Reproductive performance of "nurse sows" in Danish piggeries

Characterization of Removal Reasons for Nurse Sows and the Associated Removal Due to Their Extended Lactation Length in Hyperprolific Farrow-Wean Herds

This study aimed to characterize and quantify reasons for the removal of nurse sows and identify the removal associated with their extended lactation length (ELL). A total of 100,756 removed nurse sows within a period of 2016-2022 from 53 sow herds in the Midwest USA were analyzed. Reproductive failure was the most common removal reason (χ2 = 8748.421, p < 0.001) affecting P1, P2, and P3 nurse sows. Failure to conceive and absence of estrus were the main causes of reproductive failure (χ2 = 352.480, p < 0.001) affecting P1 and P2 nurse sows and P1 and P5 nurse sows, respectively. When P2 and P6 nurse sows had an ELL of 0-7 d, they faced a high chance (χ2 = 13.312, p = 0.021) of removal due to conception failure and failure to return to heat, respectively. When P2 and P5 nurse sows had an ELL of 8-14 d, they were highly vulnerable (χ2 = 59.847, p < 0.001) to removal due to failure to conceive and showing heat, respectively. Finally, when ELL was at 15-21 days, P4 and P5 nurse sows were more likely (χ2 = 41.751, p < 0.001) to be removed due to failure to express heat, whereas at the same time, P2 and P3 nurse sows experienced the same removal threat due to failing to conceive. These results could help producers manage nurse sow systems.

Selecting the optimal strategies when using nurse sows for supernumerous piglets

Hyper-prolific sows frequently do not have a sufficient number of functional teats for their piglets to nurse which has led to the use of nurse sows to manage these surplus piglets. This review discusses strategies for using nurse sows and factors that influence preweaning survival and weight gain of their litters, as well as those that affect their subsequent rebreeding performance. Rearing piglets using a nurse sow can be as successful as piglets reared with their biological mother and is thus a powerful management tool to decrease preweaning piglet mortality. Selecting a young sow as nurse sow is beneficial for piglet survival; however, piglets nursing first parity sows often have a lower daily weight gain than piglets nursing multiparous sows. A litter of uniform surplus piglets is preferably handled using the two-step nurse sow strategy. A consequence of nonuniform litters will most likely be an increased mortality and decreased weaning weight among the smallest piglets within a litter. The subsequent fertility of nurse sows is not compromised. There is an increased risk of lactational oestrus when using nurse sows leading to an increased weaning-to-oestrus interval; however, litter size in nurse sows is identical or even moderately higher in the subsequent parity compared with nonnurse sows.

Suckling Induces Differential Gut Enzyme Activity and Body Composition Compared to Feeding Milk Replacer in Piglets

The aim of this study was to investigate differences in growth, hematology, metabolism, small intestine (SI) morphology, and enzyme activity of sow-reared piglets (SOW) compared to artificially reared piglets (MILK) given milk replacers in two different environments. Thirty-six piglets were selected at birth based on their birth weight; eighteen were kept on a commercial farm, another eighteen transferred to an animal research facility for artificial rearing. Differences were observed in enzymatic activity, with a larger amount of sucrase in the SOW compared with MILK group across the SI. SOW piglets also had a body composition with a larger amount of fat, muscle, and bone mass content. Differences in hematology were observed, suggesting environmental influences, biochemistry differences reflective of the diets given, and finally, an increased dry matter (DM) intake in SOW piglets was estimated. No differences were observed in immune function and only small differences in the gut integrity were found between the two groups. It can be concluded that body composition and enzyme activity can be manipulated through dietary intervention and that an increase in DM during lactation is beneficial for gut function. The study warrants further investigation into what this means for the subsequent weaning period.

Piglet Viability: A Review of Identification and Pre-Weaning Management Strategies

Simple Summary

Neonatal piglet viability is decreasing in concert with the selection for ever-greater numbers of piglets born per sow per year. Their survival depends on the early intervention and management strategies used by production staff. This paper will review current and novel methods used to identify these piglets, some of the factors affecting their viability, and management strategies commonly used within production systems to improve their survival.

