Tryptophan (Trp) is an essential amino acid acting as a key nutrition factor regulating animal growth and development. But how Trp modulates food intake in pigs is still not well known. Here, we investigated the effect of dietary supplementation of Trp with different levels on food intake of growing pigs. The data showed that dietary Trp supplementation with the standardised ileal digestibility (SID) Trp to lysine (Lys) ratio at both 0·18 and 0·20 significantly increased the food intake by activating the expression of orexigenic gene agouti-related peptide (AgRP) and inhibiting the expression of anorexigenic gene pro-opiomelanocortin (POMC), cocaine- and amphetamine-regulated transcript (CART) and melanocortin receptor 4 (MC4R) in the hypothalamus. Meanwhile, the level of anorexigenic hormones appetite-regulating peptide YY (PYY) in the duodenum and serum and leptin receptor in the duodenum were also significantly decreased. Importantly, both the kynurenine and serotonin metabolic pathways were activated upon dietary Trp supplementation to downregulate MC4R expression in the hypothalamus. Further mechanistic studies revealed that the reduced MC4R expression activated the hypothalamic AMP-activated protein kinase (AMPK) pathway, which in turn inhibited the mammalian target of rapamycin (mTOR)/S6 kinase 1 (S6K1) activity to stimulate food intake. Together, our study unravels the orexigenic effect of dietary Trp supplementation in pigs and expands its potential application in developing nutrition intervention strategy in pig production.

The transition to sedentary agricultural societies in northern China fuelled considerable demographic growth from 5000 to 2000 BC. In this article, we draw together archaeobotanical, zooarchaeological and bioarchaeological data and explore the relationship between several aspects of this transition, with an emphasis on the millet-farming productivity during the Yangshao period and how it facilitated changes in animal husbandry and consolidation of sedentism. We place the period of domestication (the evolution of non-shattering, initial grain size increase and panicle development) between 8300 and 4300 BC. The domestication and post-domestication of foxtail (Setaria italica) and broomcorn (Panicum miliaceum) millet increased their productivity substantially, with much greater rate of change than for rice (Oryza sativa). However, millets are significantly less productive per hectare than wet rice farming, a point reflected in the greater geographical expanse of northern Neolithic millet cultures (5000–3000 BC) in comparison with their Yangtze rice-growing counterparts. The domestication of pigs in the Yellow River region is evidenced by changes in their morphology after 6000 BC, and a transition to a millet-based diet c. 4500–3500 BC. Genetic data and isotopic data from dogs indicate a similar dietary transition from 6000 to 4000 BC, leading to new starch-consuming dog breeds. Significant population increase associated with agricultural transitions arose predominately from the improvement of these crops and animals following domestication, leading to the formation of the first proto-urban centres and the demic-diffusion of millet agriculture beyond central northern China between 4300–2000 BC.

Qualitative Behaviour Assessment (QBA) is a welfare evaluation tool that uses a holistic approach to capturing an animal’s emotional state. Lists of QBA descriptors validated to assess pig welfare exist, but their definitions are often not described in peer-reviewed literature and the processes used to develop definitions are lacking. The objective of this study is to detail a systematic approach to creating clear definitions for a pre-existing fixed list of QBA descriptors and test their application. A fixed list of 20 descriptors from the EU Welfare Quality® assessment protocol for pigs was modified, and ten pig experts were recruited to assist with defining these descriptors in a focus group-style discussion. Half of the experts involved in creating descriptor definitions partook in a subsequent step, where the newly developed definitions were tested by implementing QBA on a video library of post-weaned sows selected to capture the breadth of sow behaviour. Experts displayed excellent agreement in identifying a PCA dimension interpreted as the valence of descriptors and good agreement for another reflecting arousal. Inter-observer reliability was also measured for each descriptor. Only two descriptors exhibited less than moderate agreement between experts whereas half of the descriptors evoked substantial agreement or better. These findings support our process to delineate clear definitions for a fixed list of QBA descriptors in pigs. This study is the first of its kind detailing the in-depth process of creating and verifying descriptor definitions for future use in sow welfare assessment.

