Date of Award:


Document Type:


Degree Name:

Doctor of Philosophy (PhD)


Animal, Dairy, and Veterinary Sciences


G. Reed Holyoak


The role of ammonia in reproductive inefficiency in early lactation dairy cows was studied in a series of experiments designed to determine the concentrations of ammonia in normal bovine follicular fluid (bFF), to determine the effects of ammonia on the bovine embryo during specific stages of development, and to test the hypothesis that elevated plasma urea nitrogen concentration is associated with elevated ammonia and urea nitrogen concentrations in the reproductive fluids.

In the first study, ammonia concentration in different size follicles and the effect of ammonia during in vitro maturation on embryo development were determined. Ammonia concentration in the bFF was significantly different (P<0.001) between each follicle size (< 1 mm, 2-4 mm, 5-8 mm, and >10 mm) and ammonia concentration decreased as follicle size increased. There was no difference (P>0.05) in cleavage rates, morula development, and blastocyst development when oocytes were exposed to various concentrations of ammonia during in vitro maturation.

In the second study, the effects of addition of ammonia in the media during in vitro fertilization (IVF), culture (IVC), and throughout maturation (IVM), IVF, and IVC were evaluated. Addition of moderate concentrations of ammonia to IVF media resulted in a significant (P<0.05) increase in embryos that developed to blastocysts and to expanding and hatching blastocysts. Ammonia in the IVC media significantly (P<0.05) decreased the proportion of ova that developed to blastocysts. When exposed to ammonia throughout IVM, IVF, and IVC, ova developing to morulae was significantly (P<0.05) higher in media containing moderate concentrations of ammonia compared to control.

In the third study, plasma urea nitrogen (PUN) concentrations were related to follicular and uterine fluid ammonia and urea concentrations in early lactation dairy cows. Mean PUN concentrations were used to distribute the cows into two groups: 1) cows with PUN ≥ 20 mg/dl (HPUN), and 2) cows with PUN<20mg/dl (LPUN). Follicular fluid ammonia and follicular fluid urea were significantly (P<0.01) higher in HPUN cows compared to LPUN cows. Uterine fluid ammonia concentration was significantly (P=0.05) higher in HPUN cows than in LPUN cows during the luteal phase, but not during the estrus phase of the estrous cycle, but not on Day 0. Uterine fluid urea nitrogen concentrations were significantly (p<0.001) higher in HPUN cows than in LPUN cows during both the luteal and estrus phases.



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