Epistasis plays important roles in evolution, for example in the evolution of recombination, but each of the current methods to study epistasis has limitations. Here, we propose a new strategy. If a quantitative trait locus (QTL) affecting a quantitative character has been identified, individuals who have the same genotype at that QTL can be regarded as comprising a subpopulation whose response to selection depends in part on interactions with other loci affecting the character. We define the marginal differences to be the differences in the average phenotypes of individuals with different genotypes of that QTL. We show that the response of the marginal differences to directional selection on the quantitative character depends on epistatic gene interactions. For a model with no interactions, the marginal differences do not differ on average from their starting values once linkage equilibrium has been re-established. If there is directional epistasis, meaning that interactions between the QTL and other loci tend to increase or decrease the character more than under an additive model, then the marginal differences will tend to increase or decrease accordingly when larger values of the character are selected for. We develop a likelihood ratio test for significant changes in the marginal differences and show that it has some power to detect directional epistasis for realistic sample sizes. We also show that epistatic interactions which affect the evolution of the marginal differences do not necessarily result in a substantial epistatic component of the genetic variance.

Life cycle assessment (LCA) and the Intergovernmental Panel on Climate Change (IPCC) guideline methodology, which are the principal greenhouse gas (GHG) quantification methods, were evaluated in this study using a dairy farm GHG model. The model was applied to estimate GHG emissions from two contrasting dairy systems: a seasonal calving pasture-based dairy farm and a total confinement dairy system. Data used to quantify emissions from these systems originated from a research study carried out over a 1-year period in Ireland. The genetic merit of cows modelled was similar for both systems. Total mixed ration was fed in the Confinement system, whereas grazed grass was mainly fed in the grass-based system. GHG emissions from these systems were quantified per unit of product and area. The results of both methods showed that the dairy system that emitted the lowest GHG emissions per unit area did not necessarily emit the lowest GHG emissions possible for a given level of product. Consequently, a recommendation from this study is that GHG emissions be evaluated per unit of product given the growing affluent human population and increasing demand for dairy products. The IPCC and LCA methods ranked dairy systems’ GHG emissions differently. For instance, the IPCC method quantified that the Confinement system reduced GHG emissions per unit of product by 8% compared with the grass-based system, but the LCA approach calculated that the Confinement system increased emissions by 16% when off-farm emissions associated with primary dairy production were included. Thus, GHG emissions should be quantified using approaches that quantify the total GHG emissions associated with the production system, so as to determine whether the dairy system was causing emissions displacement. The IPCC and LCA methods were also used in this study to simulate, through a dairy farm GHG model, what effect management changes within both production systems have on GHG emissions. The findings suggest that single changes have a small mitigating effect on GHG emissions (<5%), except for strategies used to control emissions from manure storage in the Confinement system (14% to 24%). However, when several management strategies were combined, GHG emissions per unit of product could be reduced significantly (15% to 30%). The LCA method was identified as the preferred approach to assess the effect of management changes on GHG emissions, but the analysis indicated that further standardisation of the approach is needed given the sensitivity of the approach to allocation decisions regarding milk and meat.

