105 research outputs found
Estrus synchronization of cattle in Kansas
In 22 field trials involving 1,692 cattle, we evaluated Lutalyse as an estrus-synchronization agent for both natural mating and artificial insemination. Only 52.7% of the females in all 22 trials were cycling at the start of the breeding season. Both body condition and days postpartum at the start of the breeding season influenced the response to Lutalyse. First-service pregnancy rate in the 2 or 3 days of synchronization was 38.4% for all 453 females bred artificially in 12 trials in northwestern Kansas. The rate was 59%, however, if only females observed to be in heat were counted; but only 24.5% if only those in which no heat was observed were counted
Luteinizing hormone release and plasma metabolites in mature, ovariectomized beef cows fed various lipid diets
Feeding rumen-escape lipid or soybean oil
in a range supplement to beef cow resulted in
elevated blood cholesterol and enhanced
luteinizing hormone (LH) release compared to
a control (milo and soybean meal) supplement.
Cholesterol was elevated (P<.01) within 14 d
of lipid feeding. The amplitude of each LH
pulse and maximal pulse height were greater
(P<.05) when cows were fed high-lipid diets.
The positive influence of high-lipid diets on
reproductive function may be explained in part
by enhanced LH release
Effect of various levels of Ralgro on reproductive performance of yearling heifers
Implanting heifers at weaning time with 12, 24, or 36 mg of Ralgro did not affect reproductive performance of the heifers when bred as yearlings
Effect of heifer source on reproductive performance, culling, marketing and profitability for a commercial heifer development program
A commercial heifer development operation
purchased 483 weanling Angus × Hereford
heifers from 11 sources. Heifers were fed a
common silage-based diet through an initial
developmental period and retained or culled
based on average daily gain, pelvic area, and
disposition . The percentage of heifers culled
from each source ranged from 18.1% to 94.7%
and were either sold directly through a local sale
barn or sent to a feedlot with retained
ownership . Estrus was synchronized, and
heifers were artificially inseminated (AI) for 30
days followed by 15 days of natural mating.
First service conception rates for each source
ranged from 0% to 92.3%, whereas overall
pregnancy rates for the 45-day breeding season
ranged from 81.3% to 100%. When expressed
as a percentage of the original heifers purchased
from each source, overall pregnancy rates
ranged from 5.3% to 80%. Heifers that lost
their fetuses were sold for a net loss of 160, 89 per head,
respectively. With accurate records, stringent
culling practices, and evaluation of cost and
performance, producers can optimize profit
potential of replacement heifers. Early culling
and pregnancy diagnosis also will decrease costs
while increasing opportunities to minimize the
financial risks
A three-year economic evaluation of a commercial heifer development program
In 1994, 1995, and 1996, a commercial heifer development operation purchased a total of 1542 potential replacement heifers. Heifers were purchased in the fall proceeding the spring breeding season and fed a silage-based diet during the developmental period. Before the breeding season began, heifers that failed to meet minimum requirements for pelvic area, average daily gain, body weight, disposition, or structural soundness were culled. During the first year, 42% of 483 heifers were culled, 17% of 468 heifers were culled in the second year, and 14% of 591 heifers in the third year. Estrus was synchronized and heifers were inseminated artificially (AI) for 30 days followed by 30 days of natural mating by cleanup bulls. First-service AI conception rates averaged 68% and overall pregnancy rates (AI + natural mating) averaged 95.1% over the 3-year period. Heifers culled prior to the breeding season realized a net profit of 86, and heifers that aborted lost 163 for first-service AI, 83 for bull bred
Influence of source and amount of dietary protein on the performance and reproductive function of first-calf heifers
Increasing the amount of dietary protein
above the NRC requirement increased weight
gain of nursing first-calf heifers. Feeding a
protein source with higher ruminal escape
potential and increasing protein in the diet both
improved calf gains. No significant changes
in reproductive function or milk production
were observed from either source or amount
of dietary protein
