Trade-offs between litter size and offspring fitness in domestic pigs subjected to different genetic selection pressures

Primiparous sow behaviour on the day of farrowing as one of the primary contributors to the growth of piglets in early lactation

Large White and Meishan sows differ in maternal ability and early piglet growth. We investigated the relationships between 100 maternal traits, grouped into 11 blocks according to the biological function they describe and litter growth over three successive periods after birth (D0-D1, D1-D3 and D3-D7; D0 starting at the onset of farrowing), as a measure of sow investment in early piglet production. Within- and between-breed variation was exploited to cover a maximum of the variability existing in pig maternal populations. The objective was to quantify the contribution of maternal traits, including functional traits and behavioural traits, to early litter growth. Multivariate analyses were used to depict correlations among traits. A partial least square multiblock analysis allowed quantifying the effect of maternal traits on early growth traits. Partial triadic analyses highlighted how sow behaviour changed with days, and whether it resulted in changes in litter growth. Several behavioural traits (standing activity, reactivity to different stimuli, postural activity) and functional traits (body reserves, udder quality) at farrowing contributed substantially to litter growth from D0 to D7. Sow aggression towards piglets and time spent standing at D0 were unfavourably correlated to D1-D3 litter growth. Time spent lying with udder exposed at D0 was favourably correlated to D1-D3 litter growth. The farrowing duration was negatively correlated to D0-D1 and D1-D3 litter growth. Furthermore, D3-D7 litter growth was positively correlated to feed intake in the same period. Several behavioural traits and some functional traits influence early litter growth. The contribution of sow behaviour was greater in the critical period around farrowing than in later days.

Effects of parity, season of birth, and sex on within-litter variation and pre-weaning performance of F1 Large White × Landrace pigs

Background and Aim

A piglet's pre-weaning performance significantly influences both animal welfare and profitability in pig production. Understanding piglet pre-weaning performance influencing factors is key to enhancing animal welfare, reducing losses, and boosting profitability. The study aimed to evaluate the impact of parity, season of birth, and sex on within-litter variation and pre-weaning performance of F1 Large White × Landrace pigs.

Materials and Methods

Information regarding total litter size, number of born alive, number of stillbirths, piglet weight at birth, mortality, and count of weaned F1 Large White × Landrace piglets was acquired from the farm database (April 2022-February 2023). 2602 females and 2882 males, a total of 5484 piglets were utilized, with records from 360 sows. The coefficient of variation (CV) of birth weights among piglets within a litter was calculated. The general linear model analysis in MiniTab 17 was used to evaluate the data, with Fisher's least significant difference test (p < 0.05) used for mean separation and Pearson's moment correlation coefficient calculated to assess relationships between survival rates, mortality rates, litter size, birth weight, and birth weight CV.

Results

Parity had a statistically significant impact on litter size, birth weight, and survival rate (p < 0.05). The sow's parity did not significantly (p > 0.05) impact the number of piglets born alive or weaned. Multiparous sows had a significantly larger litter size (p < 0.05) than primiparous sows at birth. The litter weights for parities 2, 4, and 5 did not significantly differ (p > 0.05), with averages of 20.95, 20.74, and 20.03 kg, respectively. About 91.29% was the highest survival rate recorded in parity 2 (p < 0.05). The 1st week of life recorded an 8.02% mortality rate. The mortality rate in parity 3-5 group was significantly (p < 0.05) higher (11.90%) in week 1 than in the other groups (parity 1: 6.79%, parity 2: 5.74%, parity 3-5: 8.54 and 9.21%). The litter sizes in autumn (17.34) and spring (17.72) were significantly larger (p < 0.05) than those in summer (16.47) and winter (16.83). In autumn and spring, the survival rate (83.15 and 85.84%, respectively) was significantly lower (p < 0.05) compared to summer (88.40%) and winter (89.07%). In all seasons, the litter weights did not significantly differ (p > 0.05). The birth weight CV was significantly (p < 0.05) lower during summer (20.11%) than during spring (22.43%), autumn (23.71%), and winter (21.69%). The season of birth had no significant effect (p > 0.05) on the number of live piglets. Males (1.34 kg) were heavier (p < 0.05) than females (1.30 kg) at birth. Notably, the birth weight CV was similar between males (22.43%) and females (22.52%). Litter size was positively correlated with average litter weight (rp = 0.576, p < 0.001), birth weight CV (rp = 0.244, p < 0.001), and mortality rate (rp = 0.378, p < 0.001). An insignificant relationship was observed between average litter weight and birth weight CV (rp = -0.028, p > 0.05) and survival rate (rp = -0.032, p > 0.05).