A meta-analysis, using information from 45 experiments on growing-finishing pigs published in 39 manuscripts, was carried out to determine the simultaneous effects of the physical environment (space allowance, group size, flooring conditions, temperature, presence of enrichment), pig traits (initial body weight (BW) for each studied time interval, sex, genetics), feeder characteristics (water provision within the feeder, feeder design (individual/collective), feeder places/pig, presence of feeder protection) and feed characteristics (feed allowance (ad libitum/restricted), net energy content, crude protein (CP) content), as well as their potential interactions, on the feeding behaviour and performance of growing-finishing pigs. The detrimental effect of low temperature on performance was particularly evident for restricted-fed pigs (P < 0.05). At reduced feeder space allowance, a reduction in the percentage of time spent eating was predicted when increasing initial BW, whereas the opposite was predicted for larger feeder space allowances (P < 0.001). The reduction in visit duration to the feeder in higher BW groups became gradually more important with increasing feeder space allowance (P < 0.01), whereas the increase in the ingestion rate and average daily feed intake (ADFI) with increasing initial BW became smaller with increasing feeder space (P < 0.05). The model predicted a reduction in feed conversion ratio (FCR) with increasing group size (P < 0.05) and floor space allowance (P < 0.01) and on solid floors with or without bedding (P < 0.05). In comparison with other feeders, wet/dry feeders were associated with more frequent but shorter feeder visits (P < 0.05), higher ingestion rates (P < 0.001) and higher ADFI (P < 0.10). The use of protection within individual feeders increased the time spent feeding (P < 0.001), reduced the number of visits per day (P < 0.01), the ingestion rate (P < 0.001) and FCR (P < 0.01) in comparison with other feeder types. Sex modulated the effect of the number of feeder places/pig on FCR (P < 0.05), with a gradual reduction of FCR in entire males and females when increasing feeder space allowance. Genetics tended to modulate the effect of diets’ CP content on FCR (P < 0.10). Overall, these results may contribute to the improvement of the welfare and performance of growing-finishing pigs by a better knowledge of the influence of the rearing environment and may help optimize the feeding strategies in current production systems.

The overall aim of the present study was to analyse and compare organic beef cattle farming in Spain with intensive and conventional systems. An on-farm study comparing farm management practices and animal health was carried out. The study also focussed on a slaughterhouse analysis by comparing impacts on the safety and quality of the cattle products. Twenty-four organic and 26 conventional farms were inspected, and farmers responded to a questionnaire that covered all basic data on their husbandry practices, farm management, veterinary treatments and reproductive performance during 2007. Furthermore, data on the hygiene and quality of 244, 2596 and 3021 carcasses of calves from organic, intensive and conventional farms, respectively, were retrieved from the official yearbook (2007) of a slaughterhouse. Differences found between organic and conventional farms across the farm analysis did not substantially reflect differences between both farm types in the predominant diseases that usually occur on beef cattle farms. However, calves reared organically presented fewer condemnations at slaughter compared with intensive and to a lesser extent with conventionally reared calves. Carcass performance also reflected differences between farm type and breed and was not necessarily better in organic farms.

Recently, the French National Institute for Agricultural Research appointed an expert committee to review the issue of pain in food-producing farm animals. To minimise pain, the authors developed a ‘3S’ approach accounting for ‘Suppress, Substitute and Soothe’ by analogy with the ‘3Rs’ approach of ‘Reduction, Refinement and Replacement’ applied in the context of animal experimentation. Thus, when addressing the matter of pain, the following steps and solutions could be assessed, in the light of their feasibility (technical constraints, logistics and regulations), acceptability (societal and financial aspects) and availability. The first solution is to suppress any source of pain that brings no obvious advantage to the animals or the producers, as well as sources of pain for which potential benefits are largely exceeded by the negative effects. For instance, tail docking of cattle has recently been eliminated. Genetic selection on the basis of resistance criteria (as e.g. for lameness in cattle and poultry) or reduction of undesirable traits (e.g. boar taint in pigs) may also reduce painful conditions or procedures. The second solution is to substitute a technique causing pain by another less-painful method. For example, if dehorning cattle is unavoidable, it is preferable to perform it at a very young age, cauterising the horn bud. Animal management and constraint systems should be designed to reduce the risk for injury and bruising. Lastly, in situations where pain is known to be present, because of animal management procedures such as dehorning or castration, or because of pathology, for example lameness, systemic or local pharmacological treatments should be used to soothe pain. These treatments should take into account the duration of pain, which, in the case of some management procedures or diseases, may persist for longer periods. The administration of pain medication may require the intervention of veterinarians, but exemptions exist where breeders are allowed to use local anaesthesia (e.g. castration and dehorning in Switzerland). Extension of such exemptions, national or European legislation on pain management, or the introduction of animal welfare codes by retailers into their meat products may help further developments. In addition, veterinarians and farmers should be given the necessary tools and information to take into account animal pain in their management decisions.