This study evaluated the importance of a correction for amino acids (AA) released into the hindgut on a measure of AA absorption kinetics and tested whether AA absorption kinetics are related to the extent of AA absorption using the growing pig as a model for humans. Thirty-six nine-week-old pigs (22·3 kg) received a diet containing whey protein as the sole protein source for 8 d. Pigs received their last meal containing the indigestible marker titanium dioxide before being euthanised at 1, 2, 3, 4, 6 and 12 h post-feeding. The entire content of each gastrointestinal tract (GIT) region was collected to determine AA released into the hindgut, and the kinetics and extent of AA absorption (uncorrected and corrected for AA entering the hindgut). Amounts of AA released into the hindgut increased over time (e.g. 33 and 180 mg of Glu for 4 and 6 h post-feeding). The corrected apparent amount of each AA absorbed from the GIT lumen after 4 h post-feeding was generally lower (P ≤ 0·05) than the uncorrected counterpart. Differences in both the kinetics and extent of AA absorption were observed across AA. For example, the time to reach half of the apparent AA absorption (T50) was 1·5 and 3·4 h for Met and Arg, respectively, whereas their extent of apparent absorption was 93 and 73 %. Negative correlations between parameters related to kinetics and the extent of apparent absorption were observed (e.g. for T50 r = −0·81; P < 0·001). The kinetics of AA absorption is related to the extent of AA absorption.

Aversion to the dip-lift stunning system and to the inhalation of 70 and 90% carbon dioxide was assessed in 18 halothane-free (NN) and 14 heterozygous halothane (Nn) slaughter weight pigs using aversion learning techniques and behavioural studies in an experimental slaughterhouse. Pigs were subjected to the treatments individually. When the dip lift system contained atmospheric air, the proportion of pigs that entered the crate voluntarily increased on subsequent days, indicating that pigs habituate to the stunning system. Based on the number of attempted retreats, for the first descent into the well with atmospheric air, Nn pigs were more reactive than NN pigs. On repeating the descent, Nn pigs showed greater habituation to the procedure. When the pit contained (either 70 or 90%) carbon dioxide, the time taken to enter the crate and the incidence of pigs that attempted to retreat increased on subsequent days, indicating aversion to the carbon dioxide concentrations. The aversion was higher when the stunning system contained 90 as opposed to 70% carbon dioxide due possibly to increased irritation of the nasal mucosal membranes and more severe hyperventilation. Conversely, a decrease in the concentration of carbon dioxide increased the time to loss of posture and, therefore, lengthened the perception of the aversive stimulus till the animal lost consciousness. These results suggest that stunning with carbon dioxide is not free from pain or distress. The degree of aversion depends on the carbon dioxide concentration. Therefore, if higher concentrations of carbon dioxide are recommended for rapid induction of anaesthesia, it needs to be assumed that this may be more aversive to pigs.

The aim of this study was to examine the effects of roughage and shelter on certain welfare indicators in growing pigs that have access to ample straw and space. The effects of the two treatments were evaluated both by recording the pigs’ use of the various areas of the pen and by measuring the frequency of two specific behaviours, ‘aggression’ and ‘play’, that are considered to be significant indicators of welfare in pigs. Seven replicates were used, each involving 96 pigs. The pigs were randomly allocated to eight experimental pens at 10 weeks of age, and were observed from 13 to 22 weeks of age. The two treatments, roughage and shelter, were distributed according to a 2 x 2 design in the pigs’ outdoor runs, four of which were located on each side of the barn (north side versus south side). The pigs spent most of their time in the straw-provided areas, and the frequency of their aggressive behaviour was also the highest in these areas, suggesting that these locations were the most attractive to the pigs. The pigs with access to roughage showed a lower frequency of aggression (P < 0.05) and spent more time in the outdoor area where the roughage was placed than those pigs with no access to roughage (P < 0.05). No other effects of treatment were found on the length of time spent in the different pen locations. Play frequency decreased with age (P < 0.05) and with increasing temperature (P < 0.01). Moreover, when housed on the south side of the building, the pigs with access to shelter played more than those without (2.0 versus 1.0 events per hour [SE = 0.3]; P < 0.05); this suggests that the opportunity to regulate the body temperature by use of shade results in improved welfare. In conclusion, the pigs’ behaviour indicated that their welfare was improved by free access to roughage and shelter.

