Evaluation of a Partially De-oiled Microalgae Product in Nursery Pig Diets

The publication we are sharing today is a collaboration between the Department of Animal Science, the Department of Food Science and nutrition and the West Central Outreach and Research Center at the University of Minnesota. It is published in open access in the journal Translational Animal Science.


The aim of this study was to evaluate the potential use of microalgae extract (MAE) as a feed ingredient in nursery pig diets.


300 weaned pigs were selected, blocked by initial body weight and allotted to 60 pens, with five pigs per pen. Ratio of gilts and barrows was balanced evenly. Pens within blocks were assigned randomly to one of five dietary treatments.

Dietary treatments included:

  1. corn and soybean meal (CON),
  2. CON with 1% MAE,
  3. CON with 5% MAE,
  4. CON with 10% MAE
  5. CON with 20% MAE.

Diets were formulated to meet the nutrient requirements of nursery pigs and fed using a 3-phase program, where each phase consisted of a 2-wk period.

Average Daily Gain (ADG), Average Daily Feed Intake (ADFI) and Gain to Feed (G:F) were measured weekly.

After 42 days, 30 pigs were harvested and intestinal samples were collected to measure mucosal length and goblet cell quantifications.


Final body weight of pigs among pens consuming MAE was greatest when consuming 1, 5, or 10% MAE compared with those fed the control diet, but feeding 20% MAE was not different from the control diet. The greater final body weight appeared to be the result of greater ADG from days 1 and 7, due to a higher ADFI.

There was no effect of feeding MAE on G:F during most weigh periods except during days 15 to 21 when G:F increased in pigs fed MAE.

Feeding diets with MAE did not result in changes in intestinal architecture measured by the height of the intestinal mucosal or presence of mucus-producing cells in the jejunum. In contrast, the ileum of pigs fed the 5% MAE diet tended to have reduced mucosal height compared with that of pigs fed 20% MAE diet. Goblet cell area of the ileum was not affected by dietary treatments.

Link to the full article


Although microalgae can be used as a source of energy and macronutrients in pig diets, there is limited information on the use of partially de-oiled microalgae co-products in swine feeding programs. The objectives of this study were to evaluate the effects of a partially de-oiled microalgae extract (MAE) in nursery pig diets on growth performance and health status. A total of 300 pigs (initial BW = 6.3 ± 2.1 kg) were used in a 42-d experiment. Treatments included a standard corn-soybean meal control diet, and diets containing 1, 5, 10, or 20% MAE replacing primarily corn. The ME content of MAE was calculated from the chemical composition, and diets were formulated to meet or exceed nutrient requirements for nursery pigs. Pigs were stratified by weaning BW into 12 blocks in a randomized complete block design, with sex distributed evenly among blocks. Pens of pigs (5 pigs/pen) were assigned randomly within block to one of 5 dietary treatments. Pig BW and feed disappearance were recorded weekly. On d 42, thirty pigs were harvested and sections of the jejunum and ileum were collected for gut morphology analysis, and a liver sample was collected for metabolomic analysis using liquid chromatography-mass spectroscopy. Data were analyzed by ANOVA with diet as treatment effect, and contrasts were used to test linear or quadratic effects of dietary MAE inclusion level. Overall, pigs fed 1 and 5% MAE had the greatest (quadratic P < 0.05) ADG, resulting from greater (quadratic P < 0.05) ADFI. There was a tendency for a greater number of pigs requiring injectable treatments (P = 0.16) and a greater mortality (P = 0.14) in pigs fed the control diet than pigs in any of the diets with the MAE. Final BW increased (P < 0.05) for pigs fed 1 and 5% MAE diets. The improvements in ADG were not explained by differences in mucosa height or goblet cell count among dietary treatments. Pigs fed diets containing 1 or 5% MAE had relatively less concentration (P < 0.05) of ammonia in the liver and had changes in metabolites associated with the urea cycle. In conclusion, feeding MAE resulted in increased growth responses and may have beneficial health effects when fed to nursery pigs.

Understanding Tail-Biting in Pigs through Social Network Analysis

Today, we are sharing a publication on pig welfare by our colleagues in the Outreach and Extension center at the University of Minnesota, Drs. Li, Zhang, Johnston and Martin. More specifically, the researchers focused their study on the effect of social network on tail-biting in pigs. The full-text of the article is available in open-access on the website of the journal Animals.