Although vitamin E has been known as an essential nutrient for almost 80 years, we are far from a complete understanding of all the aspects related to bioavailability and its effects on health and milk quality in dairy cows. Vitamin E is a generic descriptor for two families of lipid-soluble compounds, the tocopherols and the tocotrienols, of which α-tocopherol has the highest biological activity. Commercially available α-tocopherol supplements for dairy cows contain either the natural RRR form or the synthetic (all-rac) form, which contains all the eight possible stereoisomers (four possessing the 2R and four possessing the 2S configuration) in equimolar amounts. Recent data clearly suggest that an almost complete discrimination against the 2S isomers occurs in dairy cows. Thus, 1 g of the all-rac form is essentially equivalent to 0.5 g of the RRR form. With respect to the effect of vitamin E supplementation of dairy cows on health and milk quality, the majority of published studies suggests that vitamin E supplementation at the level 1000 to 4000 IU/cow per day during the dry period reduces both the frequency of intramammary infection and that of clinical mastitis and improves milk quality, as shown by a reduction in the levels of somatic cell count (SCC)/ml in milk, decreased plasmin activity and increased oxidative stability of milk. However, a recent study from the Netherlands suggested that vitamin E supplementation at the 3000 IU/cow per day level during the dry period when combined with high levels of plasma vitamin E at dry-off (>14.5 μmol/l) increases the incidence of mastitis. Data from previously unpublished survey studies and those from published vitamin E feeding trials, in which high levels of blood vitamin E were observed, were reanalyzed. All farms selected for the analysis implemented oral administration of vitamin E at the 3000 IU/cow per day level throughout or during the late dry period (4 weeks before the expected day of parturition). Dairy cows were divided into three groups, depending on blood α-tocopherol levels at dry-off: high (>6.25 μg/ml), medium (between 6.25 and 4.25 μg/ml) and low (<4.25 μg/ml). Data indicate that there were no differences in the incidence of mastitis and in the level of SCC/ml of milk between the three groups. Thus, supplementation of 3000 IU vitamin E/cow per day in the late dry period remains recommended because it is generally associated with decreased risk of mastitis. Conditional or opposite effects have not been repeated and require further research before changing recommendations for vitamin E supplementation.

This study evaluated whether differences in milk fever incidence among Swedish dairy herds could be explained partly by differences in mineral feeding during the last weeks of gestation. A case–control study was performed on dietary risk factors for a high incidence of milk fever at the herd level using information regarding feeding and management of the dry cows collected in a written questionnaire distributed by post in spring 2008. The study was conducted from September 2004 to August 2007. Data on the diets fed to dry cows, with an emphasis on the amounts of minerals (Ca, P, Mg and K) fed 3 weeks before calving and at calving, were obtained from 30 herds belonging to the 100 Swedish herds with the highest recorded incidence of veterinary treatment for milk fever (>8.8%) and from 22 herds with no recorded milk fever treatments. Multivariable logistic regression analysis showed that a linear increase in the total amount of K and less than 26 g of Mg/day fed to dry cows 3 weeks before calving was associated with an increased risk of high milk fever incidence. A large increase in the amount of dry matter (DM) fed (>3.1 kg DM extra per day at calving compared with 3 weeks before calving) was associated with a higher incidence of milk fever, but no differences were found for Ca or P intake. Breed composition, herd average milk yield and age composition of the herd did not explain any of the observed differences between the case and the control herds. The results indicate that differences in the frequency of milk fever among herds can be associated with differences in mineral feeding of the dry cows. A high amount of K in the diet may increase the risk of milk fever linearly, whereas Mg should probably be fed at a higher level than the current Nordic recommendation to prevent milk fever.