The objective of this study was to assess the effect of providing mats in the farrowing pen on behaviour and lesions in sows (n = 38) and piglets. Nineteen of the sows and their litters housed in farrowing crates with metal slatted floors were provided with mats, the remaining 19 acting as controls. Sow skin was inspected pre-farrowing and at weaning: the skin and feet of piglets were examined when they were 6 days old. Skin lesions were scored (on a scale of 0 to 6) according to severity. Total lesion scores per sow and median total lesion scores per litter were calculated. Sow behaviour was recorded by direct observation at feeding. Usage of a heat pad for lying in the presence or absence of mats was assessed over a 2hr observation period. Median skin lesion scores of sows did not differ between treatments. Litters from the control treatment had lower skin lesion scores (median [range] 8 [2-12] vs 10 [5-21]; P < 0.05). Median lesion scores of the front legs tended to be higher for piglets on mats (median [range] 8 [1.5-13] vs 4 [1.5-8]; ns). Sows on metal flooring went from kneeling to lowering their hindquarters faster (median [range] 15 [2—45] s) than sows on mats (23 [11—54] s) (P < 0.05). Furthermore, they slipped more on their front (median [range] 2.7 [0-8.7] vs 0 [0-1.3] slips min1; P < 0.001) and hind (median [range] 5.3 [0.3-31.7] vs 1.9 [0-33.3] slips min1; P < 0.05) feet while standing, than sows on mats. More piglets lay on the heat pad when it was covered by a mat (mean ± SEM 45.97 ± 4.49 %) than when no mat was provided (29.29 ± 4.47 %)(P < 0.05). Mats improve sow comfort and reduce slipping. They encourage piglets to lie on the heat pad but cause damage to the skin of the front legs. Providing pigs with mats in the farrowing house could greatly improve welfare on slatted floors, but further research is needed to identify materials that are less abrasive.

The aim of this article is to report on the expert opinion regarding the provision of environmental enrichment for pigs. A questionnaire was sent to 53 pig welfare scientists who were asked to specify which enrichment materials they considered sufficient to ensure pig welfare; 68% responded. 89% stated that providing a chain was not sufficient, while 84% stated that the provision of straw could be sufficient. ‘Sustained animal-material interactions’, ‘rootability’, ‘manipulability’ and ‘chewability’ were the main material properties referred to as being required for enriching pig pens. Areas of further research suggested by the respondents encompassed both fundamental and applied research, including preference tests and demand studies, deprivation studies and quantitative studies to determine cut-off points. A case is made for modelling the available knowledge to help close the gap between what is known in science and what is decided in society regarding animal welfare and environmental enrichment for pigs.

This study investigated the temperature of pigs’ blood as it flowed from the sticking wound at exsanguination using infra-red thermometry and how it might reflect changes in core body temperature. A total of 417 pigs were monitored over a three-day period, which included a subset of 206 pigs for which additional information concerning transport conditions and ambient temperature was also known. The range of blood temperatures recorded was large (35.6-43.2°C) with a significant number of the animals found to have blood temperatures above the pigs’ normal temperature (39 ± l°C). Within the subset of pigs, average blood temperature of all the pigs in a pen at slaughter appeared to be related to pen temperatures and position on the lorry and was sensitive enough to detect changes in environmental ambient conditions.

An experiment was conducted to investigate the incidence of travel sickness in pigs, specific hormone concentrations at exsanguination and subsequent meat quality. Fifty, 80kg slaughter pigs were transported on a lorry for 4.5h. During the journey, behavioural observations of the individually marked pigs were made by scanning every 8min to establish whether the pigs exhibited certain symptoms of travel sickness (foaming at the mouth and chomping) and incidences of retching and vomiting were noted as they occurred. Upon arrival at the slaughterhouse, pigs were unloaded, slaughtered immediately and a blood sample was taken at exsanguination for analysis of plasma Cortisol, beta-endorphin and lysine vasopressin concentrations. On the day following slaughter, the chilled carcase of each pig was assessed for meat quality (using pH, Fibre Optic Probe, and Tecpro Pork Quality Meter measurements) in the longissimus dorsi, semimembranosus and adductor muscles to determine the incidence of PSE (pale, soft, exudative) or DFD (dark, firm, dry) meat quality. Twenty-six per cent of the pigs (a total of 13 individuals) vomited or retched during the journey. There was no relationship between the incidence of travel sickness and either the concentrations of the hormones analysed at exsanguination or subsequent meat quality. Correlations revealed no significant relationship between concentrations of the hormones and meat quality measurements.

