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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.

Behavioural testing allows to exclude dogs that are fearful and aggressive from the breeding population, but relatively little is known about the effectiveness of such strategies in practice. From 2001 till 2009 parent purebred Dutch Rottweilers had to pass the Socially Acceptable Behaviour (SAB)-test for their offspring to obtain a pedigree certificate. We evaluated if this breeding policy of excluding fearful and aggressive Rottweilers, as diagnosed by the SAB-test, indeed reduced the prevalence of fear and aggression in the Dutch Rottweiler population. Owner-reported assessments of their dogs' behaviour were compared between groups of Rottweilers with or without pedigree certificates, assuming the Rottweiler look-a-likes to represent the control condition of no breeding policy regarding fear and aggression. A total of 822 Rottweiler owners filled out the Canine Behavioural Assessment and Research Questionnaire (C-BARQ) on problem behaviour, including 7 behavioural categories related to fear and aggression. Problem behaviour prevalence and explanatory factors were investigated by multivariable logistic regression.The prevalence of Stranger-directed fear (P.

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.

Reduced oestrus behaviour expression or its absence (silent oestrus) results in subfertility in high-producing dairy cows. Insight into the genomic regulation of oestrus behaviour is likely to help alleviate reproduction problems. Here, gene expression was recorded in the ventral tegmental area (VTA) of high milk production dairy cows differing in the degree of showing oestrus behaviour (H - highly expressing versus L - lowly expressing), which was then analysed. Genes regulating cell morphology and adhesion or coding for immunoglobulin G (IgG) chains were differentially expressed in VTA between cows around day 0 and 12 of the oestrus cycle, but only in cows that earlier in life tended to show high levels of oestrus behaviour (H0 versus H12). The comparisons between H and L groups of cows also revealed differential expression of several genes (e.g. those of the IgG family or encoding for pro-melanin-concentrating hormone). However, any significant changes in VTA genes expression were detected in the comparison of L0 versus L12 cows. Altogether, the genes expression profile in VTA of cows highly expressing oestrus behaviour changes together with phases of the oestrus cycle, while in case of cows expressing oestrus behaviour lowly it remains stable. This supports the existence of genomic regulation by centrally expressed genes on the expression of oestrus behaviour in dairy cows.

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.

Milk progesterone profiles were determined from samples obtained twice weekly for 100 d postpartum in 100 Holstein primiparous cows at a Dutch experimental farm. Three treatments were applied in a 2 x 2 x 2 factorial arrangement with high-low genetic merit for overall production, high-low caloric density diet, and 2-3 times milking/day as factors. Milk progesterone profiles were characterized by start of first ovarian cyclical activity (commencement of luteal activity, C-LA), length and peak milk progesterone concentration of first ovarian cycle, and number of ovarian cycles in first 100 d postpartum, as well as classified into normal, delayed, prolonged, and interrupted ovarian cyclical activity. Cows with a greater milk production had lower peak progesterone concentrations, especially if the high milk production was caused by milking 3 times a day. A more negative energy and protein balance was associated with later C-LA and less ovarian cycles within 100 d postpartum. Relationships between protein balance and C-LA differed between cows with a high genetic merit and a low genetic merit. Cows with a high genetic merit for production showed delayed C-LA with more negative protein balances, whereas this association was not observed among cows with a low genetic merit. Cows in negative energy balance had greater risk for prolonged ovarian cycles when there was no delay in C-LA than when C-LA was delayed.

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.

Milk production per cow has increased significantly as a result of breeding, feeding, and other management factors. This study aims to address concerns about udder health risks for low- and high-producing dairy cows. In a 2 x 2 x 2 factorial design, Holstein-Friesian heifers (n = 100) of low or high genetic merit for milk production, milked 2 or 3 times a day, and fed a mixed ration with low or high energy content, were compared during the first 14 wk of lactation. Milk composition and cell counts were determined weekly; quarter milk samples for bacteriology were taken in wk 2, 8, and 14; and teat condition was scored in wk 2, 6, 10, and 14 during the experiment. The experimental factors resulted in substantial differences in milk production between treatment groups (24.1 for low vs. 25.6 kg/d for high genetic merit; 23.3 for 2 times vs. 26.5 kg/d for 3 times daily milking; and 20.9 for low-energy ration vs. 29.0 kg/d for high-energy ration). Ration composition was the most important determining factor for milk production, but did not affect cell counts or intramammary bacterial infections, although cows that received low-energy rations had rougher teat ends than cows receiving high-energy rations. This indicates that high production itself is not a major risk factor for udder health in the first lactation. A higher milking frequency impaired teat condition and improved cell counts in general, but did not clearly influence bacteriological status. High genetic merit was related to higher cell count, more Staphylococcus, and less Bacillus and other environmental pathogens in cultures and did not affect teat condition. The effects of milking frequency and feeding on udder health were similar for cows with high and low genetic merit. Genetic selection on milk production, without taking udder health into account, reduces udder health. As a result, maintaining udder health will require increasing the skills and time of dairy farmers who have to divide their attention to more cows when farm sizes increase, or selection should put more emphasis on udder health traits.

