Spray-dried plasma diet helps intestinal function in weaned pigs

Monday, October 3, 2011

A North Carolina experiment suggests that adding SDPP during weaning can be effective in decreasing intestinal barrier dysfunction, mucosal inflammation and diarrhea

by JANICE MURPHY

Weaning is one of the most stressful periods in a pig's life. During weaning, young pigs are forced to deal with a whole host of stressors, ranging from separation from the sow and its littermates, to transportation and mixing with strange pigs, abrupt changes in diet and exposure to new disease challenges.

This phase of production has been proven to cause impairment in intestinal epithelial barrier function, a critical first line of defense against pathogens and other antigens in the gut. The mechanism that causes this dysfunction is not currently known. However, recent research has shown that stress-signalling pathways play a major role in this breakdown in the intestinal barrier.

Although there is evidence that dietary interventions can decrease intestinal barrier dysfunction at weaning, little research has been conducted to show the beneficial role that nutrition can play in the enhancement of intestinal barrier function in the weaned pig.

Spray-dried plasma has been consistently proven to have beneficial effects on growth and performance in weaned pigs, as well as in various disease challenge models. The mechanism whereby spray-dried plasma works appears to centre around its ability to adjust intestinal immune function in gut-associated lymphoid tissues.

A recent experiment at North Carolina State University evaluated the effects of inclusion levels of spray-dried porcine plasma (SDPP) on postweaning intestinal barrier function, inflammation of gut mucosa and clinical indicators of gut health in weaned pigs.

Forty-eight crossbred Yorkshire piglets were weaned between 17 and 19 days of age (average weight 5.49 kilograms) and offered  one of three experimental nursery diets containing zero (control), 2.5 or five per cent SDPP for seven to 14 days post weaning.

The mash diets were formulated to contain identical levels of metabolizable energy and digestible lysine to meet requirements according to the NRC Nutrient Requirements of Swine. The experimental diets are outlined in Table 1.

Harvested segments of ileum and colon were subjected to ex vivo Ussing chamber studies to assess barrier function, measuring transepithelial electrical resistance and paracellular flux of two test compounds – 3H-mannitol ( a high molecular weight marker) and 14C-inulin (a low molecular weight marker).

An Ussing chamber is a research tool used to measure the short-circuit current as an indicator of net ion transport occurring across an epithelium, like the gut mucosa, thus helping to identify where problems exist. Histological analysis and mucosal levels of proinflammatory cytokines, TNFa (Tumor Necrosis Factor-alpha) and IFNa (Interferon-gamma), were used to assess the level of intestinal inflammation.

All pigs performed well and remained healthy, exhibiting normal growth rate and feed intake throughout the experiment. Average daily gain and feed efficiency were greater in pigs fed 2.5 and five per cent SDPP compared with those fed the control diet, although statistical significance could not be established due to the limited number of pen observations. 

Fecal scores were evaluated at seven and 14 days post weaning as a clinical indicator of gut health. Pigs fed the five per cent SDPP diets had significantly lower fecal scores at seven and 14 days post weaning, compared with pigs fed control and 2.5 per cent SDPP diets.

Pigs fed diets containing 2.5 and five per cent SDPP showed reduced permeability of inulin in the colon compared with controls on day seven post weaning. Both 2.5 and five per cent dietary SDPP also reduced mannitol and inulin permeability in the ileum on day 14 postweaning. This may be an indication that SDPP causes different effects along the length of the intestinal tract.

Histological results revealed that pigs fed diets containing 2.5 and five per cent SDPP had fewer lamina propria cells in the ileum and colon on days seven and 14 postweaning (Table 2).

Levels of the proinflammatory cytokine TNFa were significantly reduced in the colon, but not ileum from pigs fed the five per cent SDPP on days seven and 14 postweaning compared with controls. IFNa levels were lower than in controls in both of the SDPP-fed groups in the ileum and colon on day seven but not on day 14 postweaning.

The effects of SDPP on barrier function and inflammation differed significantly, depending on the location within the intestine (ileum versus colon) and the time point postweaning (seven versus 14 days postweaning). In the colon, beneficial effects on barrier function were observed at seven days postweaning, but not at 14 days postweaning.

In contrast, improvements in the ileum were not evident until 14 days postweaning, suggesting that small intestinal barrier function may require a longer SDPP feeding interval. The colons of control pigs exhibited a significant recovery of barrier function from seven to 14 days postweaning. This could represent the natural time-course for barrier function repair in the colon postweaning, regardless of SDPP treatment.

Overall, the experiment confirmed that including SDPP in postweaning diets can be effective in decreasing intestinal barrier dysfunction, mucosal inflammation and diarrhea that is common during this phase of production. In order to come up with a clearer picture of the exact mechanisms involved, however, further research is necessary. BP
 
Source: R.M. Peace, J. Campbell, J. Polo, J. Crenshaw, L. Russell, and A. Moeser. 2011. Spray-Dried Porcine Plasma Influences Intestinal Barrier Function, Inflammation, and Diarrhea in Weaned Pigs. J. Nutr. 141: 1312–1317, 2011.
 
Janice Murphy is a former Ontario agriculture ministry swine nutritionist who now lives and works in Prince Edward Island.