Effect of intermittent feeding, structural components and phytase on performance and behaviour of broiler chickens.

1. Two experiments were conducted to study the effect of intermittent feeding on performance and the efficacy of an exogenous phytase, and to assess whether intermittent feeding changed the activity pattern of broiler chickens. 2. Broiler chickens were given, either ad libitum or intermittently, a phosphorus deficient pelleted diet containing either coarsely or finely ground oat hulls and either no enzyme or a phytase added from 10 d of age, in a 2 × 2 × 2 factorial arrangement. Ad libitum feeding consisted of continuous access to feed in a room with 18 h of light and 6 h of complete darkness, whereas birds on intermittent feeding had restricted access to feed from 7 d of age, with 4 1-h feeding bouts/d and one 2-h feeding bout/d from d 14. 3. Performance, characteristics of the anterior digestive tract and phosphorus retention were assessed in experiment 1, while in experiment 2, birds were observed during 4-h periods to quantify different behaviours. 4. Intermittent feeding and phytase improved performance, but intermittent feeding did not improve the efficacy of the enzyme added. Ad libitum fed broiler chickens ate and drank on average twice per hour, and spent close to three-quarters of their time resting. Apart from an increased standing and feed searching activity for intermittently fed birds compared to ad libitum fed birds during the last hour before feed was presented, no differences in activity was detected. 5. It was concluded that broiler chickens quickly adapt to intermittent feeding without reduction in final body weight and with improvements in feed efficiency, but without improving the efficacy of dietary phytase. Only small changes occur in the behaviour of intermittently fed birds compared to ad libitum fed birds.

Stressed mothers - troubled offspring: a study of behavioural maternal effects in farmed Salmo salar.

Mature female Atlantic salmon Salmo salar were given intraperitoneal cortisol implants 1 week prior to stripping to examine the influence of simulated maternal stress on offspring boldness and social dominance. Behavioural tests originally designed to investigate stress responsiveness and coping styles in salmonids (i.e. feeding in isolation, dominance tests and acute confinement) were carried out on the offspring 1·5 years after hatching. In the feeding test, there were no differences between the two treatment groups in total feeding score or number of pellets eaten, but offspring from the cortisol-implanted females made more unsuccessful feeding attempts than offspring from control females. In dominance tests, there was no difference between controls and cortisol-treated fish regarding propensity to become socially dominant. A higher proportion of individuals with bite marks, however, was observed in the cortisol group when compared to controls. Cortisol-treated offspring that gained dominant rank in the dominance tests performed more aggressive acts after stable dominance-subordinate relationships were established compared to control winners. During acute confinement stress, offspring from cortisol-implanted females showed a reduction in the proportion of time they were moving compared to the controls. These results indicate that the maternal endocrine state at spawning affects several aspects of progeny behaviour potentially related to subsequent success and survival in farmed S. salar.

Melanin-based skin spots reflect stress responsiveness in salmonid fish.

Within animal populations, genetic, epigenetic and environmental factors interact to shape individual neuroendocrine and behavioural profiles, conferring variable vulnerability to stress and disease. It remains debated how alternative behavioural syndromes and stress coping styles evolve and are maintained by natural selection. Here we show that individual variation in stress responsiveness is reflected in the visual appearance of two species of teleost fish; rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar). Salmon and trout skin vary from nearly immaculate to densely spotted, with black spots formed by eumelanin-producing chromatophores. In rainbow trout, selection for divergent hypothalamus-pituitary-interrenal responsiveness has led to a change in dermal pigmentation patterns, with low cortisol-responsive fish being consistently more spotted. In an aquaculture population of Atlantic salmon individuals with more spots showed a reduced physiological and behavioural response to stress. Taken together, these data demonstrate a heritable behavioural-physiological and morphological trait correlation that may be specific to alternative coping styles. This observation may illuminate the evolution of contrasting coping styles and behavioural syndromes, as occurrence of phenotypes in different environments and their response to selective pressures can be precisely and easily recorded.

Alterations of the pituitary-gonadal axis in the neonatal blue fox (Alopex lagopus) exposed to prenatal handling stress.