This study examined the effects of enriching the environment on the behaviour and productivity of pigs, in an attempt to assess changes in welfare. A total of 102 pigs were housed in either barren or enriched housing from birth to slaughter. The barren environments were defined as intensive housing and the enriched environments incorporated extra space, an area which contained peat and straw in a rack. Enriching the environment reduced both the amount of time pigs spent inactive and the time involved in harmful social and aggressive behaviour. Tail biting was absent from the enriched environment but four pigs were removed from barren pens with severe tail damage. Pigs housed in enriched environments spent longer durations in exploratory behaviour than those in barren housing, and young pigs in enriched environments performed locomotory behaviour more frequently than their counterparts in barren environments. Overall growth rates were similar in both treatments. These results indicate that welfare is improved by enrichment with substrates and suggest that barren pens should be modified to provide these facilities.

The stressful effects that environments have on farm and laboratory animal welfare are likely to depend on how much animals understand of the behaviour and intentions of their conspecifics as well as on their understanding of their physical environment. However, studies on animal social cognition have primarily focused on primates. Here, we report on our work on social cognition in domestic pigs. It focuses on the ability of domestic pigs to assess and use to their advantage the behaviour of conspecifics, and uses approaches pioneered in studies on primates. Our work has shown that dominant pigs use the privileged knowledge of a subordinate to their own advantage in a competitive foraging situation. While such exploitative behaviour is likely to be based on rapid learning about the subordinate ‘s behaviour, it is also possible that ‘higher’ cognitive abilities such as visual perspective taking could be involved. Ongoing work uses an adaptation of the Guesser-Knower paradigm to test whether pigs are indeed capable of visual perspective taking.

The preferences of growing pigs for substrates were investigated by giving small groups of pigs a choice between two substrates in each test. The seven substrates examined were concrete, mushroom compost (spent), peat, sand, sawdust, straw and woodbark. Thirteen comparisons of pairs of substrates were tested with four replicates of each comparison. Eleven-week-old pigs (in groups of six) were placed in specially designed choice pens where they had access to two different substrates. The pigs were allowed to habituate to the pen for 1 week and at the end of week 2 the substrates were swapped. In weeks 2 and 3 the time spent by the pigs in each substrate was recorded. Peat, mushroom compost and sawdust were preferred most, with sand next and woodbark and straw being preferred only to concrete. It is suggested that growing pigs may be attracted to substrates which are similar in texture to earth.

The effects of witnessing the slaughter of conspecifics on the stress responses of pigs were investigated. Previously catheterized pigs were allowed to see the stunning and sticking (exsanguination) of pigs in a nearby pen. Heart rate was monitored and serial blood samples were taken to assess stress responses. Packed cell volume (PCV), Cortisol and β-endorphin were determined in the samples. In addition, behavioural observations and subjective assessments of animals’ responses were made. Although the levels of hormones, PCV and heart rate tended to be generally high due to handling, there were no specific increases in response to witnessing stunning and slaughter. These results suggest that witnessing the slaughter act does not distress pigs.

The objective of the present study was to investigate the relationship between rooting behaviour and foraging in growing pigs. In study 1, forty-eight 11-week-old pigs were housed in eight groups of six with access to a rooting substrate in the form of spent mushroom compost. In half of the groups the rooting substrate contained food rewards, and in the other half of the groups it did not. All pigs had ad libitum access to feed. In study 2, one hundred and ninety-two 11-week-old pigs were housed in thirty-two groups of six, all with access to spent mushroom compost, and eight groups were each fed to 70, 80, 90 or 100% appetite. Treatments were applied over a two-week period in both studies. The number of pigs involved in active rooting (rooting in substrate while standing), inactive rooting (rooting in substrate while sitting or lying) or non-rooting activity (standing in substrate area and involved in any activity except rooting) was recorded by scan sampling. These behaviours tended to reach a peak in the morning and again in the afternoon. Inactive rooting was not significantly affected by treatments in study 1 or study 2. Food rewards in the rooting substrate led to a significant reduction in active rooting behaviour and in non-rooting activity during peak periods of the day (P < 0.05). It is suggested that learned associations between rooting behaviour and acquisition of food caused the pigs to stop rooting when all the food rewards had been consumed. The fact that rooting was performed in the absence of nutritive feedback suggests that this behaviour is performed independently of its appetitive foraging function. Restricting feed levels to 70 or 80% of appetite led to a significant increase in active rooting and in non-rooting activity during peak periods (P < 0.05). The relationship between feed restriction and active rooting behaviour tended to be linear (P < 0.08). This suggests that levels of rooting behaviour are flexible in response to nutritional needs.