Experiments were conducted to determine the effects of Newcastle disease on chicken fat metabolism. Thirty black-bone chickens were infected intraocularly with the Newcastle disease virus (NDV). Six birds were killed at 0, 12, 24, 48 and 72 h post infection, respectively. Results showed that the NDV infection decreased concentration of high-density lipoprotein cholesterol and increased concentrations of total cholesterol and low-density lipoprotein cholesterol in the plasma. Concentrations of triglycerides and free fatty acid were decreased after their initial increase. NDV infection also dramatically raised the activities of lipoprotein lipase (LPL), hepatic lipase and lipases in the serum. Furthermore, PCR results showed that the incipient infection up-regulated mRNA expression of LPL, adipose triglyceride lipase and nuclear factor peroxisome proliferator-activated receptor alpha (PPARα), but down-regulated them at later stage. Similarly, mRNA expression of fatty acid synthase, acetyl-CoA carboxylase and nuclear factor PPARγ, fatty acid transport protein 1 (FATP1), and 4(FATP4) decreased, whereas fatty acid translocase and fatty acid-binding protein increased initially. Data from Western blotting analysis showed that the changes in protein levels were consistent with mRNA expression. These results indicated that fat metabolism of the chicken was affected by the NDV infection. At the beginning of NDV infection, lipogenesis was inhibited, whereas lipolysis was strengthened. After lipolysis was strengthened, fat metabolism was found to be maximally depressed.

The present work summarizes research related to the definition of nutrient recommendations for feeds used in the intensive production of rabbit's meat. Fibre is the main chemical constituent of rabbit diets that typically contain 320 to 360 and 50 to 90 g/kg of insoluble and soluble fibre, respectively. Instead, the dietary contents of cereal grains (∼120 to 160 g/kg), fat (15 to 25 g/kg) and protein concentrates (150 to 180 g/kg) are usually low with respect to other intensively reared monogastric animals. Cell wall constituents are not well digested in rabbits, but this effect is compensated by its stimulus of gut motility, which leads to an increasing rate of passage of digesta, and allows achieving an elevated dry matter intake. A high feed consumption and an adequate balance in essential nutrients are required to sustain the elevated needs of high-productive rabbits measured either as reproductive yield, milk production or growth rate in the fattening period. Around weaning, pathologies occur in a context of incomplete development of the digestive physiology of young rabbits. The supply of balanced diets has also been related to the prevention of disorders by means of three mechanisms: (i) promoting a lower retention time of the digesta in the digestive tract through feeding fibre sources with optimal chemical and physical characteristics, (ii) restricting feed intake after weaning or (iii) causing a lower flow of easily available substrates into the fermentative area by modifying feed composition (e.g. by lowering protein and starch contents, increasing its digestibility or partially substituting insoluble with soluble fibre), or by delaying age at weaning. The alteration in the gut microbiota composition has been postulated as the possible primary cause of these pathologies.

Acceptance of and preference for a particular food depends not only on its intrinsic (e.g. nutritional) properties but also on expected or recent food experiences. An instance of this type of phenomenon has been called induction effect, which consists of an increased intake of a type of food when it precedes a hedonically preferred food in a sequence familiar to the animal, relative to controls that have access only to the less-preferred food. The purpose of our study was to assess intake induction of a low-nutritious food when followed by different high-nutritious supplements in sheep (Ovis aries). In this experiment, we ran a supplemented phase where animals fed oat hay (a low-nutritious food) in the first part of the daily feeding sessions followed by a supplement with either a high (soya bean meal; group GS) or a low (ground corn; group GC) protein–energy ratio in the second part ate more oat hay than controls that were fed oat hay in both parts of sessions (group GH). In addition, supplemented animals presented a stronger preference for oat hay over alfalfa hay than controls in a subsequent choice. When all animals received no food in the second part of the sessions (Non-supplemented phase), intake of oat hay converged to the control's intake level in all the groups, suggesting that the presence of supplements after access to oat hay was responsible for intake induction. Lastly, we repeated the supplemented phase with a different control group where animals received oat hay in the first part of the sessions and no food in the second part (group NF), thus equalizing groups in terms of the time of access to oat hay in a session. Groups GS and GC still developed higher intake of oat hay than group NF. In both supplemented phases of the experiment, we estimated animals’ daily metabolizable energy (ME) and crude protein (CP) intake. CP intake was higher in group GS than in groups GC, GH and NF, but there was no difference between group GC and the controls. In turn, groups did not differ in ME intake in the First supplemented phase, and only group GS presented higher ME intake than the rest of the groups in the Second supplemented phase. Therefore, a nutritional account of the present induction effect seems insufficient. We propose that a learned association between oat hay and the post-ingestive feedback from the subsequent high-nutritious supplements underlay sheep's intake induction and increased preference for oat hay.