Conclusion

In F1 Large White × Landrace pigs, birth uniformity among piglets declines as litter size grows larger. In parity 3-5, multiparous sows yield litters with reduced uniformity. With an increase in litter size, uniformity among piglets at birth worsens. A larger litter size and greater piglet birth weight variation are linked to a higher pre-weaning mortality rate. Producers need a balanced selection approach to boost litter size and must cull aging sows carefully to introduce younger, more productive females.

Analysis of Early Growth of Piglets from Hyperprolific Sows Using Random Regression Coefficient

Management of hyperprolific sows is challenging when it comes to controlling birth weight variability and piglet survival in large litters. The growth of low birth weight piglets can be compromised and have a negative impact on production efficiency. The objective of the study was to apply a random regression coefficient model to estimate the main effects of the growth of piglets of highly prolific sows. The dataset contained growth data for 360 piglets from 25 Pen Ar Lan Naima sows. In addition to routine procedures after farrowing, piglets were weighed five times: on day 1 after farrowing, on day 14 of life, at weaning on day 28, on day 30 of nursery period, and at the end of the nursery period when piglets were 83 days old. Data were treated as longitudinal, with body weight as the dependent variable. Fitting age as a quadratic regression within piglets in the random part of the model helped to determine the significant effect of birth weight, litter size, and parity on the growth of the piglets. Since the piglets from large litters often have non-uniform birth weights and this can affect further growth, the use of a random regression coefficient model is practical for analysing the growth of such piglets due to the ability to describe the individual growth pattern of every individual.

Effect of two milk supplements and two ways of administration on growth performance, welfare and fecal microbial ecology of suckling piglets

Introduction

The aim of this study was to evaluate the effect of two MS formulas, DanMilk™ (AB Neo, Denmark) (MS1) and Neopigg® RescueMilk (Provimi, Netherlands) (MS2) administered manually and to compare two ways of administration (manual vs automatic) of MS1 on growth performance, health, fecal microbial profile, behavior, and skin lesions of piglets during suckling and post-weaning.

Methods

Forty litters (528 piglets) were divided into 4 groups: 1) Control group receiving no MS (CON); 2) MS1 administered automatically (A-MS1); 3) MS1 administered manually (Ma-MS1) 4) MS2 administered manually (Ma-MS2). All groups had access to sow milk and creep feed. On day 5 after birth (d0), litters were equalized (13.2 piglets/litter ± 0.8 SD), thereafter no cross-fostering was allowed. Piglets were weighed at day 5 after birth (d0), at the end of milk supplementation (d14), at weaning (d21 of the trial, 26 days of age) and ten days post-weaning (d31). Piglet welfare was assessed using behavioral and lesion measures at d4 and d10. Feces were collected at d14 and d21.

Results and discussion

During the suckling period, A-MS1 had lowest mortality (p < 0.05), while Ma-MS1 had lower mortality compared with CON and Ma-MS2 (p < 0.05). Negative social behavior at d4, was more frequent in MS groups (A-MS1, Ma-MS1, Ma-MS2) compared to CON group (p = 0.03). Growth performance and lesion prevalence were not affected by MS provision. During lactation, Ma-MS2 group had a higher percentage of piglets not eating during suckling at d18 compared with Ma-MS1 (p = 0.03). MS1 increased microbial diversity compared with CON at d14 (Chao1, p = 0.02; Shannon, p = 0.03) and compared with CON (Shannon, p < 0.05; InvSimpson, p = 0.01) and Ma-MS2 (Chao1, p < 0.05; Shannon, p = 0.05, InvSimpson p = 0.01) at d21. Groups that received MS1 were characterized by genera producing short-chain fatty acids (SCFAs), i.e., Lachnospiraceae (A-MS1) and Oscillospiraceae (Ma-MS1). MS composition and availability can contribute to reduce piglet's mortality during the suckling phase and can also affect intestinal microbiota by favoring the presence of SCFAs producing bacteria.

