Masters Theses

Orcid ID

Date of Award


Degree Type


Degree Name

Master of Science


Animal Science

Major Professor

Jason Smith

Committee Members

Justin Rhinehart, Lew Strickland


Nutritional management and semen collection method are thought to influence semen quality parameters evaluated during a breeding soundness examination. Therefore, the objective of this experiment was to evaluate the effects of two feeding strategies on growth performance and semen quality of developing bulls. A secondary objective was to quantify the effects of two semen collection methods on semen quality. Angus bulls (n = 48; 332 ± 47 d of age) were stratified into one of sixteen drylot pens before random assignment to one of two iso-caloric diets: a total mixed ration (TMR; n = 8 pens) or a component-based ration (COMP; n = 8 pens). Bulls were assigned to either electroejaculation (EE; n = 24) or trans-rectal massage (RM; n = 24) and each collection method occurred twice throughout an 84-d feeding period. Rumen pH was continuously monitored via rumen boluses and dry matter intake (DMI) was measured daily. Backfat thickness and hoof conformation were measured on d 0 and 84, with body weight measured and semen collected at 21-d intervals. Semen was assessed for progressive motility, total sperm per ejaculate, and sperm cell morphology. Bulls fed the COMP ration had a greater DMI (P < 0.01) and ADG (P < 0.01), but similar feed efficiency (P = 0.19) when compared to TMR-fed bulls. Bulls fed COMP had a lower mean rumen pH (P < 0.01). Additionally, COMP-fed bulls had greater backfat thickness (P < 0.01) but similar hoof conformation scores (P ≥ 0.55) when compared to TMR-fed bulls on d 84. Bulls fed the COMP had greater semen volume (P < 0.05) but feeding management did not affect progressive motility (P = 0.42), total sperm per ejaculate (P = 0.86), or percent morphologically-normal sperm (P = 0.59). However, bulls collected via RM had greater total sperm per ejaculate (P < 0.05), and semen volume (P < 0.01), but lower percent morphologically-normal sperm (P < 0.05) and progressive motility (P < 0.01). Neither diet nor semen collection method affected BSE passage rate (P ≥ 0.34), suggesting minimal influence on BSE outcomes in developing bulls.

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