Lowered protein content The purpose of lowering the protein content in feed is to limit the amount of undigested protein in the gut. Undigested protein ferments and transforms to microbial metabolites such as NH3 and biogenic amines that change the intestinal microbiota and inhibit the mucosa function. Several Danish trials with different protein levels have shown clear reductions in diarrhoea by going from 21% to 18% protein, but this also affected productivity negatively [3]. Australian research [5] indicates that a daily protein supply of max. 60 g protein the first seven days of a pig’s life lowers the risk of diarrhoea. Danish trials show that it is possible to lower protein content to 45-50 g a day without a significantly negative impact on productivity. However, the ideal amino acid profile that benefits gut health as well as productivity is yet to be conclusively determined. In Denmark, we are therefore currently investigating different protein levels and amino acid profiles.


Protein ingredients with improved protein digestibility When protein digestibility improves, the amount of undigested protein in the gut drops. Ingredients such as milk powder, fish meal, potato protein concentrate and blood plasma are often included in piglet feed to make the weaning process as smooth as possible, but these ingredients are expensive. Soy protein products, which benefit the gut and have a higher digestibility than soybean meal, are widely used as substitutes for expensive protein ingredients. However, soy protein products are roughly twice as expensive as regular soybean meal, and there is very little evidence that these products are distinctly better than soybean meal for weaned piglets. In a trial comprising approx. 75 replicates and 3,500 pigs, SEGES Danish Pig Research Centre therefore compared regular soybean meal with three different soy protein products: HP 300, AlphaSoy and Vilosoy. The diets used in the 7-30 kg period included approx. 10% of these products and the effect was compared with a diet including 13% soybean meal in the 7-9 kg period; 20% soybean meal in the 9-15 kg period, and 25% soybean meal in the 15-30 kg period. The 7-9 kg diet did not include zinc oxide. Protein content was fairly low in the post-weaning period: 17.5%, 18.5% and 19%, respectively, in the three periods. Except for protein, all diets were identically composed in terms of energy and nutrients. Results showed no difference between the four groups in


productivity and gut health. Daily gain in the 7-30 kg period averaged 520 g a day. The inclusion of 13% soybean meal in the 7-9 kg diet did not increase the frequency of diarrhoea treatments compared with the three trial groups [6]. This trial shows, as other trials before, that lowering the protein content in the 7-9 kg period has a greater effect on diarrhoea than the use of expensive protein ingredients when pigs are weaned at roughly 25-27 days at a weaning weight of 6.5-7 kg.


Minerals Calcium in the form of calcium carbonate is commonly used in feed for weaned piglets. Calcium carbonate affects the pH gradient in the gut and Danish research has shown significant variations in diarrhoea frequencies depending on calcium content. A trial comprising 50


replicates, six groups, in which calcium content varied from 4.9 g Ca/ kg feed to 12.0 g Ca/kg feed, and a total of 3,500 pigs revealed an increase in diarrhoea frequency as calcium content increased. Results showed no significant effect on productivity [7]. The official Danish recommendation for calcium is 6.4 g/kg feed with a high inclusion of phytase. Sodium and chloride, in particular, may affect diarrhoea. In Denmark


in 2017 it was briefly difficult to use calcium formiate due to market issues. Instead sodium formiate was used, which led to a reduction in the addition of salt. At the same time, lysine chloride was replaced by lysine sulphate and this led to an overall drop in chloride content in the feed. American research [8] showed that chloride deficiency lowers protein digestibility, which may be attributed to insufficient content of chloride for synthesis of hydrochloric acid which lowers pH in the gut. A high pH and an increase in undigested protein enhance the risk of post-weaning diarrhoea. Consequently, the Danish recommendations for sodium are raised from 1.7 g to 2.8 g per kg and recommendations for chloride are raised from 2.8 g to 4.6 g per kg feed.


Organic acids It is well known that in the 7-9 kg period organic acids have a positive effect on productivity, but the effect on diarrhoea is not as clearly established. When antibiotic growth promoters were banned in pig feed at the turn of the millennium, SEGES Danish Pig Research Centre ran a series of trials with organic acids, and the main conclusion was that the effect on productivity in weaned piglets depends on type and inclusion. Many acids and acid blends showed positive effects at inclusion rates of around 1% and some showed an effect level with that of antibiotic growth promoters. However, many of these trials were not comprehensive enough to draw a conclusion on the effect on diarrhoea (this often requires 60 replicates). A trial revealed that a blend of acids (1% lactic acid, 1% formic acid and 0.5% benzoic acid) significantly lowered diarrhoea treatments (20%) compared with a control group without zinc, but not as much as zinc did [9]. Two other trials with benzoic acid [10], [11] showed that the addition of 1% benzoic acid lowered treatment frequencies by 30-50%, and the addition of 0.5% benzoic acid lowered treatment frequencies by 20-30%. Organic acids are currently considered the most effective group of additives to replace zinc oxide even though the effect is far from that of zinc oxide.


Conclusion The termination of zinc oxide is undoubtedly a difficult challenge, not unlike the situation when antibiotic growth promoters were banned where the consequences included a drop of productivity, a rise in weaner mortality and an increase in medicine consumption. If we are to avoid a repetition of this scenario, we must make an effort in a number of areas where the composition and the quality of the feed is only one element (albeit a significant one). We need a range of tools as we are unlikely to find a ‘silver bullet’ that can replace zinc oxide. It is imperative that we wean healthy, robust piglets and we must not underestimate the importance of optimum feeding of lactating sows and


FEED COMPOUNDER JANUARY/FEBRUARY 2019 PAGE 43


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