A total of 218 yearling Hereford, Angus, Santa Gertrudis and Brahman bulls was evaluated for semen traits and testieular volume at average ages of 16 and 20 months in April and August, respectively, during 2 successive years. Brahman bulls reached puberty at a later age than bulls of the Santa Gertrudis, Hereford and Angus breeds. Santa Gertrudis bulls had the largest testes with the Brahman ha...

There is concern in the beef industry that selecting bulls for feed efficiency based on residual feed intake (RFI) may have a negative impact on bull reproductive performance and fertility. Here we investigated the impact of selection of bulls for low RFI on breeding soundness evaluation (BSE), reproductive performance, and fertility of bulls under natural service in multisire mating groups on ...

Small reference populations limit the accuracy of genomic prediction in numerically small breeds, such like Danish Jersey. The objective of this study was to investigate two approaches to improve genomic prediction by increasing size of reference population in Danish Jersey. The first approach was to include North American Jersey bulls in Danish Jersey reference population. The second was to ge...

Electroejaculation is a reliable method of obtaining a semen sample for a bull breeding soundness examination, but is sometimes regarded as painful. Substance P is a neuropeptide involved in the integration of pain, stress, and anxiety. We hypothesized that substance P is a measure of pain in bulls following electroejaculation. The specific objective was to compare vocalization and plasma conce...

Seventy-two Simmental bull calves were allotted randomly at birth to either a zeranol (Ralgro) implanted (I) treatment or a nonimplanted control (C) group. At birth, bulls assigned to the I treatment were implanted with 36 mg of zeranol and reimplanted at average intervals of 84 d until slaughter. Calves were weaned at 7.2 mo, preconditioned for 2 wk, and randomly assigned by treatment to slaug...

Story in Brief Seasonal differences and growth rates were studied on 60 Hereford and Angus bulls born in the spring and fall calving seasons at Oklahoma State University. Hip height, scrotal circumference and weight measurements were taken over the two IO-month experiments. Season of birth had no influence on scrotal circumference for either Hereford or Angus bulls. Season of birth in Angus bul...

Random samples of cryopreserved, milk-extended semen, collected from 20 Holstein bulls at about 14 mo of age (young) and again at about 4 yr of age (mature), were evaluated at thawing and during 3-h incubation to compare semen quality of young versus mature bulls. Evaluation by differential interference contrast microscopy showed greater proportions of cytoplasmic droplets in semen from young v...

The purpose of this study was to describe maturation-related changes in the sexual and aggressive behaviors of Hereford bulls. Two groups of 13 and 14 bulls, respectively, were tested for sexual and aggressive behaviors every 3 mo from 3 to 24 mo of age. At 3 and 6 mo of age, the bulls were exposed, as groups, to two estrous females, whereas at 9, 12, 15, 18, 21, and 24 mo these bulls were test...

Fertility Associated Antigen in Peripubertal Beef Bulls as an Indicator of Potential Fertility. (August 2005) Joanna Lynn Gallino, B.S., California State Polytechnic University Co-Chairs of Advisory Committee: Dr. L. R. Sprott Dr. D. W. Forrest Ejaculates from peripubertal Angus (n=106), Brahman (n=156) and Brangus (n=212) bulls were evaluated for the presence of a 31 kDa protein known as ferti...

Controlling spatial positioning of cattle through use of electronic collars could provide new ways to farm under extensive conditions. This study examined the potential for bulls to be controlled during mating using mild electric shocks delivered through radio-controlled collars. Eighteen Belmont Red bulls were fitted with collars containing the Global Positioning System and that were able to e...