Agonistic behaviour, skin lesions and activity pattern of entire male, female and castrated male finishing pigs

Identifying Early Indicators of Tail Biting in Pigs by Variable Selection Using Partial Least Squares Regression

This study examined relevant variables for predicting the prevalence of pigs with a tail lesion in rearing (REA) and fattening (FAT). Tail lesions were recorded at two scoring days a week in six pens in both REA (10 batches, 840 scoring days) and FAT (5 batches, 624 scoring days). To select the variables that best explain the variation within the prevalence of pigs with a tail lesion, partial least squares regression models were used with the variable importance in projection (VIP) and regression coefficients (β) as selection criteria. In REA, five factors were extracted explaining 60.6% of the dependent variable's variance, whereas in FAT five extracted factors explained 62.4% of the dependent variable's variance. According to VIP and β, seven variables were selected in REA and six in FAT with the tail posture being the most important variable. In addition, skin lesions, treatment index in the suckling phase, water consumption (mean), activity time (mean; CV) and exhaust air rate (CV) were selected in REA. In FAT, additional musculoskeletal system issues, activity time (mean; CV) and exhaust air rate (mean; CV) were selected according to VIP and β. The selected variables indicate which variables should be collected in the stable to e.g., predict tail biting.

Welfare of pigs on farm

This scientific opinion focuses on the welfare of pigs on farm, and is based on literature and expert opinion. All pig categories were assessed: gilts and dry sows, farrowing and lactating sows, suckling piglets, weaners, rearing pigs and boars. The most relevant husbandry systems used in Europe are described. For each system, highly relevant welfare consequences were identified, as well as related animal-based measures (ABMs), and hazards leading to the welfare consequences. Moreover, measures to prevent or correct the hazards and/or mitigate the welfare consequences are recommended. Recommendations are also provided on quantitative or qualitative criteria to answer specific questions on the welfare of pigs related to tail biting and related to the European Citizen's Initiative 'End the Cage Age'. For example, the AHAW Panel recommends how to mitigate group stress when dry sows and gilts are grouped immediately after weaning or in early pregnancy. Results of a comparative qualitative assessment suggested that long-stemmed or long-cut straw, hay or haylage is the most suitable material for nest-building. A period of time will be needed for staff and animals to adapt to housing lactating sows and their piglets in farrowing pens (as opposed to crates) before achieving stable welfare outcomes. The panel recommends a minimum available space to the lactating sow to ensure piglet welfare (measured by live-born piglet mortality). Among the main risk factors for tail biting are space allowance, types of flooring, air quality, health status and diet composition, while weaning age was not associated directly with tail biting in later life. The relationship between the availability of space and growth rate, lying behaviour and tail biting in rearing pigs is quantified and presented. Finally, the panel suggests a set of ABMs to use at slaughter for monitoring on-farm welfare of cull sows and rearing pigs.

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.

A multi-suckling system combined with an enriched housing environment during the growing period promotes resilience to various challenges in pigs

Little is known about the impact of social and environmental enrichment on improving livestock resilience, i.e. the ability to quickly recover from perturbations. We evaluated the effect of an alternative housing system (AHS) on resilience of pigs, as compared to conventional housing (CONV). The AHS consisted of multi-litter housing during lactation, delayed weaning, extra space allowance and environmental enrichment at all times. We assessed recovery to a 2 h-transport challenge, an LPS injection, 2 h-heat stress and a biopsy wound in 96 pigs. Additionally, indicators of long-term “wear and tear” on the body were determined. AHS pigs had better physiological recoveries with quicker returns to baseline in the transport and LPS challenges, showed lower cortisol accumulation in hairs and lower variance in weight gain over the experimental period compared to conventionally-housed (CONV) pigs. They also had higher levels of natural antibodies binding KLH than CONV pigs. Their response to heat stress revealed a different strategy compared to CONV pigs. Taken together, AHS pigs appear to be more resilient and experience less chronic stress. Enhancing welfare by provision of social and environmental enrichment that better meets the behavioural needs of pigs seems to be a promising approach to improve their resilience.

Evaluation of Two Injection Techniques in Combination with the Local Anesthetics Lidocaine and Mepivacaine for Piglets Undergoing Surgical Castration

The present study evaluated the effects of two injection techniques in combination with lidocaine or mepivacaine for piglets undergoing castration. To improve ease of use, a cannula with side holes (one-step fenestrated (F)) was invented to simultaneously deliver a local anesthetic into the testis and scrotum and was compared to a two-step injection technique. The distribution of a lidocaine/contrast agent mixture using the two methods was examined using computed tomography. Piglets were randomly divided into treatment groups: handling, castration without pain relief and castration after lidocaine or mepivacaine injection using the one-step F or two-step method. Acute physiological responses to noxious stimuli were evaluated by measuring the mean arterial blood pressure (MAP), heart rate (HR) and nocifensive movements. Fos protein expression in the spinal dorsal cord was semi-quantitatively analyzed. Both injection techniques achieved similar distribution patterns. The one-step F method was faster and easier. Injection was not associated with significant changes in MAP or HR, but Mepi1 and NaCl elicited significantly increased nocifensive movements. Both techniques significantly reduced MAP and nocifensive movements when the spermatic cords were cut, regardless of the local anesthetic type. Compared to NaCl, only the lidocaine treatments significantly reduced HR during skin incision. Lido2 significantly reduced Fos protein expression.