Meta-analytical approach was used to quantitatively synthesize the effect of immunocastration on growth, carcass, meat quality, reproductive organs and boar taint compounds. Altogether, 41 papers were collected for effect size (θ) calculation and the comparisons were made with entire males (EM) and surgical castrates (SC). The data for reproductive organs and growth performance are numerous enough to draw firm conclusions. In contrast, data for carcass and meat quality are more limited. Results of meta-analysis show efficient immunocastration with the magnitude of the response being by far the largest for reproductive organs (θ = −2.8 to −5.0) and boar taint substances (θ = −2.8 and −0.8 for androstenone and skatole, respectively). However, compared with SC, the immunocastrates exhibit larger bulbourethral glands (θ = 1.3) and slightly higher concentrations of androstenone and skatole (θ = 0.1 and θ = 0.2, respectively). The impact of immunocastration is also remarkable on performance, where the main advantage of the immunocastrates is their boar-like performance until revaccination. In the period following the second vaccination, they eat much more than EM (θ = 2.1), resulting in large effect size for growth rate compared with both EM and SC (θ = 1.1 and θ = 1.4, respectively). Considering the whole fattening period, their feed conversion ratio is higher compared with EM (θ = 0.6) and much lower than that of SC (θ = −1.3), although exhibiting moderately faster growth compared with both (θ = 0.6 and θ = 0.2, respectively). With regard to carcass quality, the immunocastrates take intermediate position between EM and SC. Besides, our analysis suggests no difference in meat quality with SC and some meat quality advantages of immunocastrates over EM because of higher intramuscular fat content (θ = 0.4) and lower shear force (θ = −0.6).

Mixed-species stocking can foster sound landscape management while offering economic and ecological advantages compared with mono-species stocking. Producers contemplating a mixed-species enterprise should reflect on several considerations before implementing this animal management strategy. Factors applicable to a particular producer's landscape must be considered together with goals and economic constraints before implementing mixed-species stocking. A major consideration when using mixed-species stocking is how to deal with predation losses, especially among small ruminants. An approach being adopted in some commercial operations capitalizes on using innate animal behaviors to form cohesive groups of two or more livestock species that consistently remain together under free-ranging conditions. These groups are referred to as flerds. The mixing of a flock of sheep and/or goats with a herd of cattle into a flerd has been shown to protect sheep and goats from coyote predation, as well as offering other husbandry advantages. Some of the added advantages include more efficient conversion of forage into animal protein. Creation of flerds, their maintenance and advantages are discussed.