Handling is a stressor for blue foxes. The influence of preterm handling (1 min daily) of vixens was investigated in 68, 10-day-old cubs, 34 male and 34 female. Body, gonadal and pituitary weight, ano-genital distance, gonadal testosterone and oestradiol content and in vitro production, and pituitary LH content were measured in all cubs. The gonads were frozen or incubated in vitro with, or without, added hCG (2.5 IU per sample). The gonadal incubates and homogenates were analysed for testosterone and oestradiol by radioimmunoassay and the pituitary homogenates for LH by immunofluorometric assay. The results indicate that neonatal fox gonads actively produce steroids and that there are significant sex differences in basal steroid production and response of the gonads to hCG, and in pituitary LH content. Maternal stress resulted in a significant reduction of morphometric and hormonal measures of the reproductive system in neonatal blue foxes, with more drastic effects in female cubs. Gonadal weights were lower in cubs of both sexes from stressed vixens (65.7+/-4.3 v 50.6+/-1.8 mg for the ovaries and 23.2+/-1.0 v. 17.7+/-1.0 mg for the testes, control v. stressed animals, P<0.01). The ano-genital distance in female offspring of stressed vixens was reduced (1.1+/-0.04 v. 0.9+/-0.03 cm, P<0.01). Basal ovarian oestradiol and testosterone production were decreased in cubs from prenatally stressed animals in comparison with controls (43.5+/-3.5 v. 32.6+/-3.7 pg ovary(-1) h(-1) and 0.40+/-0.16 v. 0.12+/-0.03 ng ovary(-1) h , P<0.05). Prenatal stress did not affect either pituitary weights or LH content in either sex. There were no significant differences in ano-genital distance, testicular content of testosterone, or in vitro testosterone production between control and treated male cubs. In conclusion, these findings suggest that prenatal handling stress impaired the neonatal reproductive development of the female offspring, but had no marked effects on males. Sex-specific effects of prenatal handling stress on the reproductive development in foxes may be linked with the gender differences in responses of the hypothalamus-pituitary-adrenocortical axis to stress conditions in this species.

Genetic analysis of litter size, parturition length, and birth assistance requirements in primiparous sows using a joint linear-threshold animal model.

The aim of this study was to investigate whether selection for number of live born piglets has led to prolonged parturition and increased requirement for birth assistance, resulting in increased numbers of stillborn piglets. Data were collected from 6,718 primiparous Norwegian Landrace sows farrowing between 2001 and 2003. The need for birth assistance was recorded as a binary response. Physical intervention in the birth of piglets and/or hormonal treatment by the farmer was recorded as birth assistance. The duration of the parturition was analyzed as a binary trait (<4 h and >4 h). The statistical model used for analysis included contemporary groups of herd-year, litter breed, season of farrowing, parity in which the sow was born, a regression on the age of sow at farrowing, an additive genetic effect, and a service sire effect. A full Bayesian approach via Gibbs sampling was adopted to estimate the genetic relationships between these four traits. A total chain length of 100,000 iterations was run. The first 10,000 samples were discarded as burn-in, and the remaining 90,000 iterations were retained without thinning for post-Gibbs analysis. The highest direct heritability was estimated for the number of live-born piglets (h2 = 0.07), followed by the duration of farrowing (h2 = 0.05), the need for birth assistance (h2 = 0.05), and the number of stillborn piglets (h2 = 0.04). The genetic correlations revealed that the number of live and stillborn piglets was uncorrelated; however, the number of live piglets born had a moderate genetic correlation to the need for birth assistance (rg = 0.24 +/- 0.01) and duration of farrowing (rg = -0.20 +/- 0.01), whereas the number of stillborn piglets was highly correlated to the need for birth assistance (rg = 0.74 +/- 0.01) and the duration of parturition (rg = 0.66 +/- 0.01). The duration of farrowing and the need for birth assistance were genetically highly correlated (rg = 0.89 +/- 0.00). For all traits, the service sire variance was approximately one quarter in magnitude compared with its respective genetic variance. The results showed that selection for the number of live born piglets is not expected to influence the number of stillborn piglets. Increasing the number of live piglets born through selection should have a slight negative effect on farrowing duration and a minor increase in the need for birth assistance. Sows with a high genetic potential for birth assistance and prolonged parturition were more likely to give birth to greater numbers of stillborn piglets.

