Effect of multienzyme supplementation to diets containing different levels of reduced amino acids on performance, egg quality, bone characteristics, digestive system development and nutrient digestibility in laying hens

This study was conducted to determine the effects of diets formulated with and without enzyme supplementation based on the ideal amino acid (AA) concept and reduced digestible lysine levels on performance, egg quality, bone biomechanical properties, small intestine histomorphological properties, cecal microorganism populations, cecal volatile fatty acids and ileal nutrient digestibility in 30-week-old white laying hens. A total of 144 30-week-old white Super Nick laying hens were used in the experiment. The study was conducted in 6 different treatment groups according to the randomized plots experimental plan with 8 replications, in a total of 48 subgroups with 3 hens each. Six different diets were prepared for feeding the animals and they were fed with 6 different treatment diets for 84 days. The control diet and the enzyme-containing control diet were prepared by containing 0.77% digestible lysine and 16.8% crude protein (CP). The other 4 diets were prepared as enzyme-free and enzyme-containing 0.70% digestible lysine and 15.8% CP, enzyme-free and enzyme-containing 0.65% digestible lysine and 14.8% CP, respectively. Phytase (1000 FTU/kg), NSPase (16.000 BXU/kg) and protease (125 mg/kg) enzymes were added to the 3 diets containing enzymes and formulated considering the energy (125 kcal ME/kg), calcium (Ca) and available P (%0.2 AvP) enzyme's nutritional matrix values. As of the end of the study, egg production and feed consumption were significantly lower in the group fed with the diet containing 0.65% digestible lysine (%14.8 CP) without enzymes than the other groups (P<0.01). In the groups fed with diets containing 0.65% digestible lysine (14.8% CP) with and without enzyme, egg mass was significantly lower than the other groups, while feed conversion ratio was significantly higher than the other groups (P<0.01). Egg shell thickness in the control group with enzyme (0.77% digestible lysine, 16.8% CP) was significantly lower than the groups fed with diets containing 0.65% digestible lysine (14.8% CP) with and without enzyme (P<0.05). Egg shell ratio was higher in the group fed with diet containing 0.65% digestible lysine (14.8% CP) without enzyme than the control group and the groups fed with rations containing 0.70% digestible lysine (15.8% CP) (P<0.01). Egg yolk index was significantly lower in the group fed with diet containing 0.65% digestible lysine (14.8% CP) without enzyme than the other groups (P<0.01). Serum uric acid and bilirubin levels were significantly higher in the control group than in the other groups (P<0.01). Tibia diameter was significantly lower in the groups fed with diets containing 0.70% digestible lysine (15.8% CP) with enzyme and 0.65% digestible lysine (14.8% CP) with/without enzyme than in the control group (P<0.01). Tibia cross-sectional area was significantly lower in the groups fed with diets containing 0.70% and 0.65% digestible lysine without enzyme than in the control group (P<0.01). Tibia shear stress was significantly higher in the group fed with diets containing 0.65% digestible lysine with enzyme than in the groups containing 0.70% and 0.77% digestible lysine (P<0.01). Jejunum villus height, villus width, villus height/crypt depth ratio, villus surface area and goblet cell count responded positively to the reduction of AAs and CP in the diet, especially in the enzyme groups, and there were significant increases in these parameters (P<0.01; (P<0.05). While cecal short-chain fatty acid (SCFA) concentration did not respond significantly to the reduction of AAs and CP levels in the diet, it was significantly higher in the groups fed with enzyme-containing diets than those not containing enzymes (P<0.01). Total SCFA was significantly higher in the enzyme-containing diets, independent of the diet CP and AA levels (P<0.01). Cecal Lactobacillus count was significantly higher in the groups fed with enzyme-containing diets than those without enzymes (P<0.01). Ileum CP and dry matter (DM) digestibility were positively affected by the reduction of dietary AAs and CP levels and enzyme supplementation, and were significantly lower in the control group (P<0.01). Ileum P digestibility was significantly higher in the groups fed with diet AAs and CP levels (P<0.01). While it was not affected by the decrease, there was a significant increase with the use of enzymes, especially in diets containing low levels of digestible lysine (0.70% and 0.65%) and CP (15.8% and 14.8%) (P<0.01). The study results showed that reducing the diet CP level by 6% or digestible lysine level by 9% and formulating the diet according to the ideal AA ratio, together with the addition of phytase and NSPase, improved intestinal integrity and ileal digestibility of P, CP and DM in laying hens.