Abstract

Increased attention on the effects of the global push for a larger litter size has focused on the increased occurrence of piglets with decreased viability, which have lighter birthweights and a reduced ability to thrive in early life. To improve their odds of survival, interventions must be timely and targeted. This requires the early identification of low-viability pigs and appropriate strategies to manage them. Using novel measures such as abdominal circumference and crown to the rump length in conjunction with birth weight may provide an improved protocol for the identification of those at most risk of preweaning mortality. Further, identifying these at-risk piglets allows interventions to increase their colostrum intake and heat provisions shortly following birth. The appropriate management of the pre- and post-partum sows will improve the chances of decreasing the number of piglets born with lower viability. However, this outcome is constrained by limitations in resources such as technology and staffing. If these challenges can be overcome, it will allow for greater control and increased effectiveness in the implementation of current and new management strategies.

The effects of long- or short-term increased feed allowance prior to first service on litter size in gilts

Replacing stock is costly in any pig production. In addition, it takes time for young animals to reach the same level of productivity as more mature animals. Therefore, the aim of this study was to investigate the effects of long- or short-term increased feed allowance (covering the luteal and follicular phases) prior to service in the second estrus on first parity performance. In order to achieve this, altrenogest was used to synchronize the gilts cycle to allow a precise feeding strategy, and only gilts inseminated 0-10 d after altrenogest withdrawal were included in the study. Altrenogest was given at days 0-18 to control the luteal phase and, therefore, treatments covered different feeding strategies in either or both the luteal phase (days 0-18) and follicular phase (days 18-25). High feed allowance (H) was induced using 0.97 kg more feed per day compared to the low feed allowance (L) given 2.33 kg/d. Four feeding strategies, low-low (LL), high-high (HH), high-low (HL), and low-high (LH), were included. Once gilts had been inseminated, feed allowance was reduced to 2.23 kg/d to prevent the loss of embryos in early gestation. A tendency was observed between feeding strategy and backfat thickness before altrenogest treatment, showing that total born piglets were positively correlated to backfat in the LL and LH (no increased feed allowance or short-term increased feed allowance), treatments (P = 0.076), compared to when gilts had longer periods with high feed allowance (HH and HL). High feed allowance in the follicular phase (LH) tended to increase the number of total born piglets compared to the other groups (P = 0.069) when applied in the follicular phase of the second standing estrus after the gilts were given altrenogest. This would be equivalent to the last 5-7 d of a 21-d cycle in gilts. The three other feeding strategies, comprising either the luteal and follicular phases (HH) or the luteal phase (HL) or none (LL), did not increase litter size. The weight of the gilt when entering the insemination section also had an effect on total born piglets (P < 0.001) with an increase in litter size with increased weight of the sow, but no differences between treatments. In conclusion, the weight of the gilt had an influence on the total litter size and gilts with low backfat tended to respond more positively to a longer period with high feed allowance than fatter gilts.

Identifying challenges to manage body weight variation in pig farms implementing all-in-all-out management practices and their possible implications for animal health: a case study

Background

Managing body weight (BW) variation is a challenge in farrow-to-finish farms implementing all-in/all-out (AIAO) production systems due to the lack of “off-site” facilities to segregate slow growing pigs (SGP). This case study investigated different approaches to managing BW variation in a farrow-to-finish commercial pig farm with a self-declared AIAO management and the possible implications for animal health.

