Animal board invited review: The need to consider emissions, economics and pig welfare in the transition from farrowing crates to pens with loose lactating sows.

In the development and implementation of housing systems for pigs, there has been a significant focus on pig welfare including loose housing of lactating sows either indoors or outdoors. However, it is equally important to consider the environmental and economic aspects of housing systems to ensure sustainability in livestock production. The aim of this work was to review the sustainability (societal and animal welfare, environmental and economic impact) of different approaches for housing farrowing and lactating sows in indoor environments. The review illustrates that like outdoor systems, indoor housing systems are challenged in meeting the three pillars of sustainability when changing the housing of lactating sows from conventional crates with permanent confinement to systems with temporary or zero-confinement. Increased space allowance increases sow welfare, but in addition, pen designs with increased space increase ammonia emission, investment and running costs. Furthermore, indoor loose lactation systems come with an increased risk for piglet mortality, which unless effectively managed, reduces animal welfare and the economic sustainability of the system. If farms retrofit existing buildings, the larger space per loose farrowing pen leads to a reduction in pen numbers and therefore herd size, reducing the farm profitability. If farmers choose to reduce herd size to meet requirements, welfare will be reduced while emissions will be increased as more sows are brought into production again in other countries, often in conventional systems with fully slatted flooring, to meet the demand for animal protein to feed the growing global population. The review indicates there are ways to house lactating sows loose indoors with increased opportunity to perform highly motivated species-specific behaviours compared to the conventional crates with continuous confinement. These systems can offer a lower risk for environmental impact and economic risk through reducing piglet mortality. Nevertheless, a trade-off for continual freedom of sow movement may be required as zero-confinement increases the risk of piglet mortality and increased emissions. It is important to raise awareness among citizens and policy makers that loose farrowing and lactating systems if applied today, come with a higher production cost and the risk of increased environmental impact. More research and development is needed in relation to the environmental and economic impact of these systems in order to give farmers the best information to invest in new and more sustainable production systems.

Impact of litter size, supplementary milk replacer and housing on the body composition of piglets from hyper-prolific sows at weaning.

The modern hyper-prolific sow gives birth to 17 live-born piglets on average. An alternative strategy to nurse sows and artificial rearing may be providing milk replacer while letting all the piglets stay with their dam. However, milk replacer is of lower nutritional quality than sow milk and may reduce the body fat content of piglets who use milk replacer to compensate for low suckling success due to competition at the udder. Therefore, the aim of this study was to investigate the body composition at weaning of two random sow-reared piglets per litter from 93 litters by using the deuterium oxide dilution technique. The piglets were part of large study with a 2×2×2 factorial design of either 14 or 17 piglets from day 1 (LS: LS14/LS17) with or without access to milk replacer (MILK: -MILK/+MILK) and reared by crated or loose-housed sows (HOUSING: CRATE/ LOOSE). From behavioral observations day 21 in +MILK, piglets were divided according to their frequency of drinking milk replacer and suckling (Nutrition Source). Increasing LS from 14 to 17 reduced the average daily gain from 258 to 228 g/d and body fat % from 14.4 to 12.7% (P<0.01). In a two-way interaction between LS and HOUSNG, the body fat percentage was lower (P=0.04) and the water percentage tended to be higher (P=0.07) in LS17 CRATE compared to the other treatments (i.e. LS17 LOOSE, LS14 CRATE and LOOSE). There was no effect of MILK on piglet composition day 28 (P>0.1). In +MILK, the Nutrition Source affected piglet body composition (P<0.05) as piglets with low suckling frequency (LOW) had lower body fat and higher water content compared to piglets who had high suckling frequency (SUCKLE). Unexpectedly, drinking milk replacer in addition to suckling (MIXED) did not increase piglet body fat content. Relying mainly on milk replacer (CUP) caused body fat and water contents to be intermediate to piglets with high (SUCKLE and MIXED) and low suckling frequency (LOW). In conclusion, LS had a clear impact on piglet growth and body composition at weaning. In contrast, supplementation of milk and housing had only negligible impact on litter performance. Some individual piglets that had low frequency of sow milk intake benefitted from milk supplementation. Loose housing appeared to benefit piglet body fat at weaning but this was due to a greater piglet mortality.

