Laying hens in Australia exposed to pasture range may experience reduced performance, poor enteric health and increased mortality. In addition, egg quality can also be affected, indicated by the increased number of damaged and misplaced eggs as well as decreased egg-shell quality. These effects may be related to excessive fiber digestion and reduced nutrient uptake. The addition of multi-enzymes or organic acids to free-range layer diets may improve the digestion of nutrients, thus increasing performance, gut health and egg quality.
A study was conducted to investigate the effect of range types and feed additives on performance and egg quality of ranging laying hens. Sixteen week-old Lohmann Brown layers (n = 300) were fed with a wheat-soy based diet, and allocated to six treatments and five replicates of 10 birds each. The treatments were applied in a 2 × 3 factorial arrangement to test the effect of range types (R1 = gravel of average size 2 x 1 cm; R2 = pasture: Festuca arundinacea) and feed additives (T1 = phytase/xylanse; T2 = phytase/xylanse/betaglucane/xylo-glucanase/pectinase/protease; T3= phytase/xylanse/benzoic acid/essential oils).
Birds were adapted for two weeks before allowing access to range at the start of 19 weeks of age. At the age of the 24th week, five hens per house were randomly selected and sacrificed to study the intestinal pH and visceral organ weight. In addition, six eggs from each hen house were collected to investigate egg quality. Birds ranged on pasture had significantly heavier (P < 0.05) gizzards (36.7 g ± 1.06; mean ± SEM) than those on the gravel range (28.8 g ± 0.75). The crop pH was lowest (P < 0.05) in the birds fed diets added with T1 (4.88 ± 0.07) compared to T2 and T3 (5.10 ±0.04 and 5.03 ±0.049, respectively). There was no significant interaction (P > 0.05) in body weight, liver and pancreas weight, and ileum pH among any treatments. In the egg quality parameters, egg albumen height was significantly higher (P < 0.05) in birds fed T1 (8.52 mm ± 0.25) compared to T2 and T3 groups (7.90 ± 0.29; 7.52 ± 0.17). Birds on the gravel range had higher (P < 0.005) egg Haugh Unit (90.8 ± 1.17) compared to those on the pasture range (87.2 ± 0.91; but yolk color was darker (P < 0.05) for pasture ranged birds (6.90 ± 0.13) compared to gravel ranged birds (4.36 ± 0.07). There was no interaction of diet or range (P > 0.05) on egg weight, shell banding, shell reflection, shell strength, shell weight and shell thickness. In conclusion, gizzard weight, digesta pH, and some egg quality traits can be influenced by range types or feed additives.
From the Australian Poultry Science Symposium