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A study was conducted to determine the effects of dietary energy and protein intake on the partitioning of lysine in broiler breeder hens. One hundred twenty-six broiler breeders were randomly assigned to 1 of 6 dietary treatments in a 2 (390, 450 kcal/d) × 3 (22, 24, 26 g of CP/d) fashion. Thirty-six hens were administered a daily oral dose of 15 mg of (15)N-Lys for a period of 2 wk or until first egg. After the 2-wk enrichment period, no isotopes were given for 2 d. After 2 d, a daily oral dose of 15 mg of (2)D4-Lys was administered until the 2nd, 3rd, and 4th egg (saved) after the initial (2)D4-Lys was given, at which point pectoralis muscle was sampled. Weeks 25, 29, and 45 were assessed. Isotopic enrichment of pectoralis muscle, egg yolk, and albumen was determined via gas chromatography-mass spectrometry. The (15)N-Lys was intended to represent endogenous lysine, whereas the (2)D4-Lys was intended to represent dietary lysine. Greater than 78% of all labeled lysine ((15)N and (2)D4-Lys) was found in breast muscle. Endogenous muscle was the main source of lysine for yolk formation at wk 25 and 45. Diet was the main source of lysine for albumen formation at wk 25 and 29. A consistent decrease in the (15)N-Lys in breast muscle from the 2nd to the 3rd egg was observed, while also seeing an increase in the (15)N-Lys in the egg from the 3rd to the 4th egg. No difference in the partitioning of lysine was determined by energy or protein intake at levels typical for the current poultry industry. Rather, age, and possibly rate of production, appear to be the main drivers of lysine partitioning in the broiler breeder hen.

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A 3 × 2 × 2 factorial experiment, consisting of 52 hens per treatment, was conducted to determine the effects of pullet BW, dietary nonphytate phosphorus (NPP), and feeding regimen on performance, progeny quality, and bone remodeling. Cobb 500 broiler breeder pullets were reared to 3 different growth curves: 20% under, Cobb standard, and 20% over. Body weights were recorded weekly and feed adjustments made accordingly. At 21 wk, 624 hens were fed one of 2 breeder diets differing only in the amount of dietary NPP: 0.15 or 0.40%. A normal feeding regimen was appropriate for the particular growth curve; an alternative regimen considered the 3 growth curves together as a flock. At 24, 26, and 29 wk, blood was collected from 5 hens per treatment every 4 h over a 24-h period. Plasma samples were analyzed for total alkaline phosphatase, tartrate-resistant acid phosphatase, parathyroid hormone-related peptide, Ca, and inorganic P. Eggs per hen housed were diminished in hens fed the low dietary NPP and by low pullet target weight. Hens fed low dietary NPP also had lower egg weights but better eggshell quality. Mortality was significantly higher in hens fed low dietary NPP. Breeder tibia relative strength and ash were also significantly lower in hens fed low dietary NPP, regardless of the quantitative amount. Progeny tibia ash was not affected by any treatment. Total alkaline phosphatase responded to pullet BW, however by wk 29, total alkaline phosphatase also became sensitive to dietary NPP. The NPP by pullet BW interaction for tartrate-resistant acid phosphatase levels became significant by 29 wk, and pullet BW was significant at wk 24. The NPP by pullet growth curve interaction was also critical for plasma inorganic P levels throughout the sampling period. In summary, both 0.15% dietary NPP and reared pullets 20% under standard BW negatively affect egg production but do not impair progeny productivity. Body composition appears to be a main contributor in bone remodeling mechanisms, especially during the transition into egg production.