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Kansas State University

 

Beef Research News
Brought to you by Kansas State University College of Veterinary Medicine - Farm Animal Section
August 2008

 

 

 

Contents:

Timing of AI following Co-Synch

Vitamin A restriction effect on beef steers

Alternative beef production systems with or without growth promotants

Colostral response after Mycoplasma bovis vaccination

BVD PI Exposure length effect on feedlot performance

National Beef Quality Audit 2005

 



Timing of AI following Co-Synch


This 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 + controlled internal drug-release (CIDR) protocol. Cows (n = 851) at 2 locations over 2 yr (yr 1, n = 218 and 206; and yr 2, n = 199 and 228 at the 2 locations, respectively) were stratified by age, BCS, and days postpartum to 1 of 2 FTAI intervals. Cows were administered GnRH (100 µg, i.m.) and were equipped with a CIDR insert (1.38 g of progesterone) on d 0. Controlled internal drug-release inserts were removed 7 d later at the time PGF2 (25 mg, i.m.) was administered (d 7). Continuous estrus detection was performed at location 2 by using the HeatWatch Estrus Detection System; the transmitters were fitted at the time of PGF2 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 PGF2 ] 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 the pretreatment estrous 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 among those that did not (123/163 = 76% and 150/270 = 56%, respectively). There were no treatment x location interactions within year (P > 0.10) for age, days postpartum, 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% vs. 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 pretreatment cyclicity status (P = 0.30), and there was 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 those resulting from FTAI at 54 h.

D. C. Busch, D. J. Schafer, D. J. Wilson, D. A. Mallory, N. R. Leitman, J. K. Haden, M. R. Ellersieck, M. F. Smith and D. J. Patterson Timing of artificial insemination in postpartum beef cows following administration of the CO-Synch + controlled internal drug-release protocol. J. Anim Sci. 2008. 86:1519-1525. doi:10.2527/jas.2008-0925© 2008.






Vitamin A restriction effect on beef steers

Sixty-eight Angus-based steers (224 ± 7.6 kg of BW) were used to evaluate the effects of a prolonged dietary vitamin A restriction on marbling and immunocompetency. Steers were allotted randomly to 1 of 2 treatments: LOW (no supplemental vitamin A) and HIGH (diet supplemented with 2,200 IU of vitamin A/kg of DM). Diets contained 60% high-moisture corn, 20% roasted soybeans, 10% corn silage, and 10% of a protein supplement. Steers were penned and fed individually. For the first 141 d, steers were program-fed to achieve a gain of 1.1 kg/d. The last 75 d of the experiment, steers were offered feed for ad libitum intake. At slaughter, serum and liver samples were taken to determine their retinol content. To evaluate immunocompetency, 10 steers per treatment were selected randomly on d 141 and received an ovalbumen vaccine, and 21 d later, the steers were revaccinated. On d 182, blood samples were taken from the vaccinated steers to determine serum antibody titers by ELISA. Steers were slaughtered after 216 d on feed. Carcass characteristics were determined, and LM samples were taken for composition analysis. Subcutaneous fat samples were taken for fatty acid composition analysis. Performance (ADG, DMI, and G:F) was not affected by vitamin A restriction (all P > 0.10). Hot carcass weight, 12th-rib fat, and yield grade did not differ between LOW and HIGH steers (all P > 0.10). Marbling score (LOW = 574 vs. HIGH = 568, P = 0.79) and i.m. fat (LOW = 5.0 vs. HIGH = 4.7% ether-extractable fat, P = 0.57) were not increased by vitamin A restriction. Serum (LOW = 18.7 vs. HIGH = 35.7 µg/dL, P < 0.01) and liver (LOW = 6.3 vs. HIGH = 38.1 µg/g, P < 0.01) retinol levels were lower in LOW steers compared with HIGH steers at slaughter. Response to ovalbumin vaccination was not affected by vitamin A restriction (LOW = 13.1 vs. HIGH = 12.8 log2 titers, P = 0.60). Slight changes in the fatty acid profile of s.c. fat of the steers were detected. A greater proportion of MUFA (LOW = 41.7 vs. HIGH = 39.9%, P = 0.03) and fewer SFA (LOW = 47.1 vs. 48.7, P = 0.03) were observed in vitamin A-restricted steers. This suggests that vitamin A restriction may affect the activity of desaturase enzyme (desaturase activity index, LOW = 46.9 vs. HIGH = 44.9, P = 0.01). Feeding a low vitamin A diet for 216 d to Angus-based steers did not affect performance, marbling score, or animal health and immunocompetency. Slight changes in the fatty acid profile of s.c. fat were observed, suggesting that vitamin A restriction may have affected desaturase enzyme activity.

