Egg shell quality was assessed in terms of breaking strength, elasticity, and energy absorbed by the shell up to failure. Two devices were used to determine these characteristics. Simple correlation and simple linear regression analyses showed that elasticity as determined by either device gave equally reliable estimates of breaking strength of the egg shell (r = -.68). A study of the three calcium levels supplemented to a basal ration on shell quality of eggs from two reciprocal crosses of birds showed that each measurement (breaking strength, elasticity, and energy to failure) used to assess shell quality produced different conclusions. In the early part of the experiment, elasticity was significantly lower for the 2% than for the 4% or 6% calcium diets in both crosses of birds. However, there was no significant difference in the effect of 4% and 6% calcium diets on elasticity. On the basis of the energy absorbed to failure, there was no significant effect of dietary calcium in Cross I birds. In Cross 2 birds, 6% calcium produced significantly superior results on energy absorbed as compared to the 2% and 4% calcium diets. For Cross I birds, breaking strength of eggs from the 6% and 4% dietary calcium treatments were significantly higher than those from the 7% calcium treatment. For Cross 2 birds, 4% dietary calcium produced stronger shells than 2%; shell strength from the 6% calcium treatment was inter, mediate to and net significantly different than that of the 2% or 4% calcium diets. No significant difference in the effect of the three calcium diets on shell quality as assessed by any one of the three measurements was observed in the latter part of the experiment. No consistent effect of the age of birds on egg shell strength was apparent. Significant variation in shell strength was found among groups of birds within the same cross on the same ration. Eggs stored under selected environmental conditions for different durations showed that moisture affected egg shell elasticity and the effect Increased In magnitude with time of storage when the egg was not only Immersed in water but also filled with water after removal of the albumen and yolk. Neither oiling nor storage temperature affected egg shell elasticity. There was no consistent effect of storage duration on egg shell elasticity except for the two treatments in which eggs with or without the contents removed were stored under water. It was found that the difference between the two duplicate elasticity readings measured at the equator of the same egg did not change significantly with either storage condition or storage duration. / Land and Food Systems, Faculty of / Graduate

An in vivo technique was developed for the purpose of determining the rate of absorption of bile salts by the mesenteric small intestine of the chicken. Using this technique, it was found that the absorptive capacity of the intestine for sodium taurocholate and sodium glycocholate increases distally. The possibility was investigated that the amount of bile salt reabsorbed from the intestine determines the level of circulating sterols in the chicken. Intestinal absorption of sodium taurocholate was accordingly determined in birds selected to show a wide range in levels of circulating sterols. Absorption of the bile salt was tested with concentrations of taurocholate equivalent to 0.15 and 0.75% cholic acid, using open segments of intestine. Data obtained from 20 birds showed that the level of circulating sterols and the rate of bile salt absorption were not significantly correlated. The lack of a significant correlation was considered to be probably due in part to variation in the effect of diet on the availability of bile salts for reabsorption. The rate of bile acid excretion and the concentration of circulating sterols were therefore determined in birds fed diets supplemented with triglycerides, of varying degree of unsaturation, soyalecithin and beta sitosterol. It was found that a diet supplemented with 15% coconut oil induced an elevation in the level of plasma sterols when substituted for a low-fat diet but that diets supplemented with corn oil and herring oil, induced little or no change in this level. The change to a fat-enriched diet was associated with a decrease in the fecal output of bile acids. The decrease was greater when coconut oil rather than corn oil or herring oil was fed, indicating that the plasma sterol lowering property of unsaturated fats is due at least in part to their enhancing effect on bile acid excretion. Diets to which 2.5% soyalecithin and 0.5% beta sitosterol were added, effected a slight reduction in the level of plasma sterols. The addition of soyalecithin to the diet resulted in a significant increase (P < 0.01) in the growth rate of the birds studied. The amount of bile acids excreted was increased significantly (P < 0.01) by the addition of soyalecithin to the diet. The addition of beta sitosterol to the diet resulted also in an increase in bile acid excretion. The increase approached significance at the 5% level of significance (F ratio calculated = 7.53, significant F ratio = 7.71). The increase in bile acid excretion resulting from the administration of the soyalecithin supplemented diet was considered to be the net result of two opposing effects. One effect was an increase in the reabsorption of bile acids. It was evidenced by a further increase in the plasma sterol level of the lithocholic acid-fed chick in response to dietary soyalecithin. The other effect was reasoned to be an increase in the biliary excretion of bile acids and/or bacterial alteration of bile acids in the digestive tract. / Land and Food Systems, Faculty of / Graduate

