E. coli-expressed human lysozyme supplementation improves growth performance, apparent nutrient digestibility, and fecal microbiota in weaning pigs

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The E. coli-expressed human lysozyme (EHL), a new source of lysozyme that is different from egg white lysozyme and the human lysozyme expressed in the milk of transgenic animals, has not been investigated extensively. We evaluated the effects of dietary supplementation of EHL on growth performance, nutrient digestibility, fecal microbiota, fecal score, and hematology indicators in weaning pigs. A total of 150 21-day-old weaning pigs [(Landrace × Yorkshire) × Duroc] were randomly allotted to three treatments according to the initial body weight (6.73 ± 0.01 kg) for a 35-day trial (phase 1, days 1-7; phase 2, days 8-21; phase 3, days 22-35). Each treatment had ten replicate pens with five pigs (three barrows and two gilts) per pen. Dietary treatments consisted of a basal diet (CON), and a basal diet supplemented with 2.5 mg/kg antibiotic growth promoter complexes (AGP) or 1 g/kg EHL. Body weight on day 35 (P = 0.001), average daily gain during days 22-35 (P < 0.001) and 1-35 (P = 0.001), gain to feed ratio during days 22-35 (P < 0.001), growth rate during days 22-35 (P < 0.001) and 1-35 (P = 0.002), and apparent dry matter digestibility (P = 0.044) were higher, whereas fecal score during days 1-7 (P = 0.002) and fecal coliform bacteria counts (P = 0.022) were lower, in pigs fed with AGP or EHL containing diet in comparison to those fed with CON diet. Moreover, weaning pigs fed the diet supplemented with EHL had a higher gain to feed ratio during days 1-35 (P = 0.030) than the CON group. Supplementing AGP to the diet of weaning pigs led to a decrease of fecal lactic acid bacteria counts (P < 0.001) compared with those fed with EHL containing diet or the control diet. However, hematology indicators did not differ among groups. Therefore, EHL has the potential to be used as an alternative to antibiotics due to the comparable effects with AGP on the growth performance, nutrient digestibility, hematology indicators, fecal score, and fecal coliform bacteria counts, however, unlike AGP, EHL supplementation did not inhibit fecal lactic acid bacteria counts