Minimizing aggression during mixing of gestating sows with supplementation of a tryptophan-enriched diet

Intestinal tryptophan metabolism in disease prevention and swine production

Tryptophan (Trp) is an essential amino acid that cannot be synthesized by animals. It has been characterized into two different isomers, levorotation-Trp (L-Trp) and dextrorotation-Trp (D-Trp), based on their distinct molecule orientation. Intestinal epithelial cells and gut microbiota are involved in metabolizing L-Trp in the gut via the activation of the kynurenine, serotonin, and indole pathways. However, knowledge regarding D-Trp metabolism in the gut remains unclear. In this review, we briefly update the current understanding of intestinal L/D-Trp metabolism and the function of their metabolites in modulating the gut physiology and diseases. Finally, we summarize the effects of Trp nutrition on swine production at different stages, including growth performance in weaned piglets and growing pigs, as well as the reproduction performance in sows.

Systematic review of animal-based indicators to measure thermal, social, and immune-related stress in pigs

The intense nature of pig production has increased the animals’ exposure to stressful conditions, which may be detrimental to their welfare and productivity. Some of the most common sources of stress in pigs are extreme thermal conditions (thermal stress), density and mixing during housing (social stress), or exposure to pathogens and other microorganisms that may challenge their immune system (immune-related stress). The stress response can be monitored based on the animals’ coping mechanisms, as a result of specific environmental, social, and health conditions. These animal-based indicators may support decision making to maintain animal welfare and productivity. The present study aimed to systematically review animal-based indicators of social, thermal, and immune-related stresses in farmed pigs, and the methods used to monitor them. Peer-reviewed scientific literature related to pig production was collected using three online search engines: ScienceDirect, Scopus, and PubMed. The manuscripts selected were grouped based on the indicators measured during the study. According to our results, body temperature measured with a rectal thermometer was the most commonly utilized method for the evaluation of thermal stress in pigs (87.62%), as described in 144 studies. Of the 197 studies that evaluated social stress, aggressive behavior was the most frequently-used indicator (81.81%). Of the 535 publications examined regarding immune-related stress, cytokine concentration in blood samples was the most widely used indicator (80.1%). Information about the methods used to measure animal-based indicators is discussed in terms of validity, reliability, and feasibility. Additionally, the introduction and wide spreading of alternative, less invasive methods with which to measure animal-based indicators, such as cortisol in saliva, skin temperature and respiratory rate via infrared thermography, and various animal welfare threats via vocalization analysis are highlighted. The information reviewed was used to discuss the feasible and most reliable methods with which to monitor the impact of relevant stressors commonly presented by intense production systems on the welfare of farmed pigs.

Supplementary Tryptophan Fed to Sows Prior to and after Farrowing to Improve Piglet Growth and Survival

Simple Summary

Pre-weaning mortality is a significant economic and welfare issue for the Australian pig industry. Tryptophan can increase serotonin and melatonin production. Serotonin can decrease stress and indirectly increase calcium, which may improve sow health. Meanwhile, melatonin may decrease stillbirths and improve piglet viability at birth and, in turn, increase survival to weaning. This study determined whether feeding 0.16%, 0.42% or 0.56% tryptophan (per kg of feed) to sows during late pregnancy until seven days of lactation could improve piglet survival and viability to weaning and increase the levels of calcium and melatonin in sows. Supplementing tryptophan at levels of 0.42 and 0.56% increased piglet survival compared to no supplementation but did not have an effect on piglet viability. Furthermore, tryptophan supplementation did not increase sow melatonin and calcium levels compared to 0.16%. Further research is required to understand how tryptophan may improve piglet survival, particularly through sow maternal behaviour, and if 5-hydroxytryptophan (the form of tryptophan that directly converts to serotonin and melatonin) would further improve piglet survival.

Abstract

Tryptophan indirectly increases plasma calcium levels, which may improve sow health, and melatonin production, which may improve piglet survival when supplemented during late gestation and lactation. It was hypothesised that tryptophan would increase piglet survival and increase sow circulating melatonin and calcium. Seventy-two multiparous (Landrace x Large White) sows were allocated to either control (0.16% tryptophan; n = 24), low tryptophan (0.42%; n = 24) or high tryptophan (0.56%; n = 24). Piglet viability measures consisted of weights, behaviour, meconium staining, rectal temperature, blood glucose and serum immunoglobulin G concentration. Blood samples collected from sows were analysed for melatonin (two daytime and three night-time samples; n = 17) and calcium (two samples pre- and post-farrowing; n = 14). Both tryptophan treatments increased piglet survival compared to the control group (p < 0.001). Tryptophan had no effect on piglet viability (p > 0.05) and no effect on sow plasma melatonin and calcium concentrations compared with the control group (p > 0.05) except at 21:00 when low tryptophan sows had higher melatonin concentration compared with high tryptophan (p = 0.011). Further research to understand the mediating effects of tryptophan (particularly 5-hydroxytryptophan) on piglet survival, including sow behaviour, is warranted.

