No abstract

Pregnancy-associated glycoproteins (PAGs) are produced by mono- and binucleate trophoblast cells in the ruminant placenta. PAG appears in maternal blood and, from approximately 4 weeks after fertilization onward, may serve as a reliable means of diagnosing pregnancy. A range of factors are said to affect plasma PAG concentrations, such as number and sex of foetus, mass of calf and placenta, level of milk production and genetic constitution. In this study, PAG pregnancy profiles of a dual-purpose (Simmental) and two beef breeds (Uckermark and Aubrac) are compared with the profile of the specialized dairy breed Holstein-Friesian. Holstein-Friesian cows were sampled weekly; the levels of the other breeds were presented at 3-week intervals. The overall significant breed difference (p = 0.013) was founded on deviations during the initial 3 weeks of pregnancy and from 23 weeks onward. During the period critical for the detection of pregnancy, between four and 22 weeks, agreement between PAG levels of various breeds was close (p > 0.05). No significant effect of body mass of cow or calf (relative to mass of dam) was detected. These findings imply that the PAG pregnancy test may be executed uniformly irrespective of breed or type of cow, affirming the suitability of the test as a valuable asset for the cattle industry.

Completion of this doctoral dissertation was possible with the support of several people. I would like to express my sincere appreciation to all of them. I would like to express my deepest gratitude to my first supervisor Prof. Dr. Wolfgang Holtz for his guidance, caring and patience throughout my study time here in Goettingen at which he has been able to pass me some of his experience in the field of reproduction physiology and biotechnology. I owe much appreciation for my second supervisor Prof. Dr. Dr. Matthias Gauly for providing me the opportunity to work within and with his Group. Special thanks go also to Prof. Dr. Schlecht for her acceptance to be the third member of my PhD examination committee.Heartfelt thanks goes to Dr. Morten Friedrich for his support, encouragement and great assistance in the field experiments, hormone analysis and data analysis. I am very grateful to have the opportunity to work with him in this project. Special thanks also to Mrs. Elisabeth Stüwe for her car and technical assistance in the hormone laboratory I owe thanks to Mr. Knut Salzmann and his coworkers for their assistance in the experiments done in the experimental farm at Relliehausen, and mrs. Margret Roffeis at Gross-kreuz Many thanks to the animal caretakers at the institute for their help throughout the Boer Goats experiment.