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Plasma affects growth in challenging conditions

Spray-dried porcine plasma (SDPP) is considered a valuable protein source in piglet feeds. Recent studies show the positive effects of plasma on technical piglet performance are more pronounced when animals are exposed to sub-clinical microbial infections.

Spray-dried Porcine Plasma (SDPP) is manufactured in dedicated blood processing plants, like this one in Loenen, the Netherlands.

By Louis Van Deun, MSc, Sonac

As legislation in the European Union is discouraging the use of antibiotics, SDPP can function as a natural alternative to mitigate the impact of bacterial activity and stimulate animal growth. Many studies have confirmed the role of SDPP as a protein source of high biological value for monogastric livestock, especially piglets. The inclusion of SDPP has been established as a classic application for high performance pre-starter piglet feeds. A summary of related literature shows average daily feed intake (ADI) can increase with up to 25% during the first weeks of post-weaning without a negative impact on feed conversion rate (FCR) when comparing diets including SDPP to basic starter feeds. As a result, piglets raised on a diet containing SDPP generally are heavier and better adapted to successive feeding stages.

In addition to stimulating enhanced growth performance of the pig, SDPP also has a beneficial effect on the health of the young animal. Several mechanisms are believed to account for this effect. The positive aspect of SDPP on feed palatability has been observed to reduce the negative impact of the ‘weaning dip’. By stimulating feed intake after weaning, intestinal damage is prevented and intestinal integrity improved. This is demonstrated by less leakage of undesired substances like toxins or pathogens through the intestinal wall. The active immunoglobulin fraction in SDPP is believed to block the adherence of bacteria to the intestinal wall. This prevents micro-organisms from colonising, reproducing and releasing toxins in the gut.

Set-up of a challenge trial
In a recent study performed at a British agricultural college, a piglet challenge trial was set up. Piglets were weaned at 28 days of age (= day one) and were observed for the next five weeks (= day 35). During days one -14, two variables were introduced: Protein source and exposure to a sub-clinical bacterial infection, all possible combinations resulting in four experimental treatments. Animals were continuously monitored during days 15-35, all four groups receiving the same treatment. An overview of the different experimental treatments is offered in Table 1.

Two experimental diets were used ad libitum, called DSMP (dried skimmed milk powder) and SDPP. DSMP is considered a positive reference as a protein source in animal diets, with excellent nutritional and digestibility values. The feeds were formulated to be isoenergetic and have similar levels of essential amino acids (e.g. lysine), lactose and minerals. These diets were fed for 14 days from day one after weaning. Next, all pigs moved on to standard farm feeds (days 15-35).

The pigs were repeatedly experimentally infected with enterotoxigenic E. coli (ETEC) or fed with a placebo (sham). Care was taken in optimising the total infection dose, which was expected to be sufficiently high to result in reduced performance and elevated levels of acute phase proteins, with minimal effects on diarrhoea score. The treatment was expected to result in sub-clinical post weaning colibacillosis. ETEC and sham-solutions were processed into small quantities of porridge. Pigs were trained to consume the trial. All animals were dosed or sham-dosed five times starting from day four onwards to simulate  epeated exposure as experienced in commercial herds.

Classical technical performance parameters such as average daily feed intake (ADI), average daily weight gain (ADG) and feed conversion rate (FCR) all were registered for periods one-14, 15-35 and one-35. Different qualitative parameters such as faeces, cleanliness, health and dehydration were scored. In addition to these, analyses of piglet blood serum acute-phase proteins (APP) were performed on days seven and 14. The latter are proteins found in the blood which are related to inflammatory reactions after triggering of the immune response system by pathogens. High serum APP concentrations are associated with stressed animals, often resulting in reduced performance and economical losses.

As illustrated by Figure 1, the experimental design resulted in several observations. First of all, formulation of plasma increased pig feed intake and weight gain without significantly affecting feed conversion ratio when compared to skimmed milk powder.

Secondly, the positive effect of plasma is more prominent when pigs are subjected to an ETEC sub-clinical infection. The DSMP-ETEC group grew significantly less than the DSMP – sham group. Pigs fed with SDPP are more resilient, resulting in similar technical performance even when challenged.

Plasma-fed piglet groups continued to display a higher feed intake for the remainder of the trial, also between days 15-35. Feed conversion ratios remained stable, resulting in heavier piglets by the end of the trial.

Analysis of the acute-phase protein concentrations in the piglet’s blood stream supports the positive effect of SDPP on the technical piglet performance. Figure 2 shows APP (in this case haptoglobin) concentrations in all four treatment groups at days seven and 14 post-weaning.

On day seven there was a trend APP concentration in infected animals is higher – as would be expected. This effect did not show at day 14 and no significant correlation between APP concentration and infection could be detected. The data becomes more conclusive when comparing the different diets: On day seven there was a statistically significant decrease in APP concentration of the plasma fed animals when compared to the dairy protein fed group. The same trend could be observed on day 14. This data shows SDPP does change acute-phase protein concentrations and as such could compensate for related inflammatory responses and subsequent decrease in technical performance.

The first, more classical part of this trial confirmed the findings of over 100 animal trials performed in the past: Spray-dried porcine plasma is an excellent protein source for young piglets. Even when compared to a high quality protein source like dried skimmed milk powder animals fed with SDPP show a higher daily feed intake at a stable feed conversion rate, resulting in higher average daily gain and heavier piglets. Secondly, it appears the positive effects of plasma are more pronounced when piglets are stressed by for example sub-optimal hygienic raising conditions. During this trial, sub-clinical ETEC challenge clearly reduced resilience of piglets raised on the DSMP diets. Piglets fed on SDPP showed high resilience and maintained high technical performance. Next to offering a natural protein source of high biological value, plasma adds a functional component to the piglet’s feed protecting it from pathogenic activity and promoting the growth of the young animal.

According to the EU legislation 1292/2005 non-ruminant blood products are allowed in all feeds for mono-gastric animals. When processing porcine plasma, one needs to take care of a dedicated non-ruminant supply chain: Next to production of the feed, also transport and warehouse management all need to exclude possible contact with ruminants. The latter needs to be verified by national veterinarian authorities. In practice SDPP is formulated in piglet weaner diets or prestarter feeds during the first two weeks post-weaning. Typical plasma inclusion levels are at 3-5%.