Case presentation

A total of 1096 pigs (1047 pigs born within 1 week plus 49 pigs born 1 week later) were tracked until slaughter as they moved through the production stages. Piglets were individually tagged at birth and their location on the farm was recorded on a weekly basis. In total, 10.3% of pigs died during lactation. Four main cohorts of pigs were created at weaning and retrospectively identified: cohort 1 = pigs weaned at 21 days (4.5%); cohort 2 = pigs weaned at 28 days (81.0%), which was sub-divided at the end of the first nursery stage into sub-cohort 2a = pigs split at 3 weeks post-weaning (29.7%); sub-cohort 2b = pigs split at 3 weeks post-weaning from cohort 2a and split again 5 weeks post-weaning (35.5%) and sub-cohort 2c = remaining smaller size pigs from cohort 2b (10.9%); cohort 3 = pigs weaned at 35 days (2.7%) and cohort 4 = pigs weaned at 49 days (1.5%) that were later mixed with SPG, delayed pigs from other cohorts and sick/injured pigs that recovered. Four strategies to manage BW variation were identified: i) earlier weaning (cohort 1); ii) delayed weaning of SGP (cohort 3 and 4); iii) re-grading pens by BW (sub-cohorts 2a, 2b and 2c) and, iv) delayed movement of SGP to the next production stage (several pigs from all cohorts). A higher percentage of delayed pigs presented pericarditis, pleurisy and enzootic pneumonia like lesions at slaughter compared with pigs under other strategies.

Conclusion

A variety of management practices were implemented to minimise BW variation during the production cycle. However, several cohorts of pigs were created disrupting AIAO management. Earlier weaning should only be practiced under specific circumstances where optimal animal health and welfare are guaranteed. Delayed weaning of SGP and delaying pigs to move to the next production stage could negatively affect animal health and should be avoided.

Impact of nurse sows on influenza A virus transmission in pigs under field conditions

Piglets prior to weaning play a central role in maintaining influenza infections in breeding herds and the use of nurse sows is a common practice to adopt piglets that fall behind and that otherwise would die. Transmission of influenza A virus (IAV) from nurse sows to adopted pigs has been reported experimentally, however, the importance of this route of transmission under field conditions has not yet been elucidated. A cohort study to assess the IAV status in nurse and control sows and their respective litters was carried out in three influenza positive breed-to-wean farms. A total of 94 control and 90 nurse sows were sampled by collecting udder skin wipes and oral swabs at enrollment (∼ 5-7 days after farrowing) and at weaning. Six piglets per litter were sampled randomly at enrollment, 2 days post-enrollment (DPE), 4 DPE, at day 14 of lactation (14DL) and at weaning. At enrollment, 76 % (69/91) of udder wipes and 3 % (3/89) of oral swabs from nurse sows were positive by rRT-PCR compared with 23 % (21/92) of udder wipes and 0 % (0/85) of oral swabs from control sows. Of the 94 control litters sampled, 11.7 %, 14.9 %, 22.9 %, 46.8 % and 63.9 % tested rRT-PCR IAV positive at enrollment, 2DPE, 4DPE, 14 DL and weaning, respectively. Corresponding prevalence for nurse sow litters were 12.2 %, 30.2 %, 37.0 %, 59.4 % and 56.4 %. The odds of IAV positivity were significantly higher (p < 0.05) for litters from nurse sows 2 DPE (odd ratio (OR) = 6.13, 95 % CI = 1.8-21.2), 4 DPE (OR = 5.5, 95 % CI = 1.7-17.8) and 14 DL (OR = 3.7, 95 % CI = 1.1-12.3). However, there were no differences in the proportion of positive samples at weaning. Moreover, approximately 18 % of the control sows and 11 % of nurse sows that tested IAV negative in oral swabs at enrollment, tested IAV positive at weaning. This study indicates that nurse sows can contribute to the transmission and perpetuation of IAV infections in pigs prior to weaning, particularly during the first week after adoption.

