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Desexing (castrating, ovariectomizing/neutering) and a dog's sex are topics of relevance to many dog owners. We studied the relationship between desexing and three behaviors that are presumed sexually dimorphic, that is, differ in occurrence between the sexes. Urine marking, mounting, and roaming were used as models for studying the effects of desexing on (unwanted) behavior in dogs. We assessed the relationships between the occurrences of the three behaviors and the four factors of the dogs’ sex, sexual status, desexing age, and age in general. A convenience sample of dog owner reports was collected with an online survey and 982 records were analyzed with Chi-square tests. Counts were expressed in cross- tables of the behavior being present or absent and one of the aforementioned four factors. Urine marking occurred most frequently in intact male dogs (78%, N = 188), with significant differences compared with intact females (41%, N = 48; P < 0.001) and desexed males (66%, N = 202; P = 0.002). There was a trend for mounting occurring more frequently in intact males (25%, N = 60) compared with intact females (17%, N = 19; P = 0.085), and a significant difference between intact and desexed males (25%, N = 60 vs. 18%, N = 54; P = 0.043). Roaming occurred similarly in males and females, and in intact and desexed male dogs. For none of the three behaviors, there were differences between intact and desexed female dogs. In intact male dogs, age-related differences were found for the occurrence of mounting (39%, N = 29 of the dogs8 years) and roaming (46%, N = 34 of the dogs8 years). Such differences were not found for females or for urine marking in males. Mounting and roaming occurring less often in older male dogs suggest that these behaviors may decrease with age, naturally or through other factors. Our cross-sectional study shares with many earlier studies that its setup does not establish causal effects of desexing and we recommend large-scale prospective studies as a next step in providing scientific evidence for how behavior is affected by desexing. More knowledge of the influence of sex hormones on behavior in dogs is needed to support decisions on desexing individual dogs for reasons of unwanted behavior, which will benefit both the dogs and their owners.

The northern fowl mite (Ornithonyssus sylviarum) is a key pest for caged laying hens. High infestation levels can lead to anemia, reduced production, and mortality. Although the mites cause skin irritation and thus likely affect resting behavior, the nocturnal behavior of infested chickens has not yet been studied. We investigated the impact of mite infestation on nighttime behavior of 16 beak-trimmed White Leghorn hens. The hens were housed individually in wire cages. They were experimentally inoculated with approximately 35 mites at 25 weeks of age and observed for the behaviors dozing, sleeping, preening and being active. Continuous observations were made from video recordings taken from 22:00 h until 06:00 h for two consecutive nights at pre-infestation week 0 and post-infestation weeks 3, 5 and 7. Mite infestation levels were measured weekly on an 8-point scale (0 (no mites) to 7 (≥10,000 mites per hen)). For statistical analyses with linear mixed models, mite infestation levels were categorized as score 0 (no mites), 3–4 (51–500), 5 (501–1000) and 6–7 (>1000). Higher levels of mite infestation were associated with hens spending less time dozing (P < 0.001) and more time preening (P < 0.001) and being active (P = 0.012). Dozing decreased from 90% of the observed time for mite score 0 to 76% for score 6–7. Preening increased from 2% (score 0) to 9% (6–7) and time spent being active increased from 1% (0) to 7% (6–7). Mite infestation increased the number of uninterrupted bouts of all behaviors (P ≤ 0.020), especially dozing and preening (P < 0.001), suggesting restlessness in the mite-infested hens due to irritation and itching. The mite-infested hens’ increased nocturnal activity, including preening, as well as the fragmentation of behavioral activities together with decreased dozing, indicate disturbed resting behavior and suggest a reduction in the welfare of mite-infested hens.

Consistent owner-dog interaction patterns such as dog-directed parenting styles could reflect in the leash tension applied when walking a dog. Rein sensors are commonly used to measure tension applied to a horse's bit and our research aim was to evaluate the performance of this methodology for measuring leash tension. We evaluated the consistency of leash tension measurements in owner-dog dyads walking a food-distraction course and a more complex zigzag object-distraction course to confirm our prediction that the more challenging course would trigger increased leash tension. Leash tension sample points were averaged per owner-dog dyad per course, and we used restricted maximum likelihood to analyze leash tensions for effects of course difficulty and dog body weight. In 24 participating owner-dog dyads, leash tension was an average (±standard deviation) 18.29 ± 14.03 newtons. Leash tensions were 1.6 times higher (P < 0.001) during the more challenging second course than during the easier first one and variation between owner-dog dyads was consistent across the two courses (rank correlation of 0.63, P = 0.001, N = 24). Our findings support the usefulness of rein sensors for measuring leash tension, with potential applications in studies on the owner-dog relationship such as how leash exerted levels of control relate to dog-directed parenting styles.