Effect of short-term high tryptophan diet fed to sows on their subsequent piglet behavior

Housing sows in groups create the challenge of decreasing fighting amongst sows. One proposed method to do so is to feed a high tryptophan diet, but the effect on the fetus is unknown. To investigate this, 66 sows were fed one of three diets: Control (0.14% SID tryptophan), Medium (0.28% SID tryptophan), or High (0.42% SID tryptophan), from days 28 to 35 of gestation. Sows gestated in standard gestation stalls. Blood samples were taken on day 27 prior to and on day 35 after tryptophan supplementation. On days 1, 2, and 3, nursing bouts were observed so as to record disputes and displacements from teat competition. The piglets' activity and fighting were recorded on days 3, 7, and 11 from 0700 to 1700 h. On day 12, four piglets per litter were blood sampled: two to be used in later behavior tests and two to act as controls for blood cortisol levels. On day 14, the two behavior test piglets from each litter were subjected to a 10-min Isolation Test and 5-min Human Approach Test. On day 15, the behavior test piglets were paired by sex and treatment (for example, a male Medium piglet paired with another male Medium piglet from a different crate) and each pair was subjected to a 10-min Social Challenge Test and immediately blood sampled. Piglet cortisol and serotonin did not differ among treatments (P > 0.10). There were no differences (P > 0.10) for number born (12.7 ± 0.4), born alive (11.7 ± 0.4), or mortality (1.1 ± 0.2). Behavior during nursing bouts was similar, with no treatment differences in number of disputes or displacements, and similar bout lengths among treatments (199.5 ± 4.6 s, P > 0.10). No differences were detected for any of the variables for Isolation or the Human Approach Tests (P > 0.10). During the Social Challenge Test, High piglets had more contacts approaching the head of the companion piglet than did either Medium or Control piglets (14.3 ± 1.1, 10.7 ± 1.1, and 9.69 ± 0.8, respectively, P < 0.02). Total number of aggressive interactions during the test tended to be greater for Medium piglets compared to High piglets (9.3 ± 1.5 vs 5.1 ± 0.9, P < 0.07). Time budget data of the litter indicate that piglets from all three treatments spent equal amounts of time active and inactive (P > 0.10). Aggression was low with 0.3 ± 0.04% of piglets displaying aggressive behavior. Feeding high concentrations of tryptophan for a short duration early in gestation does not have a negative impact on sows' subsequent offspring.

Is Magnesium Supplementation an Effective Nutritional Method to Reduce Stress in Domestic Pigs? A Systematic Review

In commercial pig production, stressful events are common and can have detrimental impacts on the pig's health and welfare, as well as on the performance of the farm. Supplementary magnesium may reduce stress, and subsequent harmful and aggressive behaviors, that occur during stressful events, such as regrouping. However, reports on the efficacy of this treatment are mixed. We aimed to systematically review the studies in which magnesium was given to pigs to examine the effects on measures of stress. Of the 16 studies included in the final corpus, 10 reported at least one statistically significant beneficial effect of supplementary magnesium on reducing stress. However, two studies found that magnesium significantly increased stress suggesting supplementary dietary magnesium may be harmful in some cases. Overall, there are a limited number of studies investigating the possible effect of magnesium on reducing stress in pigs, and although results were varied, the majority found beneficial effects of supplementary magnesium.

Pig farmers' willingness to pay for management strategies to reduce aggression between pigs