New alternatives are necessary if the environmental impact linked to intensive poultry production is to be reduced, and different litter handling methods should be explored. Among these, acidifying amendments added to poultry litters has been suggested as a management practice to help reduce the potential environmental effect involved in multiple flock cycles. There have been several studies on the use of aluminum sulfate (alum) and its benefits, but almost no data are available under farm conditions in Europe. An experiment with Ross 308 broilers from 1 to 42 days of age was conducted to evaluate the effect of alum on litter composition, the solubility of some mineral elements and NH3 emission during a single flock-rearing period in commercial houses located in southeast Spain. Broilers were placed on clean wood shavings in four commercial houses, containing 20 000 broilers each. Before filling, alum was applied at a rate of 0.25 kg/m2 to the wood shavings of two poultry houses, whereas the remaining two were used as control. Litter from each poultry house was sampled every 3 to 5 days. Ammonia emissions from the poultry houses were monitored from 37 to 42 days of age. In comparison with the control group, alum treatment significantly reduced the pH level of the litter (P < 0.001) with an average difference of 1.32 ± 0.24 units. Alum-treated litter showed, on average, a higher electrical conductivity than the control litter (5.52 v. 3.63 dS/m). The dry matter (DM) and total N and P contents did not show differences between the treatments (P > 0.05). Regarding the NH4 +-N content, alum-treated litter showed a higher value than the untreated litter, with an average difference of 0.16 ± 0.07% (on a DM basis). On average, alum-treated litter had lower water-soluble P, Zn and Cu contents than the untreated litter. Alum noticeably reduced the in-house ammonia concentration (P < 0.001), with an average of 4.8 ppm at 42 days of age (62.9% lower than the control), and ammonia emissions from 37 to 42 days of age were significantly reduced by the alum treatment (P < 0.001), representing a reduction of 73.3%. The lower pH values might have reduced ammonia volatilization from the litter, with a corresponding positive effect on the building environment and poultry health. For these reasons, litter amendment with alum could be recommended as a way of reducing the pollution potential of European broiler facilities during a single flock cycle.

The objective of the study was to assess the post-weaning growth response of Sahiwal calves reared on four different pre-weaning dietary regimens. The four diets were: (a) whole cow's milk, starter ration (SR; CP = 20%, total digestible nutrients (TDN) = 72%) and Berseem hay (H; Egyptian clover; CP = 21%, TDN = 63%); (b) whole cow's milk + H; (c) milk replacer (MR; reconstituted to supplier specification; Sprayfo®) + SR + H; and (d) MR + H. The protein and fat percentages of reconstituted MR were 2.22 and 1.84, respectively. Milk or MR were fed at the rate of 10% of the calves’ body weight (BW) until 56 days of age, and then withdrawn gradually until weaned completely by 84 days of age. The average initial BW of calves in groups A, B, C and D were 56.3 ± 1.0, 47.5 ± 1.0, 40.4 ± 1.0 and 30.3 ± 1.0 kg, respectively. Initially, there were 12 calves in each group with six of each sex; however, one male calf died from each of groups B and C and were not replaced. During the post-weaning period, 13 to 24 weeks, the calves were fed a single total mixed ration ad libitum based on maize, canola meal, wheat straw and molasses containing 16% CP and 70% TDN. Daily feed intake and weekly BW gains were recorded. The data were analyzed by MIXED model analysis procedures using the statistical program SAS. The intake of calves as percent of their BW, feed conversion ratio and cost per kg of BW gain were not different (P > 0.05) across treatments. The daily gain at 24 weeks of age for the pre-weaning treatments A, B, C and D were 746 ± 33, 660 ± 33, 654 ± 33 and 527 ± 33 g/day and the final liveweights of calves were 119 ± 4.2, 102 ± 4.2, 95 ± 4.2 and 75 ± 4.2 kg, respectively. Gains were influenced significantly (P < 0.05) by pre-weaning treatments. The calves fed MR and H only during the pre-weaning period were unable to catch up post weaning with calves on other dietary treatments. The calves fed whole milk from birth at the rate of 10% of liveweight together with concentrates had higher weaning weight and superior growth rate post weaning as well. Thus, pre-weaning feeding was important for higher weaning weights and superior growth rates post weaning.