Analysis of image-based sow activity patterns reveals several associations with piglet survival and early growth

An activity pattern describes variations in activities over time. The objectives of this study are to automatically predict sow activity from computer vision over 11 days peripartum and estimate how sow behavior influences piglet's performance during early lactation. The analysis of video images used the convolutional neural network (CNN) YOLO for sow detection and posture classification of 21 Large White and 22 Meishan primiparous sows housed in individual farrowing pens. A longitudinal analysis and a clustering method were combined to identify groups of sows with a similar activity pattern. Traits under study are as follows: (i) the distribution of time spent daily in different postures and (ii) different activities while standing. Six postures were included along with three classes of standing activities, i.e., eating, drinking, and other, which can be in motion or not and root-pawing or not. They correspond to a postural budget and a standing-activity budget. Groups of sows with similar changes in their budget over the period (D-3 to D-1; D0 and D1-D7) were identified with the k-means clustering method. Next, behavioral traits (time spent daily in each posture, frequency of postural changes) were used as explanatory variables in the Cox proportional hazards model for survival and in the linear model for growth. Piglet survival was influenced by sow behavior on D-1 and during the period D1-D7. Piglets born from sows that were standing and doing an activity other than drinking and eating on D-1 had a 26% lower risk of dying than other piglets. Those born from sows that changed posture more frequently on D1-D7 had a 44% lower risk of dying. The number of postural changes, which illustrate sow restlessness, influenced piglet growth in the three periods. The average daily gain of piglets born from sows that were more restless on D1-D7 and that changed posture more frequently to hide their udder on D0 decreased by 22 and 45 g/d, respectively. Conversely, those born from sows that changed posture more frequently to hide their udder during the period of D1-D7 grew faster (+71 g/d) than the other piglets. Sow restlessness at different time periods influenced piglet performance.

Changes in piglet and litter characteristics across parities in two highly prolific sow hybrids in an outdoor organic herd

High piglet mortality constitutes a welfare challenge in organic pig production. Litter characteristics were investigated from parities 1-5 of two hyper-prolific hybrids with different selection traits in an organic commercial herd (DanBred vs. Topigs Norsvin [TN70]). TN70 sows had more functional teats than DanBred sows, and their offspring had higher birth weights. Several interactions between hybrid and parity were found. The total born increased with higher parity and was more pronounced for DanBred sows. Litter weight at weaning was higher in parities 1-4 for TN70 compared with DanBred, and within DanBred parities 4 and 5 had higher litter weight at weaning than parity 1. The survival rate was higher for TN70 in parities 1 and 2 compared with DanBred, and for both hybrids, the survival rate was higher in parities 1 and 2 compared with parities 4 and 5. The number of weaned piglets was stable across parities 1-4 but lower in parity 5 for both hybrids. Thus, despite a lower number of total born piglets in TN70, TN70 sows weaned the same number of piglets as DanBred, with a lower mortality rate and a heavier litter at weaning.

Risk factors differ for viable and low viable crushed piglets in free farrowing pens

Newborn piglets have a high risk of being crushed by the sow, and this risk implies welfare and economic consequences. The aim of this study was to investigate the importance of differentiating between low viable (secondary crushing losses) and viable crushed (primary crushing losses) piglets for the evaluation of risk factors for crushing related to characteristics of the sow, the litter, and the environment. Eleven Swiss farmers recorded sows' production data (parity class, gestation length, numbers of live-born and stillborn piglets), data (age, sex, weight, cause of death, and signs of weakness) for every live-born piglet that died in the first week after birth (piglet loss), and ambient temperature. Piglet losses were assigned to five categorical events: piglet loss, subdivided into not crushed and crushed, the latter being further subdivided into low viable crushed and viable crushed. Piglets recorded by the farmer as crushed were assigned to the events low viable crushed and viable crushed based on the piglet's body weight and signs of weakness (diseases, malformations). Data of 9,543 live-born piglets from 740 litters were eventually used to statistically model the hazard of dying at any given time in the first week after birth due to one of these events (mixed-effects Cox model). Five potential risk factors were analyzed as co-variates: parity class, gestation length, number of live-born piglets, number of stillborn piglets, and daily number of hours with ambient temperature >30°C. We identified two risk factors for dying from the event viable crushed that were not identified as risk factors for low viable crushed, namely shorter gestation length and higher daily number of hours with ambient temperature  > 30°C. Vice-versa, we identified additional live-born piglets in the litter as risk factor for low viable crushed, but not for viable crushed. Our results show the importance of differentiating between low viable and viable crushed piglets for the interpretation of risk factors for crushing losses. Therefore, we suggest that for breeding purposes and in research, this differentiation should be made.