Pre-weaning adaptation responses in piglets fed milk replacer with gradually increasing amounts of wheat

Hyperprolific sows rear more piglets than they have teats, and to accommodate this, milk replacers are often offered as a supplement. Milk replacers are based on bovine milk, yet components of vegetable origin are often added. This may reduce growth, but could also accelerate maturational changes. Therefore, we investigated the effect of feeding piglets a milk replacer with gradually increasing levels of wheat flour on growth, gut enzyme activity and immune function compared with a diet based entirely on bovine milk. The hypothesis tested was that adding a starch component (wheat flour) induces maturation of the mucosa as measured by higher digestive activity and improved integrity and immunity of the small intestines (SI). To test this hypothesis, piglets were removed from the sow at day 3 and fed either a pure milk replacer diet (MILK) or from day 11 a milk replacer diet with increasing levels of wheat (WHEAT). The WHEAT piglets had an increased enzyme activity of maltase and sucrase in the proximal part of the SI compared with the MILK group. There were no differences in gut morphology, histopathology and gene expression between the groups. In conclusion, the pigs given a milk replacer with added wheat displayed immunological and gut mucosal enzyme maturational changes, indicatory of adaptation towards a vegetable-based diet. This was not associated with any clinical complications, and future studies are needed to show whether this could improve responses in the subsequent weaning process.

The Stomach Capacity is Reduced in Intrauterine Growth Restricted Piglets Compared to Normal Piglets

Simple Summary

Large litters have resulted in a higher percentage of piglets suffering from intrauterine growth restriction (IUGR). There is a higher mortality in this subset of piglets and a large number die because they do not receive enough nutrients for energy within the critical first 24 h after birth. One source of nutrients for energy could be supplementation with extra colostrum from previously milked sows. However, there is no knowledge on the stomach capacity of IUGR piglets, and therefore, of how much colostrum could potentially be supplemented. This is important information in order to recommend how much supplementary colostrum IUGR piglets need in order to survive.

Abstract

Selection for increased litter sizes have decreased the average birth weight of piglets and up to 30% of newborn piglets in Danish herds show signs of intrauterine growth restriction (IUGR). It has been reported that around 48% of liveborn piglets dying between birth and weaning have empty stomachs, and that IUGR piglets do not ingest the recommended amount of colostrum to survive. The aim of this study was to investigate how much colostrum could be administrated depending on whether they were IUGR compared to normal piglets. Seventy-two piglets within 24 h of farrowing were classified as either IUGR or normal based on their head morphology. Stomach weight, length and capacity were measured along with bodyweight (BW). The results displayed a decreased BW, empty stomach weight and capacity in IUGR piglets, as well as a decreased relative stomach capacity in IUGR compared with normal piglets. In conclusion, birth weight is not the only factor influencing stomach capacity, and IUGR piglets have a smaller stomach capacity compared with normal piglets. It is estimated that IUGR piglets have the capacity to be given a bolus of 25 mL per kg/BW, whereas a normal piglet have a higher capacity (30 mL per kg/BW).

Administration of Glucose at Litter Equalization as a Strategy to Increase Energy in Intrauterine Growth Restricted Piglets

Simple Summary

Hyper-prolific sows with large litters require extra management in order to reduce piglet mortality. One of the reasons is high piglet birth weight variability in these large litters where piglets can range from 300 g to 2.5 kg in the same litter. In this study the strategy of giving energy at litter equalization to the smallest piglets was investigated as this is when most farmers handle the piglets for the first time. The treatments consisted of a control, oral and injected supplementation. There were no differences between the treatments of the piglets suggesting that it is too late to intervene at litter equalization, and if extra management actions are to have an effect then they most likely have to be given already at birth. More research is needed on how to handle the small and underdeveloped piglets in order to reduce piglet mortality.

Abstract

Hyper-prolific sows give birth to large litters and up to 25% of piglets born have been subjected to intrauterine growth restriction (IUGR). The aim of this study was to test whether an oral administration of glucose impacts the survival rate and body weight gain of IUGR piglets at weaning. Different methods (injection versus oral administration of glucose 6 mL or 12 mL, respectively) were tested on IUGR piglets at litter equalization (i.e., when piglets are handled the first time at 5–20 h after birth). Injecting glucose generated the highest whole-blood glucose level + 3 h after treatment, however, after this no differences were observed. Of the 237 IUGR piglets studied, 98 piglets died or were removed from the nurse sow (41%). Rectal temperature at litter equalization (0 h) was related to the survival of the piglets with an average temperature of 37.1 ± 0.1 °C in surviving piglets and 36.6 ± 0.1 °C in piglets that died. In conclusion, providing these extra management actions at litter equalization is too late to help piglets that have a low rectal temperature and are low on energy. More research investigating different management methods to deal with IUGR piglets are needed as many of these underdeveloped piglets will not survive.