A cautionary note regarding the use of nutritional L-tryptophan to alter aversion-related behaviour in mice.

Nutritional L-tryptophan is reported to have positive effects on the behaviour of several farm animals. The present experiment describes some effects of nutritional L-tryptophan on the aversion-related behaviour of male mice selected for high litter size. The behavioural effects of L-tryptophan were observed in the elevated plus-maze, the light/dark test and a resident-intruder test. The only significant effect was observed in the resident-intruder test, where the total occurrence of exploratory behaviour by the intruder was reduced by L-tryptophan treatment. The present experiment provides a cautionary note advising against supplementation with L-tryptophan to improve animal welfare before the consequences of such treatment are fully understood.

Social facilitation of predatory, sheep-chasing behaviour in Norwegian Elkhounds, grey.

Sheep grazing on unfenced mountain pasture may be attacked by loose dogs, which may chase and kill sheep and separate lambs from their mothers. We have earlier shown that testing dogs individually towards sheep with an electronic dog collar may effectively reduce the chasing propensity 1 year later. The aim of this study was to investigate whether and how a non-chasing and a chasing companion dog influence sheep chasing in test dogs (20 Norwegian Elkhounds, grey), and whether this varies with sex or age. The test dogs' predatory behaviour towards sheep was examined by observation of the dogs in a fenced enclosure with sheep in 5min tests together with, first, a non-chasing (Hamilton stoever, a hound breed) and 2-3 days later a chasing (Border collie) companion dog. Physical contact with sheep was prevented. Initially, the test dogs exhibited a higher chasing motivation towards sheep in tests with a chasing, as compared with a non-chasing, companion (P<0.001). During the entire test, 60% of the dogs attacked sheep when accompanied by the non-chaser. All dogs attacked sheep when the chasing companion was present (P=0.008), although in only 8 of 20 cases the companion dog chased simultaneously with the test dog. In the chasing-companion tests, the attack latency was shorter (P<0.001) than in tests with a non-chasing companion. The attack severity was higher when attacking alone than when attacking together with the chasing companion (P=0.033). In these tests, the higher the attack severity, the shorter was the attack latency (P=0.006). A sequence analysis on chasing-companion tests showed that test dogs generally started with observing or showing interest in sheep, followed by attacks, which increased in severity. No sex differences were observed. In non-chasing companion tests, dogs aged up to 2.5 years exhibited a weaker initial hunting motivation than older dogs (P=0.025), but during the entire test were more inclined to attack (P=0.019). Taken together, our findings indicate that a companion dog showing intentions of predatory behaviour stimulates predatory chase in another dog, while a non-chasing companion has a limited influence on this. In tests certifying dogs for their refrainment of chasing sheep, well trained Border collies approaching sheep on command might be used to reveal the full predatory potential of the dog being tested.

Behavioural differences between three breed groups of hunting dogs confronted with domestic sheep.

When running free in open fields, domestic dogs occasionally display predatory behaviour towards domestic sheep. This has not yet been studied scientifically. The aim of the present study was to investigate the inclination to chase sheep in three breed groups of hunting dogs that are most frequently used in areas with grazing sheep. We studied 41 elkhounds, 29 hare hunting dogs and 68 English setters. Behaviours indicative of motivation for chasing or attacking sheep were examined in three different ways. A path test examined functional traits such as hunting ability, contact willingness, reactivity to sudden noise, and response towards a lone sheep. In a sheep confrontation test, loose-leashed dogs were observed in a fenced enclosure with sheep and given electric shocks through an electronic dog collar if within 1-2m from the sheep. A questionnaire to the dog owners supplied information on their dog's previous experience with sheep and behavioural responses to various types of novel stimuli. No significant sex differences were found. The elkhounds showed the highest interest in a lone sheep in the path test, and displayed the highest initial hunting motivation, the highest percentage of dogs starting a sheep attack, the highest attack severity, and were most frequently given el. shocks. The hare hunting dogs were intermediate, while setters showed the lowest values for these variables. Dogs reported as showing low fearfulness more frequently acted as potential sheep chasers in the tests. Dogs up to 3 years of age showed a more pronounced initial hunting motivation and more frequent attacks than older dogs, although there were no age differences in the number of el. shocks given in the test. The latter may be related to the more frequent abruption of attacks among younger dogs. The main factors predicting a high hunting motivation and attack severity were lack of previous opportunity to chase sheep, low fearfulness towards gunshots and unfamiliar people, and general interest in sheep shown when encountering them. Probability of sheep chasing differed between dog breeds and age groups. Previous experience and certain character traits were indicative of a high predatory motivation towards sheep.