We know that pigs are social animals and that they naturally form social structures to maintain a cohesive group. However, we have little understanding of how those group dynamics affect deleterious behavior like tail-biting.  To answer the question of the association between social structure and incidence of tail-biting in pigs, the researchers created 18 groups of 8 pigs.

  • 6  groups were Littermates: all the 8 pigs were born from and nursed by the same sow.
  • 6 groups were Half-group of littermates: 4 pigs were born from the same sow whereas the 4 others came from the litter of another sow.
  • 6 groups were Non-littermates: all 8 pigs were born from a different sow.

Each group was housed in a nursery pen after weaning where the pigs stayed for the duration of the study until they reached 10 weeks of age. Researchers analyzed growth performances, tail injuries, and behavior.

Growth performances did not differ among groups in this study. However, littermates showed a higher incidence of tail-biting with 15% of the pigs showing chewing or puncture wounds with visible blood but no infection.

tailbiting and social networkBehavior was analyzed by videotaping the pigs 2 weeks after they were placed into their pens, 1 week later when each group was moved together to a new pen and 1 week after the move. The video recordings were viewed by a trained researcher to determine association interactions among pigs. Pigs were considered associated with each other if they were lying together frequently and with more than 50% or more of their bodies in contact with each other. For each pig (white circle in the figure above), researchers measured the direct association between each individual pig and its penmates (1) as well as the peripheral association among the penmates (2).

At the individual pig level, littermates had lower direct association than non-littermates and half-group of littermates, suggesting that littermates might be less socially connected directly among themselves. However, the indirect association among penmates did not vary.

Another interesting observation, although statistically insignificant, is that littermates appeared to spend less time in the lying posture than other groups.

Overall, littermates had a lower strength of social connections, more absent ties, and fewer weak ties, compared to non-littermates and half-group of littermates. Less social connection with pen-mates might predispose pigs in littermate pens to development of tail-biting. Regardless of litter origin, most pigs appeared connected by weak social ties and few pigs formed strong social ties with their pen mates.


The objective of this study was to investigate the association between social structure and incidence of tail-biting in pigs. Pigs (n = 144, initial weight = 7.2 ± 1.57 kg, 4 weeks of age) were grouped based on their litter origin: littermates, non-littermates, and half-group of littermates. Six pens (8 pigs/pen) of each litter origin were studied for 6 weeks. Incidence of tail injury and growth performance were monitored. Behavior of pigs was video recorded for 6 h at 6 and 8 weeks of age. Video recordings were scanned at 10 min intervals to register pigs that were lying together (1) or not (0) in binary matrices. Half weight association index was used for social network construction. Social network analysis was performed using the UCINET software. Littermates had lower network density (0.119 vs. 0.174; p < 0.05), more absent social ties (20 vs. 12; p < 0.05), and fewer weak social ties (6 vs. 14, p < 0.05) than non-littermates, indicating that littermates might be less socially connected. Fifteen percent of littermates were identified as victimized pigs by tail-biting, and no victimized pigs were observed in other treatment groups. These results suggest that littermates might be less socially connected among themselves which may predispose them to development of tail-biting.

Acclimation strategies in gilts to control Mycoplasma hyopneumoniae infection

Today we are sharing a review article regarding the acclimation strategies in gilts to control Mycoplasma hyopneumoniae infection published in Veterinary Microbiology by  the University of Barcelona in collaboration with Dr. Maria Pieters.

Key points

  • M. hyopneumoniae monitoring should be performed in incoming gilts and recipient herd.
  • Gilt acclimation against M. hyopneumoniae aids to maintain farm health stability.
  • Vaccination is the main strategy used to acclimate gilts in Europe and North America

Monitoring and diagnosis of M.hyopneumoniae

The article first covers how to assess the M. hyopneumoniae health status of the herd. Various methods of monitoring and diagnosis are detailed and compared with each other.

  • Most commonly used: M. hyopneumoniae antibody detection by ELISA but the interpretation of the results can be challenging.
  • Most useful technique: PCR on different respiratory tract samples.
  • No consensus on sample type to detect bacterial DNA in live pigs.

