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Articles by V. L. Christensen
Total Records ( 4 ) for V. L. Christensen
  V. L. Christensen , D. T. Ort , S. Suvarna , W. J. Croom , Jr. and J. L. Grimes
  The hypothesis was proposed that eggshell conductance constants (k) alter embryonic intestinal development and affect growth post hatching. Egg weight (EW), eggshell conductance (G) and length of the incubation period (IP), the three components of the conductance constant were changed to determine their effect on intestinal physiology. Eggs were selected based on EW and G properties. Half of the selected eggs were incubated using a single stage temperature profile to shorten IP in each of two experiments. EW, G and IP interacted in the first experiment to affect intestinal growth and metabolism. In Experiment 2, k reduced intestinal weight in embryos as well as poults. EW and IP affected the size and maturity of intestinal tissue at the time of hatching. Differences in EW, G and IP observed at hatching were shown to affect the growth of poults for the first week following hatching. Thus, k may act to reduce growth in poults by affecting intestinal maturation. It is suggested that large eggs with low permeability may be at risk for weak poults. This may be especially true when they are exposed to shorter IP.
  V. L. Christensen , D. T. Ort and J. L. Grimes
  The hypothesis was proposed that changes in functional qualities of eggs, or the eggshell conductance constant (k), may affect cardiac weight and physiology and predispose poults to a weakened condition. Improved knowledge of this relationship may allow selection of k to optimize hatchling cardiac health. Egg weights (EW), eggshell conductance (G) and lengths of the incubation period (IP) (the three components of k) were manipulated to determine their effect on the heart. Eggs were selected based on EW and G in Experiment 1. In Experiment 2, eggs from the same strain were obtained from flocks of different ages so they differed in EW. Half of the eggs were exposed to increased temperature treatments resulting in shorter incubation periods (IP). Interactions of EW and G affected heart weight and metabolism in Experiment 1. In Experiment 2, imposing short IP on different EW reduced cardiac weights as well as elevated glycogen to lactate ratios in the heart. Post-hatching growth was also depressed by k due to interactions of EW and IP. Thus, k affects cardiac weight and function and may contribute to weak poults.
  V. L. Christensen , J.L. Grimes , R.D. Rowland and D.T. Ort
  Embryo and hatchling survival diminish as turkey breeder hens age. Recent data indicated that a chelated calcium proteinate (CCP) additive given to turkey breeder hens improved embryo survival as hens aged but did not affect shell thickness. We hypothesized that the mechanism by which this occurred may be by improved functional shell quality and its consequent effect on cardiac physiology. To test the hypothesis, CCP was supplemented to the diet of Large White turkey breeder hens for a 25 week egg production period and compared with controls without supplementation. Eggshell conductance, conductance constants, poult growth and cardiac physiology were measured at weeks 10, 18 and 25 of production. Because elevated temperatures increase heart rates and reduce heart weight and survival, half of the eggs was incubated at 37.9°C whereas the remaining eggs were incubated at 37.5°C. Embryos and poults from the CCP group exhibited increased heart weights and improved cardiac health. The hatching poults from CCP-fed hens also grew faster for the first 3 d of life. We conclude that CCP improves eggshell conductance, and the subsequent eggshell conductance constant (k) of eggs from turkey breeder hens. The change in k improved embryo cardiac health and poult BW after hatching.
  V. L. Christensen , M. J. Wineland , I. Yildirum , D. T. Ort and K. M. Mann
  The plateau stage in oxygen consumption of turkey embryos occurs at 25 and 26 days of incubation and most embryonic deaths occur at that time (Rahn, 1981 and Christensen et al., 2003). At the plateau stage, vital gas diffusion through the shell is insufficient for oxygen to drive metabolism or for expelling the metabolic by products of water vapor and carbon dioxide. The objective of the experiments reported here was to determine the effect of environmental temperature and oxygen concentration during hypoxia and hypercapnia of the plateau stage on turkey embryo cardiac health. Three experiments were conducted. In Experiment 1, turkey embryos at the plateau stage were exposed to 36, 37, 38 or 39 C. In Experiment 2, embryos at the plateau stage were exposed to 17, 19, 21 or 23% oxygen concentrations, and in Experiment 3, the highest and lowest levels of temperature and oxygen treatments were combined to determine interaction effects on cardiac physiology. Temperatures greater than 37 C depressed heart weight but not BW and decreased cardiac tissue energy metabolism. Oxygen concentrations greater than 21% increased BW and improved the cardiac glycogen to lactate ratio with no effect on heart weight. When examined together, the two factors interacted to affect cardiac energy metabolism. It was concluded that the physiologic action of oxygen during the plateau stage favored BW whereas temperature affected cardiac tissue but not BW. Temperature and oxygen interact during the plateau to affect cardiac muscle energy metabolism.
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