Pork producers using alternative housing and production systems have been seeking ways to decrease pre-weaning mortality of piglets, thereby increasing their profits and increasing the standard of welfare on their farms. The major objectives of this research project were to identify the major factors associated with non-infectious pre-weaning mortality, to develop a management protocol to manage these factors, and to implement this protocol on farms using alternative housing and production systems.
A survey was developed and given to alternative swine producers in Minnesota and Iowa to identify the major factors associated with pre-weaning mortality on their farms. A management protocol to decrease pre-weaning mortality was developed based on the responses to this survey, and previous research completed by the authors. From those producers that completed the survey, 6 farms were chosen based on size and location to participate in the study. Producers agreed to follow as closely as possible the developed management protocol based on their time available and economic considerations.
Producers collected farrowing performance data (total born, number born alive, stillborns, litter size within the first 24 h of farrowing after crossfostering, and litter size 10 d post-farrowing). Performance data were collected from November, 2010 to May, 2011 from 255 farrowings on 4 alternative swine farms. Two farms were omitted due to lost or incomplete records. Average piglet mortality in the first 10 d post-farrowing on these 4 farms was 21.1% and ranged from 15.2% to 29.9%. Number born alive ranged from 7.5 to 10.8 piglets/litter and number of piglets that died per litter within 10 d post-farrowing ranged from 1.1 to 1.7 piglets/litter. Additionally, total born (P < 0.01), number born alive (P < 0.01), litter size 24 h post-farrowing (P < 0.01), and number of piglets alive/litter 10 d post-farrowing (P < 0.01) were greater in the spring compared to the winter.
Pre-weaning mortality on these farms was affected by a combination of factors including season, genetics, housing, and management practices. Management recommendations to decrease pre-weaning mortality based on the findings on each farm included increasing biosecurity, providing supplemental heat for piglets, proper semen storage, providing additional bedding in muddy conditions, and reviewing sow and boar environmental and nutritional management needs. The results of this study provided key focus areas on each farm aimed at decreasing pre-weaning mortality. Pre-weaning mortality is higher on alternative farms because they do not use as much proven technology as on confinement farms.
Pre-weaning mortality of piglets is a major cause of reduced efficiency in alternative swine production. Marchant et al. (2000) reported that 20 to33% of piglets may die before weaning in farrowing facilities of alternative production systems. In the Midwest U.S., average pre-weaning mortality of piglets in alternative systems is 26% (Kliebenstein et al., 2007), which is about two-fold of that (10 to 13%) in confinement systems. The majority of the pre-weaning piglet deaths are not caused by diseases, but by crushing and starvation (Edwards et al., 2002). On average, piglet crushing accounts for 75% of total pre-weaning mortality in alternative production systems (Dunn, 2005). Early piglet death not only represents economic loss, but causes welfare concerns because 70% of piglets crushed are potentially healthy and viable (Spicer et al., 1987). By reducing non-infectious pre-weaning mortality while maintaining litter size born alive, litter size weaned can be increased thereby improving production efficiency and enhancing piglet welfare.
Previous studies have indicated that pre-weaning mortality is related negatively to litter size (Lund et al., 2002) and birth weight (Quiniou, et al. 2002), and related positively to variation in birth weight and parity of sows (Hellbrugge et al., 2008b). Maternal behavior (Damn et al., 2005) is associated with piglet crushing and has been claimed as the major cause of pre-weaning mortality in both confinement and alternative farrowing systems. Andersen (2005) reported that piglet mortality mainly depends on mothering ability of sows, which tends to be consistent among individual sows across parities (Jarvis et al., 2005).
Our previous research conducted at the West Central Research and Outreach Center (WCROC), University of Minnesota indicated that by improving management practices in a loose housing system, pre-weaning mortality can be reduced from 27% to 19% (Li et al., 2010). The purpose of this project was to ask pork producers using alternative production systems to implement a management protocol specifically developed to manage the major risk factors to piglet survival while maintaining litter size at birth to increase the number of piglets weaned.
The major objectives of this research project are to develop a model to identify the major factors associated with non-infectious pre-weaning mortality, to develop a management protocol to manage these factors, and to validate this protocol on farms using alternative housing and production systems. The anticipated goal is to wean 1 more pig per litter than the average number of pigs weaned on each farm.
