Reproductive issues in welfare-friendly housing systems in pig husbandry: a review

A systematic review of the impact of housing on sow welfare during post-weaning and early pregnancy periods

Breeder animals are an important focus in farm animal welfare assessments as they typically live the longest lives and are at the greatest risk for suffering due to their longevity. For breeding pigs, the time between the end of lactation (post-weaning) and the implantation of embryos (early gestation) is very dynamic from both a physiological and husbandry perspective. However, research to date is limited on how best to house and manage sows during this critical period of their production cycle from a welfare perspective. Previous animal-based welfare outcome measures were restricted to certain health, behavioral and physiological indicators. This systematic review used Web of Science to make in-depth comparisons among welfare-based studies that focus on sow housing during the post-weaning and early pregnancy period to identify important knowledge gaps. Only a small number of studies (n = 27) were found that met our systematic search criteria. Compared to stalls, group housing requires mixing of animals and always triggers more aggression and skin lesions at the time of mixing. The predominant use of health and physiological indicators constrained the animal-based welfare outcomes in these studies. Thus, what type of housing yields the best overall welfare outcome remains to be elucidated as none of the studies found explored the mental wellbeing of sows during this period. This systematic review defines a critical knowledge gap regarding the full impact of housing on the welfare of post-weaning and early gestation sows. This gap, and thus the true welfare impact of sow housing, will only be addressed by the use of novel, more holistic assessment methods that also capture the psychological state of the sow.

Measurement of cortisol, cortisone and 11β-hydroxysteroid dehydrogenase type 2 activity in hair of sows during different phases of the reproductive cycle

Two sensitive assays based on AlphaLISA technology were developed and validated for the measurement of cortisol and cortisone in hair of pigs, that also enabled estimation of 11β-hydroxysteroid dehydrogenase type 2 activity. These assays were applied to hair samples from sows (n = 32) collected at 5 days before, and at 23 and 59 after farrowing, in reproductive cycles in two different periods: spring-summer (n = 16) and winter-spring (n = 16). The assays were precise (imprecision <12%) and accurate (recovery range, 80-115%) for cortisol and cortisone determination. Hair cortisone concentrations and the cortisone/cortisol ratio (an estimate of 11β-hydroxysteroid dehydrogenase isoenzyme type 2 activity) increased after farrowing more than cortisol, being these changes of higher magnitude during periods of higher atmospheric temperature. The measurement of hair cortisone concentrations and estimations of the activity of the 11β-hydroxysteroid dehydrogenase isoenzyme type 2, measured by the assays developed in this study, are complementary biomarkers to hair cortisol, and can increase at periods associated with stress, such as farrowing and lactation, especially at high atmospheric temperatures. .

Endoparasites in Sows and Selected Reproduction Parameters

The aim of the study was to analyze infection of sows with endoparasites depending on their physiological phase and length of exploitation, as well as to determine the effects of infection on selected parameters of reproductive performance. 300 fecal samples collected from the same 75 sows in 4 phases of the production cycle (dry sows, low pregnancy, high pregnancy, lactation) were tested in the experiment. Species and gender diversity, prevalence, OPG and EPG were determined in the study. These parameters were compared in terms of the physiological phase and the length of exploitation. Selected parameters of reproductive performance of sows were also examined, which were compared taking into account the length of exploitation and sows infection with individual parasites.

The study showed that the entire population was infected with two parasites at all physiological phases: Eimeria spp. (17% prevalence, 2275 OPG) and Ascaris suum (5% prevalence, EPG 79). The presence of parasites from Eimeria genus (prevalence 40%, OPG 2976) in sows exploited for 1 year had a negative effect on some parameters of their reproduction performance. Infected sows, compared to noninfected ones, were characterized by a lower number of live piglets (by 0.21 heads) (p≤0.05), a higher number of stillborn piglets (by 0.21 heads) (p≤0.05), as well as lower daily weight gains of piglets (by 15 g) (p≤0.05), which contributed to their lower weaning body weight (by 0.45 kg) (p≤0.05).