Intrauterine growth-restricted piglets defined by their head shape have impaired survival and growth during the suckling period

Increased litter sizes in modern pig breeds have led to a significant number of pigs being born undersised and/or exposed to different degrees of intrauterine growth restriction (IUGR). The aim of this study was to examine the effect of piglet head shape as an identification method on performance indices. Data included all piglets from 203 litters, in total 3402 crossbred piglets. Piglets were classified at birth based on their head morphology (normal, mild IUGR and IUGR) and weighed at birth, Day 14 and at weaning (mean ± s.d.: 25.5 ± 1.23 days). The relative weight of the brain (to bodyweight) was greater in the mild IUGR (4.2%) and in the IUGR piglets (5.5%) compared with the normal piglets (2.8%) (P &lt; 0.001). Weaning weight of the mild IUGR and IUGR piglets was reduced by 1.3 kg and 1.8 kg, respectively, compared with the normal piglets (P &lt; 0.001). The average daily gain of the normal piglets (228 g/day) was higher than the mild IUGR (195 g/day) and IUGR piglets (181 g/day) (P &lt; 0.001). The fractional growth rate (weight gained per day per starting weight) was, however, highest in the IUGR piglets followed by the mild IUGR and the normal piglets (P &lt; 0.001) indicating the potential for catch up growth. Mild IUGR that were liveborn had twice as high a risk of dying before weaning than normal piglets; whereas liveborn IUGR piglets had a 4.7 times greater risk of dying pre-weaning. The present study showed that piglets born with a ‘dolphin-like’ head shape have an impaired growth and increased risk of dying in the suckling period.

A Review of Success Factors for Piglet Fostering in Lactation

Simple Summary

An understanding of behavioural and physiological mechanisms responsible for piglet survival and growth will assist in developing the best recommendations in which to manage piglet movements in the farrowing house. This review has identified six key principles that should underpin successful piglet fostering. These fostering principles will improve productivity and welfare of sows and piglets in commercial pig production.

Abstract

Piglet movement from one sow to another, or fostering, is required in modern pig farming but there is little available literature on the most effective strategy. In this review, we focus on the behavioural and physiological mechanisms responsible for piglet survival and growth, and have identified six key principles. (1) Colostrum provides piglets with warmth, energy and immunity. It is most accessible during the first 12 h from the birth sow, therefore no piglet should be moved before this; (2) To ensure even intake of birth sow colostrum, techniques such as split suckling prior to piglet movement should be implemented; (3) Udder assessment for functional teats should occur at farrowing, with number of fostered piglets not exceeding teat number; (4) Primiparous sows should receive as many piglets as the udder allows to maximise mammary stimulation, although older parities should be assessed for rearing ability; (5) Piglet fostering should occur between 12 and 24 h and movement kept to a minimum to prevent transfer of disease; Litter outliers should be moved and relocated to a litter of similar size; (6) Piglet movement after 24 h should be minimised. When required, strategies such as nurse usage should be employed. These principles will result in improved farrowing house performance by increasing the litter weight weaned per sow.

