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Kansas State University


Beef Research News
Brought to you by Kansas State University College of Veterinary Medicine - Farm Animal Section
May 2007





Beef heifer development within three calving systems

Mycoplasma bovis in feedlot beef calves

Feedlot diseases and pathogens associated with mortality

Cow-calf calving seasons and marketing strategies

Endophyte levels and calf weight gains

Beef heifer development within three calving systems
Research was conducted over a 3 year period to evaluate impacts of calving system, weaning age, and post-weaning management on growth and reproduction in beef heifers. Heifer calves were weaned at either 190 or 240 d of age (Late Winter birth) or 140 or 190 d of age for late spring born calves. Heifers were fed for either constant gain or delayed gain and managed for first breeding at 14 months of age. Post-weaning feeding program did not effect weights at beginning of breeding season, however calving system and weaning age did due to initial heifer weights. Heifers born in late winter weaned at 190 days were 36 kg heavier (P<0.001) at prebreeding than other heifers. Management differences did not effect the proportion of heifers exhibiting luteal activity at the beginning of the breeding season. Treatments also had no effect (P = 0.64) on pregnancy rates. In conclusion, heifers from varied calving systems and weaning strategies can be raised to breeding using either constant or delayed gain strategies without affecting percentage of heifers cycling at the beginning of the breeding season. These results suggest that producers have multiple options for management of heifer calves from differing calving systems.

Grings, E.E., Geary, T.W., Short, R.E. and Macneil, M.D. Beef heifer development within three calving systems. published 27 April 2007, 10.2527/jas.2006-758


Mycoplasma bovis in feedlot beef calves
A study was conducted to examine lesions and infectious agents in naturally occurring Mycoplasma bovis associated bronchopneumonia and arthritis and the relationship with bovine viral diarrhea virus (BVDV) infection. Ninety-nine calves that died or were euthanized within 60 days post arrival in 72 feedlots had standardized pathologic, immunohistochemical, and microbiologic examinations performed. Cranioventral bronchopneumonia with multiple foci of caseous necrosis was identified in 54 of 99 calves, including 30 with concurrent fibrinosuppurative bronchopneumonia typical of pneumonic pasteurellosis. Mycoplasma bovis was consistently identified in these lesions by culture and immunohistochemistry, but also commonly in healthy lungs and those with pneumonia of other causes. All calves identified with arthritis had pneumonia and arthritis was present in 25 of 54 (46%) of calves with M. bovis pneumonia. BVDV infection was more common in calves with lesions of bacterial pneumonia than in those dying of other causes, but BVDV infection was not more common in calves with caseonecrotic bronchopneumonia than those with fibrinosuppurative bronchopneumonia. The findings suggest that, in at least some calves, M. bovis induces caseonecrotic bronchopneumonia within the lesions of pneumonic pasteurellosis.

Gagea, M.I., Bateman, K.G., Shanahan, R.A., et al. Naturally occurring Mycoplasma bovis-associated pneumonia and polyarthritis in feedlot beef calves. J Vet Diagn Invest 2006 Jan; 18(1):29-40


Feedlot diseases and pathogens associated with mortality
This study determined the prevalence of diseases and pathogens associated with mortality or severe morbidity in 72 Ontario beef feedlots in calves that died or were euthanized within 60 days after arrival. Routine pathologic and microbiologic investigations, as well as immunohistochemical staining for detection of bovine viral diarrhea virus (BVDV) antigen, were performed on 99 calves that died or were euthanized within 60 days after arrival. Major disease conditions identified included fibrinosuppurative bronchopneumonia (49%), caseonecrotic bronchopneumonia or arthritis (or both) caused by Mycoplasma bovis (36%), viral respiratory disease (19%), BVDV-related diseases (21%), Histophilus somni myocarditis (8%), ruminal bloat (2%), and miscellaneous diseases (8%). Viral infections identified were BVDV (35%), bovine respiratory syncytial virus (9%), bovine herpesvirus-1 (6%), parainfluenza-3 virus (3%), and bovine coronavirus (2%). Bacteria isolated from the lungs included M. bovis (82%), Mycoplasma arginini (72%), Ureaplasma diversum (25%), Mannheimia haemolytica (27%), Pasteurella multocida (19%), H. somni (14%), and Arcanobacterium pyogenes (19%). Pneumonia was the most frequent cause of mortality of beef calves during the first 2 months after arrival in feedlots, representing 69% of total deaths. The prevalence of caseonecrotic bronchopneumonia caused by M. bovis was similar to that of fibrinosuppurative bronchopneumonia, and together, these diseases were the most common causes of pneumonia and death. M. bovis pneumonia and polyarthritis has emerged as an important cause of mortality in Ontario beef feedlots.