Producers will be provided with essential information on ways to improve piglet welfare by identifying the factors that contribute to piglet mortality. In general, increased profit and improved welfare conditions for the pigs in alternative systems will contribute to the long-term viability of farmers using alternative production systems, the local economy, and the environment.
This study consisted of two phases. The objective of phase 1 was to identify risk factors contributing to pre-weaning mortality of piglets in loose farrowing systems. A survey was conducted to assess the specific causes and impact of piglet mortality on production efficiency on participating alternative swine farms in Minnesota and Iowa (Appendix 1). The survey was distributed and collected at several regional producer meetings as well as through direct contact with producers. A general management protocol was developed based on the completed producer survey and previously published data (Li et al., 2010) to minimize risk factors to piglet survival and maximize profitability on these farms (Appendix 2).
The management protocol consisted of 3 major elements: management of environment and housing, management of sows, and management of piglets. Management of environment and housing was focused on achieving acceptable environmental temperature in the barn, optimizing bedding use, and on farrowing pen design. Management of sows factors included optimizing feeding programs to maximize litter weight at birth and weaning through increased milk production, optimizing litter size by cross fostering, and identifying and managing sows, either by cross-fostering techniques or possibly later culling, that potentially put their piglets at risk. Factors involving management of piglets included taking special care of piglets with low body weight, such as cross fostering methods, creep feeding, and processing lighter birth weight piglets at a later than normal date. From those completed surveys, 6 farms were chosen to participate in the study. The farms were chosen using the following criteria: willingness to participate, size of farm, and location of farm. The objective of phase 2 was to apply the management protocol and develop management strategies to reduce pre-weaning mortality of piglets on each of the farms chosen to participate in the study.
Animals, Housing and Management
All animal procedures were approved by the Institutional Animal Care and Use Committee of the University of Minnesota, St. Paul, MN. This experiment was conducted on 6 privately owned swine farms in the Midwest. However, only data from 4 farms are presented in the results. One farm had a fire and all the recorded data were lost, and one farm was removed from the study due to poor compliance with recording requested data. Data were collected from November, 2010 to May, 2011. Winter months were defined as November to February, and spring months as March to May.
Each producer decided which parts of the management protocol (Appendix 2) that they were willing to follow based on economic and time constraints. Below is a description of the location, animals, housing, and management on each farm:
Farm 1: Farm 1 is located in North Central IA. Data from 61 farrowings were collected, 8 farrowings in spring and 53 farrowings in winter. Maternal genetics utilized were Chester White and Hereford, while terminal genetics used were Berkshire and Duroc. Sows on this farm were only first and second parity animals. The management of environment and housing was already being done as outlined in the protocol. Two different types of pen designs were utilized on this farm, the Smidley-like hut with heated floors in a hoop barn (Fig. 4.1) and old converted farrowing crates used in a pen design inside a pole barn (Fig. 4.2), both with protective rails in farrowing pens. The management of sows and piglets was already being followed as outlined in the protocol, except that the producer did not provide creep feed.
Farm 2: Farm 2 is located in Western Central MN. Data from 60 farrowings were collected, 14 farrowings in spring, and 46 farrowings in winter. Maternal genetics utilized were Chester White, and terminal genetics were Hampshire, Berkshire, and Duroc. Parity of sows on this farm ranged widely from 1 to 8. The management of environment and housing differed some from the protocol. Bedding management was followed as outlined in the protocol but protective rails and supplemental heating for piglets were not used. The sows and piglets were housed in 2 heated barns that contained Swedish deep bed pens (1.8 x 2.4 m; Fig. 4.3. and 4.4). The management of sows and piglets was already being followed as outlined in the protocol except that the producer did not provide creep feed.