When deciding whether to invest in an improvement to animal welfare, farmers must trade-off the relative costs and benefits. Despite the existence of effective solutions to many animal welfare issues, farmers’ willingness to pay for them is largely unknown. This study modelled pig farmers’ decisions to improve animal welfare using a discrete choice experiment focused on alleviating aggression between growing/finishing pigs at regrouping. Eighty-two UK and Irish pig farm owners and managers were asked to choose between hypothetical aggression control strategies described in terms of four attributes; installation cost, on-going cost, impact on skin lesions from aggression and impact on growth rate. If they did not like any of the strategies they could opt to keep their current farm practice. Systematic variations in product attributes allowed farmers’ preferences and willingness to pay to be estimated and latent class modelling accounted for heterogeneity in responses. The overall willingness to pay to reduce lesions was low at £0.06 per pig place (installation cost) and £0.01 per pig produced (running cost) for each 1% reduction in lesions. Results revealed three independent classes of farmers. Farmers in Class 1 were unlikely to regroup unfamiliar growing/finishing pigs, and thus were unwilling to adopt measures to reduce aggression at regrouping. Farmers in Classes 2 and 3 were willing to adopt measures providing certain pre-conditions were met. Farmers in Class 2 were motivated mainly by business goals, whilst farmers in Class 3 were motivated by both business and animal welfare goals, and were willing to pay the most to reduce aggression; £0.11 per pig place and £0.03 per pig produced for each 1% reduction in lesions. Farmers should not be considered a homogeneous group regarding the adoption of animal welfare innovations. Instead, campaigns should be targeted at subgroups according to their independent preferences and willingness to pay.

Including dietary fiber and resistant starch to increase satiety and reduce aggression in gestating sows

Aggression during mixing of pregnant sows impacts sow welfare and productivity. The aim of this study was to increase satiety and reduce aggression by including dietary fiber and fermentable carbohydrates. Sows were housed in individual stalls 7 to 14 d after breeding (moving day was considered d 0 of treatment) and were fed (at 0700 h) with a CONTROL (corn-soybean meal based with no additional fiber sources), RSTARCH (10.8% resistant starch), BEETPULP (27.2% sugar beet pulp), SOYHULLS (19.1% soybean hulls), or INCSOY (14.05% soybean hulls) for 21 d (5 sows/diet × 5 diets × 8 replications = 200 sows). The CONTROL diet was targeted to contain 185 g(d∙sow) NDF and the other diets were targeted to contain 350 g(d∙sow) NDF. The INCSOY diet was fed at 2.2 kg/(d∙sow) and the other diets were fed at 2 kg(d∙sow). On d 22, sows were mixed in groups of 5 (at 1200 h). Behaviors in stalls (on d 1, 7, 14, and 21) and after mixing (d 22 and 23), heart rate (on d 1, 7, 14, and 21), blood metabolites (on d 2, 8, 15, 22, and 25), and the effects of diets on production were collected and analyzed. Sows stood more ( < 0.01) and rested less ( < 0.001) over time irrespective of the diet. Sows on BEETPULP stood more ( < 0.01) and sows on SOYHULLS rested more ( < 0.01). Sham chewing increased over days irrespective of the diet. Chewing behavior (bar and feeder) increased with days on diet ( < 0.001) and was lowest in sows on the SOYHULLS diet ( = 0.045). When mixed, biting frequency in the first hour was highest for sows on the CONTROL diet (236.5 ± 62.6) and lowest for sows on the RSTARCH diet (90.5 ± 30.5). Skin lesions increased ( < 0.001) 24 h after mixing sows irrespective of diet. Blood urea nitrogen (BUN) concentration was lowest in sows fed BEETPULP and SOYHULLS ( < 0.001). Serum glucose concentration was highest in sows fed RSTARCH and BEETPULP ( = 0.04), but there was no day effect ( = 0.62) or diet × day interaction ( = 0.60). The NEFA was greatest in sows fed RSTARCH, BEETPULP, and SOYHULLS ( < 0.001). Lactate ( < 0.001) and BUN concentrations were greatest on d 2 but dropped and remained constant after d 8. Average heart rate was lowest for sows on SOYHULLS and INCSOY compared with sows on the other diets ( = 0.03). Number of piglets born and average weaning weight were not affected by diets ( > 0.05). Average birth weight was lowest in the INCSOY diet ( = 0.02). This study demonstrates that RSTARCH and SOYHULLS can improve the welfare of sows by reducing aggression and increasing satiety in limit-fed pregnant sows without affecting production.

A review of the immunomodulatory role of dietary tryptophan in livestock and poultry

Tryptophan, a nutritionally essential amino acid, is active in the regulation of immune responses in animals. The products of tryptophan metabolism, such as indoleamine 2,3-dioxygenase, kynurenine, quinolinic acid, and melatonin, may improve immunity in an organism and induce anti-inflammatory responses. The immune tolerance processes mediated by tryptophan metabolites are not well understood. Recent studies have reported that the enzymes that break down tryptophan through the kynurenine metabolic pathway are found in numerous cell types, including immunocytes. Moreover, some tryptophan metabolites have been shown to play a role in the inhibition of T lymphocyte proliferation, elevation of immunoglobulin levels in the blood, and promotion of antigen-presenting organization in tissues. This review summarizes the effects and mechanisms of tryptophan and metabolites in immune functions in livestock and poultry. It also highlights the areas in which our understanding of the role(s) of tryptophan is incomplete and suggests possible future research that might prove of benefit to livestock and poultry producers.

