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The ontogenetic development of intestinal digestive functions for avian species other than the domesticated chicken are not well documented. Therefore, this study was conducted to resolve the developmental patterns of some intestinal digestive functions in White Pekin ducks. The ducks were killed and their intestines harvested when they were 1,3, 5 and 7 wk old. Several small intestinal tissue characteristics, sucrase and alkaline phosphatase (ALP) activities of homogenates from the small intestine mucosa were measured, and the small intestinal L-threonine uptake capacities were estimated with brush border membrane vesicles prepared from the corresponding age groups. Between 1 wk (0.37 +/- 0.04 kg) and 7 wk (3.79 +/- 0.06), posthatch ducks exhibited relative body growth rates of 352, 77 and 28% from 1 to 3, 3 to 5 and 5 to 7 wk, respectively. Allometric changes in small intestine weight indicated that the small intestine grew in direct proportion to the duck's metabolic body weight. Total homogenate sucrase activity per unit body weight did not differ (P > 0.05) among the age groups studied. Total homogenate ALP activity per body weight was lower at 3 wk than at 1 wk (P < 0.05) but did not differ (P > 0.05) among 3, 5 and 7 wk-old ducks. The development pattern of L-threonine uptake capacities normalized to body weights paralleled the course of relative body growth rates.

Growth performance and utilization of nutrients and energy in three high-oil corn varieties (5.4 to 9.7% ether extract) and regular corn (4.2% ether extract) were compared in three experiments using growing pigs. Twenty-four 25-kg crossbred barrows were used in Exp. 1 to evaluate nutrient and energy digestibility in the three high-oil corn varieties and regular corn. Four diets were formulated to contain 97% of one of four varieties of corn (Control, TC1, TC2, and X122 varieties) and 3% minerals and vitamins. Digestibilities of nitrogen and ether extract were similar (P > .05) for regular corn and all three varieties of high-oil corn. The digestible energy concentrations (kcal/g; as-fed basis) for control, TC1, TC2, and X122 corn varieties were 3.29, 3.57, 3.4, and 3.41, respectively, with control lower (P < .05) than TC2 or X122 and TC1 higher (P < .05) than TC2 or X122. Metabolizable energy concentrations averaged 98.4% of digestible energy concentrations. In Exp. 2, four diets formulated to contain 79% of one of the four corn varieties, 18.25% 48% CP soybean meal, 2.45% vitamins and minerals, and .3% lysine[center dot]HCl were fed to 24 crossbred barrows (six pigs per diet) in a nutrient and energy balance study similar to the Exp. 1. Results were similar to those obtained in Exp. 1. The same four diets that were used in Exp. 2 were fed to 40 (10/diet) 20-kg crossbred pigs (20 barrows and 20 gilts) in a 28-d growth performance study (Exp. 3). Gain:feed ratios were .39, .43, .42, and .42 and growth rates (kg/d) were .68, .74, .70, and .72, for diets containing control, TC1, TC2, and X122 corn varieties, respectively. These translate to 8 to 10% improvement in feed efficiency and a numerical improvement in weight gain (3 to 9%) when high-oil corn was fed as compared with control corn. The results of nitrogen, ether extract, and energy balance and feeding experiments with growing pigs indicate efficient utilization of nutrients in diets containing high-oil corn. Key Words: High-Oil Corn, Energy, Nitrogen, Growth Performance, Pigs

The metabolic effects of isoproterenol on ractopamine-fed pigs was studied by measuring fat tissue and metabolites after intravenous administration of the drug. This resulted to enhanced production of metabolites. Blood glucose levels increased secondary to decreased tissue uptake and glycogenolysis in the muscle. Consequently, the plasma level of lactate and nonesterified fatty acids were also elevated due to lipolysis although lipogenesis in adipose tissues is decreased. The physical effects are seen as a diminished fat cell mass, increased muscle mass and the metabolic shift to the utilization of fatty acids for energy.

The effect of ractopamine on protein synthesis in muscle was evaluated in barrows given a diet containing 130 or 170 grams of protein per kilogram body weight. Results indicated that ractopamine enhanced synthesis of myofibrilar protein. Protein synthesis and breakdown in biceps femoris were likewise stimulated by ractopamine. Consequently, there was an increase in the protein composition of the longissimus dorsi and the biceps femoris.

The advent of concentrated, large animal production units presents a monumental challenge for the effective management of nutrients in animal manure. This symposium was organized to address the issue of the environmental impact of animal production and to offer suggestions on nutrient management procedures for reducing the environmental impact. There were four presentations on environmental concerns of animal manure that covered the topics of using the severe Dutch legislation that limits the amounts of nitrogen and phosphate in the manure allowed for application on cropland, potential for reducing odorous compounds in swine manure, alternatives to reduce the environmental impact of large swine production units, and, finally, perspectives on nutrient management procedures from a swine integrator's viewpoint. This introduction to the symposium highlights the major areas discussed within each of the four presentations. Key Words: Pigs, Environment, Production, Nutrient Balance