Beef Research News
Brought to you by Kansas State University
College of Veterinary Medicine - Agricultural Practices Section
May 2007
Contents:
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
________________________________________________________________
Beef Research News is produced by the Agricultural Practices section at
Kansas State University. To modify your subscription to this service
please email Erin Evanson ( eevanson@vet.ksu.edu )
For more information please contact:
Brad White
Beef Production Medicine
Q211 Mosier Hall
Manhattan, KS 66506
bwhite@vet.ksu.edu