Gorocica-Buenfil, MA, F. L. Fluharty and S. C. Loerch. Effect of vitamin A restriction on carcass characteristics and immune status of beef steers. J. Anim Sci. 2008. 86:1609-1616. doi:10.2527/jas.2007-0241.






Alternative beef production systems with or without growth promotants


Five beef cattle management regimens were evaluated for their effect on meat quality, fatty acid composition, and overall palatability of the longis-simus dorsi (LD) muscle in Angus cross steers. A 98-d growing phase was conducted using grass silage with or without supplementation of growth promotants (Revalor G and Rumensin) or soybean meal. Dietary treatments in the finishing phase were developed with or without supplementation of growth promotants based on exclusive feeding of forages with no grain supplementation, or the feeding of grain:forage (70:30) diets. Growth promotants increased (P < 0.01) shear force and tended (P = 0.06) to increase toughness of the LD muscle due to limited postmortem proteolytic activity (lower myofibrillar fragmentation index value; P = 0.02). Grain feeding increased DM and intramuscular fat content (P = 0.03 and P = 0.05, respectively) in the LD but decreased the sensory panel tenderness score (P = 0.01). Growth promotants increased (P 0.05) the proportion of C18:0, C20:0, trans isomers of C18:1, and cis-9, trans-11 C18:2. Exclusive feeding of forages increased the proportion of cis-9, cis-12, cis-15 C18:3 as well as several other isomers of the n-3 family and decreased in the ratio of n-6 to n-3 fatty acids in the LD muscle as compared with supplementing grain (P < 0.05). In addition, the forage-based diet increased (P < 0.01) the concentration in the intramuscular fat of several intermediates (cis-9, trans-11, cis-15 C18:3; trans-11, cis-15 C18:2; trans-11 C18:1) of ruminal biohydrogenation. Forage feeding also increased the proportion of cis-9, trans-11 C18:2 (P < 0.01) and decreased the concentration of trans-10 C18:1 in the LD muscle (P = 0.03). It is concluded that quality demands of health-conscious consumers can be met through a forage-finishing and growth promotants-free beef production system.

Faucitano, L., P. Y. Chouinard, J. Fortin, I. B. Mandell, C. Lafreničre, C. L. Girard and R. Berthiaume. Comparison of alternative beef production systems based on forage finishing or grain-forage diets with or without growth promotants: 2. Meat quality fatty acid composition, and overall palatability. J. Anim Sci. 2008. 86:1678-1689 . doi:10.2527/jas.2007-0756.





Colostral response after Mycoplasma bovis vaccination


The objective of this research was to determine whether vaccinating cows during late gestation against Mycoplasma bovis will result in adequate concentrations of M bovis–specific IgG1 in serum, colostrum, and milk. There were 78 dairy cows enrolled in the study. Serum samples were obtained 60 and 39 days prior to expected parturition in vaccinated and control cows from a single herd. Serum and colostrum samples were also obtained at parturition. Milk samples were obtained 7 to 14 days after parturition. Samples were analyzed for anti–M bovis IgG1 concentrations. Prior to vaccination, control and vaccinated cows had similar anti–M bovis IgG1 concentrations. After initial vaccination and subsequent booster and at parturition, there was a significant difference between the 2 groups, with vaccinated cows having higher IgG concentrations. Colostrum from vaccinated cows had higher anti–M bovis IgG1 concentrations, compared with control cows; however, IgG1 concentrations in milk did not differ between the 2 groups. Vaccination of late-gestation cows resulted in increased concentrations of anti–M bovis IgG1 in colostrum. However, ingestion of colostrum by calves may not guarantee protection against M bovis infection.

Calloway, C.D., L.G. Schultz, M. Chigerwe, R.L. Larson, R. S. Youngquist, B.J. Steevens. Determination of serologic and colostral response in late-gestation cows vaccinated with a Mycoplasma bovis bacterin. Amer J Vet Res July 2008, Vol 69(7): 912-915.