Parents raise children in consistent ways, and these parenting styles affect child wellbeing and societal adjustment. Recently, we identified such parenting styles in the owner–dog relationship. Dog owners of the authoritarian- correction orientated (AUC) type stand out for demandingness. Authoritative dog owners adopt either an intrinsic-value orientated style (AUI), of high responsiveness and attention to a dog’s needs, or an authoritative-training orientated style (AUT) of high demandingness and responsiveness in teaching a dog how to behave socially. The causes for dog owners to favor certain dog- directed parenting styles are presently unknown. Orientations toward animals could play a role, and these have previously been determined in dog owners, capsulizing views on dog ownership. A dominionistic orientation values the dog for its utility, a humanistic orientation humanizes dogs, and a protectionistic orientation acknowledges the dog’s species-specific interests. We wanted to know how these views on dog ownership are associated with dog-directed parenting styles. Therefore, orientations toward animals and dog-directed parenting styles were determined from dog-owner reports collected online (n = 518). The Likert-scale items regarding the orientations toward animals were grouped using data reduction techniques. The scores for our newly formed orientations were then rank correlated to the dog-directed parenting styles, with all scores expressed as percentages of the theoretical maximum. A dominionistic orientation was associated with AUC, indicating that combined demandingness and non-responsiveness in dog-directed parenting partly results from the owner’s perceived need to dominate the dog. A humanistic/protectionistic orientation was associated with AUI, suggesting that the combination of parenting responsiveness and relatively low demandingness is an outcome of humanizing dogs. These findings support the idea that orientations toward animals partly underlie dog-directed parenting styles and may constitute a starting point for guiding owners away from less favorable dog-directed parenting styles.

Dog-directed parenting is an aspect of the owner-dog relationship that describes the overarching emotional sphere in which the dog's guidance and training take place. How dog-directed parenting styles express in specific owner-dog interactions is presently unknown. However, such knowledge can help to advise dog owners on appropriate parenting of their dog. Child-directed parenting is regarded appropriate when it is demanding for socially adaptive behaviour as well as responsive to the child's needs. This combination of high demandingness and responsiveness is known as authoritative parenting, which in dog-directed parenting manifests in two ways. Teaching the dog socially adaptive behaviour is key to the authoritative-training style (AUT) and being responsive to the dog's perceived needs and emotions is key to the authoritative-intrinsic style (AUI). A third dog-directed parenting style, the authoritarian-correction style (AUC), of high demandingness and low responsiveness focusses on correcting the dog's undesired behaviour. We determined these three dog-directed parenting styles by an online questionnaire and tested the styles for associations with owner and dog behaviours. The behaviours were scored as the owner-dog dyads walked a short course with distractions (treats and balls) that dogs should ignore (N = 40) or when they had a ten-minute break together (N = 36). Nine out of 49 behavioural observations, such as verbally praising or correcting the dog and leash tensions, related significantly (comparison-wise two-tailed P < 0.05) to the parenting styles and Spearman rank correlations explained up to 30 % of the variance. The self-report-based dog-directed parenting styles related logically to the way owners actually interacted with their dogs, verbally and by leash. AUI and AUT parenting related directly to verbally praising the dog. AUC parenting related directly to verbally correcting the dog and to leash tensions. Also, AUC parenting related inversely and AUT parenting directly to the dog frequently looking at its owner during the course with distractions. Thus, we find evidence that verbal communication and leash tensions are telling about dog-directed parenting styles and, possibly, constitute meaningful manifestations to address in educational interventions for dog owners. We see potential merit in moving AUC parenting dog owners away from leash-related guidance towards verbal praise-based guidance and a more authoritative dog-directed parenting style.

