Minimum phosphorus requirements for laying hen feed formulations.

The objective of this contribution was to summarize from scientific literature the optimal concentration of nonphytate phosphorus (NPP) in feed for laying hens. The considered studies were one meta-analysis from 2012 and original studies published since then. Dietary treatments in the studies included variation in supplementation with mineral P sources and phytase. The studies investigated different periods of production and varied in duration but data were insufficient to analyze such factors in a systematic way. No study showed a positive effect on performance and eggshell when the NPP concentration was increased above 2.2 g NPP/kg of feed without the use of phytase. At such level, no consistent impairment of various bone quality traits were found but only few studies on bone quality traits were published. Overall, the data suggested that not more than 2.2 g NPP/kg of feed is needed for laying hens in different stages of production. This value can be reduced when phytase is added to the feed. Such reduction may differ depending on factors such as phytate content of the feed and phytase dosage. However, data are insufficient for calculating precise values of reduction. While phytate degradation in laying hens was markedly increased by phytase supplementation in several studies, effects of phytase supplementation on performance and bone traits in laying hens were less conclusive probably because the hens were supplied more than their NPP requirement. Transition to a system based on digestible P for laying hens similar to broiler chickens may support more precise P nutrition and more sustainable egg production in the future.

Femoral strength after induced lesions in rats (Rattus norvegicus).

Rats are a common model for the study of bone healing, with the cranium, femur, and tibia being the bones studied most frequently. This study examines noncritical-sized lesions that would allow rats to continue to bear weight without the need for fixation but that are sufficiently large to enable characterization of the healing process. We compared the femoral bone strength associated with 3 lesion sizes selected for use in future studies. Sprague-Dawley rats (age, 10 to 16 wk) were used to assess the ultimate breaking strength, stress, and break force of normal, unmanipulated femurs. We then created lesions of 3 different sizes in the mid- to distal diaphysis of the left and right femurs and characterized the associated decreases in bone strength. Femurs (n = 85) for this study were collected through tissue sharing from rats used in other acute surgical procedures and were tested by using a 3-point bending flexural materials-testing machine. Our hypothesis was that, as a model for bone healing, 3 induced lesions of different sizes would show incremental and proportional decreases in femoral strength, with the intermediate-sized (1.5-mm) lesion demonstrating a decrease of 20% to 40%. A lesion of 1.5 mm yielded a decrease in strength of 17% for both the left and right femurs. The strength of left femurs carrying intermediate lesions was significantly less than that of control, uninjured femur bones. In addition to providing validation for our own future bone-healing project, these data are a useful baseline for other investigators studying bone healing in a rat femur model.

Broiler diet modification and litter storage: impacts on phosphorus in litters, soils, and runoff.

Modifying broiler diets to mitigate water quality concerns linked to excess phosphorus (P) in regions of intensive broiler production has recently increased. Our goals were to evaluate the effects of dietary modification, using phytase and reduced non-phytate phosphorus (NPP) supplementation, on P speciation in broiler litters, changes in litter P forms during long-term storage, and subsequent impacts of diets on P in runoff from litter-amended soils. Four diets containing two levels of NPP with and without phytase were fed to broilers in a three-flock floor pen study. After removal of the third flock, litters were stored for 440 d at their initial moisture content (MC; 24%) and at a MC of 40%. Litter P fractions and orthophosphate and phytate P concentrations were determined before and after storage. After storage, litters were incorporated with a sandy and silt loam and simulated rainfall was applied. Phytase and reduced dietary NPP significantly reduced litter total P. Reducing dietary NPP decreased water-extractable inorganic phosphorus (IP) and the addition of dietary phytase reduced NaOH- and HCl-extractable organic P in litter, which correlated well with orthophosphate and phytic acid measured by 31P nuclear magnetic resonance (NMR), respectively. Although dry storage caused little change in P speciation, wet storage increased concentrations of water-soluble IP, which increased reactive P in runoff from litter-amended soils. Therefore, diet modification with phytase and reduced NPP could be effective in reducing P additions on a watershed scale. Moreover, efforts to minimize litter MC during storage may reduce the potential for dissolved P losses in runoff.

Influence of phytase on water-soluble phosphorus in poultry and swine manure.

The effect of dietary non-phytin phosphorus (NPP) and phytase (PHY) concentration on total phosphorus (TP) and water-soluble phosphorus (WSP) excretion was determined. Diets tested in broiler experiments were: National Research Council nutrient requirements for non-phytin phosphorus (NRC), NRC + PHY, reduced non-phytin phosphorus (RED), and RED + PHY. Turkey and swine experiment diets included NRC, RED, and RED + PHY. For all experiments, except broiler Experiment 1, excreta were: (i) boiled, antibiotic added, then frozen; (ii) boiled, antibiotic added, incubated (37 degrees C for 72 h), then frozen; and (iii) incubated, boiled, antibiotic added, then frozen. In Experiment 1, excreta were collected and frozen or incubated for 24 or 48 h. In broiler Experiment 1, WSP was not affected by phytase but increased with post-excretion incubation. In a broiler Experiment 2, reducing NPP resulted in reduced excreta TP and WSP (11.3 to 8.3 and 5.3 to 2.7 g kg(-1)). Feeding RED + PHY diets resulted in less TP and WSP (7.6 and 0.6 g kg(-1)) as compared with NRC + PHY (11.2 and 3.9 g kg(-1), Experiment 3). Incubation resulted in increased WSP, irrespective of phytase addition such that WSP as a percent of TP was similar among treatments. Addition of antibiotics before incubation prevented the increase in WSP. Similar results were observed with turkey and swine. Therefore, when phytase is used properly (i.e., with a simultaneous reduction of NPP), WSP or WSP as a percent of TP are not affected. The increase in WSP as a percent of TP post-excretion is a function of excreta microbial activity and not dietary phytase addition.