Experiments were conducted to study the effect of dietary lysine level on thyroid activity and body temperature in White Leghorn cockerel chicks. Thyroid activity was measured in birds 4-to-5 weeks of age and body temperature was measured in birds 4-to-8 weeks of age. Three diets based on corn and sesame meal and containing 20% protein and 0.64% (basal diet), 1% (control diet) or 2% of L-lysine respectively were used. These diets contained deficient, optimal and excessive amounts of L-lysine respectively. Thyroidal experiments were conducted at different times of the year. Thyroid activity was assessed by measuring the level of I¹³¹ in the plasma and thyroid or thyroid only at various times after an intravenous injection of 0.55 μc of I¹³¹ 100 gm of body weight. In August-September, thyroidal response to diet was investigated in birds fed the test diets for either 1 or 17 days prior to administration of I¹³¹. When the test diets were fed for 1 day prior to the injection of I¹³¹, data for per cent I¹³¹ per unit of thyroid weight and for the ratio of thyroidal to plasma I¹³¹ (T/P ratio) indicated that either a deficiency or an excess of dietary lysine enhanced thyroid activity. Feeding the test diets for 17 days appeared to attenuate the responses observed in the 1-day trial. In January, thyroidal response to diet was assessed in birds fed test diets either 1 day before or 3 days after the injection of I¹³¹ . Only the diets containing 0.64% and 1% of L-lysine were fed. When appropriate, 0.2% thiouracil was added to block thyroidal uptake of recycled I¹³¹. When all four diets were fed, I¹³¹ level per unit of thyroid weight and T/P ratio calculated from data obtained 5 minutes, 1 and 3 hours after I¹³¹ administration indicated that dietary lysine deficiency under the circumstances of the experiments reduced thyroidal uptake of the isotope. When I¹³¹ was injected 3 days prior to imposition of the test diets, the values for I¹³¹ per unit of thyroid weight after the feeding trials started indicated that the lysine deficiency reduced the rate of release of thyroidal I¹³¹. In a further experiment, levels of thyroidal I¹³¹ measured 5, 10, 24, 48, and 72 hours after I¹³¹ injection verified that the lysine deficiency reduced thyroid activity. In March, the effect of ambient temperature on thyroidal response to dietary lysine level was investigated. Thyroidal I¹³¹ was measured 6 hours after I¹³¹ administration to birds which had been fed the deficient diet for 1 day. Dietary lysine level and environmental temperature had an interacting effect on total thyroidal I¹³¹ and per cent I¹³¹ per 100 gm of body weight. Under the conditions of the experiment, lysine deficiency enhanced I¹³¹ uptake in a warm environment but has no effect or depressed activity in a cold environment. Temperatures were measured with thermistor probes inserted into the cloaca, the brain and the pectoral is muscle. When fed for either 18-to-30 hours or for 2 weeks, the lysine deficient diet increased muscle temperature. The diet had no apparent effect on brain or cloacal temperature but detection of a response may have been obviated by the technique used to measure temperatures in these two locations. Feeding sub-optimal or excessive levels of dietary lysine for only 1 day caused a change in thyroid activity. In a warm environment, both sub-optimal and excessive levels of lysine enhanced thyroid activity. Environmental temperature appeared to modify the thyroidal response to dietary lysine level. In a warm environment, a deficiency of lysine increased muscle temperature. / Land and Food Systems, Faculty of / Graduate

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During the early existence of the science of genetics, the area of single gene effects was the more active area of interest. Throughout the initial development of this science, studies of qualitative traits provided the basis on which the later principles were founded. [...]

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