BVD PI Exposure length effect on feedlot performance

A single experiment with a completely randomized design was conducted to evaluate the effects of long- or short-term exposure to a calf identified as persistently infected with bovine viral diarrhea virus (PI-BVD ) on feedlot performance and carcass characteristics of freshly weaned, transport-stressed beef heifers. Two hundred eighty-eight heifers that had been vaccinated for BVD before weaning and transport were processed and given a metaphylactic antibiotic treatment at arrival and were fed common receiving, growing, and finishing diets for a 215-d period. Treatments were designed to directly or adjacently expose the cattle to a PI-BVD heifer. Directly exposed treatments were 1) negative control with no PI-BVD calf exposure (control), 2) PI-BVD calf commingled in the pen for 60 h and then removed (short-term exposure), and 3) PI-BVD calf commingled in the pen for the duration of the study (long-term exposure); and spatially exposed treatments were 1) negative control with no PI-BVD calf exposure (adjacent pen control), 2) PI-BVD calf commingled in the adjacent pen for 60 h and then removed (adjacent pen short-term exposure), and 3) PI-BVD calf commingled in the adjacent pen for the duration of the study (adjacent pen long-term exposure). Exposure to a PI calf transiently (60 h) or for the duration of the feeding period (215 d) did not affect (P >0.25) final BW compared with heifers that were not exposed. Neither period nor overall DMI was affected (P >0.37) by PI-BVD calf exposure, and no differences (P >0.44) were observed between short- and long-term exposed heifers in the direct or spatially exposed groups. Likewise, total trial ADG was not affected (P >0.36) and overall efficiency of gain (P > 0.19) was unaffected by PI-BVD calf exposure in the direct or spatially exposed groups. The results from this study suggest that exposing previously vaccinated, freshly weaned, transport- stressed beef calves to a calf that is persistently infected with bovine viral diarrhea virus has little, if any, marked effects on health, performance, or carcass characteristics.

Elam, N.A., D. U. Thomson and J. F. Gleghorn. Effects of long- or short-term exposure to a calf identified as persistently infected with bovine viral diarrhea virus on feedlot performance of freshly weaned, transport-stressed beef heifers J. Anim Sci. 2008. 86:1917-1924.





National Beef Quality Audit 2005

The National Beef Quality Audit–2005 assessed the current status of quality and consistency of U.S. fed steers and heifers. Hide colors or breed-type were black (56.3%), red (18.6%), Holstein (7.9%), gray (6.0%), yellow (4.9%), brown (3.0%), white (2.3%), and brindle (1.0%). Identification method and frequency were lot visual tags (63.2%), individual visual tags (38.7%), metal-clip tags (11.8%), electronic tags (3.5%), bar-coded tags (0.3%), by other means (2.5%), and without identification (9.7%). Brand frequencies were no (61.3%), one (35.1%), and two or more (3.6%), and brands were located on the butt (26.5%), side (7.4%), and shoulder (1.2%). There were 22.3% of the cattle without horns, and the majority of those with horns (52.2%) were between 2.54 and 12.7 cm in length. Percentages of animals with mud/manure on specific body locations were none (25.8%), legs (61.4%), belly (55.9%), side (22.6%), and top-line (10.0%). Permanent incisor number and occurrence were zero (82.2%), one (5.2%), two (9.9%), three (0.4%), four (1.2%), five (0.1%), six (0.3%), seven (0.0%), and eight (0.7%). Most carcasses (64.8%) were not bruised, 25.8% had one bruise, and 9.4% had multiple bruises. Bruise location and incidence were round (10.6%), loin (32.6%), rib (19.5%), chuck (27.0%), and brisket, flank, and plate (10.3%). Condemnation item and incidence were liver (24.7%), lungs (11.5%), tripe (11.6%), heads (6.0%), tongues (9.7%), and carcasses (0.0%). Carcass evaluation revealed these traits and frequencies: steer (63.7%), heifer (36.2%), bullock (0.05%), and cow (0.04%) sex-classes; dark-cutters (1.9%); A (97.1%), B (1.7%), and C or older (1.2%) overall maturities; and native (90.9%), dairy-type (8.3%), and Bos indicus (0.8%) estimated breed-types. Mean USDA yield grade traits were USDA yield grade (2.9), HCW (359.9 kg), adjusted fat thickness (1.3 cm), LM area (86.4 cm2), and KPH (2.3%). USDA yield grades (YG) were YG 1 (16.5%), YG 2 (36.3%), YG 3 (33.1%), YG 4 (11.8%), and YG 5 (2.3%). Mean USDA quality grade traits were USDA quality grade (Select90), marbling score (Small32) , overall maturity (A64), lean maturity (A57), and skeletal maturity (A68). Marbling score distribution was Slightly Abundant or higher (2.7%), Moderate (4.3%), Modest (14.4%), Small (34.5%), Slight (41.2%), and Traces or lower (2.9%) . Information helps the beef industry measure progress and provides a benchmark for future educational and research activities.

Garcia, L.G., K.L. Nicholson, T.W. Hoffman, T.E. Lawrence, D.S. Hale, D.B. Griffin, J.W. Savell, D.L. VanOverbeke, J.B. Morgan, K.E. Belk, T.G. Field, J.A. Scanga, J.D. Tatum and G.C. Smith. National Beef Quality Audit-2005: Survey of targeted cattle and carcass characteristics related to quality, quantity, and value of fed steers and heifers. Published online first on August 1, 2008 J. Anim Sci. 1910. doi:10.2527/jas.2007-0782.






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