Behaviour test batteries are used to identify aggressive dogs. The Dutch Socially Acceptable Behaviour (SAB)-test has been used since 2001 to select against unwanted aggression and fear in specific dog breeds, though much is unknown yet regarding its reliability, validity and feasibility. In this paper the SAB-test is evaluated and the results describe its usefulness for identifying aggression towards humans in dogs. Behaviour test outcomes on 345 dogs (479 records on tests performed indoor and outdoor) scored by the judges of the Dutch Kennel Club were compared to owner reported assessments of their dogs’ behaviour prior to testing. Dogs were labelled aggressive when having bitten a human at least once according to the owner and were diagnosed by the judges as such when attacking at least once during the SAB-test. Aggressive dogs showed significantly more attacks than non-aggressive controls and a Principal Components Analysis of detailed observations on 76 dogs grouped aggressive behaviours like growl, bare teeth, snap, lunge and bite in one dimension, confirming the test's validity. Analysis of 479 test records revealed a sensitivity, specificity and accuracy of 0.33, 0.81 and 0.64, respectively. The specificity could be increased to 0.93 by raising the threshold for positive test results to at least 2 attacks during the test. The low sensitivity is explained by the decision to classify dogs as aggressive on the basis of one bite incident only and by a relative weak capacity of the test to detect specific forms of aggression. The reliability of the test was investigated by comparing test outcomes on 133 dogs when tested indoor and outdoor. The accuracy decreased from 0.67 to 0.62, but overall the indoor test outcomes were similar to those found outdoors. Scores for aggression and anxiety were significantly higher when dogs were tested for the first time in the morning than the second time in the afternoon, suggesting desensitization. Salivary cortisol concentrations in 20 dogs were not different in samples taken before and after the test, which oppose severe levels of stress. The SAB-test allows one to evaluate aggression in dogs, but present findings indicate that probably those that behave aggressively in the absence of fear remain undetected. It is recommended to increase the test's usefulness by refining or including new test components that target different forms of aggression. Formulating a risk assessment based on detailed information on a dog's behaviour during testing instead of simply producing a pass–fail judgement will facilitate a purpose specific use of the SAB-test.

Increases in genetic merit for milk yield are associated with increases in mobilization of body reserves. This study assessed the effects of genotype by environment (GxE) interactions on milk yield and energy and protein balances. Heifers (n = 100) with high or low genetic merit for milk yield were milked 2 or 3 times a day and received rations of low or high caloric density. The management factors were selected to induce substantial differences in milk production levels and model different management strategies. The 2 x 2 x 2 factorial arrangement enables the assessment of the effects of genotype, environment, and GxE interactions. Mean daily energy-corrected milk production in the first 100 d in milk varied between 21.8 and 35.2 kg among the groups. The experimental factors affected milk production in the presumed direction. Ration was the most determinant factor on milk production. Effects of milking frequency and genetic merit were significant only in the groups that were fed rations with high caloric density. Signs for severe negative energy balances, protein balances, and low body condition scores, all of which may be indicative of health risks, were not concentrated in the highest producing cows. Feed caloric density and milking frequency had stronger effects on energy balances and protein balances, with unfavorable effects of low caloric density feed and an extra milking. This emphasizes the possible effect of mismanagement on animal health risks. High genetic merit cows had significantly lower postpartum body condition scores. Genotype x environment interactions existed, but more information is needed to determine if cows of different genetic merit for milk yield are differently at risk for disease under specific conditions. High milk production levels per se will increase allostatic load, but need not compromise the health status of relatively young cows. Ongoing one-sided selection for high yield may be combined with good animal health, but because high genetic merit for milk yield seems intrinsically connected to the allocation of resources from maintenance toward milk, this puts increasing demands on farmers¿ time and management skills.

This paper considers the economic consequences and the welfare impact of foot disorders in dairy cattle and the association between them, taking into account clinical and subclinical foot disorders. In dairy farming with cubicle housing and concrete floors, foot disorders are a major welfare problem with serious economic consequences. On average, foot disorders cost €53 per cow per year, of which indirect cost factors are the main cause. Subclinical foot disorders, which are the foot disorders not recognised by dairy farmers, account for 50% of the total welfare impact and 32% of the total costs. The consequences of foot disorders can be difficult to observe and more insight into these consequences is helpful in stimulating actions to improve dairy cow foot health. Digital dermatitis (DD), an infectious foot disorder, is the most serious foot disorder from both an economic and welfare perspective. The correlation between economics and animal welfare impact suggests that reducing the problem of foot disorders from an economic perspective will positively influence the welfare of dairy cows. Insight into economic and welfare consequences of the different foot disorders, including the association between them, can help make dairy farmers more aware and help with decision-making regarding measures to improve dairy cow foot health. Keywords: animal welfare, dairy cattle, economics, foot disorders, modelling, welfare impact