Investigating the effects of two weaning methods and two genetic hybrids on play behavior in weaner pigs (Sus scrofa)

In conventional pig production, suckling pigs are typically weaned between 3 and 5 weeks of age. This involves separation from the sow, dietary change, and regrouping in a novel environment, which challenge the welfare of pigs. We investigated the effects of two weaning methods [conventional weaning: two litters mixed in a weaner pen of different size and design (MOVE) vs. litter staying in the farrowing pen after removing the sow (STAY)] and two genetic hybrids [DanBred Yorkshire × Landrace (approximately 21 total pigs born/litter; DB) vs. Topigs Norsvin TN70 Yorkshire × Landrace (approximately 16 total pigs born/litter with higher individual birth weight and weaning weight than DB; TN)] on play behavior across weaning. Both genetic hybrids were inseminated with semen of DanBred Duroc boars. Litters were reduced to the number of functional teats at birth. The durations of locomotor-rotational play (LOC) and social play (SOC) of 24 indoor-housed litters [pigs/litter: (average ± SD) 13 ± 2; age at the weaning day: 26 ± 2 days] were video-recorded continuously between 14:00 h and 22:00 h on days −1, 1, and 2 relative to weaning and statistically analyzed with mixed-effects modeling at the individual level. Before weaning, TN pigs performed LOC longer than DB pigs. On day 2 post-weaning, STAY pigs engaged in more SOC than MOVE pigs. Moreover, TN pigs and STAY pigs displayed a steeper increase in LOC from days 1 to 2 than DB pigs and MOVE pigs, respectively. We demonstrated that pigs belonging to the genetic hybrid with higher weight at birth and weaning spent more time playing on the day before weaning. Additionally, weaning pigs in the farrowing pen and, hence, avoiding social mixing and relocation to an unfamiliar environment had a positive effect on social play after weaning. Our study illustrates that weaning stress in pigs may be reduced by using a genetic hybrid featuring higher birth and weaning weight and by keeping litters intact in a familiar environment after weaning. This study also supports the use of play behavior as an animal welfare indicator.

A milk-sharing economy allows placental mammals to overcome their metabolic limits

Here, we demonstrate that a naturally evolving behavior (allonursing) has greater effect on reproductive power (mass per unit of time) and output (litter mass at birth) than does artificial selection (domestication). Additionally, we demonstrate the importance of resource optimization afforded by sociality (rather than resource abundance per se) in shaping a species’ life history profile and its ability to overcome its own physiological constraints.

Maternal resource availability and metabolism have a strong limiting effect on reproductive output. Allomaternal care and domestication increase the energy available to the mother and should correlate with an increase in reproductive output. Here, we take a comparative approach to understand how this increase is accomplished (e.g., litter mass, reproductive frequency, etc.) and the strength of the effect among different forms of external energetic supplementation. We find that domestication and all forms of allocare correlate with increased fertility. All forms of provisioning correlate with larger litters without compromising offspring size. The greatest increase we observe in reproductive power is in species that practice allonursing. Our results suggest that the ultimate factor limiting reproductive output in placental mammals is maternal metabolic power rather than resource availability.

Animal Welfare and the Acknowledgment of Cultural Differences

Pigs are considered sentient beings that have a mental capability that warrants attention to their welfare. Cultural values towards animal welfare differ in world regions. Still, authors have argued for worldwide harmonization of animal welfare rules. At the same time, the focus of many animal welfare rules do not address the most significant problems on modern commercial pig farms. The foci of animal welfare rules are often on space (quantity and quality), acute painful practices, equipment, and caretaker behavior. However, most serious animal welfare issues are related to episodic events such as compromised pigs, lack of appropriately skilled staff, and human behavior (or lack thereof) towards animals. Modern technologies such as image, sound, and building oversight by automated systems can potentially provide better individual pig care. The future should bring us solutions to identify and resolve episodic negative animal welfare events. The other issues of space and painful practices are best improved by using science-based solutions. We propose that science be the key resource to making animal welfare decisions, but with a healthy appreciation and respect for cultural differences in our views of animals and the economic impact of rules. Colonialism is not viewed positively today, and economic neo-colonialism should not be allowed to replace it. Respect for cultural differences should play a role in animal welfare rules within and among countries.

