Cow Herd Description
There are 323 mature cows and 78 replacement heifers in the SJBRC herd. The cow herd has been bred up from the System 1 cross using Red Angus bulls since 2001. Females are generally synchronized and bred using semen donated by Select Sires, followed by clean up bulls. Trials conducted in 2005-06 dictated the use of more clean-up bulls so we currently have 13 bulls.
Management practices have included feeding steers at CSU (01-03) to collect carcass data and selling all steers at weaning (04-05). Approximately 80 replacement heifers are introduced into the herd each year.
Synchronization Trials
We have utilized a combination of CIDRs and timed breeding in both heifers and cows.
Calving Study
A five year study was undertaken in 2001 to evaluate growth and reproductive traits as well as the economic viability of two different calving seasons. The traditional time of calving in Colorado occurs during the months of March and April. Interest has existed in recent years, as to the viability of calving cows and heifers at a later time period in the spring or early summer, in an effort to more closely match cow nutrient requirements with forage nutrient content.
History
The Center maintains approximately a 350 cow breeding herd
of which about 150 are purebred Hereford, Angus, Red Angus and
Brangus breeds. The remaining cattle are involved in a study
of composite crossbreeding.
Early research centered on the development of inbred lines
of Hereford cattle and subsequent line crossing among lines.
Selection for improved breeding values for economic traits was
practiced concurrently. The effects of inbreeding on reproduction
and growth traits was practiced concurrently. The effects of
inbreeding on reproduction and growth traits, along with the
effects of hybrid vigor upon crossing have been well documented.
Increased inbreeding has been shown to have detrimental effects
on reproductive traits and measures of early growth. Heterosis
estimates averaged 10% for weaning weight and ranged from 5 to
10% for postweaning growth traits. Response to selection studies
indicated that the development of inbred lines, with subsequent
line crossing, resulted in significant genetic progress over
time. Line cross calves averaged 4.62 lbs./year improvement over
a 25 year period.
The Center has pioneered work in the genetics of reproduction,
which has had a large impact on beef cattle performance programs
throughout the world. Scrotal circumference in yearling bulls,
as a measure of testicle size, had been shown to be a highly
heritable trait that is easily and accurately measured. It is
an excellent predictor of age at puberty but is independent of
bull libido or serving capacity. Complete breeding soundness
examinations have been taken on all yearling bulls at the Center
since the mid 1950s and scrotal circumference has been measured
since 1969.
In yearling heifers, age at puberty, reproductive tract score
and pelvic measures have been taken in recent years. Age at puberty
is fairly highly heritable and is lowly but favorably related
to subsequent measures of reproduction and productivity. Reproductive
tract score, obtained by rectal palpation, is a measure that
is useful in selecting replacement heifers for breeding. Pelvic
measures in both yearling bulls and heifers are highly heritable
and should respond to selection. It is expected that increased
pelvic area should result in less calving difficulty in two-year-old,
first calf heifers. Studies on calving ease indicate that the
overall measure is lowly heritable; however, component traits
such as birth weight and pelvic area are highly heritable and
emphasis is being placed on indicator traits of calving ease.
The heritabilities and the phenotypic, genetic and environmental
relationships among growth traits including birth weight, weaning
weight, yearling weight and annual cow weights through 10 years
of age have been obtained. These studies indicate that measures
of growth are moderately to highly heritable. Growth curves for
females from birth through maturity indicate large line differences
in rate of maturity. Studies are continuing to ascertain if these
line differences are primarily due to differences in levels of
mild production among the lines.
Individual feed consumption for bull calves has been obtained
for many years during the postweaning performance test. Several
different measures of feed efficiency have been evaluated and
have been shown to be moderately heritable. Improved efficiency
of feed utilization during the feeding period should enhance
the competitive nature of beef cattle with other meat producing
species.
Estimates of Expected Progeny Difference values (EPD), indicating
the genetic worth of individual animals, are being used to identify
animals that are superior for various measures of reproduction,
milk, growth and mature size for use in the selection program.
The most advanced models using Best Linear Unbiased Prediction
(BLUP) methodology are being used. Using these procedures, the
genetic improvement in these traits over the past 50 years will
be studied and compared to previous studies on the herd.
Several side studies have been conducted over the years. Cancer
eye in Hereford cattle, which usually occurs later in life, had
been shown to be moderately heritable and can be nearly eliminated
through selection. Eye, eyelid and pigmentation around the eye
studies show these traits to be highly heritable. Udder shape
and teat size and shape is also highly heritable. Hoof length
is highly heritable. All of these problem traits can be effectively
selected against and eliminated from the herd. High altitude
disease (Brisket Disease), which causes cattlemen at high altitudes
serious problems through cattle losses, has been thoroughly studied.
Pulmonary arterial pressure (PAP) measures have been shown to
be a very good indicator of susceptibility to brisket disease,
and differences in PAP values have been shown to be highly heritable.
Cattlemen at high altitudes can use bulls with low PAP values
to eliminate this problem from their herd. All bulls sold at
the Center are measured for PAP values.
In 1985, a project was designed and initiated at the Center
which sought to address several questions related to composite
cattle crossbreeding. The focal point of the project has been
to determine if crossing of phenotypically alike composite lines
which differ in breed make-up will work to reduce variation yet
produce high levels of heterosis.
Research at the Center has provided opportunities for graduate
student research projects. Over 40 M.S. theses and Ph.D. dissertations
have been written on data collected at the Center. Over 200 scientific
papers and popular articles have been published in April of each
year along with performance data on bulls offered for sale.
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