Beef Research News
Brought to you by Kansas State University
College of Veterinary Medicine - Farm Animal Section
March 2007
Contents:
Antibiotic feeding & auction exposure effect on calves
Dam nutrition & reproductive performance of heifers
Bull exposure and conception rates
Flunixin
meglumine and pregnancy establishment
Antibiotic feeding & auction exposure effect on calves
Research was performed to evaluate potential
differences in response to different antibiotic therapies in populations
of ranch-direct and auction sourced calves. The trial consisted of using
240 mixed breed steers (265.5 ± 4.8 kg) divided into two equal groups:
shipped directly from ranch to feedlot or shipped to an auction and
subsequently to same feedlot. All calves were from single ranch located
400 km from feedlot. Calves in the auction group were held overnight at
the auction without feed or water, co-mingled, sorted, run through the
auction ring and transported to the feedlot. Calves were weighed on
arrival and equipped with a radio frequency identification tag to
monitor bunk attendance. Calves sourced directly from the ranch were
heavier at arrival (273 vs. 258; P=0.01) than calves processed through
the auction barn. For calves fed 6 g/head/d chlortetracycline from days
5 to 9, feeding an additional 350 mg head/d of chlortetracycline and
sulfamethazine from days 1 to 28 improved gain/feed (P = 0.03), but only
for the first 28 d of the 84-d trial. Frequency of bunk visits were
altered by calf source and antibiotic treatment. In summary, for cattle
receiving 6 g/head/d of chlortetracycline from days 5 to 9, feeding an
additional 350 mg/head/d of chlortetracycline and sulfamethazine
improved gain/feed, but this effect did not maintain past the period in
which it was fed. Any performance effects of processing calves through
an auction barn were small and disappeared after the first month in the
feedlot. Differences in feeding behavior through the whole trial were
small.
Gibb, D., K. Schwartzkopf-Genswein, T. McAllister, B. Genswein, M.
Streeter Effect of Sub-therapeutic Antibiotics and Auction Exposure on
Health, Performance, and Feeding Behavior of Weaning Calves Can J Anim
Sci 2006 86(4) 457-460.
Neosporosis in
Bulls
Eight seronegative bulls were intravenously infected with live Neospora
caninum tachyzoites of NC-1 isolate to investigate the presence of N.
caninum in semen and blood. The presence of N. caninum in semen and
blood was assessed using a nested-PCR procedure. All eight
experimentally infected bulls showed N. caninum DNA in their semen
and/or blood samples at some time during the course of the study. A
significant increase in mean serum specific IgM antibody response to N.
caninum was detected between 10 and 28 days post-infection. Specific
anti-N. caninum IgG were detected in seminal plasma from infected bulls
and values obtained were different from seronegative controls after 25
days post-infection. The observations indicate an intermittent presence
of N. caninum in low numbers in semen and associated with chronic stage
of infection.
E. Serrano-Martnez, I. Ferre, A. Martnez, K. Osoro, A. Mateos-Sanz, I.
del-Pozo, G. Aduriz, C. Tamargo, C.O. Hidalgo, L.M. Ortega-Mora
Experimental neosporosis in bulls: Parasite detection in semen and blood
and specific antibody and interferon-gamma responses Therio 2007 67(6):
1175-1184
Dam nutrition &
reproductive performance of heifers
Research was performed over 3 years to evaluate the effects of late
gestation (LG) or early lactation (EL) dam nutrition on subsequent
heifer growth and reproduction. In LG, cows received 0.45 kg/d of 42% CP
supplement (PS) or no supplement (NS) while grazing in dormant Sandhills
range. During EL, cows from each LG treatment were feed cool-season
grass hay or grazed sub-irrigated meadow. Performance of subsequent
heifers (n=170) was evaluated. Heifer birth date and birth weight were
not affected by dam nutrition. Heifers from PS dams had greater weight
(P < 0.04) at prebreeding and pregnancy diagnosis, but these weights
were unaffected by EL nutrition. There was no effect (P>0.10) of LG or
EL dam nutrition on age at puberty or percentage of heifers cycling
before breeding. Pregnancy rates were greater (P=0.05) for heifers from
PS dams, and a greater proportion (P = 0.005) of heifers from PS dams
calved in the first 21 d of the heifers’ first calving season. Nutrition
of dams did not influence (P < 0.10) heifers’ average calving date,
calving difficulty, and calf birth weight during the initial calving
season. Heifers from PS dams had greater weight at the beginning of the
second breeding season (P = 0.005). Heifers born to PS cows were heavier
at weaning, prebreeding, first pregnancy diagnosis, and before their
second breeding season. Heifers from cows that grazed meadows during EL
were heavier at weaning but not post weaning. Despite similar ages at
puberty and similar proportions of heifers cycling before the breeding
season, a greater proportion of heifers from PS dams calved in the first
21 d of the heifers’ first calving season, and pregnancy rates were
greater compared with heifers from NS dams. Collectively, these results
provide evidence of a fetal programming effect on heifer post weaning BW
and fertility.