Stress parameters that can be measured noninvasively may help to identify poor welfare in dogs that live in private homes and institutions. Behavioural parameters are potentially useful to identify stress, but require further investigation to establish which behaviours are appropriate. In the present study, behaviours were recorded and analysed for signs of acute stress in dogs. Simultaneously, saliva cortisol and heart rate were measured to support the interpretation of the behavioural data with regard to stress. Ten dogs of either sex, different ages and various breeds were each subjected to six different stimuli: sound blasts, short electric shocks, a falling bag, an opening umbrella and two forms of restraint. Each type of stimulus had been selected for its assumed aversive properties and was administered intermittently for 1 min. The stimuli that could not be anticipated by the dogs, sound blasts, shocks and a falling bag, tended to induce saliva cortisol responses and a very low posture. The remainder of the stimuli, which were administered by the experimenter visibly to the dog, did not change the cortisol levels but did induce restlessness, a moderate lowering of the posture, body shaking, oral behaviours, and to a lesser extent, yawning and open mouth. Pronounced increases in the heart rate were nonspecifically induced by each type of stimulus. Heart rate levels normalized within 8 min after stressor administration had stopped. Saliva cortisol levels decreased to normal within the hour. Correlations between behavioural and physiological stress parameters were not significant. From the present results, we conclude that in dogs a very low posture may indicate intense acute stress since dogs show a very low posture concomitant with saliva cortisol responses. Dogs may typically show increased restlessness, oral behaviours, yawning, open mouth and a moderate lowering of the posture when they experienced moderate stress in a social setting. The nonspecific character of canine heart rate responses complicates its interpretation with regard to acute stress.

Poor housing conditions, harsh training sessions and uncontrollable or unpredictable social environments are examples of the situations that may lead to reduced welfare status in dogs. Individuals that suffer from poor welfare presumably experience stress and may consequently exhibit stress responses. In order to evaluate stress responses as potential indicators of poor welfare in dogs, we review studies dealing with dogs subjected to stressors. The reported stress responses are categorized as being behavioural, physiological or immunological, and demonstrate the various ways stress is manifested in the dog. Stressors such as noise, immobilization, training, novelty, transport or restricted housing conditions have been reported to elicit responses in behavioural, cardiovascular, endocrine, renal, gastro-intestinal, and haematological parameters. These and other parameters that change during stress may thus be indicative of poor welfare. However, several sources of misinterpretation have to be considered before stress responses may be used as valid indicators of welfare. Although analogous to the human situation, especially chronic stress may impair welfare, most studies deal with acute stress and do not address chronic stress and related phenomena. Adaptation may counteract the initial stress response and render parameters of acute stress useless for assessing chronic stress. Adaptations to stress are thus in themselves indicative of reduced welfare. Such adaptations may be discovered by challenging a stress responsive system. Additional studies are recommended to investigate acute stress parameters as possible indicators of chronic stress. Differences in stressor properties and in individual characteristics of dogs introduce variability in stress responses. Such variability will complicate a valid interpretation of stress responses with regard to welfare. Obtaining and applying fundamental knowledge of stress responses in dogs and measuring more than one stress parameter are proposed to minimize the risk of misinterpreting measurements of stress.

Subfertility has negative effects for dairy farm profitability, animal welfare and sustainability of animal production. Increasing herd sizes and economic pressures restrict the amount of time that farmers can spend on counteractive management. Genetic improvement will become increasingly important to restore reproductive performance. Complementary to traditional breeding value estimation procedures, genomic selection based on genome-wide information will become more widely applied. Functional genomics, including transcriptomics (gene expression profiling), produces the information to understand the consequences of selection as it helps to unravel physiological mechanisms underlying female fertility traits. Insight into the latter is needed to develop new effective management strategies to combat subfertility. Here, the importance of functional genomics for dairy cow reproduction so far and in the near future is evaluated. Recent gene profiling studies in the field of dairy cow fertility are reviewed and new data are presented on genes that are expressed in the brains of dairy cows and that are involved in dairy cow oestrus (behaviour). Fast-developing new research areas in the field of functional genomics, such as epigenetics, RNA interference, variable copy numbers and nutrigenomics, are discussed including their promising future value for dairy cow fertility.

Selection in dairy cattle for a higher milk yield has coincided with declined fertility. One of the factors is reduced expression of estrous behavior. Changes in systems that regulate the estrous behavior could be manifested by altered gene expression. This literature review describes the current knowledge on mechanisms and genes involved in the regulation of estrous behavior. The endocrinological regulation of the estrous cycle in dairy cows is well described. Estradiol (E2) is assumed to be the key regulator that synchronizes endocrine and behavioral events. Other pivotal hormones are, for example, progesterone, gonadotropin releasing hormone and insulin-like growth factor-1. Interactions between the latter and E2 may play a role in the unfavorable effects of milk yield-related metabolic stress on fertility in high milk-producing dairy cows. However, a clear understanding of how endocrine mechanisms are tied to estrous behavior in cows is only starting to emerge. Recent studies on gene expression and signaling pathways in rodents and other animals contribute to our understanding of genes and mechanisms involved in estrous behavior. Studies in rodents, for example, show that estrogen-induced gene expression in specific brain areas such as the hypothalamus play an important role. Through these estrogen-induced gene expressions, E2 alters the functioning of neuronal networks that underlie estrous behavior, by affecting dendritic connections between cells, receptor populations and neurotransmitter releases. To improve the understanding of complex biological networks, like estrus regulation, and to deal with the increasing amount of genomic information that becomes available, mathematical models can be helpful. Systems biology combines physiological and genomic data with mathematical modeling. Possible applications of systems biology approaches in the field of female fertility and estrous behavior are discussed.

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

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.

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.

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.