Behavioural changes and aversive conditioning in hunting dogs by the second-year confrontation with domestic sheep.

Domesticated dogs occasionally exhibit predatory behaviour towards domestic sheep when running loose in pasture. Both young and old dogs of either sex may chase sheep. Electronic dog collars applying electric shocks are utilised as one method of training dogs to refrain from attacking sheep. This device is used for a number of other training purposes which have raised concern for the welfare of the dogs being trained. This study aims at testing long-term learning effects of previous sheep tests on sheep chasing in hunting dog breeds (Norwegian elkhounds (grey), English setters, and hare hunting dogs), in particular with use of electronic dog collars, in addition to uncovering potential secondary negative effects on dogs' behaviour and mental stability. The dogs (N=114) were subjected to three tests for two subsequent years, the second year being reported here. Dogs were tested for reactions to different stimuli, including a sheep, in a path test. In a sheep confrontation test, dogs were fenced in with a sheep group and given el. shocks when approaching 1-2m from sheep. A questionnaire to the dog owners reported differences in dogs' behaviour between the years.Dogs showed weaker or delayed behavioural responses in both tests in the second year. No dogs showed interest in or attacked a lone sheep in the path test in the second year, while almost two thirds of them did so the first year. In the sheep confrontation test, the dogs exhibited comparatively hesitant initial hunting motivation the second year, being more evident in dogs which received el. shocks the first year. No dogs chased or attacked sheep as their first response in this test, while half of them did so the first year. The proportion of dogs attacking sheep during the entire test was reduced to almost one fourth. The number of el. shocks administered reduced by the second year, and only one of the dogs that received el. shocks the first year received el. shocks the second year. The owners reported no negative effect on the dogs' behaviour during the year ensuing el. shock treatment. Eighteen of the 24 dogs reported by owners to exhibit behavioural changes lost their previous interest in sheep.The second-year tests indicate that aversive conditioning with the use of electronic dog collar may be an efficient method for reducing the probability of a dog chasing or attacking grazing sheep. No adverse effects were observed with our test procedure.

Behavioural evaluation of methods for assessing fear responses in weaned pigs.

Models of anxiety and fear of novelty were evaluated using correlations and principal component analysis. A total of 84 pigs (LandracexYorkshire) from nine different litters were subjected to a tonic immobility (TI) test at the age of 2.5 weeks, an elevated plus-maze (EPM) at the age of 6 weeks, a light/dark (L/D) exploration test at the age of 7 weeks and an open-field (OF) test at the age of 8 weeks.The first component from the principal component analysis had the highest correlation with number of entries into open arms in the EPM but was also highly correlated to variables from the other three tests confirming a common aversion-related element in the four experimental tests. The second component was negatively correlated with percent entries into and time spent on open arms in the EPM, but positively correlated with the number of entries into closed arms in the same test, number of lines crossed in the OF and time spent in the lit compartment of the L/D test. The last point illustrates a negative relationship between "anxiety" and "activity" in the EPM and OF. To achieve purer measures of fear of novelty and activity in the tests, the components were rotated using the Varimax criterion. The rotated factor pattern demonstrated a simple structure where variables related to "anxiety" or "fear of novelty" (i.e., percent entries into open arms and time spent on open arms of the EPM) had the highest loading on factor 1, whereas variables related to activity (i.e., number of entries into the closed arms in the EPM, number of lines crossed in the OF and time spent in the lit compartment of the L/D test) had the highest loading on factor 2. TI duration loaded more strongly on factor 1 ("fear of novelty") than on factor 2 ("activity"), but did not represent any pure measure of either fear of novelty or activity.In conclusion, all of the test variables were related to one another. Open-arm avoidance represented the purest measure of fear of novelty, whereas entries into closed arms and number of lines crossed in the OF were the purest measures of activity. The EPM appeared to provide the best way to separate the fear of novelty and activity-related elements, indicating that the EPM may be a useful behavioural model of fear of novelty or avoidance in pigs.