The Use of Attractants to Stimulate Neonatal Piglet Interest in Rope Enrichment

Simple Summary

Piglet crushing is one of the leading causes of preweaning mortality. This loss represents reduced production efficiency, substantial economic losses for producers, and is an animal welfare concern. The goal of this study was to determine if enrichment ropes would entice neonatal piglets away from the sow and reduce preweaning mortality. Three treatments (OIL: sunflower oil; MC: milky cheese; SC: semiochemical) were applied to the enrichment ropes to increase attractiveness to piglets. Results indicate that neonatal piglets were interested in all enrichment treatments on Day 2 of life, although there was high individual variation in frequency and duration of interactions. Enrichment treatment did not impact the frequency or duration of rope interactions or litter average weight gain. Piglet mortality was impacted by treatment: MC piglets had the lowest percent mortality during the enrichment period, and SC piglets had the lowest percent mortality over the entire experimental period. This proof-of-concept study highlights the value of neonatal piglet environmental enrichment.

Abstract

In the United States swine industry, preweaning mortality represents the highest mortality rate of any production phase, nearly half attributed to crushing. The overarching aim of this study was to determine if enrichment ropes would entice neonatal piglets away from the sow and reduce preweaning mortality. Rope enrichments were provided to 161 piglets from 26 sows after farrowing. Ropes were dipped in sunflower oil (n = 7), semiochemical (n = 8), or milky cheese (n = 11). Piglet purposeful rope investigations, weight gain, and mortality were recorded. On Day 2, 75% of piglets touched the enrichment at least once, and frequency ranged from 1 to 21 investigations across all treatments. Frequency (p = 0.20) and duration (p = 0.21) of investigations were not affected by treatment. Preweaning litter average weight gain did not differ between treatments (p = 0.71). MC (milky cheese) piglets had the lowest percent mortality when the enrichment ropes were present (Days 2 to 5, p = 0.01), and SC (semiochemical) piglets had the lowest percent mortality after the enrichment ropes were removed (Days 6 to weaning, p < 0.0001). This proof-of-concept study highlights the potential value of neonatal piglet environmental enrichment.

Characterization of genetic fundamentals for piglet mortality at birth in Yorkshire, Landrace, and Duroc sows

Piglet mortality is an economically important complex trait that impacts sow prolificacy. Genetic analyses for piglet mortality at weaning have been reported in dozens of studies, but not for piglet mortality at birth. In this study, we used multi-breed data sets from Yorkshire, Landrace, and Duroc sows to characterize the genetic fundamentals of piglet mortality at birth. The heritabilities from parity I to III were estimated to be 0.0630, 0.1031, and 0.1140 respectively. By using a combined strategy, a total of 21 SNPs were detected in three parities, of which six were observed in parity I, five in parity II and 10 in parity III. Genome annotation revealed that these SNPs were harbored within or close to 19 candidate genes. The candidate genes were found to associate with the reproductive system and embryonic development in the tissue expression database, which are reasonably related to piglet mortality. These findings are expected to provide much information for understanding the genetic and genomic fundamentals of farrowing mortality.

Vitality in relation to litter size of crossbred pigs and the effect of the terminal sire line

Context Most research on sire lines is linked to growth and carcass traits. Only a limited number of field trials explore the effect of sire line on piglet vitality, litter size and the interactions between these traits. Aim The aim of this study was to examine the effect of sire line on the growth performance and vitality of progeny from birth to weaning and to evaluate the lines with respect to their impact on litter size. Methods Data included 150 litters of a Synthetic sire line (A) and 154 of a Piétrain sire line (B), with 4209 piglets born alive, which resulted from matings to 337 dams (Camborough PIC). The numbers of total born and born alive piglets per litter were recorded. Within 24 h after birth, piglet individual birthweight (BWbirth), sex (male/female) and body temperature (BT) were also recorded. At weaning, mortality rates and weaned pigs per sow were registered. At the day of weaning, 665 randomly chosen pigs were individually weighed. Weaning weights (WW) were used to calculate the weaning average daily gain (WADG). Key results Sire line significantly affected number of total born (P &lt; 0.0001), number born alive (P &lt; 0.01) and number of weaned pigs per sow (P &lt; 0.01). Across lines, each additional piglet per litter resulted in a 31.2 g decline in BWbirth (P &lt; 0.001). Larger litter sizes, higher BWbirth (P &lt; 0.01) and piglets with a lower BT (P &lt; 0.0001) were detected in litters of Sire line B compared with litters of Sire line A. No differences between lines were detected for WADG, WW and pre-weaning mortality (P &gt; 0.05). A positive correlation between birthweight and WW resulted in a correspondingly higher WADG (P &lt; 0.0001). Overall, heavier BWbirth piglets had a higher BT (P &lt; 0.0001). Conclusions The present study indicates that Sire line B would offer a possibility to maintain litter size at a high level and, simultaneously, achieve higher BWbirth, with consequently more vital piglets. Implication It is important to emphasise that further selection for litter size in dam lines is not indicated in terms of animal welfare but also production efficiency. Instead, it seems feasible to follow the above strategy and stabilise litter size at a high level, while at the same time breeding for vitality and survivability in sire lines.