Supplementing newborn intrauterine growth restricted piglets with a bolus of porcine colostrum raises rectal temperatures one degree Celsius

Hyperprolific sows have increased litter sizes but also result in more piglets that have been exposed to intrauterine growth restriction (IUGR). These IUGR piglets are likely to have a low rectal temperature and lower blood glucose levels compared with normal piglets at birth. Therefore, we hypothesized that a colostrum bolus at birth and/or heat from an external source would have a positive effect on blood glucose levels, rectal temperatures, and growth up to 8 h postpartum. In addition, liver glycogen and blood values at 8 h were investigated. Eighty-four piglets were classified at birth (time = 0) as IUGR based on their head morphology and randomly allocated to 1 of 4 treatments ( = 21) in a 2 × 2 factorial arrangement: 1) with or without a porcine colostrum bolus (12 mL/kg BW at birth) and 2) with sow or isolated from sow with external heat. Piglets were removed from the sow before they had suckled and were numbered and dried, and initial whole-blood glucose, rectal temperature, and BW were recorded. Piglets in the 2 treatments isolated from sow were placed under a heating lamp (150 W) with a temperature range of 35 to 39°C. Rectal temperatures, glucose, and BW were measured again at 1, 2, 4, 6, and 8 h after birth, and a final plasma sample and organs (liver and brain) were removed at 8 h. There was a time × colostrum bolus interaction ( = 0.026) and a time × sow interaction ( < 0.001) for whole-blood glucose. The piglets that were given a bolus had greater glucose levels after 1 h postpartum (time = 1 h) than piglets without a bolus at birth, but from time = 2 h and onward, there was no difference ( > 0.05). There was a time × colostrum bolus interaction ( < 0.001) and a time × sow interaction ( < 0.001) on rectal temperatures. One hour after birth, the piglets with a bolus had a greater rectal temperature compared with piglets without a bolus (37.5 vs. 36.6°C; < 0.001) and the piglets that had been isolated from the sow had a greater rectal temperature compared with the 2 treatments with sows (37.8 vs. 36.3°C; < 0.001). Four hours after birth, rectal temperature was not affected by treatments. In conclusion, both heat and a colostrum bolus increased rectal temperature by 1°C an hour after birth. However, after 4 h, no differences were found between the treatments. Interventions to help IUGR piglets postpartum most likely need to be frequent to have any effect on whole-blood glucose, rectal temperatures, and BW over the first 8 h.

Animal Welfare and Economic Aspects of Using Nurse Sows in Swedish Pig Production

The number of born piglets per litter has increased in Swedish pig industry, and farmers are struggling to improve piglet survival. A common practice is to make litters more equally sized by moving piglets from large litters to smaller to make sure that all piglets get an own teat to suckle. Litter equalization is not always enough, as many sows have large litters and/or damaged teats, which results in an insufficient number of available teats. One way to solve this problem is to use nurse sows. A nurse sow raises, and weans, her own piglets before receiving a foster litter. The objectives of this study were to address how the use of nurse sows affects the welfare of sows and piglets and to explore how it impacts the contribution margin of pig production in Sweden. A literature search was made to investigate welfare aspects on sows and piglets. As there were few published studies on nurse sows, an expert group meeting was organized. In order to explore the impact on the contribution margin of pig production, a partial budgeting approach with stochastic elements was used for a fictive pig farm. Standard templates for calculating costs and benefits were supplemented with figures from existing literature and the gathered expert opinions. In Sweden, the minimum suckling period is 28 days while published studies involving nurse sows, all from outside of Sweden, weaned the piglets at 21 days. A Swedish nurse sow will thus get longer lactation period which might increase the risk of poor body condition, damaged teats, and shoulder ulcers. This indicates a reduced welfare of the sow and may lead to impaired fertility and increased culling risk. On the other hand, the piglet mortality could be reduced with the use of nurse sows, but the separation and mixing of piglets could be stressful. The partial budgeting suggested that the nurse sow system is slightly more profitable (+6,838 Swedish krona) per farrowing group during one dry and one lactation period compared to the conventional system. The result is, however, highly dependent on the input values, and welfare aspects were not considered in the calculations.

