Calcium tolerance of growing chickens: Effect of ratio of dietary calcium to available phosphorus

Excess calcium intake has been shown to reduce growth and feed efficiency and to increase bone ash and bone strength in growing chickens. Source and level of dietary phosphorus have been shown to affect calcium tolerance. The effects of high calcium can be largely explained by its effects on intestinal pH. The proposed mechanism involves excess calcium reducing the soluble fraction of minerals and the proportion of minerals in small complexes. In consequence, their availability for absorption is probably also reduced. The growth depression of chickens fed on diets high in calcium may be partly caused by the decreased availability of other minerals needed for growth. Calcium tolerance of growing chickens may be increased by ensuring that there are higher than normal levels of the other required minerals in the diet

Effects of dietary calcium and available phosphorus concentration on digesta PH and on the availability of calcium, iron, magnesium and zinc from the intestinal contents of meat chickens

1. The effects of high calcium intakes on the pH and availability of calcium, iron, magnesium and zinc in the gastrointestinal tract (GIT) contents of meat chickens were studied in two experiments. 2. A high dietary concentration of calcium (25–3 vs 10–7 g/kg) increased the pH of crop and ileum contents, but did not influence the pH of the contents of other segments of the GIT. 3. The solubilities of minerals in GIT contents were reduced and the size of dissolved mineral complexes were increased as the digesta moved from the duodenum and jejunum to the ileum. 4. After feeding diets with calcium and available phosphorus concentrations (15–3 and 4–3 g vs 21-8 and 4–3 g vs 22–6 and 8–3 g/kg), centrifugation of GIT contents showed that most (70-92%) of the calcium, iron, magnesium and zinc was in an insoluble form. High calcium diets reduced the proportion of soluble zinc associated with small complexes, and high calcium and available phosphorus diets reduced the proportions of soluble magnesium and zinc associated with small complexes. 5. These findings explain the mechanism of the reduced availability of zinc and magnesium in high calcium and high available phosphorus diets

Effects of electrical field on hatchability performance of eggs from a layer-type breeder

Eggs from a layer-type breeder flock (Baladi, King Saud University) between 50 and 63 weeks of age were used in three trials to study the effects of electrical field (EF) during incubation on albumen and yolk heights, incubation temperature, egg weight loss and hatchability traits. The effects of egg size and eggshell characteristics on hatchability traits of eggs incubated under EF were investigated. 2. Eggs were weighed and graded into three weight classes (small, medium, and large). The physical dimensions, eggshell characteristics, and conductance of eggs were examined. The incubator was divided into two compartments for the control and EF treatments. Two aluminium plates were fitted on the inside walls of the EF compartment, face to face, and connected to a step up electric transformer. Eggs were exposed constantly to the EF during the first 18 d of incubation at the level of 30 kV/m, 60 Hz. 3. Egg size influenced the physical dimensions and eggshell characteristics of eggs. Large eggs had higher egg weight, egg surface area, egg volume, eggshell conductance, and eggshell weight and lower yolk weight percentage than medium or small size eggs. Small eggs had lower egg length and higher egg density than large or medium size eggs. Large eggs had higher eggshell thickness than small size eggs. 4. EF incubation of eggs raised incubation temperature by 0.06 C, and increased the percentage of egg weight loss, hatchability, and weight of hatching chicks and reduced the early embryo deaths, and length of incubation by approximately 9.8, 19.6, 1.7, 62.1 and 2.1%, respectively. 5. There was no significant difference between the two incubation treatments in the heights of albumen and yolk of incubated eggs, percentages of late embryo deaths, and pips with live and dead embryos. Hatchability traits were not significantly influenced by egg size. 6. It was concluded that EF incubation of eggs increased hatchability, chick-hatching weight, and reduced the length of incubation of Baladi eggs. Differences in the physical dimensions and eggshell characteristics of eggs did not influence hatchability traits of eggs under EF incubation

Effect of Pigment Intensity and Region of Eggshell on the Spectral Transmission of Light That Passes the Eggshell of Chickens

La investigación doctoral busca analizar el circuito de rock platense partiendo de la premisa que sostiene que el mismo se estructura y organiza a partir de disputas y luchas que se dan entre los actores participantes -o posibles participantes- por las características, sentidos y límites del mismo. Así, nos interesa rastrear procesos de distinción, de tradicionalización, de alterización y otros que se tornen relevantes en la búsqueda por identificar los principios que operan en estas disputas entre los distintos actores. No pretendemos brindar una definición a priori de la expresión "rock platense" sino que en cambio ocupará el lugar de una categoría de clasificación relevante y en disputa para los actores que forman parte del circuito.Universidad Nacional de La Plat