Physiological and economic benefits of abandoning invasive surgical procedures and enhancing animal welfare in swine production

Food-animal welfare is a major ethical and social concern. Pork is the most consumed meat worldwide, with over a billion pigs slaughtered annually. Most of these pigs routinely undergo painful surgical procedures (surgical castration, tail docking, teeth clipping), which farmers often reluctant to avoid, claiming it would increase cost and reduce production efficiency. Herein, this study indicates that these procedures compromise pigs' health and condition. Replacing surgical castration with immunocastration, avoiding tail docking and teeth clipping, and providing environmental enrichment, resulted in significant increase in weight gain, lowered risks for injuries and death, and reduced saliva and hair cortisol, both biomarkers for stress. Testosterone and DHEA analyses confirmed that immunocastration was an effective alternative to surgical castration. Economic models for the entire US swine market revealed that following across-the-board acceptance of this management, pork meat price is expected to drop, while the total annual social welfare (combined consumer and producer surplus) is expected to increase by $US 1.48 to 1.92 billion. In conclusion, sustainable swine farming management can be beneficial for both animals and farmers. Applying such welfare-friendly management is expected to reduce stress, enhance piglet/pig welfare and production, and improve the economics of swine operations in the global agro-food system.

Developments of reproductive management and biotechnology in the pig

This review aims to describe changes in production environment, management tools and technology to alleviate problems seen with the present hyperprolific sow model. Successful parturition in the pig includes the possibility to express adequate maternal behaviour, rapid expulsion of piglets, complete expulsion of placenta, elimination of uterine contamination and debris, neonatal activity and colostrum intake. We focus on management of large litters, including maternal behaviour, ease of parturition, colostrum production, piglet quality parameters and intermittent suckling. There are also some interesting developments in technology to assess colostrum and immune state of the piglet. These developments may be utilized to improve the success rate of reproductive management around farrowing, lactation and after weaning. We also discuss new insights in how to examine the health of the mammary gland, uterus and ovaries of hyperprolific sows. Finally, we assess the latest developments on breeding and technology of hyperprolific sows, including artificial insemination (AI), real-time ultrasound of the genital tract and embryo transfer (ET). We conclude that 1) for the sow to produce sufficient colostrum, both the behavioural and physiological needs of the sow need to be met before and after parturition. Furthermore, 2) new ultrasound and biopsy technology can be effectively applied for accurate diagnosis of inflammatory processes of the udder and uterus and timing of AI regarding ovulation to improve insemination efficiency. Finally, 3) developments in cryopreservation of germ cells and embryos appear promising but lack of valid oocyte collection techniques and nonsurgical ET techniques are a bottleneck to commercial ET. These latest developments in management of parturition and reproductive technology are necessary to cope with the increasing challenges associated with very large litter sizes.

Recent advances in pig reproduction: Focus on impact of genetic selection for female fertility

In the past 30 years, sows have been successfully selected for a shorter weaning-to-oestrus interval and increased litter size. This review discusses the consequences of this selection for the reproductive physiology of sows, including the consequences for litter characteristics at birth. It also discusses breeding and management opportunities to deal with this changed genetics.

Parturition effects on reproductive health in the gilt and sow

In this review, we address significant characteristics of parturition in the pig and their connection to post-partum reproductive health and fertility. We discuss the normal physiology and behaviour around parturition and the effect of the second phase (expulsion of foetuses) on the third phase of parturition (expulsion of foetal membranes). In addition, we intend to cover retained placenta, and the connection to post-partum uterine health and fertility in the contemporary prolific sow. We also explore factors that support successful parturition or can cause potential problems. Successful parturition in the pig includes the possibility to express adequate maternal behaviour, rapid expulsion of the piglets, complete expulsion of the placenta, neonatal activity and colostrum intake. Abnormal incidents during any phase of parturition can cause subsequent problems. Duration of the expulsion phase of foetuses can be used as a simple measure of whether parturition is considered successful. Prolonged parturition can impair health of the sow and piglet and fertility after weaning. New insights, such as adding more fibre to sow diets during pregnancy, and especially during the period prior to farrowing, may prevent constipation, increase water intake of the sow around parturition and increase milk intake and performance of piglets. Maternal characteristics, including maternal behaviour, ease of parturition, colostrum production and piglet quality parameters, may be utilized to improve success rate of reproductive management during farrowing and early lactation. Additionally, we share some of the recent developments in methods, including ultrasonography in evaluation of post-partum uterine health. In conclusion, successful farrowing is of the greatest importance for reproductive health of the sow and survival of the piglets. We suggest connections exist among prolonged farrowing and yield of colostrum, retained placenta, development of PDS, and impaired involution of the uterus and reduced subsequent fertility.