Farm 3: Farm 3 is located in South Central MN. Data from 85 farrowings were collected, 43 in spring and 42 in winter. Maternal genetics utilized were Yorkshire, and terminal genetics were Berkshire and Duroc. Parity of sows on this farm ranged from 1 to 5 with a majority being younger, smaller sows. The management of environment and housing was already being done as outlined in the protocol. The sows and piglets were housed in hoop barns containing Smidley huts (Marting Manufacturing, IA; Fig. 4.5 and 4.6) and huts similar to Smidley huts; however, the latter were not insulated (Fig. 5). The management of sows and piglets was already being completed as outlined in the protocol with the exception of creep feeding and the sow feeding program. Sows were given access to feeders for a set amount of time per day, usually for about 2 to 4 hours in the morning.
Farm 4: Farm 4 is located in Southeastern MN. Data from 49 farrowings were collected, 24 in spring and 25 in winter. Maternal genetics utilized were Yorkshire and terminal genetics were Duroc. Parity of sows on this farm ranged widely. The management of environment and housing was already being done as outlined in the protocol. The sows and piglets were housed in hoop barns containing Smidley-like huts (Fig. 4.7 and 4.8). The management of sows and piglets was already being followed as outlined in the protocol except that the producer did not provide creep feed.
Data were collected from 89 farrowings in the spring and 166 in the winter. Total born, born alive, and still born piglets in each litter were recorded for each sow within 24 h after farrowing. Cross-fostering was conducted within 24 h of farrowing, and litter size at 24 h after farrowing was recorded. The number of piglets in each litter was recorded again at approximately 10 d of age before pens, roller bars, or huts were removed. Litter size after cross fostering was calculated by subtracting or adding the number of piglets cross-fostered from the number of piglets born alive. Pre-weaning mortality (%) at d 10 post-farrowing was calculated using the following equation: 100% × (number of piglets dead during the first 10 d after farrowing/litter size after cross-fostering).
The Poisson regression model in the Glimmix procedure of SAS (Cary, NC) was used to test the effects of farm and season on performance measures. Tukey-Kramer adjustment was used to separate the means. The experimental unit was the individual sow. Farrowing group and farrowing group x farm interaction were the random effects.
Approximately 50 surveys were completed by producers, and from 14 of those, producers responded that they would be willing to participate in the study. Data from the 14 volunteer farms were compiled and are presented in Table 1. The number and type of sows on each farm, type of housing provided, and management procedures differed among farms.
Of the 14 producers that responded that they would be willing to participate: 1) 9 were located in MN and 4 in IA; 2) 5 had a herd size of 10 to 30 sows, 5 of 31 to 50 sows, 3 of 51 to 70 sows, and 1 of 71 to 100 sows; 3) 8 farms housed the herd indoors only, 3 in a hoop barn only, 1 a combination of indoor and pasture, 1 a combination of indoor, outdoor, and hoop, and 1 a combination of indoor, outdoor, hoop, and pasture; 4) 8 farms provided heating for sows; 5) 6 provided some kind of cooling mechanism for the sows, i.e. fans; 6) 11 farms provided protective rails in the farrowing huts or pens to try and prevent piglet crushing against the sides, 7) 12 farms provided supplemental heating for piglet, i.e. heat lamps; 8) 4 producers checked their sows and litters twice a day, 10 producers checked them 3 or more times daily; 9) 11 farms cross-fostered piglets; and 10) 11 producers from personal observation thought that pre-weaning mortality was seasonal, and higher in colder or warmer weather on their farms. From these 14 farms, 6 were chosen to participate in the study. The farms were chosen using the following criteria: willingness to participate, size of farm, and location of farm.
The production performance data are presented in Tables 4.2, 4.3 and 4.4. All four farms had an average 10 d post-farrowing pre-weaning of 21.1%, ranging from 15.2% (Farm 4) to 29.9% (Farm 1). These results are similar to published data which estimates total pre-weaning mortality during the lactation period on Midwestern alternative swine farms to be 26% (Kliebenstein et al., 2007), and the range to be 20-33% (Marchant et al., 2000). However, the farm with the lowest 10 d post-farrowing pre-weaning mortality of 15.2% was approaching the range of 10 to 13% for confinement farrowing systems for the entire lactation period (Kliebenstein et al., 2007). The farm with the highest pre-weaning mortality was diagnosed with an outbreak of Porcine Reproductive and Respiratory Syndrome (PPRS) during the beginning of the study, and this contributed to the relatively high pre-weaning mortality on this farm. In addition to the health issues on one farm, another possible explanation for these differences in pre-weaning mortality are a combination of different housing systems, genetics, and management practices (described in detail in the subsection of Individual farm results by season). Confinement systems have farrowing crates, which serve to decrease piglet mortalities by preventing certain sow movements that contribute to piglet crushing. In addition, confinement systems generally have strict biosecurity, usually shower-in shower-out facilities, and these alternative farms do not utilize these biosecurity practices.
