| dc.description.abstract | The study was done at the Department of Animal Science, University of Manitoba. Two experiments were conducted to investigate the effects of β-mannanase on nutrient utilization and performance of laying hens. Experimental diets were based on soybean meal (SBM), corn and distillers dried grains with solubles (DDGS). The first study was designed to evaluate the effect of β-mannanase (CTCZYME, CTC Bio Inc., Seoul, South Korea) on performance of laying hens and egg quality traits. A total of 160 Lohmann hens were allocated to one of 4 diet groups in 2 levels of dietary protein plus energy content [18.5% crude protein with 2,850 kcal/kg metabolizable energy (ME) (Adequate-ME&CP) vs. 17.5% crude protein with 2,700 kcal/kg ME (Low-ME&CP)]. β-mannanase was added at 0 and 0.04% of diet to both diet types. The experiment lasted for 12 weeks and was designed in a 2 × 2 factorial arrangement. Each group had 8 replicates of 5 hens. Eggs were collected daily and egg production was calculated on a hen-day basis. Egg weight, albumen height, egg specific gravity, eggshell breakage and egg shell thickness were measured bi-weekly and Haugh Units was calculated from the egg weight and albumen height. Feed intake was recorded weekly and calculated as g/hen/day. There were no significant differences in overall egg production and feed efficiency among birds fed on the 4 dietary treatments for the 12-week period. However, average feed conversion ratio (FCR) from the second to the last month of hens fed the low-ME&CP diet was higher than that of hens fed the adequate-ME&CP diet irrespective of enzyme supplementation. Feeding the low-ME&CP diet significantly increased (P<0.05) overall feed intake and reduced egg shell thickness compared with layers fed the adequate-ME&CP diet independent of β-mannanase supplementation. Neither dietary protein and energy content nor β-mannanase supplementation affected (P>0.05) egg shell strength, egg specific gravity and Haugh Units. A significant
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interaction (P<0.05) was observed in egg weight between dietary protein and energy content and β-mannanase supplementation, suggesting that β-mannanase supplementation increased egg weight only in hens fed the adequate-ME&CP diet. These results, therefore, showed that feeding adequate-ME&CP diets with added β-mannanase supplementation could be considered as a dietary strategy to improve egg weight in laying hens. In the second experiment, seventy two layers were randomly allocated to 4 treatments, each of which had 24 pens of 3 chickens per pen and were used to investigate the effects of β-mannanase on nutrient digestibility and nitrogen corrected apparent metabolizable energy (AMEn). Two diets were formulated to meet the National Research Council (NRC, 1994) nutrient requirements for layers. Diet 1 was based on corn and SBMwhereas Diet 2 was based on corn, SBM and DDGS. Each of the two diets was supplemented with either 0% or 0.04% β-mannanase. Each diet was fed to 6 groups of birds with 3 birds in each group making a total of 18 birds per treatment. For all apparent ileal digestibility (AID) calculations, the interaction between enzyme supplementation and energy levels was not significant for all treatments. Supplementing diets with β-mannanase increased apparent ileal DM digestibility of the experimental diets. Adding DDGS affected the AID of arginine, histidine, threonine, aspartate, glycine and proline, whereasβ-mannanase supplementation had no effect on AID of any of the amino acids. There was a trend towards the improvement of AID of protein with the addition of β-mannanase. Supplementing the diet with β-mannanase also improved the AMEn of DDGS containing diet but reduced the AMEn of the control diets. The results indicate that β-mannanase supplementation of corn/SBM/DDGS diets may improve calcium and energy utilization of layers, whereas it may not affect ileal amino acid digestibility | en_US |
