Delayed weaning could boost gut development, immune health in piglets

Later weaning could benefit piglet immunity and gut development, say researchers. 

A team of Argentinian researchers tracked the influence of weaning age on piglet gut health, development and immunity. The group published its results in the journal Veterinary Immunology and Immunopathology​.

“The aim of the present work was to study the effect of weaning at 14 and 21 days on systemic and mucosal immunology and on the gut morphology and bacterial community of weaned piglets in an intensive breeding farm,” ​said the researchers. “The work was conducted to provide knowledge about advantages and disadvantages of weaning at different ages and long-lasting consequences in an intensive breeding farm, where the high production indexes could be in detriment of animal welfare.”​

The team found that there were several negative effects for piglets weaned after a shorter period of time, including in intestinal morphology and innate immunity. However, there also were areas where no major effect was found.

“Biological alterations in immune system and gut physiology could occur after weaning that may have both short and long-term effects on subsequent pig growth and health,”​ said group members. “It is critical that swine producers become aware of the biological impacts of weaning age and they can decide the appropriate management strategies to minimize the adverse effects of weaning and to improve swine production, according to their facilities and rearing environment.”​

Stress and immune system ​

Weaning can be a stressful period for young pigs, and may influence immune system, intestinal and intestinal microbiome development, said the researchers. It also physiologically alters the form and function of the intestine as a pig transitions from a liquid to solid diet.

“These changes affect the absorptive capacity of the small intestine which can likely influence growth and feed efficiency (Lallès et al., 2007),” ​they said. “In addition, the immunoregulatory and immunoprotective components of maternal milk are removed; as a consequence, pigs at weaning are highly susceptible to pathogenic enteric conditions such as post-weaning diarrhea that may be caused by serotypes of enterotoxigenic Escherichia coli (Pluske, 2013 and Rist et al., 2013).”​

The makeup of the microbiota is important at weaning as the piglet still has an immature immune system and is reliant upon elements of the sow’s diet to prevent growth of pathogenic bacteria, they said. Establishing a diverse bacteria microbiota is important to maintain gastrointestinal heath.

During a natural weaning, the piglet has access to an increasing amounts of feed sources while its fermentative capacity and immune system develop for about 10 weeks, said the researchers. However, early weaning increases the amount of births per year for a sow and has been previously demonstrated to boost growth and feed efficiency in piglets.

But the practice also leads to post-weaning diarrhea, intestinal dysbiosis, they said. “There are several studies suggesting that early weaning causes substantial changes in the intestinal bacterial community (Franklin et al., 2002 and Konstantinov et al., 2006),” ​they added.

Weaning at a younger age also appears to increase stress and has been linked to changes in the gastrointestinal tract (GIT) physiology, microbiology and immunology, they said. Little work has been done documenting the longer-term influence of early weaning, they added.

The study ​

In the experiment, a group of 30 piglets was split into two groups with pigs being weaned at 14 days (14W) or 21 days (21W), said the researchers. Diarrhea and feed intake were recorded.

Blood samples were taken before weaning, immediately post-weaning and on days 4, 20 and 40-post weaning, they said. Samples were checked for IgG and cortisol levels.

Additionally, three animals from each group were harvested during pre-weaning, and post-weaning days 4, 20 and 40 and their small intestines and cecum were collected, they said. Morphometric studies were done and secretory-IgA (immunoglobulin) levels were measured along with amounts of enterobacteria, lactobacilli and anaerobes.  

Results​

Plasma levels of IgG (immunoglobulin G) dropped for both groups of piglets after weaning and gradually improved, said the researchers. Both groups also saw an increase in cortisol after weaning and no differences were found in numbers of anaerobes.

“The changes observed in the microbiota could decrease post-weaning enteric infections,” ​they said. “However, early weaning induced negative effects on the cells of gut innate immunity and villi atrophy.”​

Piglets weaned on day 14 had a larger increase in S-IgA, which could result in early synthesis of intestinal S-IgA, they said. But, that group also had a shorter villus length, which could reduce feed efficiency, and reduced goblet cells and intraepithelial lymphocytes (IEL).

“Animals from 14W group showed a significant decrease in villus length 4 days after weaning and then similar values to those obtained at the pre-weaning were observed,” ​the researchers said. “On the contrary animals from 21W group showed an increase in villus length across the time.”​

“Taking into account the results obtained for goblet cells and IEL counts, early weaning seems to have negative impacts on the gut innate immunity,”​ they said.