Variation in behavioural responses of ewes towards predator-related stimuli.

Thirty-two groups of six sheep, classified into three breed categories according to their weight class (L: light, one breed (n=7); M: medium light, two breeds (n=10); H: heavy, three breeds (n=15)) were tested for antipredatory behaviour towards seven stimulus regimes. Tests were performed on 2-5-years-old ewes with lambs inside standardised and fenced home pastures. Stimulus regimes were: man in rain poncho, trolley, ball on trolley (blind stimuli), stuffed wolverine on trolley, stuffed lynx on trolley, stuffed bear on trolley, and man in rain poncho with a dog on leash (carnivore stimuli). The L breed showed the longest recovery time, the longest flight distance and the tightest flocking behaviour. Significant regressions indicate that there were negative linear relationships between sheep weight and recovery time and between sheep weight and flight distance. Carnivore stimuli caused longer recovery times (P<0.001) and longer flight distances (P<0.001) than the blind stimuli. Our results confirm the hypothesis that lighter sheep breeds display stronger antipredatory reactions than heavier breeds.

The effects of weight asymmetry and resource distribution on aggression in groups of unacquainted pigs.

The relationship between weight asymmetry and aggression when mixing groups of unacquainted pigs in two different environments was investigated. Ten groups of 4 female (LandracexYorkshire), unacquainted pigs with a weight asymmetry of 3.1+/-0.2 kg (mean weight: 16.6+/-0.6 kg) between each pig, and another 10 groups with a weight asymmetry of 1.2+/-0.1 kg (mean weight: 14.1+/-0.1 kg), were mixed at the age of 7 weeks. Ten of the groups (five of each) were mixed in an experimental pen with a heterogeneous distribution of straw. The pen consisted of two main compartments with straw in one of them, and a passage area with concrete floor in between. The other 10 groups were mixed in the same pen, but with a homogenous distribution of straw (straw spread all over the pen).The results showed that fighting duration was significantly shorter in groups with large weight asymmetry than in groups with small weight asymmetry irrespective of the environment. The number of bites delivered during the fights in the heterogeneous environment was lower in groups with large weight asymmetry than in groups with small weight asymmetry. In the homogenous environment, however, there was no significant difference between groups with large and small weight asymmetries regarding the number of bites. The combination of a limited straw area and a small weight asymmetry resulted in the greatest number of bites. In groups with large weight asymmetry, the largest pig won around 50% of the fights, and 25% of the variation in the percentage of fights won was explained by the weight asymmetry.In groups with small weight asymmetry, less than 10% of the variation in the percentage of fights won could be explained by weight asymmetry. The two largest pigs delivered significantly more bites and spent significantly more time fighting than the smallest pig. The second largest pig received significantly more bites and body lesions than the smallest pig in the groups. Fights between the two largest pigs had a significantly longer duration than when other pigs were involved. The results were discussed in relation to sequential assessment theory and resource defence theory.

Effects of diazepam on the behaviour of weaned pigs in three putative models of anxiety.

The present study examined the effects of diazepam (a widely used anxiolytic benzodiazepine) on the behavioural response of pigs to three novel experimental situations used to measure anxiety-related behaviour in rodents. Twelve weaned pigs (two pairs from each of the three litters) were tested in an elevated plus-maze at the age of 6 weeks, a light/dark test at the age of 7 weeks and an open-field test at the age of 8 weeks. Six of the pigs were pre-treated with diazepam (valium) and the other six with saline (control). In the elevated plus-maze, diazepam-treated pigs had a higher number of entries into open arms (P=0.04), spent more time on open arms (P=0.07), and had a higher number of total arm entries (P=0.05) than pigs from the control group. However, diazepam had no significant effects on behaviour in the light/dark test (i.e., latency to enter lit compartment, number of entries into lit compartment and the time spent in lit compartment) or the open-field test (i.e., number of lines crossed, number of entries into centre). In summary, the anxiolytic effects of diazepam on the pigs' behaviour were only demonstrated in the elevated plus-maze, where the time spent on open arms and the number of entries into open arms could be interpreted as measures of anxiety in pigs.