Background The decline noticed in several fertility traits of dairy cattle over the past few decades is of major concern. Understanding of the genomic factors underlying fertility, which could have potential applications to improve fertility, is very limited. Here, we aimed to identify and study those genes that associated with a key fertility trait namely estrous behavior, among genes expressed in four bovine brain areas (hippocampus, amygdala, dorsal hypothalamus and ventral hypothalamus), either at the start of estrous cycle, or at mid cycle, or regardless of the phase of cycle. Results An average heat score was calculated for each of 28 primiparous cows in which estrous behavior was recorded for at least two consecutive estrous cycles starting from 30 days post-partum. Gene expression was then measured in brain tissue samples collected from these cows, 14 of which were sacrificed at the start of estrus and 14 around mid cycle. For each brain area, gene expression was modeled as a function of the orthogonally transformed average heat score values using a Bayesian hierarchical mixed model. Genes whose expression patterns showed significant linear or quadratic relationships with heat scores were identified. These included genes expected to be related to estrous behavior as they influence states like socio-sexual behavior, anxiety, stress and feeding motivation (OXT, AVP, POMC, MCHR1), but also genes whose association with estrous behavior is novel and warrants further investigation. Conclusions Several genes were identified whose expression levels in the bovine brain associated with the level of expression of estrous behavior. The genes OXT and AVP play major roles in regulating estrous behavior in dairy cows. Genes related to neurotransmission and neuronal plasticity are also involved in estrous regulation, with several genes and processes expressed in mid-cycle probably contributing to proper expression of estrous behavior in the next estrus. Studying these genes and the processes they control improves our understanding of the genomic regulation of estrous behavior expression.

Dog diets may differ in their effectiveness of maintaining satiety after a meal. Consequently, sensations of hunger, feeding motivation, physical activity, and sensitivity to environmental stressors may be increased. Dietary fibre may be effective in prolonging postprandial satiety depending on type and inclusion level. This study evaluated the effect of fibre fermentability on behaviour in dogs. Sixteen healthy adult dogs were housed individually and fed a low-fermentable fibre (LFF) diet containing 8.5% cellulose or a high-fermentable fibre (HFF) diet containing 8.5% sugar beet pulp and 2% inulin. Dogs were fed two equal portions at 8:30 and 18:30 according to energy requirements. Behaviour of dogs in their home-cage was recorded and analyzed by instantaneous scan sampling (2 × 24 h with 15 min intervals) and focal sampling continuous recordings (10 min per animal per hour, from 9:00 until 18:00). Dogs were subjected to a behaviour test composed of the subtests open-field, sudden-silence, novel-object, and acoustic-startle. The behavioural responses of each dog were recorded. Scores for the scan and focal samples were expressed per clock hour and DIET × TIME effects were tested statistically using Residual Maximum Likelihood (REML). Data from the tests were examined using principal component analysis resulting in the compilation of two components. Data were tested statistically for DIET and DIET × SUBTEST effects using REML. Variables specific for the open-field and novel-object test were analyzed using analysis of variance. For the scans, a significant DIET × TIME effect was found for resting. At night and in the morning, HFF dogs rested more compared to LFF dogs, but they rested less between 14:00 and 17:00. For the continuous recordings, the main findings were a tendency for DIET × TIME effect for time spent resting with a pattern consistent with that for the scans. The interaction was significant for inactive-alert (lie with head up or sitting) with HFF-fed dogs having lower values around 10:00–11:00 and higher values hereafter. Finally, time spent tail wagging was significantly higher for LFF-fed dogs just before the evening meal that may indicate higher level of arousal. For the behaviour tests, no significant DIET or DIET × SUBTEST effects were detected. It is concluded that compared to the LFF diet, the HFF diet increased inactivity in kennelled beagle dogs likely through the prolongation of postprandial satiety. This effect did not change the reaction to stressful events in kennelled laboratory dogs. Enhanced susceptibility to environmental stressors at times of hunger in sensitive companion dogs may occur but requires further study.