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.

Weaning age and post-weaning nursery feeding regime are important in improving the performance of lightweight pigs

The aim was to investigate the effect of weaning age, weaning weight, and nursery feeding regime on post-weaning performance. The focus was on pigs weaned light, as they may be better off when weaned at a later age and/or offered a specialist nursery feeding regime. Piglets (n = 1,448) from one farrowing batch of 110 sows that farrowed over 2 wk were individually weighed and their morphometric measurements were taken at birth. Pigs were weaned on the same day, but variation in birth date resulted in variable weaning ages (mean age day 34.1, SD = 2.5). The youngest 50% at weaning were classified Y and the oldest 50% as O; within an age class, the lightest 50% were classified L, the heaviest 50% as H, and housed accordingly. Pigs were individually weighed at weaning, 7 and 15 wk post-weaning. At weaning, Y were 6 d younger and 1.4 kg lighter than O pigs, whereas L were 3.2 kg lighter than H pigs. Pigs were randomly allocated to a 3-stage superior (SUP) or control (CON) nursery feeding regime, with SUP pigs having a 65% greater allowance (on a kg/pig basis) of the first and second stage feeds than the CON. Pigs weaned Y had a higher mortality rate from weaning to 7 wk post-weaning than pigs weaned O (9.14% vs. 4.98%; P = 0.046). As expected, age and weight significantly (P < 0.001) affected performance to both 7 and 15 wk post-weaning: at 15-wk pigs weaned Y were 5.5 kg lighter than pigs weaned O; pigs weaned L were 9.0 kg lighter than H pigs. It was estimated that pigs weaned YL needed ~4 d more (P = 0.018) to reach 60 kg BW than pigs weaned OL. Feed intake was not affected by feeding regime, age and weight, or their interactions. Performance was not affected by feeding regime (P > 0.05), but was affected by the weight × feeding regime interaction (P = 0.044) to 7 wk post-weaning: L pigs on SUP were 1.2 kg heavier than L pigs on the CON regime; this was not the case for the H pigs. Performance up to 7 wk post-weaning was positively associated with birth weight to cranial circumference ratio and weaning weight (P < 0.05) for both YL and OL pigs; for the latter, additional performance predictors were weaning age (P = 0.044) and feeding (P = 0.027). Improved growth for L pigs up to 7 wk post-weaning could be obtained by a greater allowance of the nursery diets. However, weaning at a later age benefitted the performance of L pigs to a common BW, suggesting that this might be a strategy with longer term benefits.

Review: Early life predisposing factors for biting in pigs

The pig industry faces many animal welfare issues. Among these, biting behaviour has a high incidence. It is indicative of an existing problem in biters and is a source of physical damage and psychological stress for the victims. We categorize this behaviour into aggressive and non-aggressive biting, the latter often being directed towards the tail. This review focusses specifically on predisposing factors in early life, comprising the prenatal and postnatal periods up to weaning, for the expression of aggressive and non-aggressive biting later in life. The influence of personality and coping style has been examined in a few studies. It varies according to these studies and, thus, further evaluation is needed. Regarding the effect of environmental factors, the number of scientific papers is low (less than five papers for most factors). No clear influence of prenatal factors has been identified to date. Aggressive biting is reduced by undernutrition, cross-fostering and socialization before weaning. Non-aggressive biting is increased by undernutrition, social stress due to competition and cross-fostering. These latter three factors are highly dependent on litter size at birth. The use of familiar odours may contribute to reducing biting when pigs are moved from one environment to another by alleviating the level of stress associated with novelty. Even though the current environment in which pigs are expressing biting behaviours is of major importance, the pre-weaning environment should be optimized to reduce the likelihood of this problem.

