Beef Research News
Brought to you by Kansas State University
College of Veterinary Medicine - Farm Animal Section
May 2008
Contents:
Timing of AI following CO-Synch and CIDR Protocol
Transportation and biomarkers of stress
Pre-shipping management effects on stress and performance
Timing of AI following CO-Synch and CIDR Protocol
The experiment was designed to compare pregnancy rates in postpartum
beef cows resulting from fixed-time AI (FTAI) at 54 or 66 h after
administration of the CO-Synch + CIDR protocol. Cows (n = 851) at two
locations over two years (yr 1; n = 218, 206: yr 2; n = 199, 228) were
stratified by age, BCS and days postpartum (DPP) to 1 of 2 FTAI
intervals. Cows were administered GnRH (100 µg, i.m.) and equipped with
a controlled internal drug release (CIDR) insert (1.38g progesterone) on
d 0. Controlled internal drug release inserts were removed 7 d later at
the time prostaglandin F2 (PG; 25 mg, i.m.) was administered (d 7).
Continuous estrus detection was performed at Location 2 using HeatWatch.
Transmitters were fitted at the time of PG and removed at the time of
AI. Artificial insemination was performed at predetermined fixed-times
[54 h (FTAI 54; n = 424) or 66 h (FTAI 66; n = 427) after PG] and all
cows were administered GnRH (100 µg, i.m.) at AI. Two blood samples were
collected on d -10 or -8 and immediately before treatment initiation to
determine pre-treatment cyclicity status of cows [progesterone 0.5 ng/mL;
(FTAI 54, 288/424, 68%; FTAI 66, 312/427, 73%); P = 0.07]. Pregnancy
rates were greater (P < 0.01) among cows that exhibited estrus than
those that did not (123/163, 76% and 150/270, 56%, respectively). There
were no treatment by location interactions within year (P > 0.10) for
age, DPP, or BCS; thus the results were pooled for the respective
treatments. Pregnancy rates were greater for FTAI 66 than FTAI 54 (P =
0.05; 286/426, 67% and 257/424, 61%, respectively). Pregnancy rates
resulting from FTAI did not differ between year (P = 0.09), farm (P =
0.80), AI sire (P = 0.11) or technician (P = 0.64). There was no
difference between pregnancy rates resulting from FTAI based on
pre-treatment cyclicity status (P = 0.30), and no difference between
treatments in final pregnancy rates (P = 0.77). In summary, pregnancy
rates resulting from FTAI following CO-Synch + CIDR at 66 h were greater
than FTAI at 54 h.
Busch, D.C., D. J. Schafer, D. J. Wilson, D. A. Mallory, N. R. Leitman,
J. K. Haden, M. R. Ellersieck, M. F. Smith, D. J. Patterson Timing of
artificial insemination in postpartum beef cows following administration
of the CO-Synch + CIDR protocol Published online first on March 14, 2008
J. Anim Sci. 1910. 0:jas.2008-0925v1. doi:10.2527/jas.2008-0925
Transportation
and biomarkers of stress
Transportation causes stress in cattle that may alter numerous
physiological variables with a negative impact on production and health.
The objectives of the current study were to investigate the
physiological effects of truck transportation and to characterize a
pattern of phenotypes in the circulation that may aid in the early
identification of stress-susceptible animals that often succumb to
severe respiratory disease. Thirty-six young beef bulls (Aberdeen Angus,
n = 12; Friesian, n = 12; and Belgian Blue x Friesian, n = 12) were
subjected to a 9-h truck transportation by road. Blood (10 mL) was
collected at -24, 0, 4.5, 9.75, 14.25, 24, and 48 h relative to
initiation of transportation (0 h). Plasma was collected for the assay
of various metabolic, inflammatory, and steroid variables, and total
leukocyte counts were determined in whole blood at each time point. Body
weight and rectal temperature were recorded at -24, 9.75, and 48 h.
Transportation decreased measures of protein metabolism in the plasma,
including albumin (P = 0.002), globulin (P < 0.001), urea (P = 0.006),
and total protein (P < 0.001), and increased creatine kinase (P <
0.001). The energy substrate -hydroxybutyrate ( HB) was not changed (P =
0.27). Acute phase proteins haptoglobin and fibrinogen were both
decreased (P < 0.001), while total leukocyte counts were elevated (P =
0.002). Circulating steroid concentrations were altered as a classical
acute increase in plasma cortisol was observed with the onset of transit
(P < 0.001) in association with a decrease in dehydroepiandrosterone (DHEA;
P = 0.07), resulting in a profound increase in cortisol:DHEA ratio (P <
0.001). Plasma testosterone was decreased, while plasma progesterone was
increased (P < 0.001) in association with the increase in cortisol (P <
0.001). There was also an effect of breed for all variables except
plasma urea, creatine kinase, and testosterone, perhaps indicating that
a genetic component contributed to the physiological response to
transportation stress, although without any clear trend. Taken together,
this profile of physiological variables in the circulation of
transportation-stressed bulls may aid in the future detection of
disease-susceptible cattle following transportation. Further research to
validate these potential biomarkers is necessary.
Buckham Sporer, K.R., J. L. Burton, B. Earley, M. A. Crowe.