No effect of variation in handling on behaviour in a porcine elevated plus-maze - a brief report.

The elevated plus-maze is a widely used model of anxiety in rodents and has recently been suggested as a putative model of anxiety or fear in swine. The aim of the present experiment was to examine the effects of a pretest blood sampling procedure on the behaviour of weaned pigs in an elevated plus-maze. Animals in the control group were lifted one-by-one into a transport trolley and moved to the test apparatus, where they were observed for a 5-min period. The treatment group differed from the control group in that these animals were immobilized with a nose snare and a blood sample was extracted from the jugular vein prior to transport to the test room. Behaviour in the porcine elevated plus-maze did not differ significantly between the two handling procedures.

Effects of handling and physical restraint on rectal temperature, cortisol, glucose and leucocyte counts in the silver fox (Vulpes vulpes).

The present paper describes the effects of handling and one hour of physical restraint on rectal temperature (Trec), plasma cortisol, plasma glucose and leucocyte counts in six 8-months old silver fox vixens (Vulpes vulpes). Mean Trec in silver foxes 5 min after capture was 40.1 degrees C and increased during restraint, showing a maximum of 40.8 degrees C at 30 min thereafter. Supplementary, deep body temperature (Tb) was recorded with surgically implanted biotelemetry devices in 6 adult silver fox vixens kept isolated from environmental disturbances in a barn. Mean Tb in these foxes ranged between 38.0-38.4 degrees C, showing a diurnal variation and being at the lowest between 0700-1600 hour. When a person approached a fox and was present for 5 min, Tb increased rapidly. The results indicated that a stress-induced hyperthermia (SIH) was evoked rapidly within the first registration at 5 min after capture, and that this response continued during one hour of physical restraint. Plasma glucose and plasma cortisol levels increased during one hour of physical restraint, whereas numbers of lymphocytes, total white blood cell counts, and total granulocytes decreased. Furthermore, previously reported base levels of plasma cortisol and plasma glucose were exceeded. The results indicate that the hypothalamic-pituitary-adrenal (HPA) axis and the sympathoadrenal medullary (SAM) system were activated within 5 min of handling and restraint. Furthermore, hyperthermia is a promising indicator of acute stress in silver foxes.

[Effect of prenatal stress on the pituitary-adrenal axis in blue foxes]. / Vliianie prenatal'nogo stressa na gipofizarno-nadpochechnikovuiu sistemu u pestsov.

Handling is a source of stress for farm bred blue foxes. The influence of handling during the late gestation period on the pituitary--adrenal axis was studied in 10-day old male and female blue foxes. Cortisol and progesterone were measured by radioimmunoassay in the plasma, adrenal homogenates, and in vitro incubates from animals of both sexes. Adrenals were incubated in vitro in the absence or presence of ACTH. In addition, the adrenal weight and plasma concentration of ACTH were assessed. In cubs of both sexes, the adrenal weight was decreased after prenatal stress. The plasma concentration of progesterone and the adrenal cortisol in vitro production were elevated in the prenatally stressed female cubs, as compared to the control, along with the adrenal progesterone in vitro production in prenatally stressed male cubs. The adrenal cortisol and progesterone content and plasma ACTH and cortisol concentrations were not affected by prenatal stress. In conclusion, the results of this study suggest that the prenatal stress induced by handling pregnant vixens can affect the pituitary--adrenal axis in neonatal offspring, this effect being more pronounced in female cubs.

[The effect of prenatal stress on steroidogenesis in the gonads of Arctic foxes (Alopex lagopus)]. / Vliianie prenatal'nogo stressa na steroidogenez v gonadakh pestsov.

Handling is a source of stress for farm-bred blue foxes. The influence of handling during the late gestational period was investigated in 10-day old male and female blue foxes. Testosterone and estradiol were measured by RIA in the plasma, gonadal homogenates and in vitro incubates from blue foxes of both sexes. The gonads were incubated in vitro without or with human chorionic gonadotropin. In cubs of both sexes, the gonad weights and ovarian estradiol production were decreased by stress. The testicular testosterone and ovarian estradiol contents were increased in prenatally stressed cubs as compared to the controls. The testicular content and baseline in vitro production of testosterone were not affected by prenatal stress, but the testicular response to human chorionic gonadotropin was higher in the stressed group. This study suggests that prenatal stress induced by handling pregnant vixens may influence gonadal steroidogenesis and this effect was more pronounced in female cubs.