Short Communication: effect of positive handling of sows on litter performance and pre-weaning piglet mortality.

Fear and environmental stressors may negatively affect the welfare of farm animals such as pigs. The present study investigated the effects of music and positive handling on reproductive performance of sows (n = 1014; parity 1 to 8) from a commercial pig farm practicing a batch farrowing system. Every 2 weeks, 56 sows were moved from the gestation unit to conventional-crated farrowing houses 1 week prior to expected farrowing. Treated (T; n = 299) and control (C; n = 715) sows were included in the study. In the farrowing houses, auditory enrichment (music from a radio) was provided to sows of T groups daily from 0600 to 1800 h until the end of lactation. Until the day of farrowing, T sows were additionally subjected, for 15 s per day per sow, to continuous back scratching by one member of farm staff. Litter performance and piglet mortality were recorded and analysed between T and C sows using linear mixed regression models. The number of liveborn piglets (C 13.85 v. T 13.26) and liveborn corrected for fostering (C 13.85 v. T 13.43) was significantly higher (P < 0.05) in C groups compared to the T groups. The number of stillborn piglets was 0.60 and 0.72 in T and C groups, respectively (P > 0.05). With regard to piglet mortality, a linear mixed regression model showed a significant overall effect of treatment in reducing piglet mortality (P < 0.01). Yet, the effect of treatment varied according to litter size (number of liveborn piglets) with a diminishing treatment effect in sows with a high litter size (P < 0.01). Pre-weaning survival was improved in the current study by the combined effect of daily back scratching of sows prior to farrowing and providing music to sows and piglets during lactation. Further research is needed to assess the separate effects of both interventions.

Effect of litter size, milk replacer and housing on production results of hyper-prolific sows.

The modern hyper-prolific sow gives birth to more piglets than she has functional teats (in the following called supernumerary piglets). The aim of the present study was (1) to investigate the production consequences of hyper-prolific sows rearing supernumerary piglets equal to the mean live-born litter size, and (2) investigate whether potential negative effects on survival and growth could be alleviated by providing access to milk replacer and/or providing easier access to the udder (by loose housing). At day 1 (D1) postpartum (pp), 93 litters were standardised to 14 or 17 piglets (LS14/LS17) after which no piglets were moved between sows leading to decreased litter size if piglets died. Litters were provided with or without milk replacer in milk cups (+MILK/-MILK), and sows were either crated or loose housed (CRATE/LOOSE) in a 2 × 2 × 2 factorial design. Piglet mortality was higher in LS17 compared to LS14 (P < 0.01; OR = 2.0), higher in -MILK compared to +MILK (P = 0.01; OR = 1.2) and higher in LOOSE compared to CRATE (P = 0.02; OR = 1.8). This study showed that sow rearing of supernumerary piglets while supplying with milk replacer can increase piglet survival. It also showed that early mortality before piglets learned to drink milk replacer posed a challenge using this automatic milk replacer system. An interaction between access to milk replacer and the standardised litter size D1 affected litter weight (P < 0.01) and piglet weight day 28 (D28) (P = 0.03). The highest litter weight D28 was found in LS17 +MILK (P < 0.01) but with a lower individual piglet weight than in LS14 -MILK. Piglet weight D28 was higher in LS14 -MILK compared to LS17 regardless of access to milk replacer. Heterogeneity in piglet weight within litters D28 was larger in LS17 (P = 0.03) but could be reduced with +MILK in CRATE (P < 0.01). No effects were found on sow weight loss and feed intake (P > 0.05). In conclusion, the results showed that sows cannot rear the supernumerary piglets without further management interventions to reduce mortality. Supplying supernumerary piglets equal to the mean live-born litter size of hyper-prolific sows with milk replacer can from results of this study be an alternative strategy to the use of nurse sows.

