An experiment was conducted to determine whether broiler litter concentration of N and P and equilibrium NH3 gas concentration can be reduced by reducing dietary CP and P levels and supplementing with amino acids and phytase, respectively, without adversely affecting bird performance. Equilibrium NH3 gas concentration above the litter was measured. The experiment was divided into a starter period (1 to 21 d) and grower period (22 to 42 d), each having two different CP and P levels in a 2 x 2 factorial arrangement. The CP treatments consisted of a control with a mean CP of 204 and 202 g/kg for starter and grower periods, respectively, and a low CP diet with means of 188 and 183 g/kg, respectively, but with similar amino acid levels as the control. The P treatments comprised starter and grower control diets containing means of 6.7 and 6.3 g/kg P, respectively, and low P treatment means of 5.8 and 5.4 g/kg P supplemented with 1.0 g/kg phytase. Reducing starter diet CP by 16 g/kg reduced weight gain by 3.5% and, hence, body weight at 21 d of age, but did not affect feed intake or feed efficiency. Reducing P did not affect feed intake and weight gain, but improved feed efficiency by 2.0%. Responses in feed intake and efficiency to CP depended on the level of dietary P. For the grower period there were no significant differences in feed intake, weight gain, and feed efficiency, nor in body weight at 42 d of age, after correcting for 21-d body weight, between CP and P treatments. There were significant (P < 0.001) reductions in litter N and P concentrations, but not equilibrium NH3 gas concentration, moisture content, or pH, for low CP and P diets. Mean equilibrium NH3 gas concentration was 63 ppm. Litter N concentration was reduced 16.3% with the low CP diets, and litter P by 23.2% in low P treatments. The results suggest that dietary manipulation shows merit for reducing litter N and P concentrations while maintaining acceptable production performance from broilers.

Two experiments were conducted to evaluate the effect of dietary phytase and increasing levels of available phosphorus (P(av)) on the growth performance and phosphorus metabolism of broiler chicks. In both experiments, graded levels of P provided by dicalcium phosphate and of phytase were added to a low-P corn-soybean meal basal diet. In Experiment 1, diets providing .21, .29, .37, and .44% P(av) without phytase; .21% P(av) plus .05, .10, or .30% phytase; and .29% P(av) plus .10% phytase were each fed to four groups of seven chicks, 3 days of age. In Experiment 2, diets providing P(av) levels of .32, .38, and .44% and phytase levels of .5, 1.0, and 1.5% (250, 500, and 750 units/kg) in a factorial arrangement were each fed to four groups of eight chicks, 5 days of age. In Experiment 1, increasing dietary P(av), but not phytase, increased feed intake, weight gain, feed conversion, plasma inorganic P, tibia and toe ash, and tibia breaking strength (P < or = .05). Plasma inorganic P responded quadratically to increasing dietary phytase. In Experiment 2, feed intake and weight gain were increased by elevating the level of P(av), but not by phytase. Toe and tibia ash and plasma inorganic P were increased by dietary phytase and increasing levels of P(av) (P < or = .01). Tibia breaking strength was improved (P < or = .05) by dietary phytase but not by increasing levels of P(av). The P excretion was elevated (P < or = .01) by increasing levels of P(av) and was decreased by supplemental phytase (P < or = .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Variations in muscle chemical composition, pH, and protein extractability were studied using male broilers of eight different genetic crosses of commercial strains. Three replicate groups of 24 birds of each cross were grown in floor pens using commercial corn-soybean meal diets. At 8 wk of age, three birds per replicate, weighing within 5% of the pen average, were slaughtered, scalded, defeathered, eviscerated, and chilled in ice slurries overnight. Muscles were excised from breasts and thighs, and trimmed of skin and external fat. Proximate analysis was conducted using ground muscle pooled within replicate groups. Breast muscle of all strain crosses contained more (P < or = .05) total protein (ranging from 20.7 to 23.6%) and moisture (74.6 to 75.9%), and less fat (1.0 to 2.0%) than thigh muscle, which contained 18.1 to 21.3% protein, 72.8 to 73.8% moisture, and 5.0 to 7.2% fat. The pH of breast muscle was lower (P < or = .05) than that of thigh muscle for four of the eight strains, and protein extractability of breast muscle was greater (P < or = .05) than that of thigh muscle for all strains. There were significant differences among strains in chemical composition, pH, and protein extractability for both breast and thigh muscles. The correlation between percentage protein and fat was positive in breast (r = .72, P < .05) and negative in thigh muscle (r = -.77, P < .05). However, no significant correlations were observed between the chemical constituents of breast muscle with the respective constituents of thigh muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Crossbred pigs (n = 144, average age and weight = 28 +/- 3 d, 7.5 kg) were used in two 6-wk trials to assess the effects of dietary pH and P source on growth performance, gastrointestinal digesta pH and chloride ion concentration (Cl-), and bone characteristics. Treatments were randomly allotted within blocks (based on weight within gender) to a 3 x 2 factorial arrangement with three dietary pH levels (5.4, 6.0, and 6.7) and two P sources: dicalcium phosphate (DCP) and defluorinated phosphate (DFP). Pigs fed the pH 6.7 diet had reduced ADG (P less than .01) and average daily feed intakes (ADFI; P less than .001) during wk 1 to 3 and overall compared with pigs fed the pH 6.0 diet, but ADG and ADFI were not affected when the pH 5.4 diet was fed. There was a dietary pH x P source interaction (P less than .05) for ADFI. Pigs had decreased ADFI as dietary pH was increased from 6.0 to 6.7 for both DCP and DFP, but ADFI was similar for the pH 6.0 and 5.4 diets with DFP, whereas ADFI was greater for the pH 5.4 diet with DCP. Dietary pH did not influence ADFI:ADG ratio (F:G; P greater than .05), and P source had no effect (P greater than .05) on either ADG, ADFI, or F:G.(ABSTRACT TRUNCATED AT 250 WORDS)

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