Impact of group housing of pregnant sows on health

Group housing of sows during gestation is mandatory in the EU since 2013. Compared to housing in individual crates, group housing allows the animals to express normal activity and behavior. The present paper discusses the impact of group housing on health, with emphasis on lameness, aggression and possible spread of infectious diseases. The prevalence of lameness is generally higher in sows housed in group than in sows housed individually. Floor space per sow, group size, pen design and flooring are the main factors of group housing involved in lameness development. Especially floor characteristics are important, and particular attention should be paid to the type, building material and quality of the floor, hygiene and the use of bedding such as straw or rubber mats. Aggression between sows is another critical issue in group housing systems. It occurs predominantly because of competition for access to a limited resource, or to establish a social hierarchy. Key factors to prevent aggression in group housing include gradual familiarization of unfamiliar animals, sufficient space and pen structure during initial mixing, minimizing opportunities for dominant sows to steal food from subordinates, provision of a good quality floor, environmental enrichment and use of straw bedding. Very scarce evidence-based information is available on the relationship between group housing and infectious disease. Compared to individual housing, sows in group housing have more nose-to-nose contact, and they have more oral contact with feces and urine. These factors could contribute to a higher or faster transmission of pathogens, but so far, there is no evidence showing more disease problems in group housing systems. In conclusion, in group housing systems, particular attention should be paid to prevention of lameness and aggression. Management is crucial but also feeding strategies, floor and bedding, and design of housing are very important as relatively minor adjustments may exert major effects on the animals.

Automatic Recognition of Aggressive Behavior in Pigs Using a Kinect Depth Sensor

Aggression among pigs adversely affects economic returns and animal welfare in intensive pigsties. In this study, we developed a non-invasive, inexpensive, automatic monitoring prototype system that uses a Kinect depth sensor to recognize aggressive behavior in a commercial pigpen. The method begins by extracting activity features from the Kinect depth information obtained in a pigsty. The detection and classification module, which employs two binary-classifier support vector machines in a hierarchical manner, detects aggressive activity, and classifies it into aggressive sub-types such as head-to-head (or body) knocking and chasing. Our experimental results showed that this method is effective for detecting aggressive pig behaviors in terms of both cost-effectiveness (using a low-cost Kinect depth sensor) and accuracy (detection and classification accuracies over 95.7% and 90.2%, respectively), either as a standalone solution or to complement existing methods.

Serotonergic outcome, stress and sexual steroid hormones, and growth in a South American cichlid fish fed with an L-tryptophan enriched diet

Reared animals for edible or ornamental purposes are frequently exposed to high aggression and stressful situations. These factors generally arise from conspecifics in densely breeding conditions. In vertebrates, serotonin (5-HT) has been postulated as a key neuromodulator and neurotransmitter involved in aggression and stress. The essential amino acid L-tryptophan (trp) is crucial for the synthesis of 5-HT, and so, leaves a gateway for indirectly augmenting brain 5-HT levels by means of a trp-enriched diet. The cichlid fish Cichlasoma dimerus, locally known as chanchita, is an autochthonous, potentially ornamental species and a fruitful laboratory model which behavior and reproduction has been studied over the last 15years. It presents complex social hierarchies, and great asymmetries between subordinate and dominant animals in respect to aggression, stress, and reproductive chance. The first aim of this work was to perform a morphological description of chanchita's brain serotonergic system, in both males and females. Then, we evaluated the effects of a trp-supplemented diet, given during 4weeks, on brain serotonergic activity, stress and sexual steroid hormones, and growth in isolated specimens. Results showed that chanchita's brain serotonergic system is composed of several populations of neurons located in three main areas: pretectum, hypothalamus and raphe, with no clear differences between males and females at a morphological level. Animals fed with trp-enriched diets exhibited higher forebrain serotonergic activity and a significant reduction in their relative cortisol levels, with no effects on sexual steroid plasma levels or growth parameters. Thus, this study points to food trp enrichment as a "neurodietary'' method for elevating brain serotonergic activity and decreasing stress, without affecting growth or sex steroid hormone levels.