Temporary confinement of loose-housed hyperprolific sows reduces piglet mortality.

The objective of this study was to investigate piglet mortality in a commercial setting where sows were accommodated in a loose-housed system with an option to confine the sow for a few days around farrowing and during early lactation. The study was conducted in a Danish piggery where records were obtained from 2,139 farrowings. Sows were randomly allocated to 1 of 3 treatments: loose-loose (LL), loose-confined (LC), and confined-confined (CC). In LL, sows were loose housed from the time they entered the farrowing pens to weaning. In LC, sows were loose housed until farrowing was finished and then confined to d 4 after farrowing. In CC, sows were confined at d 114 of gestation to d 4 after farrowing. All sows were loose housed from d 5 to weaning. Total piglet mortality was analyzed at batch level to include piglets fostered by nurse sows and at sow level to analyze the effects of confinement during different time periods. Total piglet mortality was greater in LL (26.0%) and LC (25.4%) compared with CC (22.1%; < 0.001). The proportion of stillborn piglets was not different between treatments ( = 0.21) but a larger proportion was crushed in LL (10.7%) compared with LC (9.7%; = 0.03), which again was greater than CC (7.8%; < 0.001). Piglet mortality before equalization was lower in CC (3.7%) than in LL (7.5%) and LC (7.0%; < 0.001). Confinement reduced mortality from litter equalization to d 4 (7.6% for LL vs. 6.7% for LC; = 0.01) but more so in CC (5.6%) than in LC ( < 0.001). From d 4 to weaning, LL had lower mortality (5.6%) than LC (6.9%) and CC (6.6%; = 0.01). A larger proportion of sows in CC were classified as "low mortality" compared with LL and LC both before ( < 0.001) and after ( = 0.002) litter equalization. The results in this study emphasize that the period of time from the birth of the first piglet to litter equalization is important in relation to piglet mortality. The results also suggest that confinement for 4 d after farrowing can reduce mortality in this specific period, but only confinement from d 114 of gestation to d 4 after farrowing reduced total piglet mortality.

Higher preweaning mortality in free farrowing pens compared with farrowing crates in three commercial pig farms.

If loose-housed farrowing systems are to be an alternative to traditional farrowing crates, it is important that they can deliver the same production results as can be achieved in farrowing crates under commercial conditions. The aim of this study was to compare preweaning mortality in farrowing crates and free farrowing pens (FF-pens) within herds that had both systems. The study was conducted over 2 years in three commercial Danish herds that had FF-pens as well as traditional farrowing crates in their farrowing unit. Piglet mortality was analysed in two periods: before litter equalisation and after litter equalisation. Linear models were used to analyse effects of housing (crate or pen), herd (Herd A, B or C), parity (parities 1, 2, 3 to 4 or 5 to 8) as well as the effect of number of total born piglets on mortality before litter equalisation, and the effect of equalised litter size on piglet mortality after litter equalisation. All corresponding interactions were included in the models. Before litter equalisation piglet mortality was higher (P<0.001) in pens (13.7%) than in crates (11.8%). Similarly, piglet mortality after litter equalisation was higher in pens than in crates in all three herds, but the difference between pens and crates were dissimilar (P<0.05) in the different herds. In addition, piglet mortality, both before (P<0.001) and after litter equalisation (P<0.001), grew with increasing parity of the sows. Mortality before litter equalisation moreover increased with increasing number of total born piglets per litter (P<0.001), and mortality after equalisation increased when equalised litter size increased (P<0.001). No significant interactions were detected between housing and parity or housing and litter size for any of the analysed variables. In conclusion, there is knowledge how to design pens for free farrowing; but this study showed a higher preweaning mortality in the FF-pen. Nonetheless a noteworthy proportion of the sows in the FF-pens delivered results comparable to those farrowing in crates. This indicates that FF-pens are not yet a robust type of housing for farrowing sows.