Effects of housing conditions during the rearing and laying period on adrenal reactivity, immune response and heterophil to lymphocyte (H/L) ratios in laying hens.

This study was conducted to evaluate the effect of early rearing conditions on physiological, haematological and immunological responses relevant to adaptation and long-term stress in white Leghorn hens with intact beaks housed in furnished cages (FC) or conventional cages (CC) during the laying period. Pullets were cage reared (CR) or litter floor reared (FR). From 16 to 76 weeks of age, hens were housed in FC (eight hens per cage) or in CC (three hens per cage). As measures of long-term stress at the end of the laying period, adrenal reactivity was quantified by assessing corticosterone responses to adrenocorticotropin challenge, and immune response was assessed by measuring antibody responses after immunization with sheep red blood cells (SRBC) and keyhole limpet haemocyanin (KLH). Heterophil to lymphocyte (H/L) ratio was employed as an indicator of stress. Rearing conditions significantly affected anti-SRBC titres (P < 0.0001) and tended to affect H/L ratios (P = 0.07), with the highest values found in FR hens. Layer housing affected H/L ratio (P < 0.01); the highest ratio was found in FR birds housed in FC during the laying period. This study shows that early rearing environment affects immunological indicators that are widely used to assess stress in laying hens. However, while results on H/L ratio indicated that FR birds experienced more stress particularly when they were housed in FC during the laying period, the immune responses to SRBC in FR hens was improved, indicating the opposite. This contradiction suggests that the effects on immune response may have been associated with pathogenic load due to environmental complexity in FR and FC hens rather than stress due to rearing system or housing system per se.

Genetic analysis of age at first service, return rate, litter size, and weaning-to-first service interval of gilts and sows.

The aim of this study was to estimate genetic parameters of seven traits related to sow reproductive performance. Data on all Norwegian Landrace pigs (NL) born in nucleus herds and raised in nucleus or multiplying herds from 1990 to 2000 were extracted from the Norwegian national recording scheme. Reproductive traits investigated were age at first service (AFS), return rate in gilts (RRg), age at first farrowing (AFF), live-born piglets in the first litter (NBA1), interval from weaning to first service after first litter (WTS1), return rate after first litter (RR1), live-born piglets in the second litter (NBA2), and interval from weaning to first service after second litter (WTS2). After editing, the data set comprised 12,583 to 56,042 records, depending on the trait. A mixed linear and a joint linear threshold animal model were used to estimate (co)variance components. A full Bayesian approach via Gibbs sampling was adopted. The statistical model used for analysis included contemporary groups of herd-year (-season), purebred or crossbred litter, single or double insemination, mating type, parity in which the animal was born, a regression on lactation length, and an additive genetic effect. Neither the estimated heritabilities nor the genetic correlations differed much between the two approaches, but there was a tendency for higher genetic correlations using the joint linear threshold model approach. Average heritabilities were as follows: AFS = 0.31; RRg = 0.03; RR1 = 0.02; NBA1 = 0.12; NBA2 = 0.14; WTS1 = 0.08; and WTS2 = 0.03. The highest genetic correlations were estimated between NBA1 and NBA2 (r(g) = 0.95), RR1 and WTS1 (r(g) = 0.93), and between WTS1 and WTS2 (r(g) = 0.78). The estimated genetic correlation between NBA and WTS were close to zero. Selection for increased NBA will slightly increase AFS and reduce the probability of a return. Selection for decreased AFS will have a favorable effect on WTS intervals; however, selection for decreased AFS seems to have an unfavorable effect on return rate both on gilts and sows. Conversely, selection for decreased WTS intervals will reduce the probability of a return. Potential selection candidates to include in a multivariate fertility index are AFS, NBA, and WTS1. Due to the low heritability and low, but favorable, genetic correlations to NBA and WTS, RR is not recommended as a selection candidate.