Classification of the herd based on incoming replacement and recipient herd


Proposed farm classification according to M. hyopneumoniae health status. (aELISA results (negative/positive) could depend on infection pattern in the farm and sampling time point.)


Clinical signs Lung lesions ELISA resulta PCR result
Negative Not observed Not observed Negative Negative
Provisional negative Not observed Not observed Positive Negative
Positive Subclinical infected I Not observed Not observed Positive/Negative Positive
Subclinical infected II Not observed Observed Positive/Negative Positive
Clinical affected Observed Observed Positive/Negative Positive

Prevention and control

Vaccination against M. hyopneumoniae, using commercial vaccines, is the most commonly used strategy to control its associated diseases in worldwide swine production systems.

However, since protection against M. hyopneumoniae infection by commercial vaccines is not complete, antimicrobial treatments are frequently required to control disease outcome. Several antibiotic classes are effective in reducing the incidence and severity of M. hyopneumoniae compatible lung lesions: macrolides, lincosamides, tetracycline, and fluoroquinolones among others.

Acclimation scenarios


The most common replacement origin used in Europe was external and that most respondents knew M. hyopneumoniae health status of replacement on arrival, being in most of the cases seropositive. Nevertheless, only 28% of respondents verified this theoretical M. hyopneumoniae status given as ELISA test results. Additionally, the most used strategy to acclimate gilt was vaccination alone (58%).

North America

Gilt Development Units are utilized to allow ample time to incoming gilt to gradually adopt the health status of the recipient herd. These acclimation facilities are in most of the cases continuous flow allowing an effective gilt exposure to M. hyopneumoniae. Gilt vaccination in North American swine industry was also recognized as the most common practice used at acclimation.

Natural exposure

Natural exposure was also used in both continents to help acclimate the incoming gilts to  M.hyopneumoniae. However, taking into account that pig-to-pig transmission of this bacterium has proven to be extremely slow , the ratio of infected and naïve gilts as well as the time of exposure are crucial and should be considered to achieve an effective exposure.



Mycoplasma hyopneumoniae (M. hyopneumoniae) is the primary causative agent of enzootic pneumonia (EP), one of the most economically important infectious disease for the swine industry worldwide. M. hyopneumoniae transmission occurs mainly by direct contact (nose-to-nose) between infected to susceptible pigs as well as from infected dams to their offspring (sow-to-piglet). Since disease severity has been correlated with M. hyopneumoniae prevalence at weaning in some studies, and gilts are considered the main bacterial shedders, an effective gilt acclimation program should help controlling M. hyopneumoniae in swine farms. The present review summarizes the different M. hyopneumoniae monitoring strategies of incoming gilts and recipient herd and proposes a farm classification according to their health statuses. The medication and vaccination programs against M. hyopneumoniae most used in replacement gilts are reviewed as well. Gilt replacement acclimation against M. hyopneumoniae in Europe and North America indicates that vaccination is the main strategy used, but there is a current trend in US to deliberately expose gilts to the pathogen.


Science Page: Stability of Porcine Epidemic Diarrhea Virus on Fomite Materials at Different Temperatures

This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.

This week, we are sharing the summary of Dr. Cheeran’s team study on the stability of PEDv on fomite materials at different temperatures.

Key points:

  • Type of material and temperature have an impact on PEDV stability.
  • Infectious PEDV was not recovered from any fomite material after 2 days at room temperature (25ºC / 77ºF).
  • PEDV showed higher stability on plastic, cloth, Tyvek® coveralls, aluminum foil, Styrofoam at 4ºC (39.2ºF).
  • Virus could be detected by qRT-PCR from contaminated fomites even when infectivity was not observed.

PEDV survival on fomites Cheeran et al

Click here for our full post on the subject.

Effect of floor space allowances on growth performance of finishing pigs marketed at 138 kilograms

Today on the blog, we are sharing a study by our colleagues: Dr. Lee Johnston from the College of Food, Agricultural, and Natural resources Sciences (CFANS) and Sara Schieck from the swine extension team, regarding floor space allowance and its impact on growth on finishing pigs.

The full article is available online in open access on the Journal of Animal Science website.


Most floor space allowance studies were conducted 20 years ago when pigs were sent to market when they reached 113kg (around 248 lb) whereas pigs are currently sent at 128kg (281 lb). Therefore, guidelines need to be updated.