Individual physical characteristics of neonatal piglets affect preweaning survival of piglets born in a noncrated system.

The aim of this study was to investigate the effects of individual physical characteristics on preweaning survival and growth of piglets born in a noncrate system. Data were collected from 3,402 neonatal piglets from 203 Landrace × Yorkshire sows housed in noncrate pens in a commercial Danish sow herd. Piglets were categorized into groups according to their survivability: surviving to weaning (SURV), stillborn (STILL), or dead between birth and weaning (DBW), which was subdivided into dead d 0 to 1 after farrowing (DEAD1) or dead d 2 to 26 after farrowing (DEAD26). Linear models were used to determine which physical characteristics affected survivability and growth of piglets. Results showed that characteristics related to the individual piglets had a greater degree of explanatory power in relation to survival than variables related to the sow. Survival of piglets increased if piglets were females (P < 0.001), had a greater body mass index (P < 0.001), and were born to sows of parity 3 or more (P = 0.017). Piglets with a greater birth weight were more likely to survive (P < 0.001), but birth weight was inferior to body mass index in explaining differences between SURV and DBW. Piglets that died 2 to 26 d after birth had a lower birth weight (P < 0.001), were born to sows of parity 1 or 2 (P = 0.014), and were born after a shorter gestation (P = 0.011) compared with SURV. Piglets that died on d 0 to 1 after birth had a lower body mass index (P < 0.001), displayed a greater degree of growth restriction (P = 0.004), and were born in large litters (P = 0.005). The gender of the piglets affected survivability at both d 0 to 1 (P < 0.001) and d 2 to 26 (P < 0.001). Piglets in DEAD1 differed from STILL by having a shorter crown to rump length (P < 0.001), a birth weight that deviated more from the mean weight of the litter (P = 0.001), and being more likely to be born before d 116 of gestation (P = 0.008). The only physical characteristic that was important for growth performance in the suckling period was birth weight (P < 0.001), yet using only birth weight as an indicator for survivability was too simplistic. The results of this study emphasize that individual characteristics of neonatal piglets could serve as indicators of survivability of piglets born in noncrate systems; however, the results suggest that the importance of characteristics differed in different periods of the preweaning period.

Confinement of lactating sows in crates for 4 days after farrowing reduces piglet mortality.

To reduce mortality among suckling piglets, lactating sows are traditionally housed in farrowing crates. Alternatively, lactating sows can be housed in farrowing pens where the sow is loose to ensure more behavioural freedom and consequently a better welfare for the sow, although under commercial conditions, farrowing pens have been associated with increased piglet mortality. Most suckling piglets that die do so within the first week of life, so potentially lactating sows do not have to be restrained during the entire lactation period. Therefore, the aim of the current study was to investigate whether confinement of the sow for a limited number of days after farrowing would affect piglet mortality. A total of 210 sows (Danish Landrace × Danish Yorkshire) were farrowed in specially designed swing-aside combination farrowing pens measuring 2.6 m × 1.8 m (combi-pen), where the sows could be kept loose or in a crate. The sows were either: (a) loose during the entire experimental period, (b) crated from days 0 to 4 postpartum, (c) crated from days 0 to 7 postpartum or (d) crated from introduction to the farrowing pen to day 7 postpartum. The sows and their subsequent litters were studied from introduction to the combi-pen ∼1 week before expected farrowing and until 10 days postpartum. Confinement period of the sow failed to affect the number of stillborn piglets; however, sows that were crated after farrowing had fewer live-born mortality deaths (P < 0.001) compared with the sows that were loose during the experimental period. The increased piglet mortality among the loose sows was because of higher mortality in the first 4 days after farrowing. In conclusion, the current study demonstrated that crating the sow for 4 days postpartum was sufficient to reduce piglet mortality.