This study was part of a larger study that addressed whether milk production levels affect health risks in dairy cows as influenced by genetic merit for milk yield and management factors. Plasma samples were collected from 80 Holstein Friesian heifers at 2 weeks pre-partum and at 4 and 8 weeks post-partum in a 2 × 2 × 2 factorial arrangement design with the factors breeding value for milk production (high or low), milking frequency (2 or 3 times a day) and feed energy density (high or low). The following parameters indicative of the oxidative status were measured in plasma: ferric reducing ability of plasma (FRAP), α-tocopherol level, glutathione peroxidase activity (GSH-Px), superoxide dismutase activity (SOD), thiobarbituric acid reactive substances (TBARS) concentration and paraoxonase activity (PON). There was a significant effect of time for FRAP, α-tocopherol, GSH-Px and SOD, indicating changes in the plasma oxidative status around parturition. A high merit for milk yield, three-times-daily milking and especially feeding the high energy feed all stimulated milk production level. However, the influence on oxidative status parameters was minimal. Only the FRAP value was significantly lower in the high compared to the low energy group. Cows seem to undergo some oxidative stress around parturition, which can make them more susceptible to disorders. However, there were no clear indications that breeding value, milk frequency or feed energy level jeopardizes heifers in a way oxidative stress became critical.

Improving dairy cow fertility by means of genetic selection is likely to become increasingly important, since it is now well established that declining fertility cannot only be arrested by improved management. Profit margins per kg milk produced are decreasing, therefore farmers need to reduce cost and increase herd size. This restricts the labor input per cow and the disposable cost of getting a cow pregnant, whilst at the same time hormone treatments have become less acceptable. This makes it unlikely that additional management interventions will maintain fertility at acceptable levels in the near future. Genetic improvement seems the obvious solution. Effective selection tools are available in most Western countries using traditional breeding value estimation procedures. Also, in addition to gene assisted selection using individual genes or QTL, high throughput Single Nucleotide Polymorphism (SNP) technology allows genetic improvement of fertility based on information from the whole genome (tens of thousands SNP per animal), i.e. genomic selection. Simulation studies have shown that genomic selection improves the accuracy of selecting juvenile animals compared with traditional breeding methods and compared with selection using information from a few genes or QTL only. Research in the areas genomics and proteomics promise to make genetic selection even more effective. The genomic and proteomics technologies combined with the bioinformatics tools that support the interpretation of gene functioning and protein expression facilitate an exciting starting point for the development of new management strategies and tools for the improvement of reproductive performance.

International audience; Measuring HPA axis activity is the standard approach to the study of stress and welfare in farm animals. Although the reference technique is the use of blood plasma to measure glucocorticoid hormones (cortisol or corticosterone), several alternative methods such as the measurement of corticosteroids in saliva, urine or faeces have been developed to overcome the stress induced by blood sampling itself. In chronic stress situations, as is frequently the case in studies about farm animal welfare, hormonal secretions are usually unchanged but dynamic testing allows the demonstration of functional changes at several levels of the system, including the sensitization of the adrenal cortex to ACTH and the resistance of the axis to feedback inhibition by corticosteroids (dexamethasone suppression test). Beyond these procedural aspects, the main pitfall in the use of HPA axis activity is in the interpretation of experimental data. The large variability of the system has to be taken into consideration, since corticosteroid hormone secretion is usually pulsatile, follows diurnal and seasonal rhythms, is influenced by feed intake and environmental factors such as temperature and humidity, age and physiological state, just to cite the main sources of variation. The corresponding changes reflect the important role of glucocorticoid hormones in a number of basic physiological processes such as energy metabolism and central nervous system functioning. Furthermore, large differences have been found across species, breeds and individuals, which reflect the contribution of genetic factors and environmental influences, especially during development, in HPA axis functioning. Usually, these results will be integrated with data from behavioral observation, production and pathology records in a comprehensive approach of farm animal welfare.