Variation of farrowing performance among farms
The total number of piglets born on Farm 4 (11.7 ± 0.5, Table 2) was greater than Farm 1 (8.8 ± 0.5; P < 0.03) and Farm 2 (9.9 ± 0.5; P = 0.08), and number of piglets born on Farm 3 (10.5 ± 0.4) was greater than Farm 1 (P < 0.09). The number of piglets born alive on Farm 4 (10.8 ± 0.6) was greater than Farm 1 (7.5 ± 0.7; P = 0.06). The differences in total born and born alive among farms could possibly be due to different genetics used among farms. Yorkshires, the only maternal genetics used on Farm 4, and also used on Farm 3, are known for their larger litters and longer body length (OSU, Swine Breeds, 2009). There were no differences in the number of stillborn pigs among farms. Litter size 24 h post-farrowing on Farm 4 (10.8 ± 0.7) was greater than Farm 1 (7.6 ± 0.7; P < 0.05). Litter size at 10 d post-farrowing on Farm 4 (9.2 ± 0.6) was greater than Farm 1 (6.3 ± 0.5; P < 0.03). These differences in litter size are 24 h post-farrowing and 10 d post farrowing are partly due to Farm 4 having the largest number of piglets born alive. The most plausible reason Farm 1 performed so poorly compared to the other farms, is the veterinary diagnosed outbreak of PRRS on this farm. There were no differences in the number of piglets dead/litter 10 d post-farrowing among the 4 farms.
The total number of piglets born on all of the farms was greater in spring (10.9 ± 0.4, Table 3) compared to winter (9.5 ± 0.2; P < 0.01). The number of piglets born alive was greater in spring (9.9 ± 0.6) compared to winter (8.3 ±0.4; P < 0.02). Previous studies have found that alternative production systems that may provide unfavorable climatic and environmental conditions, specifically in this case colder temperatures, may lower reproductive performance (Akos and Bilkei, 2004). There were no differences in the number of stillborns between seasons. Li et al. (2010) found the number of stillbirths tended to be greater in the summer compared to all other seasons, possibly due to heat stress. But, they also found no differences in the number of stillbirths between spring and winter. Litter size at 24 h post-farrowing was greater in spring (10.1 ± 0.6) compared to winter (8.2 ± 0.4; P < 0.01). Litter size at 10 d post-farrowing was greater in the spring (8.9 ±0.5) compared to winter (6.6 ± 0.3; P < 0.01). The number of piglets dead/litter 10 d post-farrowing was less in the spring (1.2 ± 0.2) compared to winter (1.6 ± 0.2; P = 0.09). The fact that the litter size at 24 h post-farrowing, 72 h post-farrowing and 10 d post-farrowing was greater in the spring compared to the winter was likely due to the warmer temperatures in the spring being more conducive to piglet survival. In the Midwest, the most favorable period for piglets to be born in alternative farrowing systems is from late spring through early fall (Honeyman et al., 2006). However, because one of the greatest challenges for pork niche marketers is to maintain a steady supply of pork, some niche markets will not accept new producers unless they agree to farrow pigs during winter (Honeyman et al., 2006).