J. L. Martin, K. A. Vonnahme, D. C. Adams, G. P. Lardy, and R. N.
Funston Effects of dam nutrition on growth and reproductive performance
of heifer calves
J. Anim Sci. 2007; 85:841-847.
Bull exposure and
conception rates
Three experiments were performed to evaluate the impact of exposing
primiparous, suckled beef cows to the biostimulatory effect of bulls on
breeding performance in an estrus synchronization protocol that included
GnRH followed 7 d later by PGF 2 and fixed time AI (TAI). Experiment 1
evaluated the effects of bull exposure at different days after calving,
experiment 2 evaluated the biostimulatory effects of bull excretory
products and in year three the biostimulatory effects of familiar and
unfamiliar bulls on resumption of ovarian cycling activity was examined.
In all studies, cows were exposed (biostimulated; n = 94) or not exposed
(nonbiostimulated; n = 67) to bulls or excretory products of bulls for
at least 60 d before the beginning of the estrus synchronization
protocol. The percentages of cows that exhibited estrus after PGF2 and
before TAI, the interval from PGF2 to estrus, and the percentages of
cows inseminated 12 h after estrus or at TAI did not differ between
biostimulated and nonbiostimulated cows. Conception rates for cows bred
by AI 12 h after estrus did not differ between biostimulated and
nonbiostimulated cows; however, the TAI conception rate was greater (P <
0.05) for biostimulated cows (57.6%) than for nonbiostimulated cows
(35.6%). We conclude that TAI conception rates in an estrus
synchronization protocol that includes GnRH followed 7 d later by PGF2
may be improved by the biostimulatory effect of bulls in postpartum,
primiparous cows.
Berardinelli, J.G. P. S. Joshi, and S. A. Tauck. Conception rates to
artificial insemination in primiparous, suckled cows exposed to the
biostimulatory effect of bulls before and during a gonadotropin-releasing
hormone-based estrus synchronization protocol J. Anim Sci. 2007;
85:848-852.
Flunixin meglumine
and pregnancy establishment
Research was performed to determine the effects of flunixin meglumine
(FM) administration on early embryonic mortality and circulating
prostaglandin and cortisol concentration in transported and
non-transported cows. The effects of transportation and FM at 14 d post
AI was evaluated in 483 cows. Treatments were transport (n = 129),
transport + FM (n = 128), no transport (n =130) and no transport + FM (n
= 96). Flunixin meglumine (1.1 mg/kg BW; i.m.) was administered before
separation and transportation groups were placed on semi-tractor
trailers without calves fro 4 to 6 h. Blood samples were collected
before and after treatment. Cows receiving transportation and FM tended
(P = 0.07) to have greater AI pregnancy rates (74%) than those that did
not received FM (66%) irrespective of transportation. Transportation
increased cortisol concentration (P< 0.05) relative to non-transported
cows. Pregnancy rates were increased (P < 0.05) in FM cows compared to
non-FM cows (71 and 61% respectively). The authors concluded that
transportation of cows approximately 14 d after AI increased serum
cortisol concentrations but did not affect AI pregnancy rates. However,
treatment of cows with FM increased AI pregnancy rates, irrespective of
whether they were transported.
Merrill, M.L. R.P. Ansotegui, P.D. Burns, M.D. MacNeil, T.W. Geary.
Effects of flunixin meglumine and transportation on pregnancy
establishment in beef cows. J. Anim Sci. 2007; published online 3/19/07,
doi: 10.2527.
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