Study design

Experiment 1: Pigs from 27 to 138 kg (59 to 304 lb) were housed providing either 0.71, 0.80, 0.89, 0.98, or 1.07 m2/pig of floor space (respectively 7.64, 8.61, 9.58, 10.55, 11.52 square ft/pig). Growth rate, cortisol concentration and lesion scores were measured for each pig.

Experiment 2: Pigs around 130 kg (286 lb) were housed providing either 0.71, 0.80, 0.89, 0.98, or 1.07 m2/pig of floor space (respectively 7.64, 8.61, 9.58, 10.55, 11.52 square ft/pig).


Floor space allowance finishing pigs
Impact of floor space allowance on Average Daily Gain (ADG), Average Daily Feed Intake (ADFI), and growth to feed ratio (G:F) in the last 16 weeks of the experiment.

Initial body weight of pigs was not different across floor space allowances; however, increasing floor space allowance increased final body weight (linear, P = 0.04) and tended to increase ADG (linear, P = 0.06) and ADFI (linear, P = 0.06). Gain efficiency was not influenced by increasing floor space allowance. There were no differences in initial salivary cortisol concentrations across floor space treatments. Similarly, there were no differences in salivary cortisol among floor space allowances 2 and 1 wk before the final weight, when pigs should have experienced the greatest differences in crowding among treatments.

Based on the growth performance and pig welfare data collected in Exp. 1, a clearly optimal floor space recommendation is not apparent. The equation from previously published studies estimates that 138-kg pigs require 0.91 m2 of floor space; therefore, the present study provided 2 treatments below and 2 treatments above the predicted requirement. Our data are clear that pigs in the present study did not respond to floor space allowances greater than the predicted need of 0.91 m2 with improved growth performance or welfare.

In Exp. 2, the floor space needs of heavy market pigs could be studied isolated from the diluting effects of the early growth period that were present in Exp. 1. Results of Exp. 2 indicate that 0.98 m2/pig optimized growth performance of pigs between the weights of 133 and 148 kg.


Pigs marketed at 138 kg BW optimize growth performance when provided 0.89 to 0.98 m2 of floor space per pig. However, the negative effects of low space allocations were mostly observed in heavy pigs. Therefore, the use of a pig removal strategy near the end of the finishing period may be an effective strategy to diminish the negative effects of crowding when pigs are near market weight.


Current floor space allowances were determined in research studies conducted 10 to 20 yr ago using pigs that were marketed at a BW of about 113 kg or less. Currently, pork producers are regularly marketing pigs that weigh over 128 kg. Given this precipitous increase in market weight, we conducted 2 experiments to determine if floor space allowances previously determined apply to pigs marketed at greater than 128 kg. Experiment 1 was conducted at 5 university research stations throughout the Upper Midwest region. In this experiment, we evaluated the growth performance, salivary cortisol concentrations, and lesion scores of pigs weighing between 27 and 138 kg provided 0.71, 0.80, 0.89, 0.98, or 1.07 m2/pig of floor space. Within each station, group size (range = 6 to 19 pigs) remained constant across floor space treatments but pen size was altered to achieve the desired space allocations. There were 14 replicate pens for each treatment. Overall, increasing floor space allowance increased final BW (linear, P = 0.04) and tended (linear, P < 0.06) to increase ADG and ADFI. There were no improvements in final BW or ADG beyond 0.89 m2/pig. The G:F was not influenced by increasing floor space allocation. Salivary cortisol concentrations and lesion scores were not affected by floor space allowances. Experiment 2 focused on floor space needs of pigs nearing market weight and was conducted at 4 research stations. Pigs weighing about 130 kg were assigned to pens that provided 0.71, 0.80, 0.89, 0.98, or 1.07 m2/pig of floor space. Group size ranged from 4 to 11 pigs per pen but was constant across floor space treatments within station. The study lasted 2 wk and there were 8 replicate pens per treatment. As floor space allowance increased, ADG (0.86, 0.95, 0.95, 1.10, and 1.06 kg; linear, P < 0.01), ADFI (3.03, 3.26, 3.22, 3.49, and 3.25 kg; quadratic, P < 0.05), and final BW (145.6, 145.7, 146.4, 148.3, and 147.9 kg; linear, P < 0.01) increased. Based on the results of these 2 experiments, pigs marketed at about 138 kg require at least 0.89 m2/pig to support optimal growth performance. However, heavier pigs (about 148 kg) at the end of the finishing period require 0.98 m2/pig.


