Beef Research News
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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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