Reproduction of group-housed sows

The sow is a social animal in her behavior throughout the reproductive cycle. An exception to her preference for being a part of a social group occurs one to two1–2 d days prior to farrowing, when she separates from her group and seeks for isolation in order to build up a nest. She then spends the first week or two with her piglets, mainly in the nest. After this short period of separation of 1–2 weeks, she brings her litter with her and rejoins the group. In modern intensive pig production, the sow is often restricted to an individual cage for lactation and, in many European countries, she may still spend additional periods in stalls during pregnancy. In the intensive production, isolation of the sow from the rest of the group is therefore a relatively long period of six to ten6-10 weeks, which creates a challenge for the social memory of the sow. While grouping of sows during lactation is an interesting option, until now this is encountered mostly in organic or otherwise extensive farming systems, such as outdoor farming. However, the present society is asking for more animal friendly models of production and there appears to be more need for studies of group housing issues during lactation. Grouping of sows after weaning causes stress, which imposes risks for fertility. Thus, timing of grouping is probably very critical. It is well documented that the embryonic period of the pregnancy, lasting up to Day 35, is more vulnerable for loss of pregnancy than the subsequent fetal period. There are indications that stress of grouping may cause some harm to vitality parameters of blastocysts already while at the site of fertilization in the oviduct. Later on, during the critical periods of maternal recognition of pregnancy, endocrinological models testing maintenance of pregnancy suggest that chronic stress lasting for more than two2 days may cause abortion and loss of the whole litter. However, the sow may be resistant, in terms of her reproductive function, to acute stress lasting for hours or up to a day. In conclusion, grouping of sows during lactation may be of interest in the future. At present, issues of group housed sows after weaning and early pregnancy seem to be of most practical relevance. Chronic stress of sows lasting for more than two2 days may lead to loss of the whole litter.

Hair cortisol determination in sows in two consecutive reproductive cycles

Hair analysis has been proposed as a minimally invasive technique capable of furnishing information regarding the stress response during medium- and long-term periods. Bristle samples were collected from the rump region of sows at three key physiological phases (before delivery - BD; weaning time - WT; pregnancy diagnosis - PD) during consecutive reproductive cycles in order to test swine hair as a reliable matrix of cortisol evaluation. Cortisol was extracted from the bristles and assayed using radioimmunoassay. The highest mean hair cortisol concentrations were demonstrated (p<0.001) at the PD time points (20.1±.95 and 16.29±2.15 pg/mg). Moreover, cortisol was significantly higher (p<0.001) at BD2 (10.48±0.96 pg/mg) as compared to BD1 (5.17±0.51 pg/mg) and WT1 (6.01±0.47 pg/mg). The various physiological phases had a significant effect on cortisol concentration (p<0.00001) with a higher cortisol concentration found during late pregnancy and lactation than in early-mid pregnancy. This could be due not only to the physiological hormonal status, but also to the different housing conditions (single crates vs. group housing). The season of the year was also observed to have an effect (p<0.005), with the lowest cortisol concentration recorded during the hot season.

A 25 years experience of group-housed sows-reproduction in animal welfare-friendly systems

Since January 1 2013, group housing of sows has been compulsory within the European Union (EU) in all pig holdings with more than ten sows. Sows and gilts need to be kept in groups from 4 weeks after service to 1 week before the expected time of farrowing (Article 3(4) of Directive 2008/120/EC on the protection of pigs). The legislation regarding group housing was adopted already in 2001 and a long transitional period was allowed to give member states and producers enough time for adaptation. Even so, group housing of sows still seems to be uncommon in the EU, and is also uncommon in commercial pig farming systems in the rest of the world. In this review we share our experience of the Swedish 25 years of animal welfare legislation stipulating that sows must be loose-housed which de facto means group housed. The two most important concerns related to reproductive function among group-housed sows are the occurrence of lactational oestrus when sows are group-housed during lactation, and the stress that is associated with group housing during mating and gestation. Field and clinical observations in non-lactating, group-housed sows in Sweden suggest that by making basic facts known about the pig reproductive physiology related to mating, we might achieve application of efficient batch-wise breeding without pharmacological interventions. Group housing of lactating sows has some production disadvantages and somewhat lower productivity would likely have to be expected. Recordings of behavioural indicators in different housing systems suggest a lower welfare level in stalled animals compared with group-housed ones. However, there are no consistent effects on the reproductive performance associated with different housing systems. Experimental studies suggest that the most sensitive period, regarding disturbance of reproductive functions by external stressors, is the time around oestrus. We conclude that by keeping sows according to the pig welfare-friendly Directive 2008/120/EC, it is possible to combine group-housing of sows with good reproductive performance and productivity. However, substantially increased research and development is needed to optimize these systems.