Influenza epidemiology in breed-to-wean farms and infection dynamics in nursery pigs

Fabian Chamba portrait photoEarlier this year, Dr. Fabian Chamba Pardo successfully defended his PhD under the supervision of Drs. Montse Torremorell and Marie Culhane. The focus of his thesis is influenza epidemiology with an emphasis on sow farms and nurseries. We share with you today a summary of his work.


Influenza is an economically important disease in pigs and a public health threat. Breed-to-wean (BTW) farms play a central role in influenza epidemiology and control because piglets maintain and disseminate influenza A virus (IAV) to other farms. Despite the importance of piglets in influenza epidemiology, there is limited information on IAV infection parameters in piglets, risk factors that impact IAV prevalence in piglets at weaning, and how strategies that are implemented in BTW farms affect IAV infections in weaned pigs.


In this thesis, my goal was to address some of the questions that are central to the transmission and control of influenza in BTW farms, especially infection in piglets ready to wean. The questions addressed are also critical to guide control strategies to mitigate IAV infections in the post weaning period. More specifically, I aimed to: 1) estimate herd-level prevalence and seasonality of influenza in BTW farms, 2) evaluate farm factors associated with IAV infection in piglets at weaning, 3) assess transmission patterns and parameters of influenza in nursery pigs based on IAV prevalence at weaning, and 4) evaluate the impact of maternally-derived antibodies (MDA) at weaning on IAV infection parameters in nursery pigs.

Research Chapter 1

Influenza herd-level prevalence and seasonality in breed-to-wean pig farms in the Midwestern United States

Article published in Frontiers in Veterinary Science: https://www.frontiersin.org/articles/10.3389/fvets.2017.00167/full

Results showed that IAV herd-level prevalence in piglets at weaning from Midwestern BTW farms is seasonal with higher infection rates in winter (December) and spring (May) than those in summer and fall. Additionally, influenza seasonality was partially explained by the seasonal variations of outdoor air absolute humidity and temperature. Finally, there was significant genetic diversity of influenza strains circulating in those farms and that, co-circulation of more than one genetically distinct clade over time was very common in the studied farms. This is critical knowledge that may help to identify high risk periods where influenza control measures can be placed. It may also help to create research opportunities on absolute humidity and influenza transmission in pigs and finally, it supports other studies that have shown that genetic diversity and circulation is wide and common and that new vaccines and vaccination strategies should take that into consideration.

Chamba herd level influenza prevalence in the Midwest
Influenza A virus herd-level prevalence in Midwestern US breed-to-wean pig farms.

Research Chapter 2

Breed-to-wean farm factors associated with influenza A virus infection in piglets at weaning

In this chapter, there were 24 farm factors evaluated for their association with influenza at weaning and among those, only IAV sow vaccination and the IAV-negative status of replacement breeding females (gilts) at entry to the herd were significantly associated with less IAV infected piglets at weaning. This is critical information that veterinarians and producers may use to manage IAV levels at weaning. In addition, there was also a lack of significant association with factors such as air filtration and farm density which may be indicative that endemic influenza infections are more important than airborne lateral transmissions between farms. Finally, disease control strategies such as herd closure, early weaning, batch farrowing, gilt isolation and gilt influenza vaccination were not fully evaluated in this study. Hence, more work is needed to further understand how to use these strategies to decrease influenza infections in pigs.

sow vac protocol - Copy
Influenza A virus (IAV) positive mean predicted probabilities over time for breed-to-wean farms with different sow vaccination protocols.

 Research Chapter 3

Influenza A virus transmission patterns and parameters in growing pigs

Results indicate that groups of piglets with different prevalence at weaning had different transmission patterns and parameters after weaning and these patterns were characterized by 1, 2 or no peaks of infection after weaning. Piglets with low prevalence at weaning had less influenza infections in the nursery. This information may help producers and veterinarians to make informed decisions when it comes to use control strategies such as sow vaccination aimed to reduce influenza infections in the nursery.