Transportation of young beef bulls alters circulating physiological
parameters that may be effective biomarkers of stress. Published online
first on March 14, 2008 J. Anim Sci. 1910. 0:jas.2007-0762v1.
doi:10.2527/jas.2007-0762
Pre-shipping management
effects on stress and performance
Over 2 yr, a total of 96 steers (approximately 7 mo of age) were
allocated to 1 of 4 weaning management strategies: 1) control: weaned on
the day of shipping; 2) creep-fed: allowed free-choice access to
concentrate before weaning and shipping; 3) pre-weaned: weaned and
provided supplemental concentrate on pasture before shipping; and 4)
early-weaned: weaned at 70 to 90 d of age and kept on pasture. On the
day of shipping steers were loaded together onto a commercial livestock
trailer and transported 1,600 km over 24 h before being received into
the feedlot. At the feedlot, steers were penned by treatment (4
pens/treatment) and provided access to free-choice hay and concentrate
in separate feeding spaces. Samples of blood were collected on d 0, 1,
4, 8, 15, 22, and 29 relative to shipping. Steer performance was
assessed over the receiving period, including DMI of hay and
concentrate, ADG, and G:F. Pre-determined contrasts included: control
vs. early-weaned, creep-fed vs. pre-weaned, and control vs. creep-fed
and pre-weaned. Overall ADG was greater (P < 0.01) for early-weaned vs.
control steers (1.39 vs. 0.88 kg). In wk 1, early-weaned steers consumed
more concentrate and less hay compared to control steers (P < 0.03) and
pre-weaned steers consumed more concentrate (P < 0.01), but a similar
amount of hay (P = 0.75) compared to creep-fed steers. Average DMI was
greater for pre-weaned compared to creep-fed steers (2.84 vs. 2.50% BW;
P = 0.01) and tended to be greater for early-weaned compared to control
steers (2.76 vs. 2.50% BW; P = 0.06). Feed efficiency of early-weaned
steers was greater than control (G:F = 0.17 vs. 0.12; P < 0.01), but
similar for pre-weaned compared to creep-fed steers (P = 0.72). Plasma
ceruloplasmin concentrations were less (P < 0.05) in control vs.
early-weaned steers on d 0, but increased sharply after shipping and
were greater in control vs. early-weaned steers on d 15 and 22 (P <
0.05). Creep-fed steers also experienced greater (P < 0.05) plasma
ceruloplasmin concentrations than pre-weaned steers on d 29. These data
suggest that early-weaned steers have improved performance in the
feedlot compared to steers weaned directly before transport and feedlot
entry. Differences in pre-shipping management appear to significantly
impact measures of the acute phase protein response in steers.
Arthington, J.D., X. Qiu, R. F. Cooke, J. M. B. Vendramini, D. B. Araujo,
C. C. Chase Jr., S. W. Coleman. Effects of pre-shipping management on
measures of stress and performance of beef steers during feedlot
receiving. Published online first on April 11, 2008 J. Anim Sci. 1910.
0:jas.2008-0968v1. doi:10.2527/jas.2008-0968
USDA Yield Grade
Equation
With the adoption of visual instrument grading, the calculated yield
grade can be used for payment to cattle producers selling on grid
pricing systems. The USDA beef carcass grading standards include a
relationship between required LM area (LMA) and HCW that is an important
component of the final yield grade. As noted on a USDA yield grade LMA
grid, a 272-kg (600-lb) carcass requires a 71-cm2 (11.0-in.2) LMA and a
454-kg (1,000-lb) carcass requires a 102-cm2 (15.8-in.2) LMA. This is a
linear relationship, where required LMA = 0.171(HCW) + 24.526. If a beef
carcass has a larger LMA than required, the calculated yield grade is
lowered, whereas a smaller LMA than required increases the calculated
yield grade. The objective of this investigation was to evaluate the LMA
to HCW relationship against data on 434,381 beef carcasses in the West
Texas A&M University (WTAMU) Beef Carcass Research Center database. In
contrast to the USDA relationship, our data indicate a quadratic
relationship [WTAMU LMA = 33.585 + 0.17729(HCW) –0.0000863(HCW2)]
between LMA and HCW whereby, on average, a 272-kg carcass has a 75-cm2
(11.6-in.2) LMA and a 454-kg carcass has a 96-cm2 (14.9-in.2) LMA,
indicating a different slope and different intercept than those in the
USDA grading standards. These data indicate that the USDA calculated
yield grade equation favors carcasses lighter than 363 kg (800 lb) for
having above average muscling and penalizes carcasses heavier than 363
kg (800 lb) for having below average muscling. If carcass weights
continue to increase, we are likely to observe greater proportions of
yield grade 4 and 5 carcasses because of the measurement bias that
currently exists in the USDA yield grade equation.
Lawrence, T.E., R. L. Farrow, B. L. Zollinger and K. S. Spivey.
Technical note: The United States Department of Agriculture beef yield
grade equation requires modification to reflect the current longissimus
muscle area to hot carcass weight relationship J. Anim Sci. 2008.
86:1434-1438. doi:10.2527/jas.2007-0813
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