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Piglets overcoming post-weaning stress

Optimum sow nutrition and condition, as well as a pre-weaning piglet diet are preconditions for healthy piglets post-weaning.Post-weaning piglet performance is largely influenced by the sow’s milk yield and the provision of a piglet diet sufficient in nutrients and natural substances with antimicrobial properties. They influence weaning weight and help piglets to smoothly get through the stressful weaning period.

By Dr Angela Riemensperger, technical manager, Biomin Holding GmbH

Problems occurring after weaning such as diarrhoea and the postweaning growth check are widely spread and cause severe economic losses to the pig producer. Post-weaning performance has for example a strong influence on the time to reach market weight, as pigs not suffering from the post-Schematic illustration of the interaction between the influence of sow nutrition on sow performance and live time performance of pigs.weaning growth check require fewer days to reach market weight. Post-weaning performance is a result of weaning weight (Figure 1), as pigs that are heavier at weaning are less likely to suffer any adverse effects due to the change they are undergoing post-weaning. Weaning weight in turn is a result of piglet performance during suckling, which is influenced by factors such as creep feeding and lactation performance of the sow.

The main goal during suckling is to avoid severe weight loss of the sow by maintaining optimum feed intake to enable her to produce enough milk for her piglets. This is only possible if the sow has a sufficient feed intake from day one of the suckling period. Feed intake after farrowing or whether the sow is eating at all depends on the farrowing time, as prolonged farrowing has detrimental effects on the sow’s condition. A prolonged period of labour pain is associated with a slower recovery from farrowing. An exhausted sow is less reactive, which most likely leads to a reduction in post-farrowing feed intake.

Optimising farrowing
The cause of prolonged farrowing is diverse but most likely related to a lack of calcium which is needed for muscle contraction. This lack of calcium is influenced by the acid-base balance of the feed which has a strong effect on the acid-base balance of the body. Increasing the anions in the diet results in acidic stress of the sow. Depending on the extent of acidic stress, the sow is in a metabolic stage often referred to as metabolic acidosis.

Acidic stress leads to an increase in the net-excretion of calcium from the body by increasing renal calcium excretion. The body tries to compensate this lack via an increased mobilisation of calcium from the bones, which is the biggest calcium storage of the body. At the same time the body also tries to buffer the blood pH via increasing calcium resorption. This process to increase the calcium blood levels is regulated by the parathyroid hormone and vitamin D. To prevent problems during farrowing due to a lack of calcium available for muscle contractions, the parathyroid hormone/vitamin D mechanism has to be trained to make more calcium available by feeding anionic diets. An effective way to increase anions in the diet is by adding a mixture of an inorganic acid, anionic substances and plant extracts to a diet incorporated in products such as Biomin pHD. This increases the anions in the diet, which in turn leads to metabolic acidosis and the release of calcium resulting in a shorter farrowing time and a good start for the sow into lactation.

Remaining health threats
Short farrowing times can be related to better feed intake of the sow postweaning, which in turn leads to optimum milk yield, hence optimum growth of the piglets during suckling period and high weaning weights. Even if high weaning weights can be achieved, weaning itself still remains to be a very stressful event in the life of a piglet. Severe changes such as the change of the diet from liquid to solid, the removal of the piglets from their littermates as well as changes in the environment puts the newly weaned piglet under enormous stress. Research has shown, that it often takes the piglets up to the second or third week post-weaning to consume a comparable amount of energy and grow at the same rate as prior to weaning. This means that even if the piglet was given an optimum start to life by a sufficient milk supply of the sow, health threats remain. Especially during the stressful post-weaning time piglets are vulnerable due to a weakened immune system which gives pathogenic bacteria the chance to cause severe harm.

Organic acids
The development and influence of pathogenic bacteria can be decreased by lowering the pH in feed by means of organic acids. They have been used in animal nutrition for decades and they not only have beneficial effects on feed itself but also on a lower pH in the gastro- intestinal tract (GIT). A low pH level in the GIT creates unfavourable conditions for pathogenic bacteria and shows antimicrobial effects.

Organic acids, in their non-dissociated form, however can penetrate through the cell wall of bacteria where they dissociate and reduce the intracellular pH. In response the cell tries to restore the normal pH, which is an energy requiring process. Meanwhile anions accumulate inside the cell. This leads to the disruption of the membrane and of the DNA and protein synthesis, which means that the bacterial cell cannot replicate. However, the antimicrobial effects of organic acids especially on gram-negative bacteria are limited, as gram-negative bacteria have an outer membrane which serves as an additional barrier against external damaging agents. Therefore, organic acids were in the past often combined with other nature-identical compounds in order to more effectively combat pathogenic bacteria.

Cinnamaldehyde
In vitro trials have shown that combining organic acids with cinnamaldehyde have synergistic effects on the inhibition of pathogenic bacteria. This is less surprising considering cinnamaldehyde’s mode of action as it plays a major role in the cell division of potentially harmful bacteria targeting the socalled FtsZ protein. Under normal conditions FtsZ polymerises into filaments, which assemble at the place within the cell where the cell division takes place into the polymeric structure known as Z-ring. The Z-ring is responsible for the cell division. Cinnamaldehyde inhibits not only the formation of FtsZ into filaments, but also inhibits essential processes involved in the Z-ring formation and its function. This impairs the cell division and results in a reduction of the bacterial load within the gastrointestinal tract.

Gram-negative bacteria
As indicated, effects of nature-identical compounds on gram-negative bacteria are limited due to their outer membrane protecting the cell from possibly harmful substances. However, weakening this outer membrane is possible by substances commonly referred to as permeabilisers. There are many permeabilising substances known, but the way they act differs. Some remove stabilising cations from the outer membrane, others bind to the outer membrane resulting in the loss of barrier function. Others again destabilise and disintegrate the outer membrane or displace cations from the outer membrane. However, all have the same end effect. They all damage the outer membrane, facilitating the entry of external substances capable of inhibiting or destroying cellular functions when entering into the cell resulting in sublethal injury of the bacteria.

Influence on growth performance
Combining organic acids, cinnamaldehyde and a permeabilising substance (Biotronic Top3) has beneficial effects on the inhibition of pathogenic bacteria, which was shown in vitro. Combating pathogenic bacteria this way also improves growth performance of animals. Bacteria compete with the host for nutrients, secrete toxic compounds, decrease fat digestibility, stimulate rapid turnover of absorptive epithelial cells, require an increased rate of mucus secretion by intestinal goblet cells, and stimulate immune system development and inflammatory responses. All of these effects negatively impact growth performance.

Performance of pigs fed a diet containing a mixture of organic acids, cinnamaldehyde and a permeabilising subtance compared to a control group.Therefore, it is not surprising that pigs fed a diet containing an organic acid blend, cinnamaldehyde and a permeabilising substance over a 56 day postweaning period showed, compared to a control group, a 6% increased final body weight, a 5% increased feed intake, an 8% increased daily weight gain and a 3% improved feed conversion ratio (Table 1).

These results clearly prove the importance of assuring the sow is having a high milk yield and piglets are well protected against pathogenic bacteria through the provision of organic acids, cinnamaldehyde and a permeabilising substance.