Robert L. Squibb

A simple method for carcass analysis

Abstract A relatively simple and rapid carcass analysis technique is described. First, water content is determined by drying the whole carcass. The dried carcass is then ground to a powder and the fat content is determined using an ether extraction method. The protein content is determined on the fat extracted material using a modification of the Biuret method. In this way, three separate methods are combined to provide an accurate but simple and rapid method for carcass water, fat and protein determinations. The usefulness of this method for behavioral studies involving large numbers of animals is discussed.

Dietary self-selection in active and non-active rats.

Abstract Active rats given a choice of protein and carbohydrate chose a higher proportion of carbohydrates than did non-active animals. These results were interpreted as showing that active rats differ in their nutritional requirements and that this difference reflects changes in intermediary metabolism.

Dietary self-selection at cold temperatures ☆

Abstract Animals housed in the cold (2°C) were given the opportunity to select the components of their diets from protein and carbohydrae fractions. Housing in the cold was accompanied by depressed growth, which was not affected by giving the animals the opportunity to select their diets. Animals in the cold increased total caloric intake relative to controls at room temperature (22°C). Selecting animals housed in the cold chose a lower percentage of the diet as protein (and, therefore, a higher percentage as carbohydrate) than did controls. Since protein intake levels did not differ as a function of environmental temperature, the altered dietary selection pattern was due to an increase in the absolute amount of carbohydrates consumed. These data were interpreted as suggesting that the level of protein selected is determined by age factors and the level of carbohydrate selected is determined by energy requirements.

Selection of an adequate protein-carbohydrate ratio by the domestic chick.

Abstract Male broiler chicks, given access to high protein and high carbohydrate diet fractions, demonstrated an ability to select a protein-carbohydrate ratio sufficient to maintain growth at near control levels. The level of protein selected was below that present in either control diet and declined with age. It is hypothesized that a feedback loop involving learning controls the selection mechanism although the specific cues involved were not isolated in this study.

Self-selection of natural and purified dietary protein ☆

Abstract Animals given the opportunity to select their diets from a protein fraction and a carbohydrate fraction selected a constant ratio of protein to carbohydrate regardless of the protein source. If the protein was in a natural form this ratio was such as to support growth at a rate equal to that of their controls, but if the protein was in the purified form the growth rate was depressed below even their controls. These data suggest that in the ad libitum-fed animal dietary balance as well as caloric balance appear to be the prime determinants of intake. Growth considerations do not appear to be the crucial determinants of dietary self-selection.

Purified diets: Some cautions about casein ☆

Growth and intake of weanling rats on five casein-based purified diets and matched cereal-based diets were compared. The results support Láts conjecture that the failure of animals to exhibit normal growth on some purified diets may be attributed to their failure to consume sufficient casein. Given a choice, the rats consumed both types of food, composing a diet in which the ratio of purified to cereal-based diet was 2:1, and they grew normally. Although the growth-promoting characteristics of caseins from different sources varied, the preference ratio between casein- and cereal-based diets was the same with one exception: a reduced preference for purified diet was shown by animals who had previously experienced subnormal growth for an extended period of time on a purified diet. These results show that all caseins are not equivalent in their growth-promoting properties. Further, they show that rats are exquisitely sensitive to the nutritional properties of their diets and, given the opportunity, can compose a diet which yields normal growth.

Effects of chronic and acute infections on tissue levels of carnosine, anserine and free histidine in rats and chickens.

Abstract The tissue concentrations of the imidazole-containing compounds, anserine, carnosine, and free histidine, were determined in male chickens and rats suffering from acute or chronic infections. Either type of infection resulted in a decrease in tissue carnosine concentration. The tissue anserine concentration was unaltered by either the acute or the chronic infection. The tissue free-histidine concentration increased significantly during chronic infections, but remained unaffected during the acute infections. These results were consistent with the hypothesis that carnosine acts as a tissue reservoir for histidine, ultimately serving, when called upon by the stress of an infection, as a precursor of histamine.

Relation of diurnal temperature and humidity ranges to egg production and feed efficiency of New Hampshire hens

The effect of environment on the production and size of eggs, feed efficiency and mortality of New Hampshire hens in individual cages was studied simultaneously in five areas of Guatemala having temperatures covering a range of 0°–45° C. with variable humidities. While birds housed in the tropical lowlands did show visible signs of thermo-stress, there were no significant differences in egg size, production, feed consumption, mortality and body weight between areas or between groups within areas. The inconsistency of these data with other published reports is explained on the basis of the observed extremely wide diurnal range for temperatures and humidities. An attempt is made to present accepted physiological phenomena in the form of a working hypothesis wherein the diurnal temperature range is related to the fowls tolerance to thermo-stress.

Effect of heat acclimation (32°c) on rat liver and brain substrate levels

Abstract 1. 1. Experiments were carried out to determine liver and brain enzyme, coenzyme, substrate and lipid levels in 3-month-old female rats exposed to ambient temperatures of 25° C or 32° C for 35 days. Food and water intake was observed during the acclimation period. In two male rats voluntary physical activity was also recorded during control and heat acclimation at 32° C. 2. 2. Food intake and voluntary physical activity were significantly decreased and water intake was significantly increased in the heat-acclimated group. 3. 3. Liver glutamic dehydrogenase increased and lactic dehydrogenase decreased in the acclimated group. No other metabolic changes were observed. 4. 4. The tissue changes found in this study and reported by others may be secondary to changes in dietary and physical activity patterns rather than the direct result of heat exposure.

EFFECTS OF CARBOHYDRATE SOURCE ON VOLUNTARY ACTIVITY AND MYOCARDIAL METABOLISM IN CHICKS

Abstract In an effort to study the effects of different carbohydrate sources on voluntary activity and on myocardial constituents and enzyme activities in chicks, restricted feeding was applied with equal amounts of carbohydrate in the form of glucose (GC), sucrose (SC) or fructose (FC) to induce voluntary activity measured by Wahmann activity wheels. The performance was measured as average daily wheel turns during 12 days on diet and was almost the same for the SC and FC groups but 14–18% higher in the GC group. Heart weights, and the myocardial contents of protein, RNA and DNA as well as the citrate synthase activity were similar with all three diets, but the activities of lactate dehydrogenase and cytochrome c oxidase were lower in the FC as compared to the SC and GC groups. The FC chicks had increased myocardial activity of beta-glucuronidase that was correlated to the increase in the heart per body weight ratio. Within each dietary group the protein content correlated to the content of RNA. This study shows that high levels of fructose and sucrose compared to glucose as energy source in chicks resulted in decreased capacity to perform exercise but this lower performance as not correlated to a decreased oxidative metabolic capacity of the myocardium.