Each year, millions of dogs worldwide are abandoned by their owners, relinquished to animal shelters, and euthanised because of behaviour problems. Nutrition is rarely considered as one of the possible contributing factors of problem behaviour. This contribution presents an overview of current knowledge on the influence of nutrition on canine behaviour and explores the underlying mechanisms by which diet may affect behaviour in animals. Behaviour is regulated by neurotransmitters and hormones, and changes in the availability of their precursors may influence behaviour. Tryptophan, the precursor of serotonin, may affect the incidence of aggression, self-mutilation and stress resistance. The latter may also be influenced by dietary tyrosine, a precursor to catecholamines. As diet composition, nutrient availability and nutrient interactions affect the availability of these precursors in the brain, behaviour or stress resistance may be affected. PUFA, especially DHA, have an important role as structural constituents in brain development, and dietary supply ofn-3 andn-6 PUFA could modify aspects of the dopaminergic and serotonergic system and, consequently, cognitive performance and behaviour. Finally, persistent feeding motivation between meals can increase stereotyped behaviour and aggression and decrease resting time. This feeding motivation may be altered by dietary fibre content and source. At present, few studies have been conducted to evaluate the role of nutrition in canine (problem) behaviour through the above mentioned mechanisms. Studies that explore this relationship may help to improve the welfare of dogs and their owners.

High milk production in dairy cattle can have negative side effects on health and fertility traits. This paper explores the genetic relationship of milk yield with health and fertility depending on herd environment. A total of 71,720 lactations from heifers calving in 1997 to 1999 in the Netherlands were analyzed. Herd environment was described by 4 principal components: intensity, average fertility, farm size, and relative performance indicating whether herds had good (poor) health and fertility despite a high (low) production. Fertility was evaluated by days to first service and number of inseminations (NINS); somatic cell score was used as a measure of udder health. Data were analyzed with a multitrait reaction norm model. Genetic correlation within traits across environments ranged from 0.84 to unity. Genetic correlations of the 3 traits with milk yield were antagonistic but varied over environments. Genetic correlation of milk yield with days to first service varied from 0.30 in small herds to 0.48 in herds with low average fertility. Correlations with NINS varied from 0.18 in large herds to 0.64 in high fertility herds, and with somatic cell score from 0.25 in herds with a high fertility relative to production to 0.47 in herds with a relative low fertility. Selection in environments of average value resulted in different predicted responses over environments. For example, selection for a decrease of NINS of 0.1 in an average production environment decreased milk yield by 35 kg in low production herds, but by 178 kg in high production herds.

Increasing milk yields in modern dairy cows cause concern that high yield may impair the cows' health and welfare, for example, via negative effects on metabolic status and hypothalamo-pituitary-adrenocortical (HPA) function. This study aims to investigate whether a high level of milk production, and the associated metabolic status, affects HPA function in dairy cows and changes their adaptive capacity. Additionally, it aims to establish whether possible effects of milk production level only show under challenging conditions. Holstein-Friesian cows, which produced on average 11,443 and 7727 kg of fat and protein-corrected milk (FPCM)/305 d in their previous lactation, were compared. During the dry period, the cows were fed to requirements or overfed. High milk yield and the concomitant large energy deficit were associated with 1) increased pituitary (re)activity, i.e., increased ACTH baseline concentrations and higher ACTH concentrations after corticotropin-releasing hormone (CRH) administration, and 2) decreased adrenocortical reactivity, i.e., lower cortisol responses after ACTH administration. Although significant, the effects of milk production level on HPA function were relatively small. Animals showed seemingly normal hormonal responses to CRH and ACTH administration. Also, cortisol baseline concentrations were unaffected. It seems, therefore, unlikely that the adaptive capacity of the high-producing cows was significantly impaired compared with their low-producing herdmates.

International audience; This study investigated the possible effects of milk production level on the host resistance of dairy cows. High ($n = 18$) and low ($n = 18$) producing cows on a research farm, which respectively produced 11 443 and 7 727 kg milk in their previous lactation, were compared. To enhance the possible differences in host resistance between high and low producing cows, the animals in both groups were metabolically stressed by overfeeding during the dry period or were fed according to requirements, resulting in four groups of nine cows. The metabolic status was monitored from two weeks pre-partum until 2.5-4.5 weeks post-partum. Host resistance was assessed by measuring the severity of experimentally induced Escherichia coli mastitis. Pre-partum blood glucose levels tended to be higher in overfed cows than in cows fed according to requirements. The post-partum energy balance was significantly more negative in high producing cows than in low producers, and tended to be more negative in overfed cows compared to cows fed according to the requirements. Post-partum plasma glucose, NEFA, $\beta$-OH-butyrate and urea concentrations were similar in the four groups. Plasma glucose concentrations were significantly lower and liver triacylglycerol concentrations were significantly higher in third than in second parity cows. Host resistance was not affected by the production level or feeding regimen. There were no significant correlations between the metabolic status and the severity of experimental E. coli mastitis, except for the relatively more severe mastitis in the cows with $\beta$-OH-butyrate concentrations above 1.4 mmol/L. In conclusion, milk production level did not affect host resistance in dairy cows, as measured by the severity of experimental E. coli mastitis. Even in a situation where cows were metabolically stressed by overfeeding, high producers were as able as low producers to cope with the demands of milk production, without consequences for host resistance.