Lactation estrus induction in multi- and primiparous sows in an Australian commercial pork production system

This study evaluated the effect of full physical boar exposure and split weaning on the incidence of lactation estrus within a large commercial piggery. A total of 299 multiparous (MP; parity 2.5 ± 0.03) and 303 primiparous (PP) sows of Large White × Duroc × Landrace genetics were individually housed in conventional farrowing crates from 1 wk before expected farrowing until weaning on Day 30.7 ± 0.05 postparturition. Before shed entry, sows were allocated randomly within parity to receive either boar exposure (BE; n = 454) or no BE (No BE; n = 149). Sows assigned to receive BE were then allocated to 1 of 2 litter size treatments: litter size unchanged (BE; n = 302) or BE and the litter permanently reduced (split weaned) to 7 piglets (BESPW7; n = 152) on Day 18 of lactation. From Day 18 of lactation until weaning, sows in both BE treatments were taken daily to a detection mating area where they received 15 min of full physical BE and were artificially inseminated at the first observed estrus. Providing sows with BE increased the incidence of lactation estrus, with a further increase observed when litter size was reduced to 7 piglets (16% No BE vs. 62% BE and 75% BESPW7; P < 0.05). Multiparous sows exhibited a greater incidence of lactation estrus than PP sows irrespective of treatment (81 compared to 52%, respectively; P < 0.05). Both MP and PP sows exhibited an increased incidence of lactation estrus when a portion of the litter was removed (MP: 76 vs. 89% and PP: 47 vs. 61%; P < 0.05). Farrowing rates were higher in BE MP sows mated postweaning and all BESPW7 sows mated postweaning when compared to their counterparts mated in lactation (P < 0.05). Percentage live weight loss over the course of lactation was greatest for sows in the No BE compared to the BE and BESPW7 treatments (7.7% ± 0.5 vs. 5.4% ± 0.3 and 4.5% ± 0.4, respectively; P < 0.05). Between Day 17 and weaning, piglets suckling sows in the BESPW7 treatment had a higher average weight gain than piglets suckling sows with a full litter (3.5 ± 0.06 vs. 3.1 ± 0.05 kg; P < 0.05). In conclusion these data suggest that providing MP sows with BE is effective at stimulating a synchronous lactation estrus while PP sows require, in addition to BE, a reduction in suckled litter size to 7 piglets.

Comparison of management options for sows kept in pens with electronic feeding stations

Li, Y. Z. and Gonyou, H. W. 2013. Comparison of management options for sows kept in pens with electronic feeding stations. Can. J. Anim. Sci. 93: 445–452. A variety of management options exist for group-housed sows and these may affect animal welfare and performance. A study was conducted to examine the effect of two management options on the performance and chronic injuries of gestating sows group-housed with electronic sow feeders (ESF). The management options examined were social management (static vs. dynamic groups) and stage of gestation at mixing (pre-implantation vs. post-implantation of embryos), with sows in stalls serving as reference. Multiparous sows (n = 1569 sow records, parity 1 to 9, PIC genetics) from 100 contemporary breeding groups were used. Group-housed sows (n = 1112 sow records) were assigned to a 2×2 factorial arrangement of management treatments. Each static group consisted of 35 to 40 sows that were grouped simultaneously and no further sows were added to the group. Dynamic groups consisted of 105 to 120 sows, with 35 to 40 sows being added to the group every 5 wk after the same number of sows had been moved out for farrowing. Results indicate that social management did not affect farrowing rate and weight change during gestation. However, sows in static pens sustained fewer (P = 0.01) skin lesions (cuts, swellings, and wounds) and had fewer incidences (P = 0.01) of lameness before farrowing than sows in the dynamic pen. Pre-implant sows had a lower farrowing rate (82.3% vs. 86.7%, P = 0.05), but had fewer skin lesions before farrowing (P <0.01) compared with post-implant sows. Neither social management nor stage of gestation at mixing affected total born, born alive or stillborn litter sizes. In general, sows group-housed with ESF performed similar to sows in stalls, but sustained fewer skin lesions before farrowing. These results demonstrate that management options can affect the reproductive performance and injuries of gestating sows in the ESF system.