Thesis (M.S.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains ix, 39 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 32-37).

Thesis (M. Sc. (Agricultural Economics))--University of Pretoria, 2009. / Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains vi, 83 p. Includes abstract. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains xi, 77 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Thesis (MMedVet (Altil))--University of Pretoria, 2001. / Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1964. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 63-69.

Thesis (Ph.D.)(Animal Science)--University of Pretoria, 2005. / Summaries in Afrikaans and English. Includes bibliographical references. Available on the Internet via the World Wide Web

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains v, 46 p. : col. ill. Includes abstract. Includes bibliographical references.

The objective of this study was to investigate the effects of cage density and excess vitamin D₃ on the incidence and severity of leg abnormalities in broiler chickens. In addition, sequential morphometric and radiographic characteristics of leg bone development were described in normal and abnormal broilers in an attempt to develop a pattern recognition for leg abnormalities in poultry. Twisted leg, characterized by a progressive medial (varus) or lateral (valgus) deviation of the distal tibiae was the predominant leg abnormality observed. Lateral deviations were more common than medial deviations (92% and 8%, repectively) and it occurred equally on the right and left leg. The incidence of twisted leg was considerably higher in cages than on litter (21% vs 4%, respectively). High density and excess dietary vitamin D₃ resulted in a significant increase in the incidence of twisted leg. Differences in incidence could not be explained through differences in body weight or feed consumption. However, broilers fed the excess vitamin D₃ consumed more but gained less body weight, suggesting a metabolic stress may have been involved. High density appeared to increase the severity of the disorders, while excess vitamin D₃ had no effect on severity. Morphometric and radiographic comparisons of tibiae from normal broilers and those with twisted leg suggested that the development of twisted leg may be related to a structural abnormality in the distal tibiae; namely shallow distal condyle grooves. Changes in tibiae morphology associated with the progression of the disorder appeared as functional adaptations to the deformation rather than the primary cause of the bone deviations themselves. Sequential radiography of tibae from clinically normal broilers revealed a high incidence of tibial dyschondro-plasia in the proximal metaphyses at 3, 4 and 5 weeks (60%, 20% and 20%, respectively). It was concluded that tibial dyschondroplasia may be more common than it is realized. / Land and Food Systems, Faculty of / Graduate

The effects of various aging, thawing and storage methods on the tenderness of frozen broiler Pectoralis major muscle were studied. Initial experiments were carried out to establish standard methods of freezing, cooking and tenderness evaluation to be used in subsequent experiments. The effects of varying the aging, thawing and storage techniques were then investigated using the established methods. Whole carcasses were frozen in a liquid nitrogen blast freezer after cooling in ice water for periods of 1 to 10 hours after slaughter, stored for 1 week at -31°C and thawed for varying lengths of time. The P. major muscles were removed and cooked in boiling water between metal plates. Tenderness evaluations were carried out using the Allo-Kramer shear press. The length of thawing time was shown to greatly influence the degree of toughness of the cooked muscles. When a thawing period of 4 hours in water at 25°C was used, a decrease in toughness took place in carcasses frozen between 1 and 2 hours post-mortem. This was followed by an increase to maximum toughness in birds frozen between 4 and 8 hours post-mortem. Maximum tenderness occurred in birds frozen 10 hours after death. Thawing birds in air at 4°C for 24 and 4 8 hours decreased the level of toughness attained after freezing 4 to 8 hours post-mortem. It did not significantly alter the degree of tenderness reached after 10 hours. Similarly, the decrease in toughness in birds frozen between 1 and 2 hours post-mortem, remained significant. Longer storage (3 months) at -23°C followed by rapid thawing eliminated both the decline in toughness of carcasses frozen between 1 and 2 hours post-mortem and the maximum toughness level attained by carcasses frozen 4 to 8 hours after death. An attempt was made to explain the decrease in toughness in carcasses frozen between 1 and 2 hours postmortem in terms of the aging temperature and medium used prior to freezing. No difference in the pattern was observed, however, when other pre-freezing aging techniques were used. Increases in the sarcomere lengths of muscle frozen at 2 hours post-mortem were observed, corresponding to the increase in tenderness occurring in carcasses frozen at this time. Isometric tension measurements, however, did not correlate well with these observations. Taste panel members were unable to discern differences in the tenderness of muscle frozen between 1 and 3 hours post-mortem although excellent correlations were obtained between Allo-Kramer shear press values and sarcomere length measurements. The results of these experiments therefore show that the ultimate tenderness of broiler muscle can be greatly influenced by the interaction of pre-freezing aging time, length of storage and thawing techniques used prior to cooking. / Land and Food Systems, Faculty of / Graduate