Selection for a higher milk yield increases metabolic load via a higher yield per se and/or via physiological processes that facilitate milk yield, and it is difficult to differentiate between these two. Here, we aim to identify important pathways that contribute to the reduction in fertility following selection for higher yield. The associations between milk yield and fertility may run via pleiotropic effects, i.e. via functional pathways (for example related to intake), or linkage of genes and may involve changes in levels of hormones and metabolites. A number of studies have investigated the effects of genetic merit for milk yield on fertility, feed intake, energy balance and levels of metabolic and fertility hormones or metabolites. Differences in genetic merit were associated with differences in: (1) feed intake; (2) energy balance; and (3) plasma levels especially of GH, IGF-I, prolactin, progesterone, insulin, glucose, NEFAs and ketones. In the discussion we focus on the possible roles that energy balance, the growth hormone axis, and glucose together with insulin may have in the reduced fertility that is associated with high yield. The overall conclusion is that many minor pathways probably contribute, but that reduced metabolic fuel availability, rather than direct effects of hormone concentrations, is an important cause of poorer fertility with increasing genetic merit. (C) 2003 Elsevier B.V. All rights reserved.

The consumption of food goes beyond the basic provision of energy and essential nutrients for the maintenance of physical health. Studies in rats, pigs, and human subjects have shown that behaviour and mood can be influenced by specific nutrients consumed. The research described in this thesis aimed to evaluate the impact of dietary composition on two physiological systems involved in the regulation of canine behaviour. In other studies it has been shown that physical activity of pigs can be influenced by dietary fibre type, likely through sustaining satiety after a meal. It appears that the fermentable fibres can stimulate several mechanisms involved in sustaining satiety including the stimulation of the secretion of satiety-related metabolites by the gastrointestinal tract. Furthermore, hunger has been found to influence anxiety in rats. The current study evaluated the potential impact of dietary fibre types for effects on satiety and behaviour in dogs. Two in vitro fermentation studies were conducted to evaluate the microbial fermentation activity in the canine gastrointestinal tract and to screen the fermentability of various fibrous ingredients. Based on these in vitro fermentability data, two diets were formulated expected to differ in fibre fermentability in vivo. The difference in fibre fermentability between diets was confirmed in an in vivo study by evaluation of fibre degradation and concentrations of faecal short-chain fatty acids. In this latter study, the secretion of satiety-related hormones was found not to differ between treatment groups. Feeding dogs a high-fermentable fibre diet did result in a lower motivation to eat 6 hours after their morning meal and a lower activity in their home-kennel compared to dogs fed a low-fermentable fibre diet. Treatment groups did not differ in their responses to short-lasting challenges in a test arena conducted 5 to 7 hours after their morning meal. The second dietary strategy investigated was the use of the essential amino acid tryptophan, the precursor of the neurotransmitter serotonin in the brain. It has been shown that dietary tryptophan supplementation reduces anxiety in rats and increases resilience in dealing with stress in pigs. To investigate if similar effects would occur in dogs, a study was designed and conducted in mildly anxious privately-owned dogs fed diets differing in tryptophan content. Dogs were fed the study diet for 8 weeks using a randomised double-blinded, placebo-controlled design. Intake of the tryptophan supplemented diet increased plasma tryptophan concentrations by 37.4% and its ratio with large neutral amino acids by 31.2% compared to the control diet but the data reported by owners did not show a significant change in the behavioural of the dogs over time that could be attributed to the specific dietary treatment. More controlled behavioural tests conducted on a subset of dogs in both dietary treatment groups failed to show a significant difference of supplementation of the diet with tryptophan. In conclusion, the present work has shown that dietary fibre type can have an impact on canine behaviour through feeding motivation. The measured satiety-related metabolites were not affected by dietary fibre type indicating that other mechanisms were involved in sustaining satiety. Dietary supplementation of tryptophan had no effect on the behaviour of privately-owned dogs.