Assessment of mass-produced animal-housing equipment can serve as a basis for improving animal welfare. A number of European countries have adopted various legal approaches to such assessment. In Germany, welfare assessment of housing equipment is voluntary, but minimum standards can be set by regulation for the assessment procedure and for the qualifications of the persons involved. From a scientific perspective, the time and resource constraints pose some problems, particularly as they apply to a voluntary procedure. For reasons of practicability, certain compromises will be required. Nevertheless, it is important to ensure that each assessment procedure is based upon scientific principles and considers animal welfare aspects to a sufficient extent. A proposal for the minimum standards of an assessment procedure has been elaborated by the Animal Welfare Committee of the German Agricultural Society (Deutsche Landwirtschafts-Gesellschaft, DLG), a shortened version of which is presented here. The animal welfare impact of such a regulated but voluntary procedure will be less than that of an obligatory assessment; however, the relatively flexible approach may still significantly contribute to the improvement of welfare aspects of livestock housing.

The severity of respiratory distress occurring prior to loss of posture during exposure to: 20, 30, 40, 50, 60, 70, 80 or 90 per cent carbon dioxide in air; 2 or 5 per cent residual oxygen in argon; 30 per cent carbon dioxide in argon with either 2 or 5 per cent residual oxygen; or 40 per cent carbon dioxide in argon with either 2 or 5 per cent residual oxygen, was subjectively determined in pigs from their behaviour. The results indicated that exposure to 2 per cent oxygen in argon (anoxia) induced minimal respiratory distress, 30 per cent carbon dioxide in argon with 2 per cent residual oxygen induced a moderate distress and exposure to all the concentrations of carbon dioxide in air induced severe respiratory distress in the pigs. From the animal welfare point of view, using 2 per cent oxygen in argon (anoxia) appears to be the optimum choice for gas stunning pigs. Secondly, a mixture of 30 per cent carbon dioxide in argon with 2 per cent residual oxygen is preferred to 90 per cent carbon dioxide in air.

One hundred and twenty-eight pigs were reared in barren or enriched environments from birth to slaughter at 21 weeks of age. Pigs remained as litter-mate groups until 8 weeks of age when they were mixed into groups of eight animals. These groups were balanced for gender and weight and contained two pigs from each of four different litters. Each pig was assigned high or low social status on the basis of relative success in aggressive interactions at mixing. Injury levels were assessed on a weekly basis from 8 to 21 weeks of age. Pigs were exposed to two group food competition tests after a period of food restriction at 10 weeks of age, and to an individual novel pen test at 11 weeks of age. Behavioural and plasma cortisol responses to both types of test were recorded. Low social status was associated with increased injuries to the head, neck and ears, and therefore reduced welfare. Pigs with low social status showed reduced resource-holding ability in the food competition test, and greater avoidance of a novel object during the novel pen test It is suggested that avoidance of the novel object reflected ‘learned’ fearfulness in these individuals. Environmental enrichment did not negate the effect of low social status on injury levels, but did appear to reduce the negative influence of low social status on stress during food restriction, and led to a reduction in fearfulness in response to the novel pen test. These results suggest that environmental enrichment may improve the welfare of growing pigs with low social status.

This study examined the effects of environmental enrichment on aggressive behaviour and dominance relationships in growing pigs. Three hundred and twenty pigs were reared from birth to 15 weeks of age in either barren or enriched environments. The barren environments were defined by common intensive housing conditions (ie with slatted floors and in terms of recommended space allowances), while the enriched environments incorporated extra space and substrates for manipulation. Aggressive behaviour was observed in a social confrontation test during the suckling period and dominance relationships were assessed from a food competition test at 12 weeks of age. Animals were weighed at regular intervals throughout the experiment. Environmental enrichment reduced the expression of aggressive behaviour. Pigs from enriched rearing environments fought significantly less with unfamiliar animals than those from barren environments when tested under standard conditions (mean of 1.46 vs 2.75 fights per 30min test for enriched vs barren environments; SEM 0.20, P < 0.001). The nature of dominance relationships also appeared to differ between barren and enriched environments. In barren environments, dominance among pen mates was correlated with aggression (r = 0.33, P < 0.01), whereas in enriched environments it was correlated with body weight (r = 0.24, P < 0.01). Correlations between behaviour in the social confrontation and food competition tests suggested that dominance characteristics were established early in life and remained stable through the growing period.