Two experiments were conducted to study effects of dietary insoluble fiber (IF) on digestive enzyme function in layer poultry. In Experiment 1, 8 wk old pullets were fed a control diet (Group C) or a diet (Group IF) supplemented with 1% IF (Arbocel RC). After 5 wk, 6 pullets per group were killed and organ samples collected. The remaining pullets in Group C were divided into two groups: half were fed the control diet (Group C) and half were given the IF diet (Group C-IF). Similarly, half the pullets in Group IF continued on the IF diet (Group IF) and half on the control diet (Group IF-C). At 10 wk, organ samples were collected. BW at wk 5 (IF, 1364.8 g; C, 1342.9 g) and 10 wk (IF, 1678.1 g; IF-C, 1630.5 g; C-IF, 1617.1 g; C, 1580.4 g) were not different. At wk 5, the relative proventricular weight (0.41 g/100 g BW) and activities of pepsin (75.3 pepsin units/g proventriculus/min) and pancreatic general proteolytic activity (GP) (122.9 μmol tyrosine produced/g tissue) were greater (P < 0.05) than those of Group C (proventricular relative weight, 0.36; pepsin activity, 70.6; GP activity, 94.3). At wk 10, relative weights of liver and gizzard of Group IF were heavier (P < 0.05) than other treatments; activities of pepsin, GP, trypsin and chymotrypsin of IF pullets were significantly greater than other treatments as was mRNA expression for pepsinogens A (25.9 vs. 22.9) and C (13.1 vs. 10.8). In Experiment 2, 19 wk old hens were fed a control diet or a diet containing 0.8% IF (Arbocel RC) for 12 wk. Final BW after 12 wk was not different (IF, 1919.4 g; C, 1902.1 g). Pancreatic GP activity was greater (P < 0.05) in Group IF hens than Group C at wk 12 (122.2 vs. 97.0 μmol tyrosine released/min/g tissue)) as was relative gizzard weight (1.32 vs 1.10 g/100 g BW). The significantly improved digestive organ weights and enzyme activities in IF pullets may contribute to an improvement in feed utilization.

Recent studies suggest that hypercalcemia of sarcoidosis is due to high blood concentrations of calcitriol and that this compound may be synthesized at an extra-renal site. We report that sarcoid lymph node homogenate metabolized calcifediol to a substance indistinguishable from calcitriol, whereas six nonsarcoid lymph nodes failed to produce this compound.

The effect of vitamin A on calcium-regulating hormones was studied in rats. A single oral dose of 30 mg retinol equivalents (RE) given to adult rats caused no change to serum biologically active parathyroid hormone (bioactive-PTH) concentrations. Bioactive-PTH secretion from rat thyroparathyroid gland complexes was not significantly altered after in vitro incubation with 1.18 X 10(-6) M retinol. Chronically intoxicated rats given 15 mg RE 3 times a week for 6 wk, showed higher osteoclast numbers and lower osteoid than controls. Serum bioactive-PTH was not detectable and serum 25-hydroxyvitamin D (25-OHD) (25.2 +/- 12.5 nmol/L) was significantly (P less than 0.03) lower than controls (43.3 +/- 3.1). In acutely intoxicated rats (60 mg RE/d for 2 d), serum bioactive-PTH levels were significantly lower (0.02 +/- 0.05 ng/ml, P less than 0.03) than in control animals (0.14 +/- 0.08). Lower doses of vitamin A, 7.5 mg RE 3 times a week for 3 wk, suppressed serum bioactive-PTH to undetectable levels but had no significant effect on serum 25-OHD. Serum calcium and 25-OHD levels were significantly lower in vitamin D-intoxicated rats given 7.5 mg RE 3 times a week (ca. 3.16 +/- 0.19 mmol/L; 25-OHD 599.7 +/- 110.6 nmol/L) than vitamin D-intoxicated controls (3.42 +/- 0.17; 789.3 +/- 17.7). These results suggest that hypervitaminosis A can alter the metabolism of calcium-regulating hormones.

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1. Effects of food restriction on growth rate and relative growth rates of supply organs (liver, heart, lungs and kidneys, digestive tract) and demand organs (breast, back, thighs, abdominal fat) of broiler chickens were studied. 2. Birds were restricted in intake to 50% (group FI 50) or 75% (group FI 75) of ad libitum from 5 to 11 d of age; all birds were fed ad libitum from 12 to 39 d of age. 3. Relative growth rates from 12 to 39 d of age of group FI 50 were higher (P < 0.05) than group FI 75 and control group. 4. No significant differences in food conversion ratio, carcase fat and abdominal fat between groups were observed. 5. At 12 d of age, relative weight of the empty digestive tract of group FI 50 was higher (P < 0.05) than that of the control group and group FI 75. 6. The increased weight of the empty digestive tract may have contributed to the ability of the chickens to achieve compensatory growth after the restriction period.