Dietary supplement rich in fiber fed to late gestating sows during transition reduces rate of stillborn piglets

The beneficial effects of dietary fiber (DF) from a behavioral and welfare perspective have been thoroughly studied. However, data on the effects of DF on reproductive performance are scarce. Therefore, the aim of this study was to investigate the impact of increased DF supply during the last 2 wk of gestation on stillbirth rate, preweaning mortality, and total piglet mortality. A total of 644 sows were selected for the experiment from a commercial farm, and the sows were inseminated in weekly batches. Sows in the control group ( = 310) were fed according to the normal feeding strategy of the farm with a gestation diet until 1 wk before expected farrowing, then a transition diet until d 5 of lactation, and then a lactation diet until weaning. Sows in the treatment group ( = 334) were fed as the control group except that 280 g/d of the gestation diet (from d 102 to 108 of gestation) and 570 g/d of the transition diet (from d 109 of gestation until farrowing) was daily replaced with 350 and 700 g/d, respectively, of a DF-rich supplement. Both groups received isocaloric diets on a NE basis. The numbers of live-born and stillborn piglets as well as mortality of live-born piglets with presumed causes of death were recorded. The supplemented DF reduced the proportion of stillborn piglets from 8.8 to 6.6% ( < 0.001) and mortality of total born piglets from 22.3 to 19.9% ( = 0.004) but had no impact on preweaning mortality of the piglets ( = 0.21). Moreover, supplemented DF reduced the proportion of death due to poor viability ( < 0.001; 2.8 vs. 1.5% in the control and treatment groups, respectively) and prevalence of piglet diarrhea ( = 0.004; 0.7 vs. 0.3% in the control and treatment groups, respectively). Crushing, low birth weight, and poor viability were the top 3 contributors to preweaning mortality of live-born piglets, in descending order. In conclusion, the supplemented DF reduced the proportion of stillborn piglets and total piglet mortality as well as mortality due to poor viability and piglet diarrhea in lactation.

The effect of double nursing, an alternative nursing strategy for the hyper-prolific sow herd, on herd performance

BACKGROUND

Hyper-prolific sows produce more piglets than they can suckle, as the number of milk producing teats of the sow is lower (twelve to sixteen) than the number of live born piglets per litter. Farmers and farm workers are struggling to feed this surplus of piglets. To minimize suckling piglet mortality, litter size at 24 hours after parturition should not exceed the number of functional teats of the sow. Strategies to adequately nurse or feed the surplus of piglets after 24 hours are limited and mostly restricted to either fostering piglets by other sows, supplying milk replacers (formula) or early weaning and rearing on formula.

CASE PRESENTATION

In this case report we describe the design and application of a so called 'double nursing' strategy, for which one sow simultaneously nurses two litters from birth to weaning. Piglet mortality and reproductive parameters of sows that have nursed two litters are compared, over a three year period, with those that nursed one litter.

CONCLUSION

In this herd, the double nursing strategy appeared to be a successful strategy. Double nursing sows experienced a lower piglet mortality, despite the double nursing strategy. The negative effects on reproduction proved to be limited, there was a negative effect on litter size in subsequent litters, but no significant effect on the interval weaning to next conception. It has to be noted though that not all characteristics on which double nursing selection takes place, could be taken into account during statistical analyses.

Factors for improving reproductive performance of sows and herd productivity in commercial breeding herds

We review critical factors associated with reproductive performance of female breeding pigs, their lifetime performance and herd productivity in commercial herds. The factors include both sow-level and herd-level factors. High risk sow-level groups for decreasing reproductive performance of female pigs are low or high parity, increased outdoor temperature, decreased lactation feed intake, single inseminations, increased lactation length, prolonged weaning-to-first-mating interval, low birth weight or low preweaning growth rate, a few pigs born alive at parity 1, an increased number of stillborn piglets, foster-in or nurse sow practices and low or high age at first-mating. Also, returned female pigs are at risk having a recurrence of returning to estrus, and female pigs around farrowing are more at risk of dying. Herd-level risk groups include female pigs being fed in low efficiency breeding herds, late insemination timing, high within-herd variability in pig flow, limited numbers of farrowing spaces and fluctuating age structure. To maximize the reproductive potential of female pigs, producers are recommended to closely monitor females in these high-risk groups and improve herd management. Additionally, herd management and performance measurements in high-performing herds should be targeted.