Abstract
SummaryA study was conducted to evaluate productive performance in laying hens fed diets with reduced nutrient density based on the nutritional contribution of a Buttiauxella phytase in laying-hen diets from 21-57 weeks of age. A commercial laying hen diet was offered ad libitum to the 480 ISA Brown laying hens from 18-21 weeks of age. From 21 weeks onwards, the hens received one of four dietary treatments: a positive control (PC) diet, a down specified diet (DS1) + phytase at 300 FTU/kg, a second down-specified diet (DS2) + phytase at 600 FTU/kg and a third test diet formulated as per DS1 + phytase at 1,200 FTU/kg feed. The PC was formulated based on ISA breeder recommendations. DS1 was formulated with reduction of 0.149% available P, 0.134% Ca, 55 kcal/kg AME, 0.33% CP, digestible amino acids (up to 0.015%) and 0.013% Na based on the contribution of Buttiauxella phytase at 300 FTU/kg. DS2 was formulated with reduction of 0.177% available P, 0.159% Ca, 60 kcal/kg AME, 0.61% CP, digestible amino acids (up to 0.028%) and 0.02% Na based on the contribution of Buttiauxella phytase at 600 FTU/kg. Every dietary treatment was fed to 12 cages containing 10 hens each. The trial treatments did not include a full, DS negative control, as ethical considerations regarding birds' welfare when feeding such diets over such an extended period of time did not permit this. No significant differences were seen in hen-day egg production, feed intake, egg weight, feed to egg mass ratio, shell, yolk or albumen proportion, unsaleable eggs or shell breaking strength in laying hens fed the PC diet or the DS diets with added phytase. Yolk colour increased significantly with phytase supplementation. Supplementing the DS1 diet with 300 FTU and the DS2 diet with 600 FTU resulted in non-significant differences in tibia ash, Ca and P, compared to the PC diet. The data from this study indicated that applying the nutrient contributions for Buttiauxella phytase at 300 and 600 FTU/kg maintained the egg production, BW and egg quality parameters compared to PC. The best economic efficiency value during the whole experimental period was recorded with phytase at 600 FTU/kg when full matrix values are used. When commercial diets are formulated based on ISA breeder recommendations, lowering diet nutrient density while supplementing with phytase reduced the overall diet cost, which should contribute to the profitability of egg production.
Highlights
Phytase is commonly supplemented in laying hen diets to improve phytate phosphorus (P) availability and retention and to reduce excretion (Ravindran et al, 2000, Jalal and Scheideler, 2001, Gao et al, 2013, Gosh et al, 2015)
Phytase recovery analyses was variable among phases, but on average for the three phase diets values were within targets (309, 725 and 1,308 FTU/kg feed above positive control (PC) diet for the treatments 300, 600 and 1,200 FTU/kg feed, respectively, Table 4)
No significant differences were found for hen-day egg production, feed intake, egg weight, feed to egg mass ratio, shell, yolk or albumen proportion, unsaleable eggs or shell breaking strength in laying hens fed the PC diet or the DS diets with added phytase (Table 4)
Summary
Phytase is commonly supplemented in laying hen diets to improve phytate phosphorus (P) availability and retention and to reduce excretion (Ravindran et al, 2000, Jalal and Scheideler, 2001, Gao et al, 2013, Gosh et al, 2015). Phytate can complex with amino acids (Ravindran et al, 2000, Rutherfurd et al, 2004), starch and fat (Ravindran et al, 2001, Newkirk and Classen, 2001), reducing the absorption of these nutrients. Phytase supplementation improves the availability of nutrients such as protein and amino acids (Ravindran et al, 2000, Rutherfurd et al, 2004) and energy (Kornegay et al, 1996, Namkung and Leeson, 1999, Ravindran et al, 2000, 2001, Newkirk and Classen, 2001, Hughes et al, 2009) in poultry
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