ISSUE FOCUS 46 FEED & ADDITIVE MAGAZINE May 2024 cantly higher amount of total fatty acid apparent ileal digestibility of 2% (P<0.05). Knowing vitamin A is absorbed via fat, these two findings can be linked to each other. Goes et al, confirmed the improvement of nutrient absorption by measuring blood carotenoids levels. The muramidase supplemented birds had 23% higher total carotenoid concentrations in their blood (P=0.007). In all studies, the nutrient digestibility and absorption improvement lead to an improved performance of 57g BW (2%; NS) and 7 points FCR (5%; P=0.45) in Sais et al., 2019, 45g BW (2%; NS) and 4 points FCR (3%; P=0.001) in Goodarzi et al., 2019 and 80g BW (3%; NS) and 6 points FCR (4%; P=0.004) in Goes et al., 2022. Footpad lesions are a visual sign of reduced gut functionality. Muramidase supplementation decreased litter moisture and footpad lesion scores (Pirgozliev., 2020), which was confirmed in several trials. When evaluating meat yield data from the slaughterhouse, Brugaletta et al., 2002 showed that muramidase supplementation improved breast yield% with 2.3% (>750 observations/group; 3 groups total), without increasing myopathies (wooden breast, white striping and spaghetti meat). Other trials also showed breast meat yield improvement, with an average of 3%, including higher carcass and thigh weights (data unpublished). Table 1 shows a summary of the performance, digestibility and absorption improvements described above. THE LINK BETWEEN GUT FUNCTIONALITY, BIRD PERFORMANCE AND MEAT YIELD How can we explain the improved meat yield when muramidase was fed to the birds? Ni et al., 2022 found that geese with higher villus height/crypt depth ratio had improved muscle fiber density and breast muscle/ Performance Nutrient digestibility* Nutrient absorption Reference BW FCR Energy Protein Vitamin A Carotenoids Fat Parameters: improvement of muramidase treatment vs. control 2.0% 2.0% 3.0% 5.0% 3.0% 4.0% 2.0%** 2.0% 16% 4.0% 6.5% 7.0% 18%** 23% Sais et al., 2019 Goodarzi et al., 2019 Goes et al., 2022 Table 1. Summary performance, digestibility and nutrient absorption data Muramidase trials * Apparent ileal digestibility ** measured at day 9 of age
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