Individual farm results by season
Farm 1: This farm had an outbreak of PRRS while participating in this study. Total piglets born (P < 0.05; Table 3), number born alive (P = 0.10), litter size 24 h post-farrowing (P < 0.05), and litter size 10 d post-farrowing were all greater (P < 0.01) in the spring compared to the winter. However, there was no difference in the number of piglets that died within 10 d post-farrowing between the two seasons. The outbreak of PRRS likely contributed to the poor performance in winter, when the disease was diagnosed, compared to spring, when the farm was recovering, as shown in Table 3. Previous research has shown that herds testing positive for PRRS and showing clinical signs had reduced reproductive parameters including fewer mean total pigs born, fewer mean live pigs born, fewer mean pigs weaned per sow, and increased pre-weaning mortality (Baysinger et al., 1997). Personal observations on this farm concluded that 2 people living in the household, due to their professions, may have intermittent contact with other swine herds. Increasing biosecurity on this farm, by decreasing these family members’ contact with this herd, as well as visitors and vehicles who may have had contact with other pigs, will help to increase the health of this herd and decrease pre-weaning mortality.
Farm 2: The number of piglets that died 10 d post-farrowing was less in the spring compared to the winter (P < 0.01). However, there were no differences in any of the other performance measures between the two seasons. This indicates that this particular farm should focus on management techniques or the housing environment for piglets during the winter to decrease pre-weaning mortality. This farm does not provide supplemental heating for piglets which may help to draw the piglets away from the sow, or have protective bars in the pens to decrease crushing of piglets against the sides of the pens, both of which may serve to decrease pre-weaning mortality. This farm should consider installing heat lamps, and possibly protective bars in the pens to provide an area for piglets to be warm and safe. Additionally, sow management should be reviewed, specifically the sow environmental and nutritional needs, to ensure adequate milk production for piglets in the winter.
Farm 3: The litter size 10 d post-farrowing (P < 0.05) was greater in spring compared to winter. However, there were no differences for any of the other performance measures between spring and winter. This farm should focus on increasing the number of piglets born alive in the winter to decrease overall pre-weaning mortality. This farm could also improve housing or management techniques in the winter to increase the number of piglets alive 10 d post-farrowing. For example, personal observations were made noting that the farrowing hut area was muddy on several occasions. Keeping the hoop barn dry, with the addition of more bedding, may help prevent piglet deaths. During one winter lactation, the producer had a large number of piglets die in the hoop barn just after taking the farrowing huts out at approximately 2 wks post-farrowing. The veterinarian was called out, posted several pigs and determined the piglets died of starvation. Keeping farrowing huts inside the barn for a longer period of time or providing a heated creep area may decrease piglet losses due to chilling and starvation in the winter. Additionally, allowing sows ad libitum access to feed that will meet their nutritional needs may help to decrease these piglet losses by increasing sow milk production.
Farm 4: Total born (P < 0.01), number born alive (P < 0.03), litter size 24 h post-farrowing (P < 0.01), and litter size 10 d post-farrowing (P < 0.01) are greater in the spring compared to winter. However, there was no difference in the number of piglets that died within 10 d post-farrowing between the two seasons. This farm should focus on increasing number born alive in the winter, but also decreasing the number of piglets that die during winter and spring. Artificial insemination is used to generate replacement gilts, and natural breeding is used for all other matings. Artificial insemination protocols could be improved (as described for Farm 4). Boar management should be reviewed to ensure that adequate housing temperatures and nutrition are provided to ensure maximum boar fertility. Additionally, sow management in breeding and gestation during the winter should be modified to ensure that sows are being housed in adequate temperatures and being fed according to their nutrient needs to maintain adequate body conditions and to ensure the best conception and farrowing rates.
Pre-weaning mortality is an economic and welfare issue in both confinement and alternative swine production systems. Confinement systems have a decreased pre-weaning mortality compared to alternative systems because of the confinement of sows to a crate that decreases her chances of crushing of piglets. The alternative systems do not house sows in crates, but instead allow them to have a larger area that facilitates more sow movement and contact with piglets. Genetics, management, and other aspects of housing can be improved to decrease pre-weaning mortality, which will increase piglet welfare and increase producer profits on alternative farms.
Pre-weaning mortality on these 4 farms was affected by a combination of factors including season, genetics, housing, and management practices. Each of these farms had different genetics, different housing systems, and differed slightly in their management procedures. Due to these differences, each alternative swine farm faced different challenges for pre-weaning mortality. This study was able to pinpoint differences and give each producer recommendations, based on performance on the farm and knowledge of current management practices, of where to focus their efforts in the future in order to have the greatest impact on decreasing pre-weaning mortality.