Gagea, M.I., Bateman, K.G., van Dreumel, T., et al. Diseases and pathogens associated with mortality in Ontario beef feedlots. J Vet Diagn Invest 2006 Jan; 18(1):18-28


Evaluation of cow-calf calving seasons and marketing strategies
Research was performed to evaluate alternative calving seasons in a range managed cow-calf enterprise in the Northern Great Plains using a bio-economic model. Researchers compared three calving seasons: spring (SP, beginning March 15, weaning Oct 31), summer (SU, beginning May 15, weaning December 15), and fall (FA, beginning August 15, weaning Feb 1). Additionally, a 5% increase in calf mortality (SP-IM) and an early weaning summer program (SU-EW, weaned October 31) were simulated. The models consisted of herd sizes between 500 and 609 cows with expected weight weaned per cow exposed varying by season. Cattle and feed prices were representative of the peak, descending, valley, and ascending phases of the 1990s cattle cycle adjusted for inflation. Ranch gross margin (RGM) or the gross returns minus variable costs was estimated for each system and compared. The spring calving system had the highest RGM followed by SP-IM, SU, SU-EW, and FA, and ranks were consistent across all phases of the cattle cycle. In beef enterprises representative of the Northern Great Plains, with a restricted grazing season, limited access to low-cost high quality grazable forage, and with calves sold at weaning, switching from early spring to a summer or fall calving date is not expected to improve profitability. If delayed calving improves calf survival calving in early summer may be a competitive choice.

Reisenauer Leesburg, V.L., Tess, M.W., Griffith, D. Evaluation of calving seasons and marketing strategies in Northern Great Plains beef enterprises: I. Cow-calf systems. J. Anim. Sci published online 15 May 2007, 10.2527/jas.2007-0051


Endophyte levels and calf weight gains
Research was performed to examine the effect of endophyte infection level of tall fescue (Festuca arundinacea Schreb.) used for stockpiled forage on performance of lactating, fall-calving beef cows and their calves. The trial compared three levels of endophyte infection: low (20%), medium (51%), and high (89%) Sixty cow-calf pairs were evenly divided into 4 replicates of each of the three treatments in the study. Each set of cows grazed the allotted treatment pasture for 84 days beginning in December and the trial was repeated in the following year. After grazing, animals were co-mingled and fed as a single group until April. Apparent intake (pre-grazing minus post-grazing forage DM yield) of infected stockpiled tall fescue was not effected by treatment. Cow ADG was higher (P< 0.01) in the low treatment (-0.47 kg/d) than the medium (-0.64) or high (-0.74) treatments. By April the cow BW did not differ between groups. Body condition score for the low treatment was greater than the other two treatments at the end of the 84 day grazing and this effect maintained until the end of the trial in April. In contrast to cow performance, calf ADG was unaffected (P=0.10) by endophyte level. The data suggests that fall calving herds can utilize highly-infected tall fescue when stockpiled for winter grazing with little impact on cow performance and no impact on calf gain.

Curtis, L.E. and Kallenbach, R.L. Endophyte infection level of tall fescue stockpiled for winter grazing does not alter the gain of calves nursing lactating beef cows. J. Anim. Sci published online 15 May 2007, 10.2527/jas.2006-848

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For more information please contact:
Brad White
Beef Production Medicine
Q211 Mosier Hall
Manhattan, KS 66506