Figure 1

Research Chapter 4

Effect of maternally-derived antibodies on influenza A virus infection in growing pigs

In my last chapter, I reported that if pigs had high levels of strain-specific maternally-derived antibodies at weaning, IAV infection occurred later and it was of shorter duration after weaning. Piglets with hemagglutination inhibition (HI) titers of 1:40 or higher were less likely to test IAV positive at weaning and during the nursery. These results indicate that strain-specific maternally-derived antibodies generated with sow vaccination pre-farrow significantly reduce influenza infections at weaning and in the nursery.

Figure 1 (1)


Knowledge of influenza seasonality and what factors are significantly associated with influenza in breed-to-wean farms can help producers and veterinarians to better use and allocate influenza control strategies such as sow vaccination. In addition, lower prevalence of influenza at weaning due to high strain-specific maternally-derived antibodies levels may help decrease influenza spread from wean-to-finish farms. Reducing the burden of influenza in growing pigs should decrease influenza-associated economic losses and the generation of novel strains, including strains with pandemic potential. More studies are needed to further elucidate control strategies to limit influenza infections and spread in pigs.

Stability of Porcine Epidemic Diarrhea Virus on Fomite Materials at Different Temperatures

Today, we are presenting a paper published by Dr. Maxim Cheeran‘s lab in Veterinary Sciences regarding the stability of PEDV on fomite materials at different temperatures.

The full article is available in open access on the journal’s website.

Porcine Epidemic Diarrhea virus and its transmission

Porcine epidemic diarrhea virus (PEDV) causes highly contagious viral enteritis in swine. In May 2013, a PEDV strain, genetically related to a Chinese strain, was introduced in the US and spread rapidly across the country causing high mortality in piglets. Over eight million pigs were killed during this outbreak, leading to an estimated loss of 1.8 billion US dollars.

Transmission of PEDV primarily occurs by the fecal-oral route, but indirect transmission can occur when an animal comes in contact with inanimate objects (fomites) contaminated with the feces of PEDV-infected animals.


200 μL of virus containing 2.1 × 106 TCID50/mL was applied on various fomite material: Styrofoam, nitrile gloves, cardboard, aluminum foil, Tyvek® coveralls, cloth, metal, rubber, and plastic. The virus-contaminated fomites were then stored at either 4◦C or at room temperature. Samples were then taken at 0,1 2, 5, 10, 15, 20 and 30 days post-contamination to test for virus stability.

PEDV survival on fomites Cheeran et al


Infectious PEDV was recovered from fomite materials for up to 15 days post application at 4◦C; only 1 to 2 logs of virus were inactivated during the first 5 days post application. On the other hand, PEDV survival decreased precipitously at room temperature within 1 to 2-days post application, losing 2 to 4 log titers within 24 h as can be seen on the figure above.

Immunoplaque assay was used to identify positive fomites after 20 days of storage at 4◦C. Immunoplaque assay is much more sensitive than PCR and can detect virus as low concentration as 24 focus forming units/mL. Titers of approximately 1 × 10^3 FFU/mL were observed in eluates from Styrofoam, metal, and plastic, representing a 3-log virus inactivation after 20 days. The surviving virus on Tyvek® coverall and rubber surfaces was moderately above detection limit (24 FFU/mL).


Indirect transmission of porcine epidemic diarrhea virus (PEDV) ensues when susceptible animals contact PEDV-contaminated fomite materials. Although the survival of PEDV under various pHs and temperatures has been studied, virus stability on different fomite surfaces under varying temperature conditions has not been explored. Hence, we evaluated the survival of PEDV on inanimate objects routinely used on swine farms such as styrofoam, rubber, plastic, coveralls, and other equipment. The titer of infectious PEDV at 4 °C decreased by only 1 to 2 log during the first 5 days, and the virus was recoverable for up to 15 days on Styrofoam, aluminum, Tyvek® coverall, cloth, and plastic. However, viral titers decreased precipitously when stored at room temperature; no virus was detectable after one day on all materials tested. A more sensitive immunoplaque assay was able to detect virus from Styrofoam, metal, and plastic at 20 days post application, representing a 3-log loss of input virus on fomite materials. Recovery of infectious PEDV from Tyvek® coverall and rubber was above detection limit at 20 days. Our findings indicate that the type of fomite material and temperatures impact PEDV stability, which is important in understanding the nuances of indirect transmission and epidemiology of PEDV.