Reproductive status effects of pair-housed male pigs on natural, agonistic and sexual behaviours

Boar rearing, which avoids pain and suffering caused by surgical castration, provides better performance, a greater deposition of muscle tissue and leaner carcasses and thus has beneficial effects on both animal welfare and the product. Some countries that do not slaughter boars must consider their boar taint and aggressive and sexual behaviours. Considering that pigs are housed in large groups, which may complicate the formation of social hierarchies and increase fighting and mounting behaviours, some studies have conducted research with reduced numbers of pigs per pen, but these behaviours continued to be observed. However, a study of the reproductive status of pair-housed male pigs has yet to be reported. The aim of this study was to determine whether the reproductive status of uncastrated, immunocastrated and surgically castrated pair-housed male pigs alters their natural, agonistic and sexual behaviours. A total of 48 male pigs from Agroceres PIC™ genetics were assigned to three groups: surgically castrated (barrows), immunocastrated and uncastrated (boars). Natural, aggressive and sexual behaviours of the pigs were assessed by direct observations during four periods of 12 h each (six, five and three weeks before slaughter and the slaughter week). The pigs were housed in pairs from the growing phase until slaughter. Animal behaviour was observed from the finishing phase to slaughter. Carcass lesions were assessed according to five different classes (one: no injury; two to five: severely injured). Overall, boars spent more time lying and less time eating and drinking than barrows. In total of all the periods (48 h), boars expressed more aggressive and sexual behaviours than barrows, whereas immunocastrated pigs displayed similar behaviours to boars, before and after the second vaccine dose. No differences in carcass lesions between treatments and no prevalence of carcasses with severe injuries were observed. In conclusion, the reproductive status of pair-housed male pigs did not change the natural behaviour of boars, immunocastrated pigs or barrows. The agonistic and sexual behaviours of boars and barrows remained unchanged. When housing pigs in pairs, immunocastrated pigs presented similar agonistic and sexual behaviours to boars before and after the second immunocastration vaccine dose. The use of pair-housed uncastrated male pigs has generated welfare benefits for these animals, as the number of carcasses with injuries did not differ from barrows and immunocastrated pigs.

Welfare Aspects of Raising Entire Male Pigs and Immunocastrates

Simple Summary

Surgical castration of male piglets without pain treatment and anaesthesia is not only a welfare problem but also violates the integrity of the animals. The favoured alternatives of raising entire male pigs (EM) with or without immunocastration (vaccination against boar taint) may, however, impose additional welfare problems under the current housing and management conditions. This focused review is intended to summarise the current state of scientific knowledge and practical reports on critical welfare issues and risk factors. Raising EM with or without subsequent immunocastration could be a welfare conform, future-oriented alternative to conventional surgical castration of pigs, provided that they are kept in a healthy and socially stable environment with sufficient physical resources, as safeguarded by measures of enhanced animal care and management control.

Abstract

For a long time, scientists assumed that newborns have a severely limited sense of pain (if any). However, this assumption is wrong and led to a “start of the exit” from piglet surgical castration. Some of the currently discussed or already implemented alternatives such as general or local anaesthesia during surgical castration raise additional welfare concerns as well as legal problems and/or are hardly applicable. The favoured long-term, welfare-friendly “gold standard” is to raise entire male pigs (EM). However, this may also impose certain welfare problems under the current conventional housing and management conditions. The specific types of behaviour displayed by EM such as mounting and aggressive behaviours but also increased exploration, which are partially linked to sexual maturation, increase the risk for injuries. The current status of knowledge (scientific literature and farmer experiences) on housing of EM suggests that environmental enrichment, space, group-stability, social constellation, feeding (diet and feeder space), health and climate control are critical factors to be considered for future housing systems. From an animal welfare point of view, an intermediate variant to be favoured to reduce problematic behaviour could be to slaughter EM before reaching puberty or to immunize boars early on to suppress testicular function. Immunization against endogenous GnRH can reduce EM-specific problems after the 2nd vaccination.

