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Biomedical subjects

R J Mitchell

Publications and source records attributed to R J Mitchell.

At least 109 records · Page 6Linked to original sources
PubMed1976

Performance of chicks fed diets formulated to minimize excess levels of essential amino acids.

Studies were conducted in which levels of essential amino acids in excess of the minimum requirements were minimized in broiler diets composed of commercially available feed stuffs and synthetic amino acid supplements. Growth rate and efficiency of feed utilization of chicks fed such diets were equal to that attained by chicks fed diets formulated by conventional means when grown under conditions where heat stress was not a factor and significantly improved when fed under conditions of heat stress. Improvements were obtained in efficiency of protein and calorie utilization using this technique of formulation.

Amino Acids, Essential↗
PubMed1975

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%.

Animals↗
PubMedDate not supplied

Change in creep rate and microstructure in an aged, low-copper amalgam.

Low-copper amalgams aged at 37 degrees C, 50 degrees C, 60 degrees C, 70 degrees C, and 80 degrees C for periods of 7 and 30 days were examined using a scanning electron microscope and an x-ray diffractometer. Gamma-one Ag-Hg grain size and gamma 2 Sn-Hg volume fraction, and surface area were determined by quantitative metallography. At 60 degrees C and below, gamma 1 was the predominant matrix phase. Little beta 1 Ag-Hg was found. In this temperature range, both gamma 1 grain size and ADA creep were found to obey an Arrhenius law. A linear relationship was found between the log of the mean ADA creep and the mean gamma 1 grain size. Above 60 degrees C, the gamma 1 phases and the majority of the gamma Ag-Sn particles disappeared. In their place, beta 1 appeared. Gamma-two volume fraction increased during aging at temperatures over 60 degrees C, but a coarsening of gamma 2, reflected in a decrease in gamma 2 surface area per unit volume, also took place. Aging for 30 days or less resulted in decreases in ADA creep. At 60 degrees C and below, the decrease was caused by increases in gamma 1 grain size. Above 60 degrees C, the decrease in ADA creep was caused by several factors, one of which was the appearance of large beta 1 grains.

Copper↗