Are Larger Litters a Concern for Piglet Survival or an Effectively Manageable Trait?

As sows continue to be selected for greater prolificacy, it is important to review problems that arise in larger litters, and whether these issues can be appropriately managed. Although a proportion of piglets in larger litters can be born underweight, proper supervision around farrowing and adequate colostrum intake has the potential to improve the survival of low-birth-weight piglets and their ongoing growth to weaning. As larger litters can impart greater stress and discomfort on sows, implementing a low-stress environment leading up to parturition may improve sow performance and subsequent survival of piglets. Additionally, treating sows with anti-inflammatory compounds, either dietary or pharmacologically, shows some promise for alleviating sow discomfort and improving piglet survival in larger litters. Understanding that selecting sows for larger litters not only affects piglet survival but the well-being of the sow, the decision to continue selecting for larger litters, regardless of management strategies, remains a topic of ethical concern.

Future global pig production systems according to the Shared Socioeconomic Pathways

Global pork production has increased fourfold over the last 50 years and is expected to continue growing during the next three decades. This may have considerable implications for feed use, land requirements, and nitrogen emissions. To analyze the development of the pig production sector at the scale of world regions, we developed the IMAGE-Pig model to describe changes in feed demand, feed conversion ratios (FCRs), nitrogen use efficiency (NUE) and nitrogen excretion for backyard, intermediate and intensive systems during the past few decades as a basis to explore future scenarios. For each region and production system, total production, productive characteristics and dietary compositions were defined for the 1970-2005 period. The results show that due to the growing pork production total feed demand has increased by a factor of two (from 229 to 471Tg DM). This is despite the improvement of FCRs during the 1970-2005 period, which has reduced the feed use per kg of product. The increase of nitrogen use efficiency was slower than the improvement of FCRs due to increasing protein content in the feed rations. As a result, total N excretion increased by more than a factor of two in the 1970-2005 period (from 4.6 to 11.1 Tg N/year). For the period up to 2050, the Shared Socio-economic Pathways (SSPs) provide information on levels of human consumption, technical development and environmental awareness. The sustainability of pig production systems for the coming decades will be based not only on the expected efficiency improvements at the level of animal breeds, but also on four additional pillars: (i) use of alternative feed sources not competing with human food, (ii) reduction of the crude protein content in rations, (iii) the proper use of slurries as fertilizers through coupling of crop and livestock production and (iv) moderation of the human pork consumption.

Ethics in animal breeding

Ethical breeding involves the use of healthy animals true to their species in behaviour and physical appearance, and when applicable, showing a sustainable performance. The concerns for the species/breed are essential parts of the breeding goals, including preservation of genetic resources within the species/breed, and the health and welfare of the individual animal. Ethical and welfare considerations were often not prioritized in developing new breeds of production or companion animals. As a result, animal breeding practices are increasingly becoming part of the debate on animal welfare. In companion animals, breeding for curiosity or "cuteness" may be a goal in itself, although dogs are also bred for utility. In production animals, breeding focus is on performance, i.e., quantitative entities and financial income, rather than physical appearance. For instance, dairy cows are bred to be larger and to have higher milk yields, sows and ewes to produce more offspring, and horses are designed for riding, racing, and companionship. Overbreeding in relation to current demand of horses, cats, and dogs raises welfare issues due to abandonment or killing of horses and millions of cats and dogs every year. There is variable regulation of health requirements for breeding animals in different countries of the world. In many countries, consumers are becoming increasingly aware of animal welfare issues such as negative effects of certain production traits in farm animals, leading to decreased demand for their meat at a time where increased food production is becoming crucial. Amidst these dilemmas are the veterinarians. This paper deals with issues connected to traditional breeding as well as some of the breeding technologies, and includes food safety, ethics, and animal welfare.