Effect of monensin on weight gain, growth traits, and semen characteristics in yearling beef bulls
Feeding the ionophore monensin to yearling beef bulls improved (P\u3c.05) weight gain by 4.2%. Final hip height was similar between treatments, but bulls fed monensin had almost 1 cm greater (P\u3c.01) scrotal circumference and more than 10 cm 2 larger (P\u3c.01) pelvic area. Semen characteristics generally were unaffected by treatment. However, bulls fed monensin had less (P\u3c.01) semen motility than controls. Approximately 30 sperm morphology traits were evaluated; values were similar between treatments except for those traits listed. Collection date tended to influence (P\u3c.15) volume, concentration, motility, and postfreeze characteristics
A novel estrus-synchronization program for anestrous and cycling, suckled, beef cows
We used four herds at three Kansas ranches
to evaluate the potential of two new estrus
synchronization strategies to increase estrus
expression and fertility of 911 crossbred suckled
beef cows. The treatments included: 1) 100 μg
of GnRH and a 6-mg norgestomet ear implant
on day -7 and 25 mg of PG F2" and implant
removal on day 0 (GnRH+NORG+PG F2"); 2)
100 μg of GnRH on day - 7 and 25 mg of PGF 2"
on day 0 (GnRH+PG F2"); and 3 ) (control) 25-
mg injections of PG F2" on days -14 and 0;
(2×PGF2" control) . The GnRH+NORG+ PGF 2"
and GnRH+PGF treatments increased (P<.01) 2"
the overall percentages of cows detected in
estrus by 49% and 27% and pregnancy rates by
46% and 37%, respectively, over the control
group, without altering conception rate. Both
treatments increase d the estrus, conception, and
pregnancy rates of noncycling cows, compared
to controls
Ralgro-implanted bulls: Performance, carcass characteristics, longissimus palatability and carcass electrical stimulation
Twenty of 40 Angus bulls were implanted
(I) five times with 36 mg of Ralgro| at average
intervals of 106 d, beginning near birth. All
bulls and their dams were on bluestem pasture
initially and, at an average age of 320 d bulls
were fed a concentrate diet until they were
slaughtered, weighing either 454 or 499 kg. One
side of each carcass was electrically stimulated.
Average daily gain and feed efficiency of I
bulls improved 6.5 to 10.4% and 7.9 to 8.1%,
respectively, depending upon the end point
comparison with nonimplanted (NI) bulls. Implanted
bulls attained their slaughter weights 42
d sooner than did NI bulls. Implantation
decreased (P<.05) penis weight and length,
testicle weight, volume and density, but did not
affect (P>.05) seminal vesicle and pituitary
weights. Carcasses from I bulls had more
(P<.05) skeletal ossification and were fatter
than carcasses from NI bulls. Marbling scores,
quality grades and longissimus cooking losses
and juiciness scores were not affected (P>.05)
by implantation. Taste panel flavor intensity
and detectable connective tissue scores were
higher (P<.05) for steaks from I bulls than
from NI bulls. Longissimus steak tenderness
evaluations were higher (P<.05) for both I
slaughter groups than for the NI light-weight group and were higher (P<.05) for the I lightweight
group than for the NI heavy-weight
group. Longissimus tenderness tended (P = .11)
to be higher for steaks from the I heavy-weight
group than those from the NI heavy-weight
group. Electrical stimulation produced (P<.05)
a softer, coarser textured lean, but it did not
affect lean color, marbling or quality grade.
Steaks from electrically stimulated sides tended
to have higher (P = .09) myofibrillar tenderness
scores and lower (P = .06) flavor scores than
steaks from nonstimulated sides
Effects of dietary energy on reproductive function and production in suckled beef cows
Twenty-eight Hereford x Angus cows were utilized to determine the effects of dietary energy level before and after calving on reproductive function and production in suckled beef cows. Low levels of dietary energy before calving resulted in losses of body composition prior to calving, reduced calf birth weight, lengthened intervals from calving to ovulation, and decreased milk production and calf weight at 70 d of age (P\u3c.05). Low levels of dietary energy after calving decreased measures of body composition after calving, reduced the percentage of cows that ovulated following calving, and decreased cow milk production and calf weight at 70 d of age (P\u3c .05). We conclude that dietary energy before and after calving impacts the reproductive function and production of suckled beef cows
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