Abstract
Simple SummaryDiarrhoea is a challenge after weaning in pigs, and medicinal zinc oxide has been used to decrease this problem. Additionally, soy protein concentrate improves protein digestion and thereby increases growth compared to soybean meal. The aim was to test the effect of different low-protein diets on diarrhoea and productivity. This study demonstrates that a diet with very low-protein levels supplemented with amino acids decreases diarrhoea similar to zinc oxide, but also limits growth performance. Moreover, the study found no effect of low-protein diets with different protein sources. Based on these results, there is potential in feeding extremely low-protein diets to weaned pigs as a tool to decrease diarrhoea and thereby antibiotics usage. Additionally, this study presents an opportunity to use both soy protein concentrate and soybean meal as the main protein source, without affecting pig health and productivity.Soy protein concentrate improves nutrient utilization and growth performance compared to soybean meal, and diets with a low crude protein (CP) level decreases diarrhoea. The objectives were to (1) test a low CP diet based on different soy products, and (2) to test a very-low CP diet (15.1%) with amino acids (AA) on diarrhoea and productivity. A total of 5,635 weaned pigs (~28 days), were assigned to five dietary treatments; PC (positive control): Standard CP levels (192, 189, 191 g/kg CP) with 2500 ppm ZnO; NC (negative control): Same as PC without ZnO; SP (Soy protein concentrate): Low CP levels (176, 174, 191 g/kg CP); SB (Soybean meal): Low CP levels (177, 176, 191 g/kg CP); and XLA (X-low CP + AA): Very low CP levels (154, 151, 191 g/kg CP) with AA. The PC and XLA diets reduced diarrhoea by 41 and 61%, respectively, compared to the NC group, while no difference between SB and SP were observed. The XLA diet reduced feed intake and daily gain compared with PC and NC, where SP, SB, and XLA had a poorer feed conversion compared with PC. Conclusively, the SP and SB low-protein diets did not reduce diarrhoea or growth performance, whereas the XLA diet decreased both diarrhoea and performance.
Highlights
A low crude protein (CP) allocation is well-documented to reduce post-weaning diarrhoea [3,4,5], as a high-protein diet increases the amount of undigested protein available for fermentation in the colon, which may lead to proliferation of pathogenic bacteria in the gastrointestinal tract [5,6]
PC = positive control; NC = negative control, SP = soy protein concentrate, SB = soybean meal, XLA = X-low-protein + amino acids; CP = crude protein; 3 SID = standardized ileal digestible: the contents of SID CP and amino acids were calculated based on analysed total values of the six dietary treatments and on SID digestibility coefficients of the feed ingredients from Danish Agro (Sjölund, Denmark)
There was a peak in diarrhoea treatments per pig starting around day 10 until day 30 in the NC, SP, and SB pigs, whereas the PC and XLA pigs only had a small peak around day 24
Summary
Medicinal zinc oxide (ZnO) is well-documented to have a reducing effect on diarrhoea in weaned pigs two weeks post-weaning [1,2]. As medicinal ZnO has been banned in the EU from June 2022, an increased diarrhoea frequency resulting in higher antibiotics (AB) use is feared. A low crude protein (CP) allocation is well-documented to reduce post-weaning diarrhoea [3,4,5], as a high-protein diet increases the amount of undigested protein available for fermentation in the colon, which may lead to proliferation of pathogenic bacteria in the gastrointestinal tract [5,6]. The inclusion of free amino acids (AA) in low CP diets is essential, as the low CP allocation results in an undersupply of essential AA and reduces productivity [4,7]
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