Sow communication with piglets while being active is a good predictor of maternal skills, piglet survival and litter quality in three different breeds of domestic pigs (Sus scrofa domesticus)

Maternal care behaviour is crucial for offspring quality and survival in pigs. Defining care is therefore essential for ensuring the welfare of pigs and sustainability of pig production. The aim of the present study was to investigate the relationship between sow nest building, communication with piglets (sniffing, nudging, grunting) during resting and activity, and piglet survival in three different sow breeds: a maternal line selected for high weaned pig production (Landrace), a paternal line selected for meat traits (Duroc), and a crossbred line (Landrace and Yorkshire). We predicted that a higher frequency of nest building and sow communication would have a positive impact on piglet survival. Secondly, we predicted that a high level of maternal care outside the time of nursing (nest building and communication) would increase the quality of the litter (weight at weaning). We also predicted that nest building activity and sow communication would be more pronounced in maternal sow lines selected for maternal traits than in a non-selected, paternal line, and that primiparous sows would perform more nest building behaviour and communicate more than multiparous sows due to high investment in their first litter. Finally, an impaired condition around farrowing (i.e. low body condition score and presence of shoulder lesions) was predicted to be negatively correlated to care behaviours. Data was collected on 38 sows with 511 born piglets. Sows with their litters, were loose-housed in individual farrowing pens until weaning. Nest building activity can be partly considered as maternal care behaviour as it prepares the sows for motherhood and is associated with a lower proportion of stillborn piglets (P < 0.001), starved piglets (P = 0.004), and overlaid piglets (P = 0.034). As predicted, sows that communicated more while being active had lower postnatal piglet mortality (starvation (P < 0.001), less overlying (P < 0.001), overlying with (P < 0.001), and without the milk in the stomach (P < 0.001) and fewer that died of other causes (P < 0.001), higher piglet survival (P < 0.001) and litter weight (P < 0.001) at weaning irrespective of the breed. A higher level of communication while active was associated with more pronounced shoulder lesions in sows (P = 0.010), suggesting a positive association between good maternal care and prevalence of shoulder lesions. We also found that resting sows that communicated more with piglets outside the time of nursing, had higher postnatal piglet mortality (P < 0.001) due to starvation (P < 0.001), overlying (P < 0.001), overlying with (P < 0.001), or without milk (P < 0.001). Communication during resting was more pronounced with increasing litter size at birth (P < 0.001), especially for thin sows (P < 0.001). Communication during resting was more pronounced in the non-selected Duroc line (P < 0.001). Our results suggest that sow communication while being active is a good predictor of good maternal care, piglet survival and litter quality in three different breeds of domestic pigs.

Can we improve maternal care in sows? Maternal behavioral traits important for piglet survival in loose-housed sow herds

The primary objective of this survey was to investigate the relationship between qualitative maternal behavioral scores (nest building activities, sow communication, and sow carefulness), piglet mortality, and the number of weaned piglets on commercial farms with loose-housed lactating (Norsvin Landrace × Yorkshire) sows. Second, the impact of these scores on productivity compared with the physical condition of sows (movement disorders, body condition, and shoulder lesions) was assessed. Data on maternal care behaviors and physical condition were collected on 895 sows from 45 commercial farms. Farmers scored sows on their physical condition (movement disorders [MD], BCS, and shoulder lesions [SL]) and qualitative maternal care behaviors (nest building activities [NEST] prior to farrowing and sow communication [COM] and sow carefulness [CARE] after farrowing, while sows were standing and moving and just before lying down). There was a low positive correlation between NEST and COM ( = 0.10, = 0.026) and between NEST and CARE ( = 0.15, = 0.010) but a high positive correlation between COM and CARE ( = 0.57, < 0.001). Higher COM and CARE were associated with lower piglet mortality ( ˂ 0.001 and = 0.013, respectively), and a greater number of weaned piglets was associated with higher scores for NEST ( = 0.009), COM ( < 0.001), and CARE ( = 0.009). Maternal care behavior had a greater impact on piglet mortality and the number of weaned piglets than sow physical condition (MD, BCS, and SL). We tested 7 different models (combinations of behavioral scores) and compared their relative predictive accuracies using Akaike information criteria. The model including COM and CARE had the best predictive accuracy for piglet mortality/weaned piglets. There was between-sow variation in maternal care behaviors (COM and CARE), and both were unaffected by litter size. Because these behaviors were also easy to score for the farmers, combining COM and CARE has the greatest potential to be tested in nucleus herds for calculation of genetic variation and heritability and should be taken into account in future breeding programs for sows.