Influence of melengesterol acetate (MGA®) and Implus-H® implants on rate of gain, feed efficiency, and carcass characteristics of culled beef cows fed a high concentrate ration

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Introduction
Melengesterol acetate (MGA)suppresses grain and sorghum silage.Ration net energy behavioral and hormonal changes associated was increased incrementally in five steps with the estrous cycle of intact bovine through day 24.The sixth and final ration females.Riding behavior associated with was fed from day 25 through the end of the cycling heifers and cows is thought to be feeding period on day 57.The final ration associated with decreased performance.The (dry basis) consisted of 68.6% corn, 19.1% objective of this study was to evaluate the sorghum silage, 6.1% supplement, 3.5% effects of MGA alone, Implus-H alone, and alfalfa hay, and 2.7% molasses.Dry matter the combination of the two on feedlot perfor-intake was calculated daily for each pen.For mance and carcass characteristics of culled those groups receiving MGA, the product beef cows.
was added to the ration at 4.0 mg/head/day Experimental Procedures control, MGA only, Implus-H implant only, cates.
All cows were fed a ration based on corn beginning on day 2 of the trial.Rumensin was added at a rate of 30g/ton to the base REA, 0.27 in.for fat thickness, 53.0% for ration formulation for all experimental dressing percent, 153.4 (Utility grade= 100groups. 199) for USDA QG, and 2.6 for YG.
Cows were monitored twice daily for Estrus was detected in 37 cows.Average estrus and health status.All animals in stand-daily gains were 3.91 lb for those cows dising estrus were identified, and the date was playing estrus and 3.79 lb for those not disrecorded.All animals showing signs of playing estrus.The difference was not statisillness were pulled for medical examination tically significant.and treatment.Cows with severe medical conditions were removed from the trial.
During the feeding period, 29 animals On day 29 of the trial, the cows were ment (Table 2).No differences in number of weighed.At the end of the trial on day 56 animals treated were found among experiand the morning of day 57, the cows were mental groups.At slaughter, post-mortem weighed, and the weights averaged to calcu-examination revealed 35 cows with single or late final weight.On day 57, the cows were multiple pathological conditions of a minor to shipped to the Excel, Inc. processing plant at severe nature.The type and frequency of Sterling, CO for slaughter.
postmortem finding were comparable to Health information was recorded for each condemnations, which were 10% greater than cow at evisceration.Hot carcass weight USDA reports.Based upon texture and (HCW); fat thickness; ribeye area (REA); physical characteristics, the liver abscesses kidney, pelvic, and heart fat percent (KPH%); appeared to be healed and had been of conskeletal maturity; lean maturity; marbling; and siderable duration.No acute or wet lesions fat color were recorded for each carcass.
were found.Whether this higher than ex-Dressing percent, USDA quality grade pected incidence was due to feedlot manage-(USDA QG) and yield grade (YG) were ment practices or to preexisting hepatic insult determined for each cow.
is unknown.One or more bruises requiring extensive tissue trimming were found on 53% Mean gain, intake, and feed/gain ratio of the carcasses.Average daily gains for were tabulated for each treatment group for cows pulled and treated or having pathology days 1-28, days 29-56, and days 1-56.
at slaughter were lower than gains for other Means for each treatment group were com-cows on trial (3.58 vs 3.99 lb, P<0.09).pared by analysis of variance.Frequency of disease was tabulated.Twenty-two cows Cull cows are market-ready from the first (chronic, dead, or pregnant at slaughter) were day in the feedlot.The option to slaughter removed from the study and not considered before the projected slaughter date can be in the final statistical analysis.
used when unanticipated price fluctuations

Results and Discussion
No significant differences (P>.05) were and anthelmintic should be selected for the detected between treatment and control shortest withdraw times or their use should group means for gains, feed intakes, or effi be avoided.ciencies (Table 1) or carcass traits.Means across all treatments were 9.8 in.for 2 were pulled for evaluation and medical treat-USDA reports for cull cows, except for liver occur or a cow exhibits poor performance, becomes lame, goes off-feed, or is injured.Thus, products such as vaccines, insecticides,