Hydrolysed wheat proteins for piglets and calves

Animal scientists are constantly looking for alternative protein sources to include in starter feed and milk replacer. However, young animals have immature digestive and immune systems and are very sensitive to the quality of the proteins used. Some protein sources may reduce digestibility or harm gut health. Hydrolysed wheat proteins (HWP) are a soluble protein source produced from vital wheat gluten by a specific process based on hydrolysis, purification, and drying. HWP are a highly concentrated protein source with around 80% crude protein, 6% fat, 3% starch and 1% fibre on a product basis. No signs of anti-nutritional factors have been seen when using the product in different animal species. These characteristics make HWP interesting as candidates to be included in starter feed diets and in milk replacers.

Highly digestible proteins

Dietary proteins may play an important role in the development of intestinal disorders leading to high diarrhoea incidence associated with increased microbial fermentation of undigested proteins and with greater proliferation of proteolytic and potentially pathogenic bacteria¹. Thus, it is important to choose highly digestible protein sources in order to minimise the part of undigested proteins that will be fermented. Substituting 10% of high quality LT herring meal with 9.5% HWP in diets of weaned piglets (28 days of age) significantly increases apparent digestibility of dry matter, organic matter, and crude protein calculated from 0 to 2 weeks after weaning and significantly increases apparent digestibility of crude protein calculated from 3 to 5 weeks after weaning² (Figure 1). Additionally, no significant differences on apparent digestibility of dry matter, organic matter, and crude protein are observed when 8% spray-dried porcine plasma are replaced by 8% HWP in diets of 21-day old piglets for a 28-day period³. In 12-week old veal calves, ileal crude protein digestibility of HWP is similar to that of whey proteins. It is about 95% as digestible as proteins in milk where HWP provided 36 and 76% of crude protein completed by skim milk powder⁴. Furthermore, apparent ileal digestibility of most essential amino acids is comparable to that obtained with whey powder, which is considered as a high-quality protein source for calves⁵.

No damage to the gut

In piglets, weaning is often associated to gut damage. This is because there is a period of transient villous atrophy and crypt hyperplasia after weaning, probably due to anorexia. A correlation between anorexia, crypt hypertrophy, and local inflammatory responses is observed when piglets are fed with a diet based on soybean meal compared with those fed a milk replacer⁶. As previously seen, proteins are known to influence gut health of piglets so that their effects on gut morphology and function have been extensively studied. It is shown that diets based on legumes may reduce activities of most duodenal enzymes and total tract digestibility of energy and N compared with a diet based on casein⁷. Feeding animal protein sources, whey protein concentrate or fishmeal to piglets results in higher villous height and lower counts of caecal C. perfringens compared with plant proteins such as soybean meal, fermented soy protein and rice protein concentrate⁸. HWP do not reduce villous height and even slightly increases it when compared to animal proteins, and notably fishmeal⁹(Figure 2). Similar results are reported when 8% spray dried porcine plasma are replaced with 8% HWP¹⁰. Significant increases of villous height and digestive enzyme activities are observed in broilers and fish when HWP partly replaces soy proteins in the diet^11,12. Beside effects on gut structure and activity, a modulation of immune or antioxidative system is observed in rats and fish^13,14. Feeding rats with HWP increases secreted IgAs in intestinal contents and the phagocytic activity of peritoneal macrophages while it improves antioxidative system in juvenile hybrid sturgeon.

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Effect on growth performance

Several studies performed in post-weaned piglets and in veal calves demonstrated that the replacement of 5 to 15% animal or milk proteins in diets by HWP does not impair growth performance. Replacing the protein from skimmed milk powder with a mixture of whey products and HWP (HWP providing 49% of crude protein from day 29 to day 83 and 61% from day 84 to day 146) does not significantly change carcass colour, carcass conformation, and body score condition in veal calves after slaughtering. Similarly, it does not alter dressing and haematocrit percentages¹⁵. In weaning piglets, replacing 4 to 10% of fishmeal or spray-dried porcine plasma with HWP during the first 5 weeks after weaning does not modify growth performance of weaned piglets^16,17. Furthermore, using HWP does not increase incidence of diarrhoea in weaned piglets. Indeed, experimental results¹⁸ indicate no difference in growth performance but a lower diarrhoea index for pigs fed 4% spray-dried porcine plasma plus 4% HWP or 8% HWP. Using HWP improves N utilisation in the small intestine. Indeed, digestive contents contain the lowest ammonia-N concentration when piglets are fed with HWP¹⁹. Such measure may be considered as an indication of microbial deamidation and therefore a high ammonia-N concentration is related to reducing amino-acid availability in the small intestine. A recent trial performed in US demonstrates that using a blend of fishmeal and HWP in order to replace blood porcine plasma 10 days after weaning allows achieving same growth performance at 42 days after weaning while the cost by lb of body gain drops from US$1.19 to 1.15²⁰ (Figure 3).

Conclusion

An inclusion of 3 to 15% hydrolysed wheat proteins in the diet of piglets and veal calves ensures high growth performance by maintaining gut health. HWP are high-protein sources, devoid of anti-nutritional activities, and highly digestible for young animals. Furthermore, including HWP in diets allows gut health to be maintained. As a result, partial replacement of animal proteins by these wheat proteins allows same level of performance while it is economically more competitive.

References 1-20 are available on request.