Levels Of Nutrient Density Research Articles

Inhibition of the promotional phase of azoxymethane-induced colon carcinogenesis in the F344 rat by calcium lactate: effect of simulating two human nutrient density levels

The effects of 2 levels of dietary calcium and 2 types of dietary fat on the promotional phase phase of azoxymethane-induced colon cancer in the F344 rat were investigated. During the initiation phase of carcinogenesis all animals were fed a 5% corn oil AIN-76A diet containing 0.32% Ca in the form of calcium lactate. Rats were then injected with azoxymethane (AOM) weekly for 8 weeks. Thereafter, the rats were fed 1 of 3 diet formulations: a 5% corn oil diet or a 20% corn oil or 20% American Blend oil fat diet, with the level of Ca set at either 0.32% of the diet, a nutrient density simulating a daily human intake of ∼ 1700 mg Ca/day, or at 0.04% of the diet, reflecting a human daily intake of ∼ 200–250 mg of Ca/day, thus modeling 2 human nutrient density levels for calcium. Measurements of fecal pH during the experiment indicated an acidic adaptation of the large bowel to the lactate anion. Analysis of collected fecal samples showed more total fatty acids to be present in the colon when higher amounts of calcium were consumed. However, results of the tumorigenesis study indicated that calcium lactate fed at the 0.32% level significantly inhibited the development of colonic adenocarcinoma in all dietary groups. Taken together, this investigation supports the hypothesis that calcium supplementation can inhibit colon neoplasia in rats fed a high fat diet; however, under the conditions of this study, the 20% fat level did not significantly promote colon cancer as compared to a 5% fat level.

Characterization of the Response of Broiler Chickens to Diets Varying in Nutrient Density Content

Studies have been conducted to examine the response of broilers to diets varying in nutrient density. Constant energy:nutrient ratios were maintained in diets for growing broilers fed 2970 to 3740 M.E. kcal./kg. and measurements made of weight gain, feed consumption, efficiency of feed utilization, calorie:gain ratios, and various carcass characteristics.Growth rate and efficiency of feed utilization were almost direct functions of the dietary nutrient density level. Broilers offered higher energy diets consumed a greater number of calories but converted these to gain with little impairment in caloric efficiency. Regression analyses were used to derive equations for predicting changes in feed consumption and growth rate associated with changes in dietary nutrient density level.

The Phosphorus Needs of Young Broiler Chicks in Relationship to Dietary Nutrient Density Level

A study was conducted to determine if the dietary need of the broiler chick for available phosphorus remained in constant ratio to the energy content of the diet. Corn-soybean meal diets were prepared with dietary energy levels of 2970, 3190 and 3410 M.E. kcal./kg. with inorganic P levels from 0.13 to 0.63% in increments of 0.10%. Least squares analyses were used to determine points of maximum response for body weight tibia ash, and efficiency of feed utilization through 28 days of age. Small but consistent reductions were observed in available phosphorus:energy ratios as the dietary energy level increased. For maximum response chicks needed the following levels of inorganic phosphorus per 1000 M.E. kcal./kg. at 2970, 3190 and 3410 M.E. kcal./kg., respectively: (a) for body weight, 0.159, 0.153, 0.144%; (b) for tibia ash, 0.170, 0.168, 0.151%; (c) for feed utilization, 0.153, 0.145, 0.138%.

The Phosphorus Needs of Finishing Broilers in Relationship to Dietary Nutrient Density Levels

Studies were conducted to examine the phosphorus needs of the broiler chick from the period of four to eight weeks of age in relation to the dietary nutrient density. Graded levels of phosphorus were added to broiler diets containing metabolizable energy levels of 2970 to 3410 kcal./kg. The adequacy of the diets was measured by weight gains, feed utilization, tibia ash and bone breaking strength. The results of these studies would indicate that there was little improvement in performance to be gained with the addition of more than 0.12 percent of supplemental inorganic phosphorus to an all-plant broiler diet containing 0.42 percent total phosphorus. The energy content of the diet, over the range tested, had no effect on the chick’s need for phosphorus during this period.