The objectives of this study were to quantify the errors in economic values (EVs) for traits affected by cost or price thresholds when skewed or kurtotic distributions of varying degree are assumed to be normal and when data with a normal distribution is subject to censoring. EVs were estimated for a continuous trait with dichotomous economic implications because of a price premium or penalty arising from a threshold ranging between −4 and 4 standard deviations from the mean. In order to evaluate the impacts of skewness, positive and negative excess kurtosis, standard skew normal, Pearson and the raised cosine distributions were used, respectively. For the various evaluable levels of skewness and kurtosis, the results showed that EVs can be underestimated or overestimated by more than 100% when price determining thresholds fall within a range from the mean that might be expected in practice. Estimates of EVs were very sensitive to censoring or missing data. In contrast to practical genetic evaluation, economic evaluation is very sensitive to lack of normality and missing data. Although in some special situations, the presence of multiple thresholds may attenuate the combined effect of errors at each threshold point, in practical situations there is a tendency for a few key thresholds to dominate the EV, and there are many situations where errors could be compounded across multiple thresholds. In the development of breeding objectives for non-normal continuous traits influenced by value thresholds, it is necessary to select a transformation that will resolve problems of non-normality or consider alternative methods that are less sensitive to non-normality.

Infertility in cattle is a major concern of farmers worldwide and despite the enormous improvements in assisted reproduction technologies, the success rates of pregnancies are still low. Embryonic loss is considered one of the main factors of infertility in cattle. As such, the identification of genetic markers for embryo quality and development can help elucidate the molecular mechanisms involved in the formation of embryos with the highest developmental potential. In a previous study, using next-generation RNA sequencing, we identified novel transcripts and alternatively spliced genes that were associated with embryo quality. The objectives of this study were to characterize these transcripts and validate their expression in new biological replications of embryos using quantitative real-time PCR. Two types of embryos differing in morphological and developmental statuses (blastocysts and degenerate embryos) were produced using in vitro fertilization. Quantitative expression of eight novel transcripts revealed a range of 2.5- to 90-fold difference in expression between degenerate embryos and blastocysts. Some of these novel transcripts showed sequence similarity to human and cattle genes known to affect differentiation, growth and development. In addition, expression analysis of alternative splicing isoforms of five genes (MYL6, NOP10, RNF187, RPS24 and RPS28) revealed significant differential expression of these isoforms in the different embryo types. Thus, results of this study suggest that novel transcripts and alternatively spliced genes, found to be differentially expressed between blastocysts and degenerate embryos, can be used as markers for blastocyst formation and development.

The aim of the study was to determine changes of serum cortisol and biochemical, haematological and antioxidant enzyme variables in the blood of horses sampled during the pre-slaughter period (in the lairage and in the stunning box) and during exsanguination. A total of 24 Slovenian warm-blooded horses were observed. Blood samples for determination of serum cortisol and biochemical, haematological (red blood cell count, haematocrit, haemaglobin concentration) and antioxidant enzyme (whole blood superoxide dismutase and glutathione peroxidase) variables were collected by venipuncture of the left jugular vein in the lairage pen, 60 min before stunning (lairage) and immediately before stunning (stunning box). At exsanguination, blood samples were collected from the wound at the time of jugular vein sticking. During blood collection in the lairage pen and in the stunning box, horses were gently restrained with a halter. They were stunned using a penetrating captive bolt pistol impelled by air and were bled by jugular vein sticking. Horses were physically active in the lairage pen and in the race before entering the stunning box. After stunning, the horses showed paddling movements with their legs. In horses, the plasma lactate and glucose concentrations, the serum potassium concentration, the activities of the serum muscle enzymes aspartate aminotransferase and creatine kinase, and values of most of the other biochemical (Table 1) and haematological variables (Table 2), were significantly (P < 0.05) higher at exsanguination, than in blood sampled while they were in the lairage and in the stunning box. The serum concentrations of cortisol and chloride and the activities of alanine aminotransferase and antioxidant enzymes were not significantly different between the pre-slaughter period and exsanguination. All selected blood variables were not significantly different between the lairge and the stunning box sampling time, indicating no physiological stress responses of the investigated horses to stressors, such as novelty of the pre-slaughter environment and handling, present in the slaughterhouse between the lairage and the stunning box. However, the significantly higher values, at exsanguination, for the plasma lactate and glucose concentrations, serum muscle enzyme activities and haematological variables, than during the pre-slaughter period, might partially be attributed to stimulation of the sympathetic nervous system, caused by stunning and bleeding.