Local Anesthesia in Piglets Undergoing Castration-A Comparative Study to Investigate the Analgesic Effects of Four Local Anesthetics Based on Defensive Behavior and Side Effects

Simple Summary

More than 80 million male piglets are castrated every year within the first week of life mostly without pain relief in the EU. Castration is performed to prevent boar taint, to minimize aggressive and sexual behavior associated with intact males and to gain a constant quality of meat. It is an important animal welfare issue to eliminate pain caused by castration. Local anesthesia, meaning the sole injection of a local anesthetic into the testicles and in the surrounding tissue of conscious piglets, prior to castration is a currently discussed method in Germany. Thus, it was the aim of the present study to investigate the effect of four local anesthetics (procaine, lidocaine, bupivacaine and mepivacaine) on pain relief during surgical castration in conscious piglets. To assess pain, defensive behavior of piglets undergoing injection and castration was evaluated. In addition, attention was paid to possible side effects. Considering healing, bleeding and weight gain no negative impacts were observed, but impairments of locomotor activity occurred. The results indicate that lidocaine and mepivacaine are able to achieve significant pain relief during the castration procedure, whereas procaine and bupivacaine only during the severing of the spermatic cord.

Abstract

The aim of the present study was to investigate the effect of four local anesthetics on pain relief during surgical castration under standardized conditions in conscious piglets. Therefore, 71 male piglets (three to seven days) were distributed into control groups (handling, castration without anesthesia or analgesia) and local anesthetic trial groups (procaine, lidocaine, bupivacaine, mepivacaine). Then, 20 min prior to castration, animals of the treatment groups, except piglets in the handling group, received an injection of a local anesthetic or sodium chloride of 0.5 mL intratesticularly and 0.5 mL subscrotally. During injection and castration, defensive behavior was evaluated. Locomotor activity, as well as postoperative bleeding, wound healing and average daily weight gain were assessed to detect side effects. The injection caused increased defensive movements, significantly in the bupivacaine group. Lidocaine and mepivacaine significantly reduced defensive movements during castration, and procaine and bupivacaine only during severing of the spermatic cord. Impairments of locomotor activity were found in piglets injected with lidocaine, bupivacaine or sodium chloride. Considering healing, bleeding and weight gain, no negative impacts were observed. In conclusion, lidocaine and mepivacaine were able to achieve significant pain relief during the castration procedure, whereas procaine and bupivacaine only during the severing of the spermatic cord. Moreover, the injection of bupivacaine seemed to be painful itself.

Social genetic effects for growth in pigs differ between boars and gilts

Background

Average daily gain (ADG) in pigs is affected by the so-called social (or indirect) genetic effects (SGE). However, SGE may differ between sexes because boars grow faster than gilts and their social behaviours differ. We hypothesized that direct genetic effects (DGE) and SGE for ADG in pigs differ between boars and gilts and that accounting for these differences will improve the predictive ability of a social genetic effects model (SGM). Our data consisted of ADG from 30 to 94 kg for 32,212 uncastrated males (boars) and 48,252 gilts that were raised in sex-specific pens. Data were analyzed using a univariate model with sex as a fixed effect and a bivariate model with ADG in boars and gilts as separate traits using both a classical animal model (CM) and a SGM.

Results

With the univariate model, the heritability for ADG was 0.22 ± 0.01 for the CM, while the estimate of the total heritable variance (T²) was 0.23 ± 0.01 with the SGM. With the bivariate model, the genetic variance for SGE was higher for boars (13.8 ± 5.8) than for gilts (9.3 ± 3.9). For the bivariate model, T² was 0.32 ± 0.02 for boars and 0.27 ± 0.01 for gilts. Estimates of the genetic correlations between DGE (0.88 ± 0.02) and SGE (0.30 ± 0.30) for boars versus gilts indicated that ADG in boars and gilts are different traits. Moreover, the estimate of the genetic correlation between DGE and SGE indicated presence of genetic effects of competition among gilts but not among boars. Compared to a CM, the univariate SGM improved predictive ability significantly only for gilts and the bivariate SGM improved predictive ability significantly for both boars and gilts.

Conclusions

We found significant genetic variances of SGE for ADG. The covariance between DGE and SGE was much more negative for gilts than for boars when applying the bivariate model. Because the estimate of the genetic correlation for ADG between gilts and boars differed significantly from 1 and the predictive ability for boars and gilts was improved significantly with the bivariate model, we recommend the use of a bivariate model to estimate both SGE and DGE for ADG in pigs.

Effect of piglet castration with nonsurgical sterilant on the zootechnical performance and pork carcass quality

ABSTRACT A non-surgical sterilant (NSS) was used with the objective of assessing the zootechnical performance, carcass and meat quality, and hormone levels. 90 male piglets were selected with birthweights varying between 1.5kg to 2.0kg. The control group was constituted of 45 males castrated by the conventional surgical method, at the seventh day of age, and the treated group was constituted of 45 males castrated with NSS (active principle of zinc gluconate in the concentration of 26.2mg/mL associated to the dimethyl sulfoxide at 0.5%), with the application of the first dose on the seventh day of age and the second dose on the fourteenth day of age. The zootechnical assessments were carried out on the farm and consisted: weight gain in the periods per animal and feed conversion. The slaughter of the animals and the assessment of the carcass and meat quality and hormone levels were carried out in a slaughterhouse and the municipality of Campinas (SP). The study demonstrated that the use of NSS was a viable alternative in relation to the zootechnical performance and the carcass quality. In relation to the meat quality there was no significant difference in the majority of the assessed parameters.