Adult Leghorn roosters were precision-fed 44% protein soybean meal (SBM) or 80% ethanol-extracted soybean meal (ESBM) to determine nutritional differences due to the removal of oligosaccharides. Dry-matter digestibility and TMEn as well as apparent hemicellulose and cellulose digestion were determined. The transit time, rate of passage, and pH of the cecal contents were also established with roosters that had consumed a .3% chromic-oxide diet that contained SBM or ESBM. The protein content of the SBM and the ESBM was 46.1 and 64.4%, respectively. The true-dry matter digestibility of SBM was 54%. The TMEn of the SBM on a dry-matter basis was 2,794 kcal per kg; and the apparent hemicellulose and cellulose digestibility was 9% and 0%, respectively. The true dry-matter digestibility of the ESBM was 67%. On a dry-matter basis, the TMEn of the ESBM was 3,368 kcal per kg; and the apparent hemicellulose and cellulose digestibility was 62% and 35%, respectively. Oligosaccharide digestion occurred mainly anterior to the ileo-cecal junction. Hemicellulose and cellulose digestion occurred predominantly in the lower gastrointestinal tract. The transit time for the ESBM diet was 115 min, compared to 71 min for the SBM diet. Based on a 16-h collection of excreta, the rate of passage was approximately 50% slower for the ESBM diet than for the SBM diet. The pH of the cecal contents from roosters consuming the ESBM diet was 7.21 versus 6.51 for the SBM diet.
An experiment with a factorial arrangement of treatment (3 by 2 by 2 by 2) was conducted to determine the effect of ascorbic-acid supplementation (0, 100, and 200 ppm) on the performance of two commercial layer strains housed at a density of either 3 or 4 birds per cage and relative humidities (RH) of 40% or 60%. The hens were subjected to a continuous heat stress of 31.1 degrees C for the 3-mo experimental period. As a comparison with an unstressed control group, an additional group of hens was housed at 23.9 degrees C and 40% RH and was fed the diet without ascorbic-acid supplementation. Mortality was reduced by ascorbic-acid supplementation. Shell weight per unit surface area showed a small increase with the added ascorbic acid. Values (in Haugh units) were increased by ascorbic-acid supplementation at the 200 ppm level and by the lower relative humidity. The higher RH reduced egg production by 4.16% and changed feed efficiency from 2.29 to 2.45 g of feed intake per gram of egg mass. There were differences in blood pH, blood CO2, blood HCO3-, and blood and adrenal ascorbic-acid levels due to the housing temperature. The higher RH produced blood-chemistry changes that were typical of respiratory alkalosis, which has been shown to occur in layers at high temperatures. Higher cage density, on the other hand, showed no change in the HCO3 level; but blood pCO2 was increased while blood pH was decreased. These results demonstrate that ascorbic-acid supplementation can be effective in reducing laying-hen mortality due to environmental stress and has small influences on egg quality.
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