic differences in response of feeding rate to interrupted lighting. 3. Intermittently-illuminated hens consumed about 20% of their food during the scotoperiods which interrupted the apparent day of a 1.5L:0.5D:10(0.5L:0.5D):4L:8D regimen, although there was significant genetic variation from 10 to 22%. None of the genotypes ate during the 8-h night. 4. Across 4 genotypes neither crop weight nor rate of crop emptying was affected by the lighting treatments, although a heavier mean crop weight under interrupted lighting approached significance in one breed (P less than 0.10). 5. Interrupted lighting did not cause any ocular disorders.     

Effect of foraging material and food form on feather pecking in laying hens

1. The aim was to test whether provision of foraging material and food form influence feather pecking and feather damage in laying hens. 2. From week 19 of age, 16 groups of 11 hens (white Lohman Selected Leghorn hybrids) were kept in pens with or without access to long-cut straw as foraging material and fed on either mash or pellets. 3. Foraging behaviour was increased in hens with access to straw and time spent feeding was increased in hens fed on mash. In addition, hens fed on mash had longer feeding bouts and higher rates of pecking at the food during feeding than hens fed on pellets. 4. There were interaction effects of foraging material and food form on both feather pecking and feather damage. High rates of feather pecking and pronounced feather damage were only found in hens housed without access to straw and fed on pellets. In groups characterised by high rates of feather pecking the hens also showed more severe forms of this behaviour. 5. Differences in the time budgets of hens kept in different housing conditions suggested that birds fed on mash used the food not only for feeding but also as a substrate for foraging behaviour. 6. In order to avoid problems with feather pecking it is recommended that laying hens are provided with foraging material and fed on mash.     

Feeding motivation and plasma metabolites in pregnant sows fed diets rich in dietary fiber either once or twice daily

The present study investigated the effects of source and level of dietary fiber (DF) and feeding frequency (once vs. twice daily) on feeding motivation and plasma metabolites at 4 different time points post feeding. Sixty pregnant sows (Sus scrofa, 4 blocks of 15 sows) were allocated to 1 of 5 diets within blocks. Four diets were restricted (approximately 35 MJ ME/d): a barley and wheat control diet (171 g DF/kg DM; 12 g DF/MJ ME), and 3 fiber diets formulated to contain 35% DF by including pectin residue (323 g DF/kg DM; 25 g DF/MJ ME), potato pulp (404 g DF/kg DM; 29 g DF/MJ ME), or sugar beet pulp (367 g DF/kg DM; 25 g DF/MJ ME). The fifth diet was a mixture including an equal amount of the 3 fiber diets offered semi ad libitum (ad libitum access to feed during 6 periods of 1 h starting at 0300, 0600, 1100, 1500, 1800, and 2300; 354 g DF/kg DM; 25 g DF/MJ ME). The experimental period included 2 periods of 4 wk each. Restricted-fed sows were fed once daily (0800 h) during the first period and twice daily (0800 and 1500 h) during the second period, or vice versa. Semi ad libitum fed sows had access to feed 6 times a day in both periods. In each period, the feeding motivation was assessed in an operant conditioning test, and samples of peripheral blood were taken in a balanced design, at 0900, 1200, 1900, and 0700 h, corresponding to 1, 4, 11, and 23 h after feeding for restricted sows fed once daily. No differences in the feeding motivation were found between the 4 restricted diets at any of the time points post feeding, but semi ad libitum fed sows had a decreased feeding motivation (P < 0.001). Among the restricted-fed sows, feeding twice daily resulted in decreased feeding motivation at 1900 h (P < 0.001) and at 0700h (P < 0.05) compared with feeding once daily, but not at 0900 and 1200 h, indicating that feeding twice daily reduced feeding motivation during the night compared with feeding once daily. Among restricted-fed sows, plasma concentrations of short-chain fatty acids (SCFA) were greater in sows fed high-fiber diets compared with the control (P = 0.02). Nonesterified fatty acid was least in sows on the control diet and greatest in sows on the potato diet, whereas sows on the pectin and sugar beet diets were intermediate (P < 0.001). Less diurnal variation in glucose (P < 0.001) was seen in sows on high-fiber diets. In spite of the found effects on plasma metabolites, the applied level of fiber in the diet of restrictedly fed sows did not reduce their feeding motivation irrespective of fiber source.     

Defaecation and weight of the gastrointestinal tract contents after feed and water withdrawal in broilers

1. Broilers were held under constant light for up to 24 h with access to feed and water, access to water only, or access to neither feed nor water. 2. Birds given continuous access to feed ate evenly over the 24-h period. Feed deprivation reduced drinking behaviour to about half of that when feed was available. Deprivation of feed, or of feed and water, had similar effects on defaecation and the reduction in the weight of the gut contents. It reduced the overall number of defaecations over the 24-h period to about 40% of that in birds given food and water, and the weight of the contents by about 75%. The maximum effect of deprivation on defaecation was seen after about 4 h, and on gut contents weight after about 12 h. 3. With longer fasting the contents of most parts of the gut, except the caeca, became wetter. 4. The findings may have implications for the practice of preslaughter food withdrawal to reduce the potential for soiling of the live birds and contamination of the carcase after slaughter. However, the likelihood is that relatively short overall feed deprivation times of not more than 8 to 12 h before killing may be desirable, but specifying firm recommendations on optimal feed withdrawal times requires further work.     

Selected pharmacokinetic parameters for Cefovecin in hens and green iguanas

The third generation cephalosporin cefovecin has been shown to have an exceptionally long elimination half-life in dogs and cats, making it suitable for antibacterial treatment with a 14-day dosing interval in these species. Pharmacokinetic parameters for cefovecin were investigated in juvenile hens and green iguanas, following subcutaneous injections with 10 mg cefovecin/kg bodyweight. Preliminary studies in eight additional species of birds and reptiles were performed and results were compared with the parameters found in hens and green iguanas. The kinetics were characterized by rapid absorption with peak plasma concentration of 6 ± 2 μg/mL in hens and 35 ± 12 μg/mL in green iguanas. The mean plasma half-life for cefovecin was 0.9 ± 0.3 h for hens and 3.9 h in green iguanas. Volume of distribution was 1.6 ± 0.5 L/kg for hens and 0.3 L/kg for green iguanas and clearance was 1252 ± 185 mL·h/kg for hens and 53 mL·h/kg for green iguanas. Results from preliminary studies did not differ notably from those seen in hens and green iguanas. Cefovecin is not suitable for the treatment of bacterial infections with a 14-day dosing interval in hens or green iguanas and seems not to be in a number of other bird and retile species either.     

Space use at night and social relationship between roosting partners in a large flock of laying hens

1. Laying hens in two aviary flocks of 1250 females and 12 males were investigated to determine if hens used the same roosting site more often than expected by chance and whether hens that roost next to each other for two consecutive nights (close groups) had fewer agonistic interactions than hens roosting far away from each other (distant groups) when put into a new environment in groups of 4 birds.

2. Hens showed a significant preference for using the same roosting site on consecutive nights. There was no difference between close groups and distant groups in agonistic interactions. However, in close but not distant groups, a low or high level of interaction on day 1 predicted a low or high level on day 2 that might reflect established relationships in the close groups.

3. It was concluded that hens prefer the same roosting site in the short term but further research is needed to investigate whether hens roosting next to each other recognise roosting partners or not.     

Effect of a change in environmental temperature on heat tolerance in laying fowl

Laying hens when transferred from accommodation at an ambient temperature (Ta) of 30 degrees C to one of 20 degrees C failed to acclimatise to intermittent heat stress (Ta 38 degrees C) commencing one day after the transfer. After 21 d of intermittent exposure to 38 degrees C these hens showed little or no increase in heat tolerance, whereas hens living constantly at either Ta 20 degrees C or 30 degrees C acclimatised normally. The failure to acclimatise was also observed when hens were transferred from Ta 30 degrees C to 5 degrees C but not when transferred from Ta 5 degrees C to 30 degrees C. The failure to acclimatise following transfer from a warm to a cool environment was accompanied by an increase in food intake; if food intake was not allowed to increase the hens acclimatised normally to heat stress.     

Effect of density and season on stress and behaviour in broiler breeder hens

1. We examined the effect of density (5, 7, 9 and 11 birds/m2) and season (summerand winter; different hens each season) on stress and behaviour in two flocks of 64 broiler breeder females divided among 8 pens. 2. The hens, approximately the same age and body mass in each season, were maintained on hard-packed ground, without litter, in an open-sided chicken house and were offered the same amount of food each season. 3. Mean house max/min temperatures varied between 18 and 33 degrees C in summer and 7 and 17 degrees C in winter. Mean relative humidity in summer varied between 68% at 08:00 h and 42% at 14:00 h and in winter was 64% at 08:00 h and 47% at 14:00 h. 4. No difference was found in heterophil:lymphocyte ratios among densities and between seasons; however, basophil numbers were higher in winter than in summer indicating prolonged stress in winter. 5. Stereotyped pecking increased with an increase in density and was higher in winter than in summer. Pecking on the ground was higher in winter, but was not affected by density. 6. In summer the hens spent more time lying and eating than in winter, whereas in winter the hens spent more time walking, preening and drinking than in summer. They spent the same amount of time standing in both seasons. None of these behaviours was density dependent. 7. We conclude that season had more of an effect than density on stress and behaviour in broiler breeder hens under the conditions of our study.